diff options
| -rw-r--r-- | src/corelib/text/qbytearray.cpp | 65 | ||||
| -rw-r--r-- | tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp | 13 |
2 files changed, 45 insertions, 33 deletions
diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp index 28094ec34e..7aae6973b4 100644 --- a/src/corelib/text/qbytearray.cpp +++ b/src/corelib/text/qbytearray.cpp @@ -506,15 +506,6 @@ quint16 qChecksum(QByteArrayView data, Qt::ChecksumType standard) The default value is -1, which specifies zlib's default compression. -//![compress-limit-note] - \note The maximum size of data that this function can consume is limited by - what the platform's \c{unsigned long} can represent (a Zlib limitation). - That means that data > 4GiB can be compressed and decompressed on a 64-bit - Unix system, but not on a 64-bit Windows system. Portable code should - therefore avoid using qCompress()/qUncompress() to compress more than 4GiB - of input. -//![compress-limit-note] - \sa qUncompress(const QByteArray &data) */ @@ -526,8 +517,6 @@ quint16 qChecksum(QByteArrayView data, Qt::ChecksumType standard) Compresses the first \a nbytes of \a data at compression level \a compressionLevel and returns the compressed data in a new byte array. - - \include qbytearray.cpp compress-limit-note */ #ifndef QT_NO_COMPRESS @@ -687,30 +676,40 @@ QByteArray qCompress(const uchar* data, qsizetype nbytes, int compressionLevel) if (compressionLevel < -1 || compressionLevel > 9) compressionLevel = -1; - ulong len = nbytes + nbytes / 100 + 13; - QByteArray bazip; - int res; - do { - bazip.resize(len + HeaderSize); - res = ::compress2(reinterpret_cast<uchar *>(bazip.data()) + HeaderSize, &len, - data, nbytes, - compressionLevel); - - switch (res) { - case Z_OK: - bazip.resize(len + HeaderSize); - qToBigEndian(qt_saturate<CompressSizeHint_t>(nbytes), bazip.data()); - break; - case Z_MEM_ERROR: - return tooMuchData(ZLibOp::Compression); - - case Z_BUF_ERROR: - len *= 2; - break; + QArrayDataPointer out = [&] { + constexpr qsizetype SingleAllocLimit = 256 * 1024; // the maximum size for which we use + // zlib's compressBound() to guarantee + // the output buffer size is sufficient + // to hold result + qsizetype capacity = HeaderSize; + if (nbytes < SingleAllocLimit) { + // use maximum size + capacity += compressBound(uLong(nbytes)); // cannot overflow (both times)! + return QArrayDataPointer{QTypedArrayData<char>::allocate(capacity)}; } - } while (res == Z_BUF_ERROR); - return bazip; + // for larger buffers, assume it compresses optimally, and + // grow geometrically from there: + constexpr qsizetype MaxCompressionFactor = 1024; // max theoretical factor is 1032 + // cf. http://www.zlib.org/zlib_tech.html, + // but use a nearby power-of-two (faster) + capacity += std::max(qsizetype(compressBound(uLong(SingleAllocLimit))), + nbytes / MaxCompressionFactor); + return QArrayDataPointer{QTypedArrayData<char>::allocate(capacity, QArrayData::Grow)}; + }(); + + if (out.data() == nullptr) // allocation failed + return tooMuchData(ZLibOp::Compression); + + qToBigEndian(qt_saturate<CompressSizeHint_t>(nbytes), out.data()); + out.size = HeaderSize; + + return xxflate(ZLibOp::Compression, std::move(out), {data, nbytes}, + [=] (z_stream *zs) { return deflateInit(zs, compressionLevel); }, + [] (z_stream *zs, size_t inputLeft) { + return deflate(zs, inputLeft ? Z_NO_FLUSH : Z_FINISH); + }, + [] (z_stream *zs) { deflateEnd(zs); }); } #endif diff --git a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp index a3534f30a4..7f48c60b7c 100644 --- a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp +++ b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp @@ -360,6 +360,19 @@ void tst_QByteArray::qUncompress4GiBPlus() QCOMPARE(c.size(), 4 * GiB + 1); QCOMPARE(std::string_view{c}.find_first_not_of('X'), std::string_view::npos); + + // re-compress once + // (produces 18MiB, we shouldn't use much more than that in allocated capacity) + c = ::qCompress(c); + QVERIFY(!c.isNull()); + + // and un-compress again, to make sure compression worked (we + // can't compare with compressed_3x, because zlib may change): + c = ::qUncompress(c); + + QCOMPARE(c.size(), 4 * GiB + 1); + QCOMPARE(std::string_view{c}.find_first_not_of('X'), + std::string_view::npos); } } |