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Avoid modifying trailer when writing

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When preparing the trailer for writing to the new file, trim a copy of
the trailer instead of the original file's trailer.
This commit is contained in:
Jay Berkenbilt 2012-12-31 05:50:43 -05:00
parent 0ea70e5dae
commit 9eb5982fa3
2 changed files with 16 additions and 10 deletions
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1
include/qpdf/QPDFWriter.hh
View File

@ -322,6 +322,7 @@ class QPDFWriter
void setDataKey(int objid);
int openObject(int objid = 0);
void closeObject(int objid);
QPDFObjectHandle getTrimmedTrailer();
void prepareFileForWrite();
void writeStandard();
void writeLinearized();

25
libqpdf/QPDFWriter.cc
View File

@ -1057,7 +1057,7 @@ void
QPDFWriter::writeTrailer(trailer_e which, int size, bool xref_stream,
qpdf_offset_t prev)
{
QPDFObjectHandle trailer = pdf.getTrailer();
QPDFObjectHandle trailer = getTrimmedTrailer();
if (! xref_stream)
{
writeString("trailer <<");
@ -1932,20 +1932,19 @@ QPDFWriter::generateObjectStreams()
}
}
void
QPDFWriter::prepareFileForWrite()
QPDFObjectHandle
QPDFWriter::getTrimmedTrailer()
{
// Remove keys from the trailer that necessarily have to be
// replaced when writing the file.
QPDFObjectHandle trailer = pdf.getTrailer();
QPDFObjectHandle trailer = pdf.getTrailer().shallowCopy();
// Note that removing the encryption dictionary does not interfere
// with reading encrypted files. QPDF loads all the information
// it needs from the encryption dictionary at the beginning and
// never looks at it again.
// Remove encryption keys
trailer.removeKey("/ID");
trailer.removeKey("/Encrypt");
// Remove modification information
trailer.removeKey("/Prev");
// Remove all trailer keys that potentially come from a
@ -1958,6 +1957,12 @@ QPDFWriter::prepareFileForWrite()
trailer.removeKey("/Type");
trailer.removeKey("/XRefStm");
return trailer;
}
void
QPDFWriter::prepareFileForWrite()
{
// Do a traversal of the entire PDF file structure replacing all
// indirect objects that QPDFWriter wants to be direct. This
// includes stream lengths, stream filtering parameters, and
@ -1967,7 +1972,7 @@ QPDFWriter::prepareFileForWrite()
// holders.
std::list<QPDFObjectHandle> queue;
queue.push_back(pdf.getTrailer());
queue.push_back(getTrimmedTrailer());
std::set<int> visited;
while (! queue.empty())
@ -2861,7 +2866,7 @@ QPDFWriter::writeStandard()
writeString(this->extra_header_text);
// Put root first on queue.
QPDFObjectHandle trailer = pdf.getTrailer();
QPDFObjectHandle trailer = getTrimmedTrailer();
enqueueObject(trailer.getKey("/Root"));
// Next place any other objects referenced from the trailer