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https://github.com/qpdf/qpdf.git
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Let optimize filter stream parameters instead of making them direct
Also removes preclusion of stream references in stream parameters of filterable streams and reduces write times by about 8% by eliminating an extra traversal of the objects.
This commit is contained in:
Jay Berkenbilt
parent
1a62cce940
commit
858c7b89bc
@ -1,3 +1,11 @@
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2020-12-25 Jay Berkenbilt <ejb@ql.org>
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* Refactor write code to eliminate an extra full traversal of
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objects in the file and to remove assumptions that preclude stream
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references from appearing in /DecodeParms of filterable streams.
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This results in an approximately 8% performance reduction in write
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times.
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2020-12-23 Jay Berkenbilt <ejb@ql.org>
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* Allow library users to provide their own decoders for stream
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@ -2452,84 +2452,14 @@ QPDFWriter::getTrimmedTrailer()
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void
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QPDFWriter::prepareFileForWrite()
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{
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// Do a traversal of the entire PDF file structure replacing all
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// indirect objects that QPDFWriter wants to be direct. This
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// includes stream lengths, stream filtering parameters, and
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// document extension level information.
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// Make document extension level information direct as required by
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// the spec.
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this->m->pdf.fixDanglingReferences(true);
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std::list<QPDFObjectHandle> queue;
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queue.push_back(getTrimmedTrailer());
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std::set<int> visited;
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while (! queue.empty())
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{
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QPDFObjectHandle node = queue.front();
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queue.pop_front();
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if (node.isIndirect())
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{
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if (visited.count(node.getObjectID()) > 0)
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{
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continue;
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}
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indicateProgress(false, false);
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visited.insert(node.getObjectID());
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}
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if (node.isArray())
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{
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int nitems = node.getArrayNItems();
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for (int i = 0; i < nitems; ++i)
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{
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QPDFObjectHandle oh = node.getArrayItem(i);
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if (! oh.isScalar())
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{
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queue.push_back(oh);
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}
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}
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}
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else if (node.isDictionary() || node.isStream())
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{
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bool is_stream = false;
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bool is_root = false;
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bool filterable = false;
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QPDFObjectHandle dict = node;
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if (node.isStream())
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{
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is_stream = true;
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dict = node.getDict();
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// See whether we are able to filter this stream.
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filterable = node.pipeStreamData(
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0, 0, this->m->stream_decode_level, true);
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}
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else if (this->m->pdf.getRoot().getObjectID() == node.getObjectID())
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{
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is_root = true;
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}
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std::set<std::string> keys = dict.getKeys();
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for (std::set<std::string>::iterator iter = keys.begin();
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iter != keys.end(); ++iter)
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{
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std::string const& key = *iter;
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QPDFObjectHandle oh = dict.getKey(key);
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bool add_to_queue = true;
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if (is_stream)
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{
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if (oh.isIndirect() &&
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((key == "/Length") ||
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(filterable &&
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((key == "/Filter") ||
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(key == "/DecodeParms")))))
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{
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QTC::TC("qpdf", "QPDFWriter make stream key direct");
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add_to_queue = false;
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oh.makeDirect();
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dict.replaceKey(key, oh);
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}
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}
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else if (is_root)
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QPDFObjectHandle root = this->m->pdf.getRoot();
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for (auto const& key: root.getKeys())
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{
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QPDFObjectHandle oh = root.getKey(key);
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if ((key == "/Extensions") && (oh.isDictionary()))
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{
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bool extensions_indirect = false;
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@ -2537,9 +2467,8 @@ QPDFWriter::prepareFileForWrite()
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{
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QTC::TC("qpdf", "QPDFWriter make Extensions direct");
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extensions_indirect = true;
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add_to_queue = false;
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oh = oh.shallowCopy();
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dict.replaceKey(key, oh);
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root.replaceKey(key, oh);
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}
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if (oh.hasKey("/ADBE"))
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{
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@ -2554,14 +2483,6 @@ QPDFWriter::prepareFileForWrite()
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}
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}
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}
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if (add_to_queue)
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{
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queue.push_back(oh);
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}
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}
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}
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}
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}
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void
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@ -2737,14 +2658,11 @@ QPDFWriter::write()
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{
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doWriteSetup();
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// Set up progress reporting. We spent about equal amounts of time
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// preparing and writing one pass. To get a rough estimate of
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// progress, we track handling of indirect objects. For linearized
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// files, we write two passes. events_expected is an
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// approximation, but it's good enough for progress reporting,
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// which is mostly a guess anyway.
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// Set up progress reporting. For linearized files, we write two
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// passes. events_expected is an approximation, but it's good
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// enough for progress reporting, which is mostly a guess anyway.
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this->m->events_expected = QIntC::to_int(
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this->m->pdf.getObjectCount() * (this->m->linearized ? 3 : 2));
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this->m->pdf.getObjectCount() * (this->m->linearized ? 2 : 1));
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prepareFileForWrite();
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@ -3138,8 +3056,21 @@ QPDFWriter::writeLinearized()
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discardGeneration(this->m->object_to_object_stream,
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this->m->object_to_object_stream_no_gen);
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bool need_xref_stream = (! this->m->object_to_object_stream.empty());
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this->m->pdf.optimize(this->m->object_to_object_stream_no_gen);
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auto skip_stream_parameters = [this](QPDFObjectHandle& stream) {
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bool compress_stream;
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bool is_metadata;
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if (willFilterStream(stream, compress_stream, is_metadata, nullptr))
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{
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return 2;
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}
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else
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{
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return 1;
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}
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};
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this->m->pdf.optimize(this->m->object_to_object_stream_no_gen,
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true, skip_stream_parameters);
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std::vector<QPDFObjectHandle> part4;
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std::vector<QPDFObjectHandle> part6;
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@ -3173,6 +3104,7 @@ QPDFWriter::writeLinearized()
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int after_second_half = 1 + second_half_uncompressed;
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this->m->next_objid = after_second_half;
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int second_half_xref = 0;
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bool need_xref_stream = (! this->m->object_to_object_stream.empty());
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if (need_xref_stream)
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{
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second_half_xref = this->m->next_objid++;
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@ -234,7 +234,6 @@ QPDFWriter extra header text no newline 0
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QPDFWriter extra header text add newline 0
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QPDF bogus 0 offset 0
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QPDF global offset 0
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QPDFWriter make stream key direct 0
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QPDFWriter copy V5 0
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QPDFWriter increasing extension level 0
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QPDFWriter make Extensions direct 0
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@ -716,7 +716,7 @@ my @bug_tests = (
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["99b", "object 0", 2],
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["100", "xref reconstruction loop", 2],
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["101", "resolve for exception text", 2],
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["117", "other infinite loop", 2],
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["117", "other infinite loop", 3],
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["118", "other infinite loop", 2],
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["119", "other infinite loop", 3],
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["120", "other infinite loop", 3],
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@ -13,4 +13,4 @@ WARNING: issue-117.pdf (object 7 0, offset 1791): unknown token while reading ob
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WARNING: issue-117.pdf (object 7 0, offset 1267): /Length key in stream dictionary is not an integer
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WARNING: issue-117.pdf (object 7 0, offset 1418): attempting to recover stream length
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WARNING: issue-117.pdf (object 7 0, offset 1418): recovered stream length: 347
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attempt to make a stream into a direct object
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qpdf: operation succeeded with warnings; resulting file may have some problems
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