mirror of https://github.com/qpdf/qpdf.git
Add new private method QPDF::readStream
This commit is contained in:
m-holger
parent
2643ed4dd9
commit
c422b918b1
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@ -1008,6 +1008,7 @@ class QPDF
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void setLastObjectDescription(std::string const& description, QPDFObjGen const& og);
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QPDFObjectHandle readTrailer();
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QPDFObjectHandle readObject(std::string const& description, QPDFObjGen og);
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void readStream(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset);
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QPDFObjectHandle readObjectInStream(std::shared_ptr<InputSource>, QPDFObjGen og);
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size_t recoverStreamLength(
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std::shared_ptr<InputSource> input, QPDFObjGen const& og, qpdf_offset_t stream_offset);
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165
libqpdf/QPDF.cc
165
libqpdf/QPDF.cc
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@ -1296,7 +1296,7 @@ QPDF::readObject(std::string const& description, QPDFObjGen og)
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std::shared_ptr<StringDecrypter> decrypter_ph;
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StringDecrypter* decrypter = nullptr;
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if (m->encp->encrypted) {
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decrypter_ph = std::make_shared<StringDecrypter>(this, og);
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decrypter_ph = std::make_unique<StringDecrypter>(this, og);
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decrypter = decrypter_ph.get();
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}
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auto object = QPDFParser(m->file, m->last_object_description, m->tokenizer, decrypter, this)
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@ -1309,85 +1309,7 @@ QPDF::readObject(std::string const& description, QPDFObjGen og)
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// check for stream
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qpdf_offset_t cur_offset = m->file->tell();
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if (readToken(m->file).isWord("stream")) {
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// The PDF specification states that the word "stream" should be followed by either a
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// carriage return and a newline or by a newline alone. It specifically disallowed
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// following it by a carriage return alone since, in that case, there would be no way to
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// tell whether the NL in a CR NL sequence was part of the stream data. However, some
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// readers, including Adobe reader, accept a carriage return by itself when followed by
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// a non-newline character, so that's what we do here. We have also seen files that have
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// extraneous whitespace between the stream keyword and the newline.
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bool done = false;
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while (!done) {
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done = true;
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char ch;
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if (m->file->read(&ch, 1) == 0) {
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// A premature EOF here will result in some other problem that will get reported
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// at another time.
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} else if (ch == '\n') {
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// ready to read stream data
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QTC::TC("qpdf", "QPDF stream with NL only");
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} else if (ch == '\r') {
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// Read another character
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if (m->file->read(&ch, 1) != 0) {
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if (ch == '\n') {
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// Ready to read stream data
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QTC::TC("qpdf", "QPDF stream with CRNL");
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} else {
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// Treat the \r by itself as the whitespace after endstream and start
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// reading stream data in spite of not having seen a newline.
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QTC::TC("qpdf", "QPDF stream with CR only");
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m->file->unreadCh(ch);
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warn(damagedPDF(
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m->file->tell(),
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"stream keyword followed by carriage return only"));
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}
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}
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} else if (QUtil::is_space(ch)) {
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warn(damagedPDF(
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m->file->tell(), "stream keyword followed by extraneous whitespace"));
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done = false;
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} else {
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QTC::TC("qpdf", "QPDF stream without newline");
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m->file->unreadCh(ch);
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warn(damagedPDF(
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m->file->tell(), "stream keyword not followed by proper line terminator"));
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}
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}
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// Must get offset before accessing any additional objects since resolving a previously
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// unresolved indirect object will change file position.
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qpdf_offset_t stream_offset = m->file->tell();
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size_t length = 0;
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try {
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auto length_obj = object.getKey("/Length");
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if (!length_obj.isInteger()) {
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if (length_obj.isNull()) {
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QTC::TC("qpdf", "QPDF stream without length");
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throw damagedPDF(offset, "stream dictionary lacks /Length key");
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}
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QTC::TC("qpdf", "QPDF stream length not integer");
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throw damagedPDF(offset, "/Length key in stream dictionary is not an integer");
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}
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length = toS(length_obj.getUIntValue());
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// Seek in two steps to avoid potential integer overflow
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m->file->seek(stream_offset, SEEK_SET);
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m->file->seek(toO(length), SEEK_CUR);
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if (!readToken(m->file).isWord("endstream")) {
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QTC::TC("qpdf", "QPDF missing endstream");
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throw damagedPDF("expected endstream");
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}
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} catch (QPDFExc& e) {
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if (m->attempt_recovery) {
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warn(e);
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length = recoverStreamLength(m->file, og, stream_offset);
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} else {
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throw;
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}
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}
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object = newIndirect(og, QPDF_Stream::create(this, og, object, stream_offset, length));
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readStream(object, og, offset);
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} else {
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m->file->seek(cur_offset, SEEK_SET);
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}
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@ -1398,6 +1320,89 @@ QPDF::readObject(std::string const& description, QPDFObjGen og)
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return object;
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}
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// After reading stream dictionary and stream keyword, read rest of stream.
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void
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QPDF::readStream(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset)
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{
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// The PDF specification states that the word "stream" should be followed by either a carriage
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// return and a newline or by a newline alone. It specifically disallowed following it by a
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// carriage return alone since, in that case, there would be no way to tell whether the NL in a
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// CR NL sequence was part of the stream data. However, some readers, including Adobe reader,
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// accept a carriage return by itself when followed by a non-newline character, so that's what
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// we do here. We have also seen files that have extraneous whitespace between the stream
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// keyword and the newline.
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bool done = false;
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while (!done) {
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done = true;
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char ch;
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if (m->file->read(&ch, 1) == 0) {
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// A premature EOF here will result in some other problem that will get reported at
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// another time.
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} else if (ch == '\n') {
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// ready to read stream data
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QTC::TC("qpdf", "QPDF stream with NL only");
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} else if (ch == '\r') {
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// Read another character
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if (m->file->read(&ch, 1) != 0) {
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if (ch == '\n') {
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// Ready to read stream data
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QTC::TC("qpdf", "QPDF stream with CRNL");
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} else {
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// Treat the \r by itself as the whitespace after endstream and start reading
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// stream data in spite of not having seen a newline.
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QTC::TC("qpdf", "QPDF stream with CR only");
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m->file->unreadCh(ch);
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warn(damagedPDF(
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m->file->tell(), "stream keyword followed by carriage return only"));
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}
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}
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} else if (QUtil::is_space(ch)) {
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warn(damagedPDF(m->file->tell(), "stream keyword followed by extraneous whitespace"));
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done = false;
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} else {
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QTC::TC("qpdf", "QPDF stream without newline");
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m->file->unreadCh(ch);
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warn(damagedPDF(
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m->file->tell(), "stream keyword not followed by proper line terminator"));
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}
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}
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// Must get offset before accessing any additional objects since resolving a previously
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// unresolved indirect object will change file position.
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qpdf_offset_t stream_offset = m->file->tell();
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size_t length = 0;
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try {
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auto length_obj = object.getKey("/Length");
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if (!length_obj.isInteger()) {
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if (length_obj.isNull()) {
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QTC::TC("qpdf", "QPDF stream without length");
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throw damagedPDF(offset, "stream dictionary lacks /Length key");
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}
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QTC::TC("qpdf", "QPDF stream length not integer");
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throw damagedPDF(offset, "/Length key in stream dictionary is not an integer");
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}
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length = toS(length_obj.getUIntValue());
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// Seek in two steps to avoid potential integer overflow
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m->file->seek(stream_offset, SEEK_SET);
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m->file->seek(toO(length), SEEK_CUR);
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if (!readToken(m->file).isWord("endstream")) {
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QTC::TC("qpdf", "QPDF missing endstream");
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throw damagedPDF("expected endstream");
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}
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} catch (QPDFExc& e) {
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if (m->attempt_recovery) {
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warn(e);
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length = recoverStreamLength(m->file, og, stream_offset);
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} else {
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throw;
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}
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}
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object = newIndirect(og, QPDF_Stream::create(this, og, object, stream_offset, length));
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}
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QPDFObjectHandle
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QPDF::readObjectInStream(std::shared_ptr<InputSource> input, QPDFObjGen og)
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{
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