qpdf/libqpdf/QPDF.cc

#include <qpdf/qpdf-config.h> // include first for large file support

#include <qpdf/QPDF.hh>

#include <algorithm>
#include <atomic>
#include <limits>
#include <map>
#include <memory.h>
#include <regex>
#include <sstream>
#include <stdlib.h>
#include <string.h>
#include <vector>

#include <qpdf/BufferInputSource.hh>
#include <qpdf/FileInputSource.hh>
#include <qpdf/OffsetInputSource.hh>
#include <qpdf/Pipeline.hh>
#include <qpdf/Pl_Discard.hh>
#include <qpdf/Pl_OStream.hh>
#include <qpdf/QPDFExc.hh>
#include <qpdf/QPDFLogger.hh>
#include <qpdf/QPDFObject_private.hh>
#include <qpdf/QPDFParser.hh>
#include <qpdf/QPDF_Array.hh>
#include <qpdf/QPDF_Dictionary.hh>
#include <qpdf/QPDF_Null.hh>
#include <qpdf/QPDF_Reserved.hh>
#include <qpdf/QPDF_Stream.hh>
#include <qpdf/QPDF_Unresolved.hh>
#include <qpdf/QTC.hh>
#include <qpdf/QUtil.hh>

// This must be a fixed value. This API returns a const reference to
// it, and the C API relies on its being static as well.
std::string const QPDF::qpdf_version(QPDF_VERSION);

static char const* EMPTY_PDF = (
    // force line break
    "%PDF-1.3\n"
    "1 0 obj\n"
    "<< /Type /Catalog /Pages 2 0 R >>\n"
    "endobj\n"
    "2 0 obj\n"
    "<< /Type /Pages /Kids [] /Count 0 >>\n"
    "endobj\n"
    "xref\n"
    "0 3\n"
    "0000000000 65535 f \n"
    "0000000009 00000 n \n"
    "0000000058 00000 n \n"
    "trailer << /Size 3 /Root 1 0 R >>\n"
    "startxref\n"
    "110\n"
    "%%EOF\n");

namespace
{
    class InvalidInputSource: public InputSource
    {
      public:
        virtual ~InvalidInputSource() = default;
        virtual qpdf_offset_t
        findAndSkipNextEOL() override
        {
            throwException();
            return 0;
        }
        virtual std::string const&
        getName() const override
        {
            static std::string name("closed input source");
            return name;
        }
        virtual qpdf_offset_t
        tell() override
        {
            throwException();
            return 0;
        }
        virtual void
        seek(qpdf_offset_t offset, int whence) override
        {
            throwException();
        }
        virtual void
        rewind() override
        {
            throwException();
        }
        virtual size_t
        read(char* buffer, size_t length) override
        {
            throwException();
            return 0;
        }
        virtual void
        unreadCh(char ch) override
        {
            throwException();
        }

      private:
        void
        throwException()
        {
            throw std::logic_error(
                "QPDF operation attempted on a QPDF object with no input "
                "source."
                " QPDF operations are invalid before processFile (or another"
                " process method) or after closeInputSource");
        }
    };
} // namespace

QPDF::ForeignStreamData::ForeignStreamData(
    std::shared_ptr<EncryptionParameters> encp,
    std::shared_ptr<InputSource> file,
    QPDFObjGen const& foreign_og,
    qpdf_offset_t offset,
    size_t length,
    QPDFObjectHandle local_dict) :
    encp(encp),
    file(file),
    foreign_og(foreign_og),
    offset(offset),
    length(length),
    local_dict(local_dict)
{
}

QPDF::CopiedStreamDataProvider::CopiedStreamDataProvider(
    QPDF& destination_qpdf) :
    QPDFObjectHandle::StreamDataProvider(true),
    destination_qpdf(destination_qpdf)
{
}

bool
QPDF::CopiedStreamDataProvider::provideStreamData(
    QPDFObjGen const& og,
    Pipeline* pipeline,
    bool suppress_warnings,
    bool will_retry)
{
    std::shared_ptr<ForeignStreamData> foreign_data = foreign_stream_data[og];
    bool result = false;
    if (foreign_data.get()) {
        result = destination_qpdf.pipeForeignStreamData(
            foreign_data, pipeline, suppress_warnings, will_retry);
        QTC::TC("qpdf", "QPDF copy foreign with data", result ? 0 : 1);
    } else {
        auto foreign_stream = foreign_streams[og];
        result = foreign_stream.pipeStreamData(
            pipeline, nullptr, 0, qpdf_dl_none, suppress_warnings, will_retry);
        QTC::TC(
            "qpdf", "QPDF copy foreign with foreign_stream", result ? 0 : 1);
    }
    return result;
}

void
QPDF::CopiedStreamDataProvider::registerForeignStream(
    QPDFObjGen const& local_og, QPDFObjectHandle foreign_stream)
{
    this->foreign_streams[local_og] = foreign_stream;
}

void
QPDF::CopiedStreamDataProvider::registerForeignStream(
    QPDFObjGen const& local_og,
    std::shared_ptr<ForeignStreamData> foreign_stream)
{
    this->foreign_stream_data[local_og] = foreign_stream;
}

QPDF::StringDecrypter::StringDecrypter(QPDF* qpdf, QPDFObjGen const& og) :
    qpdf(qpdf),
    og(og)
{
}

void
QPDF::StringDecrypter::decryptString(std::string& val)
{
    qpdf->decryptString(val, og);
}

std::string const&
QPDF::QPDFVersion()
{
    // The C API relies on this being a static value.
    return QPDF::qpdf_version;
}

QPDF::EncryptionParameters::EncryptionParameters() :
    encrypted(false),
    encryption_initialized(false),
    encryption_V(0),
    encryption_R(0),
    encrypt_metadata(true),
    cf_stream(e_none),
    cf_string(e_none),
    cf_file(e_none),
    user_password_matched(false),
    owner_password_matched(false)
{
}

QPDF::Members::Members() :
    log(QPDFLogger::defaultLogger()),
    file(new InvalidInputSource()),
    encp(new EncryptionParameters)
{
}

QPDF::QPDF() :
    m(new Members())
{
    m->tokenizer.allowEOF();
    // Generate a unique ID. It just has to be unique among all QPDF
    // objects allocated throughout the lifetime of this running
    // application.
    static std::atomic<unsigned long long> unique_id{0};
    m->unique_id = unique_id.fetch_add(1ULL);
}

QPDF::~QPDF()
{
    // If two objects are mutually referential (through each object
    // having an array or dictionary that contains an indirect
    // reference to the other), the circular references in the
    // std::shared_ptr objects will prevent the objects from being
    // deleted. Walk through all objects in the object cache, which is
    // those objects that we read from the file, and break all
    // resolved indirect references by replacing them with an internal
    // object type representing that they have been destroyed. Note
    // that we can't break references like this at any time when the
    // QPDF object is active. The call to reset also causes all direct
    // QPDFObjectHandle objects that are reachable from this object to
    // release their association with this QPDF. Direct objects are
    // not destroyed since they can be moved to other QPDF objects
    // safely.

    // At this point, obviously no one is still using the QPDF object,
    // but we'll explicitly clear the xref table anyway just to
    // prevent any possibility of resolve() succeeding.
    this->m->xref_table.clear();
    auto null_obj = QPDF_Null::create();
    for (auto const& iter: this->m->obj_cache) {
        iter.second.object->disconnect();
        iter.second.object->destroy();
    }
}

std::shared_ptr<QPDF>
QPDF::create()
{
    return std::make_shared<QPDF>();
}

void
QPDF::processFile(char const* filename, char const* password)
{
    FileInputSource* fi = new FileInputSource(filename);
    processInputSource(std::shared_ptr<InputSource>(fi), password);
}

void
QPDF::processFile(
    char const* description, FILE* filep, bool close_file, char const* password)
{
    FileInputSource* fi = new FileInputSource(description, filep, close_file);
    processInputSource(std::shared_ptr<InputSource>(fi), password);
}

void
QPDF::processMemoryFile(
    char const* description,
    char const* buf,
    size_t length,
    char const* password)
{
    processInputSource(
        std::shared_ptr<InputSource>(
            // line-break
            new BufferInputSource(
                description,
                new Buffer(QUtil::unsigned_char_pointer(buf), length),
                true)),
        password);
}

void
QPDF::processInputSource(
    std::shared_ptr<InputSource> source, char const* password)
{
    this->m->file = source;
    parse(password);
}

void
QPDF::closeInputSource()
{
    this->m->file = std::shared_ptr<InputSource>(new InvalidInputSource());
}

void
QPDF::setPasswordIsHexKey(bool val)
{
    this->m->provided_password_is_hex_key = val;
}

void
QPDF::emptyPDF()
{
    processMemoryFile("empty PDF", EMPTY_PDF, strlen(EMPTY_PDF));
}

void
QPDF::registerStreamFilter(
    std::string const& filter_name,
    std::function<std::shared_ptr<QPDFStreamFilter>()> factory)
{
    QPDF_Stream::registerStreamFilter(filter_name, factory);
}

void
QPDF::setIgnoreXRefStreams(bool val)
{
    this->m->ignore_xref_streams = val;
}

std::shared_ptr<QPDFLogger>
QPDF::getLogger()
{
    return this->m->log;
}

void
QPDF::setLogger(std::shared_ptr<QPDFLogger> l)
{
    this->m->log = l;
}

void
QPDF::setOutputStreams(std::ostream* out, std::ostream* err)
{
    setLogger(QPDFLogger::create());
    this->m->log->setOutputStreams(out, err);
}

void
QPDF::setSuppressWarnings(bool val)
{
    this->m->suppress_warnings = val;
}

void
QPDF::setAttemptRecovery(bool val)
{
    this->m->attempt_recovery = val;
}

void
QPDF::setImmediateCopyFrom(bool val)
{
    this->m->immediate_copy_from = val;
}

std::vector<QPDFExc>
QPDF::getWarnings()
{
    std::vector<QPDFExc> result = this->m->warnings;
    this->m->warnings.clear();
    return result;
}

bool
QPDF::anyWarnings() const
{
    return !this->m->warnings.empty();
}

size_t
QPDF::numWarnings() const
{
    return this->m->warnings.size();
}

bool
QPDF::validatePDFVersion(char const*& p, std::string& version)
{
    bool valid = QUtil::is_digit(*p);
    if (valid) {
        while (QUtil::is_digit(*p)) {
            version.append(1, *p++);
        }
        if ((*p == '.') && QUtil::is_digit(*(p + 1))) {
            version.append(1, *p++);
            while (QUtil::is_digit(*p)) {
                version.append(1, *p++);
            }
        } else {
            valid = false;
        }
    }
    return valid;
}

bool
QPDF::findHeader()
{
    qpdf_offset_t global_offset = this->m->file->tell();
    std::string line = this->m->file->readLine(1024);
    char const* p = line.c_str();
    if (strncmp(p, "%PDF-", 5) != 0) {
        throw std::logic_error("findHeader is not looking at %PDF-");
    }
    p += 5;
    std::string version;
    // Note: The string returned by line.c_str() is always
    // null-terminated. The code below never overruns the buffer
    // because a null character always short-circuits further
    // advancement.
    bool valid = validatePDFVersion(p, version);
    if (valid) {
        this->m->pdf_version = version;
        if (global_offset != 0) {
            // Empirical evidence strongly suggests that when there is
            // leading material prior to the PDF header, all explicit
            // offsets in the file are such that 0 points to the
            // beginning of the header.
            QTC::TC("qpdf", "QPDF global offset");
            this->m->file = std::shared_ptr<InputSource>(
                new OffsetInputSource(this->m->file, global_offset));
        }
    }
    return valid;
}

bool
QPDF::findStartxref()
{
    if (readToken(m->file).isWord("startxref") &&
        readToken(m->file).isInteger()) {
        // Position in front of offset token
        this->m->file->seek(this->m->file->getLastOffset(), SEEK_SET);
        return true;
    }
    return false;
}

void
QPDF::parse(char const* password)
{
    if (password) {
        this->m->encp->provided_password = password;
    }

    // Find the header anywhere in the first 1024 bytes of the file.
    PatternFinder hf(*this, &QPDF::findHeader);
    if (!this->m->file->findFirst("%PDF-", 0, 1024, hf)) {
        QTC::TC("qpdf", "QPDF not a pdf file");
        warn(damagedPDF("", 0, "can't find PDF header"));
        // QPDFWriter writes files that usually require at least
        // version 1.2 for /FlateDecode
        this->m->pdf_version = "1.2";
    }

    // PDF spec says %%EOF must be found within the last 1024 bytes of
    // the file.  We add an extra 30 characters to leave room for the
    // startxref stuff.
    this->m->file->seek(0, SEEK_END);
    qpdf_offset_t end_offset = this->m->file->tell();
    qpdf_offset_t start_offset = (end_offset > 1054 ? end_offset - 1054 : 0);
    PatternFinder sf(*this, &QPDF::findStartxref);
    qpdf_offset_t xref_offset = 0;
    if (this->m->file->findLast("startxref", start_offset, 0, sf)) {
        xref_offset =
            QUtil::string_to_ll(readToken(this->m->file).getValue().c_str());
    }

    try {
        if (xref_offset == 0) {
            QTC::TC("qpdf", "QPDF can't find startxref");
            throw damagedPDF("", 0, "can't find startxref");
        }
        try {
            read_xref(xref_offset);
        } catch (QPDFExc&) {
            throw;
        } catch (std::exception& e) {
            throw damagedPDF(
                "", 0, std::string("error reading xref: ") + e.what());
        }
    } catch (QPDFExc& e) {
        if (this->m->attempt_recovery) {
            reconstruct_xref(e);
            QTC::TC("qpdf", "QPDF reconstructed xref table");
        } else {
            throw e;
        }
    }

    initializeEncryption();
    this->m->parsed = true;
}

void
QPDF::inParse(bool v)
{
    if (this->m->in_parse == v) {
        // This happens if QPDFParser::parse tries to
        // resolve an indirect object while it is parsing.
        throw std::logic_error(
            "QPDF: re-entrant parsing detected. This is a qpdf bug."
            " Please report at https://github.com/qpdf/qpdf/issues.");
    }
    this->m->in_parse = v;
}

void
QPDF::warn(QPDFExc const& e)
{
    this->m->warnings.push_back(e);
    if (!this->m->suppress_warnings) {
        *this->m->log->getWarn()
            << "WARNING: " << this->m->warnings.back().what() << "\n";
    }
}

void
QPDF::warn(
    qpdf_error_code_e error_code,
    std::string const& object,
    qpdf_offset_t offset,
    std::string const& message)
{
    warn(QPDFExc(error_code, this->getFilename(), object, offset, message));
}

void
QPDF::setTrailer(QPDFObjectHandle obj)
{
    if (this->m->trailer.isInitialized()) {
        return;
    }
    this->m->trailer = obj;
}

void
QPDF::reconstruct_xref(QPDFExc& e)
{
    if (this->m->reconstructed_xref) {
        // Avoid xref reconstruction infinite loops. This is getting
        // very hard to reproduce because qpdf is throwing many fewer
        // exceptions while parsing. Most situations are warnings now.
        throw e;
    }

    this->m->reconstructed_xref = true;
    // We may find more objects, which may contain dangling references.
    this->m->fixed_dangling_refs = false;

    warn(damagedPDF("", 0, "file is damaged"));
    warn(e);
    warn(damagedPDF("", 0, "Attempting to reconstruct cross-reference table"));

    // Delete all references to type 1 (uncompressed) objects
    std::set<QPDFObjGen> to_delete;
    for (auto const& iter: this->m->xref_table) {
        if (iter.second.getType() == 1) {
            to_delete.insert(iter.first);
        }
    }
    for (auto const& iter: to_delete) {
        this->m->xref_table.erase(iter);
    }

    this->m->file->seek(0, SEEK_END);
    qpdf_offset_t eof = this->m->file->tell();
    this->m->file->seek(0, SEEK_SET);
    qpdf_offset_t line_start = 0;
    // Don't allow very long tokens here during recovery.
    static size_t const MAX_LEN = 100;
    while (this->m->file->tell() < eof) {
        this->m->file->findAndSkipNextEOL();
        qpdf_offset_t next_line_start = this->m->file->tell();
        this->m->file->seek(line_start, SEEK_SET);
        QPDFTokenizer::Token t1 = readToken(this->m->file, MAX_LEN);
        qpdf_offset_t token_start =
            this->m->file->tell() - toO(t1.getValue().length());
        if (token_start >= next_line_start) {
            // don't process yet -- wait until we get to the line
            // containing this token
        } else if (t1.isInteger()) {
            QPDFTokenizer::Token t2 = readToken(this->m->file, MAX_LEN);
            if ((t2.isInteger()) &&
                (readToken(m->file, MAX_LEN).isWord("obj"))) {
                int obj = QUtil::string_to_int(t1.getValue().c_str());
                int gen = QUtil::string_to_int(t2.getValue().c_str());
                insertXrefEntry(obj, 1, token_start, gen, true);
            }
        } else if (!this->m->trailer.isInitialized() && t1.isWord("trailer")) {
            QPDFObjectHandle t =
                readObject(this->m->file, "trailer", QPDFObjGen(), false);
            if (!t.isDictionary()) {
                // Oh well.  It was worth a try.
            } else {
                setTrailer(t);
            }
        }
        this->m->file->seek(next_line_start, SEEK_SET);
        line_start = next_line_start;
    }

    if (!this->m->trailer.isInitialized()) {
        // We could check the last encountered object to see if it was
        // an xref stream.  If so, we could try to get the trailer
        // from there.  This may make it possible to recover files
        // with bad startxref pointers even when they have object
        // streams.

        throw damagedPDF(
            "",
            0,
            "unable to find trailer dictionary while recovering damaged file");
    }

    // We could iterate through the objects looking for streams and
    // try to find objects inside of them, but it's probably not worth
    // the trouble.  Acrobat can't recover files with any errors in an
    // xref stream, and this would be a real long shot anyway.  If we
    // wanted to do anything that involved looking at stream contents,
    // we'd also have to call initializeEncryption() here.  It's safe
    // to call it more than once.
}

void
QPDF::read_xref(qpdf_offset_t xref_offset)
{
    std::map<int, int> free_table;
    std::set<qpdf_offset_t> visited;
    while (xref_offset) {
        visited.insert(xref_offset);
        char buf[7];
        memset(buf, 0, sizeof(buf));
        this->m->file->seek(xref_offset, SEEK_SET);
        // Some files miss the mark a little with startxref. We could
        // do a better job of searching in the neighborhood for
        // something that looks like either an xref table or stream,
        // but the simple heuristic of skipping whitespace can help
        // with the xref table case and is harmless with the stream
        // case.
        bool done = false;
        bool skipped_space = false;
        while (!done) {
            char ch;
            if (1 == this->m->file->read(&ch, 1)) {
                if (QUtil::is_space(ch)) {
                    skipped_space = true;
                } else {
                    this->m->file->unreadCh(ch);
                    done = true;
                }
            } else {
                QTC::TC(
                    "qpdf",
                    "QPDF eof skipping spaces before xref",
                    skipped_space ? 0 : 1);
                done = true;
            }
        }

        this->m->file->read(buf, sizeof(buf) - 1);
        // The PDF spec says xref must be followed by a line
        // terminator, but files exist in the wild where it is
        // terminated by arbitrary whitespace.
        if ((strncmp(buf, "xref", 4) == 0) && QUtil::is_space(buf[4])) {
            if (skipped_space) {
                QTC::TC("qpdf", "QPDF xref skipped space");
                warn(damagedPDF(
                    "", 0, "extraneous whitespace seen before xref"));
            }
            QTC::TC(
                "qpdf",
                "QPDF xref space",
                ((buf[4] == '\n')       ? 0
                     : (buf[4] == '\r') ? 1
                     : (buf[4] == ' ')  ? 2
                                        : 9999));
            int skip = 4;
            // buf is null-terminated, and QUtil::is_space('\0') is
            // false, so this won't overrun.
            while (QUtil::is_space(buf[skip])) {
                ++skip;
            }
            xref_offset = read_xrefTable(xref_offset + skip);
        } else {
            xref_offset = read_xrefStream(xref_offset);
        }
        if (visited.count(xref_offset) != 0) {
            QTC::TC("qpdf", "QPDF xref loop");
            throw damagedPDF("", 0, "loop detected following xref tables");
        }
    }

    if (!this->m->trailer.isInitialized()) {
        throw damagedPDF("", 0, "unable to find trailer while reading xref");
    }
    int size = this->m->trailer.getKey("/Size").getIntValueAsInt();
    int max_obj = 0;
    if (!this->m->xref_table.empty()) {
        max_obj = (*(this->m->xref_table.rbegin())).first.getObj();
    }
    if (!this->m->deleted_objects.empty()) {
        max_obj = std::max(max_obj, *(this->m->deleted_objects.rbegin()));
    }
    if ((size < 1) || (size - 1 != max_obj)) {
        QTC::TC("qpdf", "QPDF xref size mismatch");
        warn(damagedPDF(
            "",
            0,
            ("reported number of objects (" + std::to_string(size) +
             ") is not one plus the highest object number (" +
             std::to_string(max_obj) + ")")));
    }

    // We no longer need the deleted_objects table, so go ahead and
    // clear it out to make sure we never depend on its being set.
    this->m->deleted_objects.clear();
}

bool
QPDF::parse_xrefFirst(std::string const& line, int& obj, int& num, int& bytes)
{
    // is_space and is_digit both return false on '\0', so this will
    // not overrun the null-terminated buffer.
    char const* p = line.c_str();
    char const* start = line.c_str();

    // Skip zero or more spaces
    while (QUtil::is_space(*p)) {
        ++p;
    }
    // Require digit
    if (!QUtil::is_digit(*p)) {
        return false;
    }
    // Gather digits
    std::string obj_str;
    while (QUtil::is_digit(*p)) {
        obj_str.append(1, *p++);
    }
    // Require space
    if (!QUtil::is_space(*p)) {
        return false;
    }
    // Skip spaces
    while (QUtil::is_space(*p)) {
        ++p;
    }
    // Require digit
    if (!QUtil::is_digit(*p)) {
        return false;
    }
    // Gather digits
    std::string num_str;
    while (QUtil::is_digit(*p)) {
        num_str.append(1, *p++);
    }
    // Skip any space including line terminators
    while (QUtil::is_space(*p)) {
        ++p;
    }
    bytes = toI(p - start);
    obj = QUtil::string_to_int(obj_str.c_str());
    num = QUtil::string_to_int(num_str.c_str());
    return true;
}

bool
QPDF::parse_xrefEntry(
    std::string const& line, qpdf_offset_t& f1, int& f2, char& type)
{
    // is_space and is_digit both return false on '\0', so this will
    // not overrun the null-terminated buffer.
    char const* p = line.c_str();

    // Skip zero or more spaces. There aren't supposed to be any.
    bool invalid = false;
    while (QUtil::is_space(*p)) {
        ++p;
        QTC::TC("qpdf", "QPDF ignore first space in xref entry");
        invalid = true;
    }
    // Require digit
    if (!QUtil::is_digit(*p)) {
        return false;
    }
    // Gather digits
    std::string f1_str;
    while (QUtil::is_digit(*p)) {
        f1_str.append(1, *p++);
    }
    // Require space
    if (!QUtil::is_space(*p)) {
        return false;
    }
    if (QUtil::is_space(*(p + 1))) {
        QTC::TC("qpdf", "QPDF ignore first extra space in xref entry");
        invalid = true;
    }
    // Skip spaces
    while (QUtil::is_space(*p)) {
        ++p;
    }
    // Require digit
    if (!QUtil::is_digit(*p)) {
        return false;
    }
    // Gather digits
    std::string f2_str;
    while (QUtil::is_digit(*p)) {
        f2_str.append(1, *p++);
    }
    // Require space
    if (!QUtil::is_space(*p)) {
        return false;
    }
    if (QUtil::is_space(*(p + 1))) {
        QTC::TC("qpdf", "QPDF ignore second extra space in xref entry");
        invalid = true;
    }
    // Skip spaces
    while (QUtil::is_space(*p)) {
        ++p;
    }
    if ((*p == 'f') || (*p == 'n')) {
        type = *p;
    } else {
        return false;
    }
    if ((f1_str.length() != 10) || (f2_str.length() != 5)) {
        QTC::TC("qpdf", "QPDF ignore length error xref entry");
        invalid = true;
    }

    if (invalid) {
        warn(damagedPDF("xref table", "accepting invalid xref table entry"));
    }

    f1 = QUtil::string_to_ll(f1_str.c_str());
    f2 = QUtil::string_to_int(f2_str.c_str());

    return true;
}

qpdf_offset_t
QPDF::read_xrefTable(qpdf_offset_t xref_offset)
{
    std::vector<QPDFObjGen> deleted_items;

    this->m->file->seek(xref_offset, SEEK_SET);
    bool done = false;
    while (!done) {
        char linebuf[51];
        memset(linebuf, 0, sizeof(linebuf));
        this->m->file->read(linebuf, sizeof(linebuf) - 1);
        std::string line = linebuf;
        int obj = 0;
        int num = 0;
        int bytes = 0;
        if (!parse_xrefFirst(line, obj, num, bytes)) {
            QTC::TC("qpdf", "QPDF invalid xref");
            throw damagedPDF("xref table", "xref syntax invalid");
        }
        this->m->file->seek(this->m->file->getLastOffset() + bytes, SEEK_SET);
        for (qpdf_offset_t i = obj; i - num < obj; ++i) {
            if (i == 0) {
                // This is needed by checkLinearization()
                this->m->first_xref_item_offset = this->m->file->tell();
            }
            std::string xref_entry = this->m->file->readLine(30);
            // For xref_table, these will always be small enough to be ints
            qpdf_offset_t f1 = 0;
            int f2 = 0;
            char type = '\0';
            if (!parse_xrefEntry(xref_entry, f1, f2, type)) {
                QTC::TC("qpdf", "QPDF invalid xref entry");
                throw damagedPDF(
                    "xref table",
                    "invalid xref entry (obj=" + std::to_string(i) + ")");
            }
            if (type == 'f') {
                // Save deleted items until after we've checked the
                // XRefStm, if any.
                deleted_items.push_back(QPDFObjGen(toI(i), f2));
            } else {
                insertXrefEntry(toI(i), 1, f1, f2);
            }
        }
        qpdf_offset_t pos = this->m->file->tell();
        if (readToken(m->file).isWord("trailer")) {
            done = true;
        } else {
            this->m->file->seek(pos, SEEK_SET);
        }
    }

    // Set offset to previous xref table if any
    QPDFObjectHandle cur_trailer =
        readObject(this->m->file, "trailer", QPDFObjGen(), false);
    if (!cur_trailer.isDictionary()) {
        QTC::TC("qpdf", "QPDF missing trailer");
        throw damagedPDF("", "expected trailer dictionary");
    }

    if (!this->m->trailer.isInitialized()) {
        setTrailer(cur_trailer);

        if (!this->m->trailer.hasKey("/Size")) {
            QTC::TC("qpdf", "QPDF trailer lacks size");
            throw damagedPDF("trailer", "trailer dictionary lacks /Size key");
        }
        if (!this->m->trailer.getKey("/Size").isInteger()) {
            QTC::TC("qpdf", "QPDF trailer size not integer");
            throw damagedPDF(
                "trailer", "/Size key in trailer dictionary is not an integer");
        }
    }

    if (cur_trailer.hasKey("/XRefStm")) {
        if (this->m->ignore_xref_streams) {
            QTC::TC("qpdf", "QPDF ignoring XRefStm in trailer");
        } else {
            if (cur_trailer.getKey("/XRefStm").isInteger()) {
                // Read the xref stream but disregard any return value
                // -- we'll use our trailer's /Prev key instead of the
                // xref stream's.
                (void)read_xrefStream(
                    cur_trailer.getKey("/XRefStm").getIntValue());
            } else {
                throw damagedPDF(
                    "xref stream", xref_offset, "invalid /XRefStm");
            }
        }
    }

    // Handle any deleted items now that we've read the /XRefStm.
    for (auto const& og: deleted_items) {
        insertXrefEntry(og.getObj(), 0, 0, og.getGen());
    }

    if (cur_trailer.hasKey("/Prev")) {
        if (!cur_trailer.getKey("/Prev").isInteger()) {
            QTC::TC("qpdf", "QPDF trailer prev not integer");
            throw damagedPDF(
                "trailer", "/Prev key in trailer dictionary is not an integer");
        }
        QTC::TC("qpdf", "QPDF prev key in trailer dictionary");
        xref_offset = cur_trailer.getKey("/Prev").getIntValue();
    } else {
        xref_offset = 0;
    }

    return xref_offset;
}

qpdf_offset_t
QPDF::read_xrefStream(qpdf_offset_t xref_offset)
{
    bool found = false;
    if (!this->m->ignore_xref_streams) {
        QPDFObjGen x_og;
        QPDFObjectHandle xref_obj;
        try {
            xref_obj = readObjectAtOffset(
                false,
                xref_offset,
                "xref stream",
                QPDFObjGen(0, 0),
                x_og,
                true);
        } catch (QPDFExc&) {
            // ignore -- report error below
        }
        if (xref_obj.isStreamOfType("/XRef")) {
            QTC::TC("qpdf", "QPDF found xref stream");
            found = true;
            xref_offset = processXRefStream(xref_offset, xref_obj);
        }
    }

    if (!found) {
        QTC::TC("qpdf", "QPDF can't find xref");
        throw damagedPDF("", xref_offset, "xref not found");
    }

    return xref_offset;
}

qpdf_offset_t
QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj)
{
    QPDFObjectHandle dict = xref_obj.getDict();
    QPDFObjectHandle W_obj = dict.getKey("/W");
    QPDFObjectHandle Index_obj = dict.getKey("/Index");
    if (!(W_obj.isArray() && (W_obj.getArrayNItems() >= 3) &&
          W_obj.getArrayItem(0).isInteger() &&
          W_obj.getArrayItem(1).isInteger() &&
          W_obj.getArrayItem(2).isInteger() &&
          dict.getKey("/Size").isInteger() &&
          (Index_obj.isArray() || Index_obj.isNull()))) {
        throw damagedPDF(
            "xref stream",
            xref_offset,
            "Cross-reference stream does not have proper /W and /Index keys");
    }

    int W[3];
    size_t entry_size = 0;
    int max_bytes = sizeof(qpdf_offset_t);
    for (int i = 0; i < 3; ++i) {
        W[i] = W_obj.getArrayItem(i).getIntValueAsInt();
        if (W[i] > max_bytes) {
            throw damagedPDF(
                "xref stream",
                xref_offset,
                "Cross-reference stream's /W contains impossibly large values");
        }
        entry_size += toS(W[i]);
    }
    if (entry_size == 0) {
        throw damagedPDF(
            "xref stream",
            xref_offset,
            "Cross-reference stream's /W indicates entry size of 0");
    }
    unsigned long long max_num_entries =
        static_cast<unsigned long long>(-1) / entry_size;

    std::vector<long long> indx;
    if (Index_obj.isArray()) {
        int n_index = Index_obj.getArrayNItems();
        if ((n_index % 2) || (n_index < 2)) {
            throw damagedPDF(
                "xref stream",
                xref_offset,
                "Cross-reference stream's /Index has an invalid number of "
                "values");
        }
        for (int i = 0; i < n_index; ++i) {
            if (Index_obj.getArrayItem(i).isInteger()) {
                indx.push_back(Index_obj.getArrayItem(i).getIntValue());
            } else {
                throw damagedPDF(
                    "xref stream",
                    xref_offset,
                    ("Cross-reference stream's /Index's item " +
                     std::to_string(i) + " is not an integer"));
            }
        }
        QTC::TC("qpdf", "QPDF xref /Index is array", n_index == 2 ? 0 : 1);
    } else {
        QTC::TC("qpdf", "QPDF xref /Index is null");
        long long size = dict.getKey("/Size").getIntValue();
        indx.push_back(0);
        indx.push_back(size);
    }

    size_t num_entries = 0;
    for (size_t i = 1; i < indx.size(); i += 2) {
        if (indx.at(i) > QIntC::to_longlong(max_num_entries - num_entries)) {
            throw damagedPDF(
                "xref stream",
                xref_offset,
                ("Cross-reference stream claims to contain too many entries: " +
                 std::to_string(indx.at(i)) + " " +
                 std::to_string(max_num_entries) + " " +
                 std::to_string(num_entries)));
        }
        num_entries += toS(indx.at(i));
    }

    // entry_size and num_entries have both been validated to ensure
    // that this multiplication does not cause an overflow.
    size_t expected_size = entry_size * num_entries;

    std::shared_ptr<Buffer> bp = xref_obj.getStreamData(qpdf_dl_specialized);
    size_t actual_size = bp->getSize();

    if (expected_size != actual_size) {
        QPDFExc x = damagedPDF(
            "xref stream",
            xref_offset,
            ("Cross-reference stream data has the wrong size; expected = " +
             std::to_string(expected_size) +
             "; actual = " + std::to_string(actual_size)));
        if (expected_size > actual_size) {
            throw x;
        } else {
            warn(x);
        }
    }

    size_t cur_chunk = 0;
    int chunk_count = 0;

    bool saw_first_compressed_object = false;

    // Actual size vs. expected size check above ensures that we will
    // not overflow any buffers here.  We know that entry_size *
    // num_entries is equal to the size of the buffer.
    unsigned char const* data = bp->getBuffer();
    for (size_t i = 0; i < num_entries; ++i) {
        // Read this entry
        unsigned char const* entry = data + (entry_size * i);
        qpdf_offset_t fields[3];
        unsigned char const* p = entry;
        for (int j = 0; j < 3; ++j) {
            fields[j] = 0;
            if ((j == 0) && (W[0] == 0)) {
                QTC::TC("qpdf", "QPDF default for xref stream field 0");
                fields[0] = 1;
            }
            for (int k = 0; k < W[j]; ++k) {
                fields[j] <<= 8;
                fields[j] += toI(*p++);
            }
        }

        // Get the object and generation number.  The object number is
        // based on /Index.  The generation number is 0 unless this is
        // an uncompressed object record, in which case the generation
        // number appears as the third field.
        int obj = toI(indx.at(cur_chunk));
        if ((obj < 0) ||
            ((std::numeric_limits<int>::max() - obj) < chunk_count)) {
            std::ostringstream msg;
            msg.imbue(std::locale::classic());
            msg << "adding " << chunk_count << " to " << obj
                << " while computing index in xref stream would cause"
                << " an integer overflow";
            throw std::range_error(msg.str());
        }
        obj += chunk_count;
        ++chunk_count;
        if (chunk_count >= indx.at(cur_chunk + 1)) {
            cur_chunk += 2;
            chunk_count = 0;
        }

        if (saw_first_compressed_object) {
            if (fields[0] != 2) {
                this->m->uncompressed_after_compressed = true;
            }
        } else if (fields[0] == 2) {
            saw_first_compressed_object = true;
        }
        if (obj == 0) {
            // This is needed by checkLinearization()
            this->m->first_xref_item_offset = xref_offset;
        }
        if (fields[0] == 0) {
            // Ignore fields[2], which we don't care about in this
            // case. This works around the issue of some PDF files
            // that put invalid values, like -1, here for deleted
            // objects.
            fields[2] = 0;
        }
        insertXrefEntry(obj, toI(fields[0]), fields[1], toI(fields[2]));
    }

    if (!this->m->trailer.isInitialized()) {
        setTrailer(dict);
    }

    if (dict.hasKey("/Prev")) {
        if (!dict.getKey("/Prev").isInteger()) {
            throw damagedPDF(
                "xref stream",
                "/Prev key in xref stream dictionary is not an integer");
        }
        QTC::TC("qpdf", "QPDF prev key in xref stream dictionary");
        xref_offset = dict.getKey("/Prev").getIntValue();
    } else {
        xref_offset = 0;
    }

    return xref_offset;
}

void
QPDF::insertXrefEntry(int obj, int f0, qpdf_offset_t f1, int f2, bool overwrite)
{
    // Populate the xref table in such a way that the first reference
    // to an object that we see, which is the one in the latest xref
    // table in which it appears, is the one that gets stored.  This
    // works because we are reading more recent appends before older
    // ones.  Exception: if overwrite is true, then replace any
    // existing object.  This is used in xref recovery mode, which
    // reads the file from beginning to end.

    // If there is already an entry for this object and generation in
    // the table, it means that a later xref table has registered this
    // object.  Disregard this one.
    { // private scope
        int gen = (f0 == 2 ? 0 : f2);
        QPDFObjGen og(obj, gen);
        if (this->m->xref_table.count(og)) {
            if (overwrite) {
                QTC::TC("qpdf", "QPDF xref overwrite object");
                this->m->xref_table.erase(og);
            } else {
                QTC::TC("qpdf", "QPDF xref reused object");
                return;
            }
        }
        if (this->m->deleted_objects.count(obj)) {
            QTC::TC("qpdf", "QPDF xref deleted object");
            return;
        }
    }

    switch (f0) {
    case 0:
        this->m->deleted_objects.insert(obj);
        break;

    case 1:
        // f2 is generation
        QTC::TC("qpdf", "QPDF xref gen > 0", ((f2 > 0) ? 1 : 0));
        this->m->xref_table[QPDFObjGen(obj, f2)] = QPDFXRefEntry(f1);
        break;

    case 2:
        this->m->xref_table[QPDFObjGen(obj, 0)] = QPDFXRefEntry(toI(f1), f2);
        break;

    default:
        throw damagedPDF(
            "xref stream",
            "unknown xref stream entry type " + std::to_string(f0));
        break;
    }
}

void
QPDF::showXRefTable()
{
    auto& cout = *this->m->log->getInfo();
    for (auto const& iter: this->m->xref_table) {
        QPDFObjGen const& og = iter.first;
        QPDFXRefEntry const& entry = iter.second;
        cout << og.unparse('/') << ": ";
        switch (entry.getType()) {
        case 1:
            cout << "uncompressed; offset = " << entry.getOffset();
            break;

        case 2:
            *this->m->log->getInfo()
                << "compressed; stream = " << entry.getObjStreamNumber()
                << ", index = " << entry.getObjStreamIndex();
            break;

        default:
            throw std::logic_error("unknown cross-reference table type while"
                                   " showing xref_table");
            break;
        }
        this->m->log->info("\n");
    }
}

// Resolve all objects in the xref table. If this triggers a xref table
// reconstruction abort and return false. Otherwise return true.
bool
QPDF::resolveXRefTable()
{
    bool may_change = !this->m->reconstructed_xref;
    for (auto& iter: this->m->xref_table) {
        if (isUnresolved(iter.first)) {
            resolve(iter.first);
            if (may_change && this->m->reconstructed_xref) {
                return false;
            }
        }
    }
    return true;
}

// Ensure all objects in the pdf file, including those in indirect
// references, appear in the object cache.
void
QPDF::fixDanglingReferences(bool force)
{
    if (this->m->fixed_dangling_refs) {
        return;
    }
    if (!resolveXRefTable()) {
        QTC::TC("qpdf", "QPDF fix dangling triggered xref reconstruction");
        resolveXRefTable();
    }
    this->m->fixed_dangling_refs = true;
}

size_t
QPDF::getObjectCount()
{
    // This method returns the next available indirect object number.
    // makeIndirectObject uses it for this purpose. After
    // fixDanglingReferences is called, all objects in the xref table
    // will also be in obj_cache.
    fixDanglingReferences();
    QPDFObjGen og;
    if (!this->m->obj_cache.empty()) {
        og = (*(this->m->obj_cache.rbegin())).first;
    }
    return toS(og.getObj());
}

std::vector<QPDFObjectHandle>
QPDF::getAllObjects()
{
    // After fixDanglingReferences is called, all objects are in the
    // object cache.
    fixDanglingReferences();
    std::vector<QPDFObjectHandle> result;
    for (auto const& iter: this->m->obj_cache) {
        result.push_back(newIndirect(iter.first, iter.second.object));
    }
    return result;
}

void
QPDF::setLastObjectDescription(
    std::string const& description, QPDFObjGen const& og)
{
    this->m->last_object_description.clear();
    if (!description.empty()) {
        this->m->last_object_description += description;
        if (og.isIndirect()) {
            this->m->last_object_description += ": ";
        }
    }
    if (og.isIndirect()) {
        this->m->last_object_description += "object " + og.unparse(' ');
    }
}

QPDFObjectHandle
QPDF::readObject(
    std::shared_ptr<InputSource> input,
    std::string const& description,
    QPDFObjGen const& og,
    bool in_object_stream)
{
    setLastObjectDescription(description, og);
    qpdf_offset_t offset = input->tell();

    bool empty = false;
    std::shared_ptr<StringDecrypter> decrypter_ph;
    StringDecrypter* decrypter = nullptr;
    if (this->m->encp->encrypted && (!in_object_stream)) {
        decrypter_ph = std::make_shared<StringDecrypter>(this, og);
        decrypter = decrypter_ph.get();
    }
    auto object =
        QPDFParser(
            input, m->last_object_description, m->tokenizer, decrypter, this)
            .parse(empty, false);
    if (empty) {
        // Nothing in the PDF spec appears to allow empty objects, but
        // they have been encountered in actual PDF files and Adobe
        // Reader appears to ignore them.
        warn(damagedPDF(
            input, input->getLastOffset(), "empty object treated as null"));
    } else if (object.isDictionary() && (!in_object_stream)) {
        // check for stream
        qpdf_offset_t cur_offset = input->tell();
        if (readToken(input).isWord("stream")) {
            // The PDF specification states that the word "stream"
            // should be followed by either a carriage return and
            // a newline or by a newline alone.  It specifically
            // disallowed following it by a carriage return alone
            // since, in that case, there would be no way to tell
            // whether the NL in a CR NL sequence was part of the
            // stream data.  However, some readers, including
            // Adobe reader, accept a carriage return by itself
            // when followed by a non-newline character, so that's
            // what we do here. We have also seen files that have
            // extraneous whitespace between the stream keyword and
            // the newline.
            bool done = false;
            while (!done) {
                done = true;
                char ch;
                if (input->read(&ch, 1) == 0) {
                    // A premature EOF here will result in some
                    // other problem that will get reported at
                    // another time.
                } else if (ch == '\n') {
                    // ready to read stream data
                    QTC::TC("qpdf", "QPDF stream with NL only");
                } else if (ch == '\r') {
                    // Read another character
                    if (input->read(&ch, 1) != 0) {
                        if (ch == '\n') {
                            // Ready to read stream data
                            QTC::TC("qpdf", "QPDF stream with CRNL");
                        } else {
                            // Treat the \r by itself as the
                            // whitespace after endstream and
                            // start reading stream data in spite
                            // of not having seen a newline.
                            QTC::TC("qpdf", "QPDF stream with CR only");
                            input->unreadCh(ch);
                            warn(damagedPDF(
                                input,
                                input->tell(),
                                "stream keyword followed by carriage return "
                                "only"));
                        }
                    }
                } else if (QUtil::is_space(ch)) {
                    warn(damagedPDF(
                        input,
                        input->tell(),
                        "stream keyword followed by extraneous whitespace"));
                    done = false;
                } else {
                    QTC::TC("qpdf", "QPDF stream without newline");
                    input->unreadCh(ch);
                    warn(damagedPDF(
                        input,
                        input->tell(),
                        "stream keyword not followed by proper line "
                        "terminator"));
                }
            }

            // Must get offset before accessing any additional
            // objects since resolving a previously unresolved
            // indirect object will change file position.
            qpdf_offset_t stream_offset = input->tell();
            size_t length = 0;

            try {
                std::map<std::string, QPDFObjectHandle> dict =
                    object.getDictAsMap();

                if (dict.count("/Length") == 0) {
                    QTC::TC("qpdf", "QPDF stream without length");
                    throw damagedPDF(
                        input, offset, "stream dictionary lacks /Length key");
                }

                QPDFObjectHandle length_obj = dict["/Length"];
                if (!length_obj.isInteger()) {
                    QTC::TC("qpdf", "QPDF stream length not integer");
                    throw damagedPDF(
                        input,
                        offset,
                        "/Length key in stream dictionary is not "
                        "an integer");
                }

                length = toS(length_obj.getUIntValue());
                // Seek in two steps to avoid potential integer overflow
                input->seek(stream_offset, SEEK_SET);
                input->seek(toO(length), SEEK_CUR);
                if (!readToken(input).isWord("endstream")) {
                    QTC::TC("qpdf", "QPDF missing endstream");
                    throw damagedPDF(
                        input, input->getLastOffset(), "expected endstream");
                }
            } catch (QPDFExc& e) {
                if (this->m->attempt_recovery) {
                    warn(e);
                    length = recoverStreamLength(input, og, stream_offset);
                } else {
                    throw e;
                }
            }
            object = newIndirect(
                og,
                QPDF_Stream::create(this, og, object, stream_offset, length));
        } else {
            input->seek(cur_offset, SEEK_SET);
        }
    }

    // Override last_offset so that it points to the beginning of the
    // object we just read
    input->setLastOffset(offset);
    return object;
}

bool
QPDF::findEndstream()
{
    // Find endstream or endobj. Position the input at that token.
    auto t = readToken(m->file, 20);
    if (t.isWord("endobj") || t.isWord("endstream")) {
        this->m->file->seek(this->m->file->getLastOffset(), SEEK_SET);
        return true;
    }
    return false;
}

size_t
QPDF::recoverStreamLength(
    std::shared_ptr<InputSource> input,
    QPDFObjGen const& og,
    qpdf_offset_t stream_offset)
{
    // Try to reconstruct stream length by looking for
    // endstream or endobj
    warn(damagedPDF(
        input, stream_offset, "attempting to recover stream length"));

    PatternFinder ef(*this, &QPDF::findEndstream);
    size_t length = 0;
    if (this->m->file->findFirst("end", stream_offset, 0, ef)) {
        length = toS(this->m->file->tell() - stream_offset);
        // Reread endstream but, if it was endobj, don't skip that.
        QPDFTokenizer::Token t = readToken(this->m->file);
        if (t.getValue() == "endobj") {
            this->m->file->seek(this->m->file->getLastOffset(), SEEK_SET);
        }
    }

    if (length) {
        qpdf_offset_t this_obj_offset = 0;
        QPDFObjGen this_og;

        // Make sure this is inside this object
        for (auto const& iter: this->m->xref_table) {
            QPDFXRefEntry const& entry = iter.second;
            if (entry.getType() == 1) {
                qpdf_offset_t obj_offset = entry.getOffset();
                if ((obj_offset > stream_offset) &&
                    ((this_obj_offset == 0) ||
                     (this_obj_offset > obj_offset))) {
                    this_obj_offset = obj_offset;
                    this_og = iter.first;
                }
            }
        }
        if (this_obj_offset && (this_og == og)) {
            // Well, we found endstream\nendobj within the space
            // allowed for this object, so we're probably in good
            // shape.
        } else {
            QTC::TC("qpdf", "QPDF found wrong endstream in recovery");
        }
    }

    if (length == 0) {
        warn(damagedPDF(
            input,
            stream_offset,
            "unable to recover stream data; treating stream as empty"));
    } else {
        warn(damagedPDF(
            input,
            stream_offset,
            "recovered stream length: " + std::to_string(length)));
    }

    QTC::TC("qpdf", "QPDF recovered stream length");
    return length;
}

QPDFTokenizer::Token
QPDF::readToken(std::shared_ptr<InputSource> input, size_t max_len)
{
    return this->m->tokenizer.readToken(
        input, this->m->last_object_description, true, max_len);
}

QPDFObjectHandle
QPDF::readObjectAtOffset(
    bool try_recovery,
    qpdf_offset_t offset,
    std::string const& description,
    QPDFObjGen exp_og,
    QPDFObjGen& og,
    bool skip_cache_if_in_xref)
{
    bool check_og = true;
    if (exp_og.getObj() == 0) {
        // This method uses an expect object ID of 0 to indicate that
        // we don't know or don't care what the actual object ID is at
        // this offset. This is true when we read the xref stream and
        // linearization hint streams. In this case, we don't verify
        // the expect object ID/generation against what was read from
        // the file. There is also no reason to attempt xref recovery
        // if we get a failure in this case since the read attempt was
        // not triggered by an xref lookup.
        check_og = false;
        try_recovery = false;
    }
    setLastObjectDescription(description, exp_og);

    if (!this->m->attempt_recovery) {
        try_recovery = false;
    }

    // Special case: if offset is 0, just return null.  Some PDF
    // writers, in particular "Mac OS X 10.7.5 Quartz PDFContext", may
    // store deleted objects in the xref table as "0000000000 00000
    // n", which is not correct, but it won't hurt anything for to
    // ignore these.
    if (offset == 0) {
        QTC::TC("qpdf", "QPDF bogus 0 offset", 0);
        warn(damagedPDF(0, "object has offset 0"));
        return QPDFObjectHandle::newNull();
    }

    this->m->file->seek(offset, SEEK_SET);

    QPDFTokenizer::Token tobjid = readToken(this->m->file);
    QPDFTokenizer::Token tgen = readToken(this->m->file);
    QPDFTokenizer::Token tobj = readToken(this->m->file);

    bool objidok = tobjid.isInteger();
    bool genok = tgen.isInteger();
    bool objok = tobj.isWord("obj");

    QTC::TC("qpdf", "QPDF check objid", objidok ? 1 : 0);
    QTC::TC("qpdf", "QPDF check generation", genok ? 1 : 0);
    QTC::TC("qpdf", "QPDF check obj", objok ? 1 : 0);

    try {
        if (!(objidok && genok && objok)) {
            QTC::TC("qpdf", "QPDF expected n n obj");
            throw damagedPDF(offset, "expected n n obj");
        }
        int objid = QUtil::string_to_int(tobjid.getValue().c_str());
        int generation = QUtil::string_to_int(tgen.getValue().c_str());
        og = QPDFObjGen(objid, generation);
        if (objid == 0) {
            QTC::TC("qpdf", "QPDF object id 0");
            throw damagedPDF(offset, "object with ID 0");
        }
        if (check_og && (exp_og != og)) {
            QTC::TC("qpdf", "QPDF err wrong objid/generation");
            QPDFExc e =
                damagedPDF(offset, "expected " + exp_og.unparse(' ') + " obj");
            if (try_recovery) {
                // Will be retried below
                throw e;
            } else {
                // We can try reading the object anyway even if the ID
                // doesn't match.
                warn(e);
            }
        }
    } catch (QPDFExc& e) {
        if (try_recovery) {
            // Try again after reconstructing xref table
            reconstruct_xref(e);
            if (this->m->xref_table.count(exp_og) &&
                (this->m->xref_table[exp_og].getType() == 1)) {
                qpdf_offset_t new_offset =
                    this->m->xref_table[exp_og].getOffset();
                QPDFObjectHandle result = readObjectAtOffset(
                    false, new_offset, description, exp_og, og, false);
                QTC::TC("qpdf", "QPDF recovered in readObjectAtOffset");
                return result;
            } else {
                QTC::TC("qpdf", "QPDF object gone after xref reconstruction");
                warn(damagedPDF(
                    "",
                    0,
                    ("object " + exp_og.unparse(' ') +
                     " not found in file after regenerating cross reference "
                     "table")));
                return QPDFObjectHandle::newNull();
            }
        } else {
            throw e;
        }
    }

    QPDFObjectHandle oh = readObject(this->m->file, description, og, false);

    if (!readToken(this->m->file).isWord("endobj")) {
        QTC::TC("qpdf", "QPDF err expected endobj");
        warn(damagedPDF("expected endobj"));
    }

    if (isUnresolved(og)) {
        // Store the object in the cache here so it gets cached
        // whether we first know the offset or whether we first know
        // the object ID and generation (in which we case we would get
        // here through resolve).

        // Determine the end offset of this object before and after
        // white space.  We use these numbers to validate
        // linearization hint tables.  Offsets and lengths of objects
        // may imply the end of an object to be anywhere between these
        // values.
        qpdf_offset_t end_before_space = this->m->file->tell();

        // skip over spaces
        while (true) {
            char ch;
            if (this->m->file->read(&ch, 1)) {
                if (!isspace(static_cast<unsigned char>(ch))) {
                    this->m->file->seek(-1, SEEK_CUR);
                    break;
                }
            } else {
                throw damagedPDF(m->file->tell(), "EOF after endobj");
            }
        }
        qpdf_offset_t end_after_space = this->m->file->tell();
        if (skip_cache_if_in_xref && this->m->xref_table.count(og)) {
            // Ordinarily, an object gets read here when resolved
            // through xref table or stream. In the special case of
            // the xref stream and linearization hint tables, the
            // offset comes from another source. For the specific case
            // of xref streams, the xref stream is read and loaded
            // into the object cache very early in parsing.
            // Ordinarily, when a file is updated by appending, items
            // inserted into the xref table in later updates take
            // precedence over earlier items. In the special case of
            // reusing the object number previously used as the xref
            // stream, we have the following order of events:
            //
            // * reused object gets loaded into the xref table
            // * old object is read here while reading xref streams
            // * original xref entry is ignored (since already in xref table)
            //
            // It is the second step that causes a problem. Even
            // though the xref table is correct in this case, the old
            // object is already in the cache and so effectively
            // prevails over the reused object. To work around this
            // issue, we have a special case for the xref stream (via
            // the skip_cache_if_in_xref): if the object is already in
            // the xref stream, don't cache what we read here.
            //
            // It is likely that the same bug may exist for
            // linearization hint tables, but the existing code uses
            // end_before_space and end_after_space from the cache, so
            // fixing that would require more significant rework. The
            // chances of a linearization hint stream being reused
            // seems smaller because the xref stream is probably the
            // highest object in the file and the linearization hint
            // stream would be some random place in the middle, so I'm
            // leaving that bug unfixed for now. If the bug were to be
            // fixed, we could use !check_og in place of
            // skip_cache_if_in_xref.
            QTC::TC("qpdf", "QPDF skipping cache for known unchecked object");
        } else {
            updateCache(og, oh.getObj(), end_before_space, end_after_space);
        }
    }

    return oh;
}

void
QPDF::resolve(QPDFObjGen og)
{
    if (!isUnresolved(og)) {
        return;
    }

    if (this->m->resolving.count(og)) {
        // This can happen if an object references itself directly or
        // indirectly in some key that has to be resolved during
        // object parsing, such as stream length.
        QTC::TC("qpdf", "QPDF recursion loop in resolve");
        warn(damagedPDF(
            "", "loop detected resolving object " + og.unparse(' ')));
        updateCache(og, QPDF_Null::create(), -1, -1);
        return;
    }
    ResolveRecorder rr(this, og);

    if (m->xref_table.count(og) != 0) {
        QPDFXRefEntry const& entry = this->m->xref_table[og];
        try {
            switch (entry.getType()) {
            case 1:
                {
                    qpdf_offset_t offset = entry.getOffset();
                    // Object stored in cache by readObjectAtOffset
                    QPDFObjGen a_og;
                    QPDFObjectHandle oh =
                        readObjectAtOffset(true, offset, "", og, a_og, false);
                }
                break;

            case 2:
                resolveObjectsInStream(entry.getObjStreamNumber());
                break;

            default:
                throw damagedPDF(
                    "",
                    0,
                    ("object " + og.unparse('/') +
                     " has unexpected xref entry type"));
            }
        } catch (QPDFExc& e) {
            warn(e);
        } catch (std::exception& e) {
            warn(damagedPDF(
                "",
                0,
                ("object " + og.unparse('/') +
                 ": error reading object: " + e.what())));
        }
    }

    if (isUnresolved(og)) {
        // PDF spec says unknown objects resolve to the null object.
        QTC::TC("qpdf", "QPDF resolve failure to null");
        updateCache(og, QPDF_Null::create(), -1, -1);
    }

    auto result(this->m->obj_cache[og].object);
    result->setDefaultDescription(this, og);
}

void
QPDF::resolveObjectsInStream(int obj_stream_number)
{
    if (this->m->resolved_object_streams.count(obj_stream_number)) {
        return;
    }
    this->m->resolved_object_streams.insert(obj_stream_number);
    // Force resolution of object stream
    QPDFObjectHandle obj_stream = getObjectByID(obj_stream_number, 0);
    if (!obj_stream.isStream()) {
        throw damagedPDF(
            "supposed object stream " + std::to_string(obj_stream_number) +
            " is not a stream");
    }

    // For linearization data in the object, use the data from the
    // object stream for the objects in the stream.
    QPDFObjGen stream_og(obj_stream_number, 0);
    qpdf_offset_t end_before_space =
        this->m->obj_cache[stream_og].end_before_space;
    qpdf_offset_t end_after_space =
        this->m->obj_cache[stream_og].end_after_space;

    QPDFObjectHandle dict = obj_stream.getDict();
    if (!dict.isDictionaryOfType("/ObjStm")) {
        QTC::TC("qpdf", "QPDF ERR object stream with wrong type");
        warn(damagedPDF(
            "supposed object stream " + std::to_string(obj_stream_number) +
            " has wrong type"));
    }

    if (!(dict.getKey("/N").isInteger() && dict.getKey("/First").isInteger())) {
        throw damagedPDF(
            ("object stream " + std::to_string(obj_stream_number) +
             " has incorrect keys"));
    }

    int n = dict.getKey("/N").getIntValueAsInt();
    int first = dict.getKey("/First").getIntValueAsInt();

    std::map<int, int> offsets;

    std::shared_ptr<Buffer> bp = obj_stream.getStreamData(qpdf_dl_specialized);
    auto input = std::shared_ptr<InputSource>(
        // line-break
        new BufferInputSource(
            (this->m->file->getName() + " object stream " +
             std::to_string(obj_stream_number)),
            bp.get()));

    for (int i = 0; i < n; ++i) {
        QPDFTokenizer::Token tnum = readToken(input);
        QPDFTokenizer::Token toffset = readToken(input);
        if (!(tnum.isInteger() && toffset.isInteger())) {
            throw damagedPDF(
                input,
                this->m->last_object_description,
                input->getLastOffset(),
                "expected integer in object stream header");
        }

        int num = QUtil::string_to_int(tnum.getValue().c_str());
        long long offset = QUtil::string_to_int(toffset.getValue().c_str());
        offsets[num] = toI(offset + first);
    }

    // To avoid having to read the object stream multiple times, store
    // all objects that would be found here in the cache.  Remember
    // that some objects stored here might have been overridden by new
    // objects appended to the file, so it is necessary to recheck the
    // xref table and only cache what would actually be resolved here.
    for (auto const& iter: offsets) {
        QPDFObjGen og(iter.first, 0);
        QPDFXRefEntry const& entry = this->m->xref_table[og];
        if ((entry.getType() == 2) &&
            (entry.getObjStreamNumber() == obj_stream_number)) {
            int offset = iter.second;
            input->seek(offset, SEEK_SET);
            QPDFObjectHandle oh = readObject(input, "", og, true);
            updateCache(og, oh.getObj(), end_before_space, end_after_space);
        } else {
            QTC::TC("qpdf", "QPDF not caching overridden objstm object");
        }
    }
}

QPDFObjectHandle
QPDF::newIndirect(QPDFObjGen const& og, std::shared_ptr<QPDFObject> const& obj)
{
    obj->setDefaultDescription(this, og);
    return {obj};
}

void
QPDF::updateCache(
    QPDFObjGen const& og,
    std::shared_ptr<QPDFObject> const& object,
    qpdf_offset_t end_before_space,
    qpdf_offset_t end_after_space)
{
    object->setObjGen(this, og);
    if (isCached(og)) {
        auto& cache = m->obj_cache[og];
        cache.object->assign(object);
        cache.end_before_space = end_before_space;
        cache.end_after_space = end_after_space;
    } else {
        m->obj_cache[og] = ObjCache(object, end_before_space, end_after_space);
    }
}

bool
QPDF::isCached(QPDFObjGen const& og)
{
    return m->obj_cache.count(og) != 0;
}

bool
QPDF::isUnresolved(QPDFObjGen const& og)
{
    return !isCached(og) || m->obj_cache[og].object->isUnresolved();
}

QPDFObjGen
QPDF::nextObjGen()
{
    int max_objid = toI(getObjectCount());
    if (max_objid == std::numeric_limits<int>::max()) {
        throw std::range_error(
            "max object id is too high to create new objects");
    }
    return QPDFObjGen(max_objid + 1, 0);
}

QPDFObjectHandle
QPDF::makeIndirectFromQPDFObject(std::shared_ptr<QPDFObject> const& obj)
{
    QPDFObjGen next{nextObjGen()};
    m->obj_cache[next] = ObjCache(obj, -1, -1);
    return newIndirect(next, m->obj_cache[next].object);
}

QPDFObjectHandle
QPDF::makeIndirectObject(QPDFObjectHandle oh)
{
    if (!oh.isInitialized()) {
        throw std::logic_error(
            "attempted to make an uninitialized QPDFObjectHandle indirect");
    }
    return makeIndirectFromQPDFObject(oh.getObj());
}

QPDFObjectHandle
QPDF::newStream()
{
    return makeIndirectFromQPDFObject(QPDF_Stream::create(
        this, nextObjGen(), QPDFObjectHandle::newDictionary(), 0, 0));
}

QPDFObjectHandle
QPDF::newStream(std::shared_ptr<Buffer> data)
{
    auto result = newStream();
    result.replaceStreamData(
        data, QPDFObjectHandle::newNull(), QPDFObjectHandle::newNull());
    return result;
}

QPDFObjectHandle
QPDF::newStream(std::string const& data)
{
    auto result = newStream();
    result.replaceStreamData(
        data, QPDFObjectHandle::newNull(), QPDFObjectHandle::newNull());
    return result;
}

QPDFObjectHandle
QPDF::reserveObjectIfNotExists(QPDFObjGen const& og)
{
    if (!isCached(og) && m->xref_table.count(og) == 0) {
        updateCache(og, QPDF_Reserved::create(), -1, -1);
        return newIndirect(og, m->obj_cache[og].object);
    } else {
        return getObject(og);
    }
}

QPDFObjectHandle
QPDF::reserveStream(QPDFObjGen const& og)
{
    return {
        QPDF_Stream::create(this, og, QPDFObjectHandle::newDictionary(), 0, 0)};
}

QPDFObjectHandle
QPDF::getObject(QPDFObjGen const& og)
{
    // This method is called by the parser and therefore must not
    // resolve any objects.
    if (!isCached(og)) {
        m->obj_cache[og] = ObjCache(QPDF_Unresolved::create(this, og), -1, -1);
    }
    return newIndirect(og, m->obj_cache[og].object);
}

QPDFObjectHandle
QPDF::getObject(int objid, int generation)
{
    return getObject(QPDFObjGen(objid, generation));
}

QPDFObjectHandle
QPDF::getObjectByObjGen(QPDFObjGen const& og)
{
    return getObject(og);
}

QPDFObjectHandle
QPDF::getObjectByID(int objid, int generation)
{
    return getObject(QPDFObjGen(objid, generation));
}

void
QPDF::replaceObject(int objid, int generation, QPDFObjectHandle oh)
{
    replaceObject(QPDFObjGen(objid, generation), oh);
}

void
QPDF::replaceObject(QPDFObjGen const& og, QPDFObjectHandle oh)
{
    if (oh.isIndirect() || !oh.isInitialized()) {
        QTC::TC("qpdf", "QPDF replaceObject called with indirect object");
        throw std::logic_error(
            "QPDF::replaceObject called with indirect object handle");
    }
    updateCache(og, oh.getObj(), -1, -1);
}

void
QPDF::replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement)
{
    QTC::TC("qpdf", "QPDF replaceReserved");
    reserved.assertReserved();
    replaceObject(reserved.getObjGen(), replacement);
}

QPDFObjectHandle
QPDF::copyForeignObject(QPDFObjectHandle foreign)
{
    // Here's an explanation of what's going on here.
    //
    // A QPDFObjectHandle that is an indirect object has an owning
    // QPDF. The object ID and generation refers to an object in the
    // owning QPDF. When we copy the QPDFObjectHandle from a foreign
    // QPDF into the local QPDF, we have to replace all indirect
    // object references with references to the corresponding object
    // in the local file.
    //
    // To do this, we maintain mappings from foreign object IDs to
    // local object IDs for each foreign QPDF that we are copying
    // from. The mapping is stored in an ObjCopier, which contains a
    // mapping from the foreign ObjGen to the local QPDFObjectHandle.
    //
    // To copy, we do a deep traversal of the foreign object with loop
    // detection to discover all indirect objects that are
    // encountered, stopping at page boundaries. Whenever we encounter
    // an indirect object, we check to see if we have already created
    // a local copy of it. If not, we allocate a "reserved" object
    // (or, for a stream, just a new stream) and store in the map the
    // mapping from the foreign object ID to the new object. While we
    // do this, we keep a list of objects to copy.
    //
    // Once we are done with the traversal, we copy all the objects
    // that we need to copy. However, the copies will contain indirect
    // object IDs that refer to objects in the foreign file. We need
    // to replace them with references to objects in the local file.
    // This is what replaceForeignIndirectObjects does. Once we have
    // created a copy of the foreign object with all the indirect
    // references replaced with new ones in the local context, we can
    // replace the local reserved object with the copy. This mechanism
    // allows us to copy objects with circular references in any
    // order.

    // For streams, rather than copying the objects, we set up the
    // stream data to pull from the original stream by using a stream
    // data provider. This is done in a manner that doesn't require
    // the original QPDF object but may require the original source of
    // the stream data with special handling for immediate_copy_from.
    // This logic is also in replaceForeignIndirectObjects.

    // Note that we explicitly allow use of copyForeignObject on page
    // objects. It is a documented use case to copy pages this way if
    // the intention is to not update the pages tree.
    if (!foreign.isIndirect()) {
        QTC::TC("qpdf", "QPDF copyForeign direct");
        throw std::logic_error(
            "QPDF::copyForeign called with direct object handle");
    }
    QPDF& other = foreign.getQPDF();
    if (&other == this) {
        QTC::TC("qpdf", "QPDF copyForeign not foreign");
        throw std::logic_error(
            "QPDF::copyForeign called with object from this QPDF");
    }

    ObjCopier& obj_copier = this->m->object_copiers[other.m->unique_id];
    if (!obj_copier.visiting.empty()) {
        throw std::logic_error("obj_copier.visiting is not empty"
                               " at the beginning of copyForeignObject");
    }

    // Make sure we have an object in this file for every referenced
    // object in the old file.  obj_copier.object_map maps foreign
    // QPDFObjGen to local objects.  For everything new that we have
    // to copy, the local object will be a reservation, unless it is a
    // stream, in which case the local object will already be a
    // stream.
    reserveObjects(foreign, obj_copier, true);

    if (!obj_copier.visiting.empty()) {
        throw std::logic_error("obj_copier.visiting is not empty"
                               " after reserving objects");
    }

    // Copy any new objects and replace the reservations.
    for (auto& to_copy: obj_copier.to_copy) {
        QPDFObjectHandle copy =
            replaceForeignIndirectObjects(to_copy, obj_copier, true);
        if (!to_copy.isStream()) {
            QPDFObjGen og(to_copy.getObjGen());
            replaceReserved(obj_copier.object_map[og], copy);
        }
    }
    obj_copier.to_copy.clear();

    return obj_copier.object_map[foreign.getObjGen()];
}

void
QPDF::reserveObjects(QPDFObjectHandle foreign, ObjCopier& obj_copier, bool top)
{
    if (foreign.isReserved()) {
        throw std::logic_error(
            "QPDF: attempting to copy a foreign reserved object");
    }

    if (foreign.isPagesObject()) {
        QTC::TC("qpdf", "QPDF not copying pages object");
        return;
    }

    if ((!top) && foreign.isPageObject()) {
        QTC::TC("qpdf", "QPDF not crossing page boundary");
        return;
    }

    if (foreign.isIndirect()) {
        QPDFObjGen foreign_og(foreign.getObjGen());
        if (obj_copier.visiting.find(foreign_og) != obj_copier.visiting.end()) {
            QTC::TC("qpdf", "QPDF loop reserving objects");
            return;
        }
        if (obj_copier.object_map.find(foreign_og) !=
            obj_copier.object_map.end()) {
            QTC::TC("qpdf", "QPDF already reserved object");
            return;
        }
        QTC::TC("qpdf", "QPDF copy indirect");
        obj_copier.visiting.insert(foreign_og);
        auto mapping = obj_copier.object_map.find(foreign_og);
        if (mapping == obj_copier.object_map.end()) {
            obj_copier.to_copy.push_back(foreign);
            QPDFObjectHandle reservation;
            if (foreign.isStream()) {
                reservation = newStream();
            } else {
                reservation = QPDFObjectHandle::newReserved(this);
            }
            obj_copier.object_map[foreign_og] = reservation;
        }
    }

    if (foreign.isArray()) {
        QTC::TC("qpdf", "QPDF reserve array");
        int n = foreign.getArrayNItems();
        for (int i = 0; i < n; ++i) {
            reserveObjects(foreign.getArrayItem(i), obj_copier, false);
        }
    } else if (foreign.isDictionary()) {
        QTC::TC("qpdf", "QPDF reserve dictionary");
        for (auto const& key: foreign.getKeys()) {
            reserveObjects(foreign.getKey(key), obj_copier, false);
        }
    } else if (foreign.isStream()) {
        QTC::TC("qpdf", "QPDF reserve stream");
        reserveObjects(foreign.getDict(), obj_copier, false);
    }

    if (foreign.isIndirect()) {
        QPDFObjGen foreign_og(foreign.getObjGen());
        obj_copier.visiting.erase(foreign_og);
    }
}

QPDFObjectHandle
QPDF::replaceForeignIndirectObjects(
    QPDFObjectHandle foreign, ObjCopier& obj_copier, bool top)
{
    QPDFObjectHandle result;
    if ((!top) && foreign.isIndirect()) {
        QTC::TC("qpdf", "QPDF replace indirect");
        QPDFObjGen foreign_og(foreign.getObjGen());
        auto mapping = obj_copier.object_map.find(foreign_og);
        if (mapping == obj_copier.object_map.end()) {
            // This case would occur if this is a reference to a Page
            // or Pages object that we didn't traverse into.
            QTC::TC("qpdf", "QPDF replace foreign indirect with null");
            result = QPDFObjectHandle::newNull();
        } else {
            result = obj_copier.object_map[foreign_og];
        }
    } else if (foreign.isArray()) {
        QTC::TC("qpdf", "QPDF replace array");
        result = QPDFObjectHandle::newArray();
        int n = foreign.getArrayNItems();
        for (int i = 0; i < n; ++i) {
            result.appendItem(
                // line-break
                replaceForeignIndirectObjects(
                    foreign.getArrayItem(i), obj_copier, false));
        }
    } else if (foreign.isDictionary()) {
        QTC::TC("qpdf", "QPDF replace dictionary");
        result = QPDFObjectHandle::newDictionary();
        std::set<std::string> keys = foreign.getKeys();
        for (auto const& iter: keys) {
            result.replaceKey(
                iter,
                replaceForeignIndirectObjects(
                    foreign.getKey(iter), obj_copier, false));
        }
    } else if (foreign.isStream()) {
        QTC::TC("qpdf", "QPDF replace stream");
        QPDFObjGen foreign_og(foreign.getObjGen());
        result = obj_copier.object_map[foreign_og];
        result.assertStream();
        QPDFObjectHandle dict = result.getDict();
        QPDFObjectHandle old_dict = foreign.getDict();
        std::set<std::string> keys = old_dict.getKeys();
        for (auto const& iter: keys) {
            dict.replaceKey(
                iter,
                replaceForeignIndirectObjects(
                    old_dict.getKey(iter), obj_copier, false));
        }
        copyStreamData(result, foreign);
    } else {
        foreign.assertScalar();
        result = foreign;
        result.makeDirect();
    }

    if (top && (!result.isStream()) && result.isIndirect()) {
        throw std::logic_error("replacement for foreign object is indirect");
    }

    return result;
}

void
QPDF::copyStreamData(QPDFObjectHandle result, QPDFObjectHandle foreign)
{
    // This method was originally written for copying foreign streams,
    // but it is used by QPDFObjectHandle to copy streams from the
    // same QPDF object as well.

    QPDFObjectHandle dict = result.getDict();
    QPDFObjectHandle old_dict = foreign.getDict();
    if (this->m->copied_stream_data_provider == nullptr) {
        this->m->copied_stream_data_provider =
            new CopiedStreamDataProvider(*this);
        this->m->copied_streams =
            std::shared_ptr<QPDFObjectHandle::StreamDataProvider>(
                this->m->copied_stream_data_provider);
    }
    QPDFObjGen local_og(result.getObjGen());
    // Copy information from the foreign stream so we can pipe its
    // data later without keeping the original QPDF object around.

    QPDF& foreign_stream_qpdf =
        foreign.getQPDF("unable to retrieve owning qpdf from foreign stream");

    auto stream = foreign.getObjectPtr()->as<QPDF_Stream>();
    if (stream == nullptr) {
        throw std::logic_error("unable to retrieve underlying"
                               " stream object from foreign stream");
    }
    std::shared_ptr<Buffer> stream_buffer = stream->getStreamDataBuffer();
    if ((foreign_stream_qpdf.m->immediate_copy_from) &&
        (stream_buffer == nullptr)) {
        // Pull the stream data into a buffer before attempting
        // the copy operation. Do it on the source stream so that
        // if the source stream is copied multiple times, we don't
        // have to keep duplicating the memory.
        QTC::TC("qpdf", "QPDF immediate copy stream data");
        foreign.replaceStreamData(
            foreign.getRawStreamData(),
            old_dict.getKey("/Filter"),
            old_dict.getKey("/DecodeParms"));
        stream_buffer = stream->getStreamDataBuffer();
    }
    std::shared_ptr<QPDFObjectHandle::StreamDataProvider> stream_provider =
        stream->getStreamDataProvider();
    if (stream_buffer.get()) {
        QTC::TC("qpdf", "QPDF copy foreign stream with buffer");
        result.replaceStreamData(
            stream_buffer, dict.getKey("/Filter"), dict.getKey("/DecodeParms"));
    } else if (stream_provider.get()) {
        // In this case, the remote stream's QPDF must stay in scope.
        QTC::TC("qpdf", "QPDF copy foreign stream with provider");
        this->m->copied_stream_data_provider->registerForeignStream(
            local_og, foreign);
        result.replaceStreamData(
            this->m->copied_streams,
            dict.getKey("/Filter"),
            dict.getKey("/DecodeParms"));
    } else {
        auto foreign_stream_data = std::make_shared<ForeignStreamData>(
            foreign_stream_qpdf.m->encp,
            foreign_stream_qpdf.m->file,
            foreign.getObjGen(),
            stream->getParsedOffset(),
            stream->getLength(),
            dict);
        this->m->copied_stream_data_provider->registerForeignStream(
            local_og, foreign_stream_data);
        result.replaceStreamData(
            this->m->copied_streams,
            dict.getKey("/Filter"),
            dict.getKey("/DecodeParms"));
    }
}

void
QPDF::swapObjects(int objid1, int generation1, int objid2, int generation2)
{
    swapObjects(
        QPDFObjGen(objid1, generation1), QPDFObjGen(objid2, generation2));
}

void
QPDF::swapObjects(QPDFObjGen const& og1, QPDFObjGen const& og2)
{
    // Force objects to be read from the input source if needed, then
    // swap them in the cache.
    resolve(og1);
    resolve(og2);
    m->obj_cache[og1].object->swapWith(m->obj_cache[og2].object);
}

unsigned long long
QPDF::getUniqueId() const
{
    return this->m->unique_id;
}

std::string
QPDF::getFilename() const
{
    return this->m->file->getName();
}

PDFVersion
QPDF::getVersionAsPDFVersion()
{
    int major = 1;
    int minor = 3;
    int extension_level = getExtensionLevel();

    std::regex v("^[[:space:]]*([0-9]+)\\.([0-9]+)");
    std::smatch m;
    if (std::regex_search(this->m->pdf_version, m, v)) {
        major = QUtil::string_to_int(m[1].str().c_str());
        minor = QUtil::string_to_int(m[2].str().c_str());
    }

    return PDFVersion(major, minor, extension_level);
}

std::string
QPDF::getPDFVersion() const
{
    return this->m->pdf_version;
}

int
QPDF::getExtensionLevel()
{
    int result = 0;
    QPDFObjectHandle obj = getRoot();
    if (obj.hasKey("/Extensions")) {
        obj = obj.getKey("/Extensions");
        if (obj.isDictionary() && obj.hasKey("/ADBE")) {
            obj = obj.getKey("/ADBE");
            if (obj.isDictionary() && obj.hasKey("/ExtensionLevel")) {
                obj = obj.getKey("/ExtensionLevel");
                if (obj.isInteger()) {
                    result = obj.getIntValueAsInt();
                }
            }
        }
    }
    return result;
}

QPDFObjectHandle
QPDF::getTrailer()
{
    return this->m->trailer;
}

QPDFObjectHandle
QPDF::getRoot()
{
    QPDFObjectHandle root = this->m->trailer.getKey("/Root");
    if (!root.isDictionary()) {
        throw damagedPDF("", 0, "unable to find /Root dictionary");
    } else if (
        // Check_mode is an interim solution to request #810 pending a more
        // comprehensive review of the approach to more extensive checks and
        // warning levels.
        m->check_mode && !root.getKey("/Type").isNameAndEquals("/Catalog")) {
        warn(damagedPDF("", 0, "catalog /Type entry missing or invalid"));
        root.replaceKey("/Type", "/Catalog"_qpdf);
    }
    return root;
}

std::map<QPDFObjGen, QPDFXRefEntry>
QPDF::getXRefTable()
{
    if (!this->m->parsed) {
        throw std::logic_error("QPDF::getXRefTable called before parsing.");
    }

    return this->m->xref_table;
}

void
QPDF::getObjectStreamData(std::map<int, int>& omap)
{
    for (auto const& iter: this->m->xref_table) {
        QPDFObjGen const& og = iter.first;
        QPDFXRefEntry const& entry = iter.second;
        if (entry.getType() == 2) {
            omap[og.getObj()] = entry.getObjStreamNumber();
        }
    }
}

std::vector<QPDFObjGen>
QPDF::getCompressibleObjGens()
{
    // Return a list of objects that are allowed to be in object
    // streams.  Walk through the objects by traversing the document
    // from the root, including a traversal of the pages tree.  This
    // makes that objects that are on the same page are more likely to
    // be in the same object stream, which is slightly more efficient,
    // particularly with linearized files.  This is better than
    // iterating through the xref table since it avoids preserving
    // orphaned items.

    // Exclude encryption dictionary, if any
    QPDFObjectHandle encryption_dict = this->m->trailer.getKey("/Encrypt");
    QPDFObjGen encryption_dict_og = encryption_dict.getObjGen();

    std::set<QPDFObjGen> visited;
    std::list<QPDFObjectHandle> queue;
    queue.push_front(this->m->trailer);
    std::vector<QPDFObjGen> result;
    while (!queue.empty()) {
        QPDFObjectHandle obj = queue.front();
        queue.pop_front();
        if (obj.isIndirect()) {
            QPDFObjGen og = obj.getObjGen();
            if (visited.count(og)) {
                QTC::TC("qpdf", "QPDF loop detected traversing objects");
                continue;
            }
            if (og == encryption_dict_og) {
                QTC::TC("qpdf", "QPDF exclude encryption dictionary");
            } else if (!(obj.isStream() ||
                         (obj.isDictionaryOfType("/Sig") &&
                          obj.hasKey("/ByteRange") &&
                          obj.hasKey("/Contents")))) {
                result.push_back(og);
            }
            visited.insert(og);
        }
        if (obj.isStream()) {
            QPDFObjectHandle dict = obj.getDict();
            std::set<std::string> keys = dict.getKeys();
            for (std::set<std::string>::reverse_iterator iter = keys.rbegin();
                 iter != keys.rend();
                 ++iter) {
                std::string const& key = *iter;
                QPDFObjectHandle value = dict.getKey(key);
                if (key == "/Length") {
                    // omit stream lengths
                    if (value.isIndirect()) {
                        QTC::TC("qpdf", "QPDF exclude indirect length");
                    }
                } else {
                    queue.push_front(value);
                }
            }
        } else if (obj.isDictionary()) {
            std::set<std::string> keys = obj.getKeys();
            for (std::set<std::string>::reverse_iterator iter = keys.rbegin();
                 iter != keys.rend();
                 ++iter) {
                queue.push_front(obj.getKey(*iter));
            }
        } else if (obj.isArray()) {
            int n = obj.getArrayNItems();
            for (int i = 1; i <= n; ++i) {
                queue.push_front(obj.getArrayItem(n - i));
            }
        }
    }

    return result;
}

bool
QPDF::pipeStreamData(
    std::shared_ptr<EncryptionParameters> encp,
    std::shared_ptr<InputSource> file,
    QPDF& qpdf_for_warning,
    QPDFObjGen const& og,
    qpdf_offset_t offset,
    size_t length,
    QPDFObjectHandle stream_dict,
    Pipeline* pipeline,
    bool suppress_warnings,
    bool will_retry)
{
    std::vector<std::shared_ptr<Pipeline>> to_delete;
    if (encp->encrypted) {
        decryptStream(
            encp, file, qpdf_for_warning, pipeline, og, stream_dict, to_delete);
    }

    bool success = false;
    try {
        file->seek(offset, SEEK_SET);
        char buf[10240];
        while (length > 0) {
            size_t to_read = (sizeof(buf) < length ? sizeof(buf) : length);
            size_t len = file->read(buf, to_read);
            if (len == 0) {
                throw damagedPDF(
                    file,
                    "",
                    file->getLastOffset(),
                    "unexpected EOF reading stream data");
            }
            length -= len;
            pipeline->write(buf, len);
        }
        pipeline->finish();
        success = true;
    } catch (QPDFExc& e) {
        if (!suppress_warnings) {
            qpdf_for_warning.warn(e);
        }
    } catch (std::exception& e) {
        if (!suppress_warnings) {
            QTC::TC("qpdf", "QPDF decoding error warning");
            qpdf_for_warning.warn(
                // line-break
                damagedPDF(
                    file,
                    "",
                    file->getLastOffset(),
                    ("error decoding stream data for object " +
                     og.unparse(' ') + ": " + e.what())));
            if (will_retry) {
                qpdf_for_warning.warn(
                    // line-break
                    damagedPDF(
                        file,
                        "",
                        file->getLastOffset(),
                        "stream will be re-processed without"
                        " filtering to avoid data loss"));
            }
        }
    }
    if (!success) {
        try {
            pipeline->finish();
        } catch (std::exception&) {
            // ignore
        }
    }
    return success;
}

bool
QPDF::pipeStreamData(
    QPDFObjGen const& og,
    qpdf_offset_t offset,
    size_t length,
    QPDFObjectHandle stream_dict,
    Pipeline* pipeline,
    bool suppress_warnings,
    bool will_retry)
{
    return pipeStreamData(
        this->m->encp,
        this->m->file,
        *this,
        og,
        offset,
        length,
        stream_dict,
        pipeline,
        suppress_warnings,
        will_retry);
}

bool
QPDF::pipeForeignStreamData(
    std::shared_ptr<ForeignStreamData> foreign,
    Pipeline* pipeline,
    bool suppress_warnings,
    bool will_retry)
{
    if (foreign->encp->encrypted) {
        QTC::TC("qpdf", "QPDF pipe foreign encrypted stream");
    }
    return pipeStreamData(
        foreign->encp,
        foreign->file,
        *this,
        foreign->foreign_og,
        foreign->offset,
        foreign->length,
        foreign->local_dict,
        pipeline,
        suppress_warnings,
        will_retry);
}

// Throw a generic exception when we lack context for something
// more specific. New code should not use this. This method exists
// to improve somewhat from calling assert in very old code.
void
QPDF::stopOnError(std::string const& message)
{
    throw damagedPDF("", message);
}

// Return an exception of type qpdf_e_damaged_pdf.
QPDFExc
QPDF::damagedPDF(
    std::shared_ptr<InputSource> const& input,
    std::string const& object,
    qpdf_offset_t offset,
    std::string const& message)
{
    return QPDFExc(
        qpdf_e_damaged_pdf, input->getName(), object, offset, message);
}

// Return an exception of type qpdf_e_damaged_pdf.  The object is taken from
// m->last_object_description.
QPDFExc
QPDF::damagedPDF(
    std::shared_ptr<InputSource> const& input,
    qpdf_offset_t offset,
    std::string const& message)
{
    return damagedPDF(input, m->last_object_description, offset, message);
}

// Return an exception of type qpdf_e_damaged_pdf.  The filename is taken from
// m->file.
QPDFExc
QPDF::damagedPDF(
    std::string const& object, qpdf_offset_t offset, std::string const& message)
{
    return QPDFExc(
        qpdf_e_damaged_pdf, m->file->getName(), object, offset, message);
}

// Return an exception of type qpdf_e_damaged_pdf.  The filename is taken from
// m->file and the offset from .m->file->getLastOffset().
QPDFExc
QPDF::damagedPDF(std::string const& object, std::string const& message)
{
    return damagedPDF(object, m->file->getLastOffset(), message);
}

// Return an exception of type qpdf_e_damaged_pdf. The filename is taken from
// m->file and the object from .m->last_object_description.
QPDFExc
QPDF::damagedPDF(qpdf_offset_t offset, std::string const& message)
{
    return damagedPDF(m->last_object_description, offset, message);
}

// Return an exception of type qpdf_e_damaged_pdf.  The filename is taken from
// m->file, the object from m->last_object_description and the offset from
// m->file->getLastOffset().
QPDFExc
QPDF::damagedPDF(std::string const& message)
{
    return damagedPDF(
        m->last_object_description, m->file->getLastOffset(), message);
}

bool
QPDF::everCalledGetAllPages() const
{
    return this->m->ever_called_get_all_pages;
}

bool
QPDF::everPushedInheritedAttributesToPages() const
{
    return this->m->ever_pushed_inherited_attributes_to_pages;
}

void
QPDF::removeSecurityRestrictions()
{
    auto root = getRoot();
    root.removeKey("/Perms");
    auto acroform = root.getKey("/AcroForm");
    if (acroform.isDictionary() && acroform.hasKey("/SigFlags")) {
        acroform.replaceKey("/SigFlags", QPDFObjectHandle::newInteger(0));
    }
}