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Merge pull request #939 from lz4/fix927

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LZ4F_decompress requires a valid dctx state
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Yann Collet 2020-11-07 09:37:27 -08:00 committed by GitHub
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3 changed files with 10 additions and 7 deletions
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10
lib/README.md
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@ -49,7 +49,7 @@ and `LZ4F_PUBLISH_STATIC_FUNCTIONS`.
The following build macro can be selected to adjust source code behavior at compilation time :
- `LZ4_FAST_DEC_LOOP` : this triggers a speed optimized decompression loop, more powerful on modern cpus.
This loop works great on x86, x64 and aarch64 cpus, and is automatically enabled for them.
This loop works great on `x86`, `x64` and `aarch64` cpus, and is automatically enabled for them.
It's also possible to enable or disable it manually, by passing `LZ4_FAST_DEC_LOOP=1` or `0` to the preprocessor.
For example, with `gcc` : `-DLZ4_FAST_DEC_LOOP=1`,
and with `make` : `CPPFLAGS+=-DLZ4_FAST_DEC_LOOP=1 make lz4`.
@ -66,8 +66,8 @@ The following build macro can be selected to adjust source code behavior at comp
Should this be a problem, it's generally possible to make the compiler ignore these warnings,
for example with `-Wno-deprecated-declarations` on `gcc`,
or `_CRT_SECURE_NO_WARNINGS` for Visual Studio.
Another project-specific method is to define `LZ4_DISABLE_DEPRECATE_WARNINGS`
before including the LZ4 header files.
This build macro offers another project-specific method
by defining `LZ4_DISABLE_DEPRECATE_WARNINGS` before including the LZ4 header files.
- `LZ4_FORCE_SW_BITCOUNT` : by default, the compression algorithm tries to determine lengths
by using bitcount instructions, generally implemented as fast single instructions in many cpus.
@ -78,8 +78,8 @@ The following build macro can be selected to adjust source code behavior at comp
but it can be legitimately considered for less common platforms.
- `LZ4_ALIGN_TEST` : alignment test ensures that the memory area
passed as argument to become a compression state is suitable aligned.
This test can be disabled, if it proves flaky, by setting this value to 0.
passed as argument to become a compression state is suitably aligned.
This test can be disabled if it proves flaky, by setting this value to 0.
#### Amalgamation

1
lib/lz4frame.c
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@ -1405,6 +1405,7 @@ size_t LZ4F_decompress(LZ4F_dctx* dctx,
if (decompressOptionsPtr==NULL) decompressOptionsPtr = &optionsNull;
*srcSizePtr = 0;
*dstSizePtr = 0;
assert(dctx != NULL);
/* behaves as a state machine */

6
lib/lz4frame.h
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@ -431,8 +431,10 @@ LZ4FLIB_API size_t LZ4F_getFrameInfo(LZ4F_dctx* dctx,
const void* srcBuffer, size_t* srcSizePtr);
/*! LZ4F_decompress() :
* Call this function repetitively to regenerate compressed data from `srcBuffer`.
* The function will read up to *srcSizePtr bytes from srcBuffer,
* Call this function repetitively to regenerate data compressed in `srcBuffer`.
*
* The function requires a valid dctx state.
* It will read up to *srcSizePtr bytes from srcBuffer,
* and decompress data into dstBuffer, of capacity *dstSizePtr.
*
* The nb of bytes consumed from srcBuffer will be written into *srcSizePtr (necessarily <= original value).