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| author | Ivan Solovev <ivan.solovev@qt.io> | 2024-02-01 11:50:25 +0100 |
|---|---|---|
| committer | Ivan Solovev <ivan.solovev@qt.io> | 2024-02-07 15:02:19 +0100 |
| commit | a1bfac287ee5d3719646d68dc91dc8e8e4cec04e (patch) | |
| tree | f2324565be8b6d787645d319268408a10caa4a64 /src/corelib/serialization/qdatastream.cpp | |
| parent | dd514160ce169734e23a146a2c115fed55a69260 (diff) | |
QDataStream::readBytes(): make the growth of the buffer geometric
The algorithm tries to allocate the memory using 1 Mb blocks.
When the input data is large, this results in a lot of reallocations,
which is slow and inefficient.
This patch modifies the algorithm in such way that the allocation size
increases at each step, resulting in geometric growth of the buffer.
Pick-to: 6.7 6.6 6.5
Change-Id: I071df68d51ba1dbd8b2eb5f94eb078a33223505f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib/serialization/qdatastream.cpp')
| -rw-r--r-- | src/corelib/serialization/qdatastream.cpp | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/src/corelib/serialization/qdatastream.cpp b/src/corelib/serialization/qdatastream.cpp index d0421f70fad..32f827c69e7 100644 --- a/src/corelib/serialization/qdatastream.cpp +++ b/src/corelib/serialization/qdatastream.cpp @@ -1074,13 +1074,13 @@ QDataStream &QDataStream::readBytes(char *&s, qint64 &l) return *this; } - constexpr qsizetype Step = 1024 * 1024; + qsizetype step = 1024 * 1024; qsizetype allocated = 0; char *prevBuf = nullptr; char *curBuf = nullptr; do { - qsizetype blockSize = qMin(Step, len - allocated); + qsizetype blockSize = qMin(step, len - allocated); prevBuf = curBuf; curBuf = new char[allocated + blockSize + 1]; if (prevBuf) { @@ -1092,6 +1092,7 @@ QDataStream &QDataStream::readBytes(char *&s, qint64 &l) return *this; } allocated += blockSize; + step *= 2; } while (allocated < len); s = curBuf; |