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Use smart-growing buffer size for compression #28

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Use smart-growing buffer size for compression #28

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67 changes: 40 additions & 27 deletions src/gui/painting/qprintengine_pdf.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -833,7 +833,31 @@ class jpg_header_reader {

};

bool QPdfEnginePrivate::smartCompressDeflate(const char *source, int size, QByteArray& compressed, unsigned long maxSize)
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Make this a static function, as it's unlikely to be used outside of this file.

{
if (maxSize == 0) {
maxSize = ::compressBound(size);
}

const unsigned long initialBufferSize = 10 * 1024 * 1024;

unsigned long destLen = min(initialBufferSize, maxSize);

while (true) {
compressed.resize(destLen);
if (Z_OK == ::compress(reinterpret_cast<Bytef *>(compressed.data()), &destLen, reinterpret_cast<const Bytef *>(source), size)) {
compressed.truncate(destLen);
break;
}
if (static_cast<unsigned long>(compressed.size()) >= maxSize) {
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According to the manual, compressBound returns an upper bound on the compressed size after the compress call. So not really sure what this is supposed to protect against? Z_BUF_ERROR is obviously not going to happen, so maybe you should check for Z_MEM_ERROR directly if that was what you had in mind.

compressed.clear();
return false;
}
destLen = min(static_cast<unsigned long>(compressed.size()) * 2, maxSize);
}

return true;
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shouldn't this check maxSize with compressed.size() e.g. as in line 930 (uLongf)destLen < target?

}

/*!
* Adds an image to the pdf and return the pdf-object id. Returns -1 if adding the image failed.
Expand Down Expand Up @@ -907,33 +931,25 @@ int QPdfEnginePrivate::addImage(const QImage &img, bool *bitmap, qint64 serial_n
if (noneScaled && noneScaled->rect() != image.rect()) {
QByteArray imageData2;
convertImage(*noneScaled, imageData2);
uLongf len = imageData2.size();
uLongf destLen = len + len/100 + 13; // zlib requirement
Bytef* dest = new Bytef[destLen];
if (Z_OK == ::compress(dest, &destLen, (const Bytef*) imageData2.data(), (uLongf)len) &&
(uLongf)destLen < target) {
imageData=imageData2;
target=destLen;
dct=false;
uns=true;
QByteArray compressed;
if (smartCompressDeflate(imageData2.data(), imageData2.size(), compressed, target)) {
imageData = imageData2;
target = compressed.size();
dct = false;
uns = true;
}
delete[] dest;
}

{
QByteArray imageData2;
convertImage(image, imageData2);
uLongf len = imageData2.size();
uLongf destLen = len + len/100 + 13; // zlib requirement
Bytef* dest = new Bytef[destLen];
if (Z_OK == ::compress(dest, &destLen, (const Bytef*) imageData2.data(), (uLongf)len) &&
(uLongf)destLen < target) {
imageData=imageData2;
target=destLen;
dct=false;
uns=false;
QByteArray compressed;
if (smartCompressDeflate(imageData2.data(), imageData2.size(), compressed, target)) {
imageData = imageData2;
target = compressed.size();
dct = false;
uns = false;
}
delete[] dest;
}


Expand Down Expand Up @@ -1182,16 +1198,13 @@ int QPdfEnginePrivate::writeCompressed(const char *src, int len)
{
#ifndef QT_NO_COMPRESS
if(doCompress) {
uLongf destLen = len + len/100 + 13; // zlib requirement
Bytef* dest = new Bytef[destLen];
if (Z_OK == ::compress(dest, &destLen, (const Bytef*) src, (uLongf)len)) {
stream->writeRawData((const char*)dest, destLen);
QByteArray compressed;
if (smartCompressDeflate(src, len, compressed)) {
stream->writeRawData((const char*)compressed.data(), compressed.size());
} else {
qWarning("QPdfStream::writeCompressed: Error in compress()");
destLen = 0;
}
delete [] dest;
len = destLen;
len = compressed.size();
} else
#endif
{
Expand Down
1 change: 1 addition & 0 deletions src/gui/painting/qprintengine_pdf_p.h
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Original file line number Diff line number Diff line change
Expand Up @@ -233,6 +233,7 @@ class QPdfEnginePrivate : public QPdfBaseEnginePrivate
streampos += data.size();
}

bool smartCompressDeflate(const char *source, int size, QByteArray& compressed, unsigned long maxSize = 0);
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Remove this.

int writeCompressed(const char *src, int len);
inline int writeCompressed(const QByteArray &data) { return writeCompressed(data.constData(), data.length()); }
int writeCompressed(QIODevice *dev);
Expand Down