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Code Issues Releases Wiki Activity

Move QPDF::read_xref to QPDF::Xref_table

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This commit is contained in:
m-holger 2024-08-10 12:40:59 +01:00
parent f30a5eb05a
commit a4db9b3149
3 changed files with 28 additions and 26 deletions
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1
include/qpdf/QPDF.hh
View File

@ -759,7 +759,6 @@ class QPDF
void parse(char const* password);
void inParse(bool);
void read_xref(qpdf_offset_t offset);
bool resolveXRefTable();
void setLastObjectDescription(std::string const& description, QPDFObjGen const& og);
QPDFObjectHandle readTrailer();

43
libqpdf/QPDF.cc
View File

@ -468,7 +468,7 @@ QPDF::parse(char const* password)
throw damagedPDF("", 0, "can't find startxref");
}
try {
read_xref(xref_offset);
m->xref_table.read(xref_offset);
} catch (QPDFExc&) {
throw;
} catch (std::exception& e) {
@ -625,7 +625,7 @@ QPDF::Xref_table::reconstruct(QPDFExc& e)
}
if (max_offset > 0) {
try {
qpdf.read_xref(max_offset);
read(max_offset);
} catch (std::exception&) {
throw damaged_pdf(
"error decoding candidate xref stream while recovering damaged file");
@ -664,8 +664,10 @@ QPDF::Xref_table::reconstruct(QPDFExc& e)
}
void
QPDF::read_xref(qpdf_offset_t xref_offset)
QPDF::Xref_table::read(qpdf_offset_t xref_offset)
{
auto* m = qpdf.m.get();
std::map<int, int> free_table;
std::set<qpdf_offset_t> visited;
while (xref_offset) {
@ -700,7 +702,7 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
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"));
warn_damaged("extraneous whitespace seen before xref");
}
QTC::TC(
"qpdf",
@ -714,46 +716,43 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
while (QUtil::is_space(buf[skip])) {
++skip;
}
xref_offset = m->xref_table.read_table(xref_offset + skip);
xref_offset = read_table(xref_offset + skip);
} else {
xref_offset = m->xref_table.read_stream(xref_offset);
xref_offset = read_stream(xref_offset);
}
if (visited.count(xref_offset) != 0) {
QTC::TC("qpdf", "QPDF xref loop");
throw damagedPDF("", 0, "loop detected following xref tables");
throw damaged_pdf("loop detected following xref tables");
}
}
if (!m->xref_table.trailer) {
throw damagedPDF("", 0, "unable to find trailer while reading xref");
if (!trailer) {
throw damaged_pdf("unable to find trailer while reading xref");
}
int size = m->xref_table.trailer.getKey("/Size").getIntValueAsInt();
int size = trailer.getKey("/Size").getIntValueAsInt();
int max_obj = 0;
if (!m->xref_table.empty()) {
max_obj = m->xref_table.rbegin()->first.getObj();
if (!empty()) {
max_obj = rbegin()->first.getObj();
}
if (!m->xref_table.deleted_objects.empty()) {
max_obj = std::max(max_obj, *(m->xref_table.deleted_objects.rbegin()));
if (!deleted_objects.empty()) {
max_obj = std::max(max_obj, *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) + ")")));
warn_damaged("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.
m->xref_table.deleted_objects.clear();
deleted_objects.clear();
// Make sure we keep only the highest generation for any object.
QPDFObjGen last_og{-1, 0};
for (auto const& item: m->xref_table) {
for (auto const& item: *this) {
auto id = item.first.getObj();
if (id == last_og.getObj() && id > 0) {
removeObject(last_og);
qpdf.removeObject(last_og);
}
last_og = item.first;
}

10
libqpdf/qpdf/QPDF_private.hh
View File

@ -12,9 +12,7 @@ class QPDF::Xref_table: public std::map<QPDFObjGen, QPDFXRefEntry>
{
}
qpdf_offset_t read_table(qpdf_offset_t offset);
qpdf_offset_t read_stream(qpdf_offset_t offset);
void read(qpdf_offset_t offset);
void reconstruct(QPDFExc& e);
QPDFObjectHandle trailer;
@ -32,9 +30,14 @@ class QPDF::Xref_table: public std::map<QPDFObjGen, QPDFXRefEntry>
qpdf_offset_t first_item_offset{0}; // actual value from file
private:
// Methods to parse tables
qpdf_offset_t read_table(qpdf_offset_t offset);
bool parse_first(std::string const& line, int& obj, int& num, int& bytes);
bool read_entry(qpdf_offset_t& f1, int& f2, char& type);
bool read_bad_entry(qpdf_offset_t& f1, int& f2, char& type);
// Methods to parse streams
qpdf_offset_t read_stream(qpdf_offset_t offset);
qpdf_offset_t process_stream(qpdf_offset_t offset, QPDFObjectHandle& xref_stream);
std::pair<int, std::array<int, 3>>
process_W(QPDFObjectHandle& dict, std::function<QPDFExc(std::string_view)> damaged);
@ -45,6 +48,7 @@ class QPDF::Xref_table: public std::map<QPDFObjGen, QPDFXRefEntry>
int max_num_entries,
std::function<QPDFExc(std::string_view)> damaged);
// Methods to insert table entries
void insert_reconstructed(int obj, qpdf_offset_t f1, int f2);
void insert(int obj, int f0, qpdf_offset_t f1, int f2);
void insert_free(QPDFObjGen);