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Refactor Xref_table::parse_first

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Rename to Xref_table::subsection.
Return results instead of using out parameters.
Take on responsibility for throwing exception and calculation of offset of
first subsection entry.
This commit is contained in:
m-holger 2024-08-14 13:08:52 +01:00
parent 0c56cec6c3
commit cee8d5c92d
2 changed files with 20 additions and 18 deletions
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33
libqpdf/QPDF.cc
View File

@ -776,9 +776,14 @@ QPDF::Xref_table::read(qpdf_offset_t xref_offset)
}
}
bool
QPDF::Xref_table::parse_first(std::string const& line, int& obj, int& num, int& bytes)
QPDF::Xref_table::Subsection
QPDF::Xref_table::subsection(std::string const& line)
{
auto terminate = [this]() -> void {
QTC::TC("qpdf", "QPDF invalid xref");
throw damaged_table("xref syntax invalid");
};
// 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();
@ -790,7 +795,7 @@ QPDF::Xref_table::parse_first(std::string const& line, int& obj, int& num, int&
}
// Require digit
if (!QUtil::is_digit(*p)) {
return false;
terminate();
}
// Gather digits
std::string obj_str;
@ -799,7 +804,7 @@ QPDF::Xref_table::parse_first(std::string const& line, int& obj, int& num, int&
}
// Require space
if (!QUtil::is_space(*p)) {
return false;
terminate();
}
// Skip spaces
while (QUtil::is_space(*p)) {
@ -807,7 +812,7 @@ QPDF::Xref_table::parse_first(std::string const& line, int& obj, int& num, int&
}
// Require digit
if (!QUtil::is_digit(*p)) {
return false;
terminate();
}
// Gather digits
std::string num_str;
@ -818,10 +823,10 @@ QPDF::Xref_table::parse_first(std::string const& line, int& obj, int& num, int&
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;
return {
QUtil::string_to_int(obj_str.c_str()),
QUtil::string_to_int(num_str.c_str()),
file->getLastOffset() + toI(p - start)};
}
bool
@ -968,14 +973,8 @@ QPDF::Xref_table::read_table(qpdf_offset_t xref_offset)
while (true) {
line.assign(50, '\0');
file->read(line.data(), line.size());
int obj = 0;
int num = 0;
int bytes = 0;
if (!parse_first(line, obj, num, bytes)) {
QTC::TC("qpdf", "QPDF invalid xref");
throw damaged_table("xref syntax invalid");
}
file->seek(file->getLastOffset() + bytes, SEEK_SET);
auto [obj, num, offset] = subsection(line);
file->seek(offset, SEEK_SET);
for (qpdf_offset_t i = obj; i - num < obj; ++i) {
if (i == 0) {
// This is needed by checkLinearization()

5
libqpdf/qpdf/QPDF_private.hh
View File

@ -118,11 +118,14 @@ class QPDF::Xref_table
}
private:
// Object, count, offset of first entry
typedef std::tuple<int, int, qpdf_offset_t> Subsection;
void read(qpdf_offset_t offset);
// 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);
Subsection subsection(std::string const& line);
bool read_entry(qpdf_offset_t& f1, int& f2, char& type);
bool read_bad_entry(qpdf_offset_t& f1, int& f2, char& type);