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fix #876

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by introducing a max limit acceleration value
This commit is contained in:
Yann Collet 2020-08-10 11:03:27 -07:00
parent b01c58000e
commit 7b1b078dfc
2 changed files with 16 additions and 6 deletions
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19
lib/lz4.c
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@ -45,10 +45,16 @@
#endif #endif
/* /*
* ACCELERATION_DEFAULT : * LZ4_ACCELERATION_DEFAULT :
* Select "acceleration" for LZ4_compress_fast() when parameter value <= 0 * Select "acceleration" for LZ4_compress_fast() when parameter value <= 0
*/ */
#define ACCELERATION_DEFAULT 1 #define LZ4_ACCELERATION_DEFAULT 1
/*
* LZ4_ACCELERATION_MAX :
* Any "acceleration" value higher than this threshold
* get treated as LZ4_ACCELERATION_MAX instead (fix #876)
*/
#define LZ4_ACCELERATION_MAX 65537
/*-************************************ /*-************************************
@ -1200,7 +1206,8 @@ int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int
{ {
LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse; LZ4_stream_t_internal* const ctx = & LZ4_initStream(state, sizeof(LZ4_stream_t)) -> internal_donotuse;
assert(ctx != NULL); assert(ctx != NULL);
if (acceleration < 1) acceleration = ACCELERATION_DEFAULT; if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
if (maxOutputSize >= LZ4_compressBound(inputSize)) { if (maxOutputSize >= LZ4_compressBound(inputSize)) {
if (inputSize < LZ4_64Klimit) { if (inputSize < LZ4_64Klimit) {
return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, 0, notLimited, byU16, noDict, noDictIssue, acceleration); return LZ4_compress_generic(ctx, source, dest, inputSize, NULL, 0, notLimited, byU16, noDict, noDictIssue, acceleration);
@ -1230,7 +1237,8 @@ int LZ4_compress_fast_extState(void* state, const char* source, char* dest, int
int LZ4_compress_fast_extState_fastReset(void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration) int LZ4_compress_fast_extState_fastReset(void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration)
{ {
LZ4_stream_t_internal* ctx = &((LZ4_stream_t*)state)->internal_donotuse; LZ4_stream_t_internal* ctx = &((LZ4_stream_t*)state)->internal_donotuse;
if (acceleration < 1) acceleration = ACCELERATION_DEFAULT; if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
if (dstCapacity >= LZ4_compressBound(srcSize)) { if (dstCapacity >= LZ4_compressBound(srcSize)) {
if (srcSize < LZ4_64Klimit) { if (srcSize < LZ4_64Klimit) {
@ -1514,7 +1522,8 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream,
if (streamPtr->dirty) { return 0; } /* Uninitialized structure detected */ if (streamPtr->dirty) { return 0; } /* Uninitialized structure detected */
LZ4_renormDictT(streamPtr, inputSize); /* avoid index overflow */ LZ4_renormDictT(streamPtr, inputSize); /* avoid index overflow */
if (acceleration < 1) acceleration = ACCELERATION_DEFAULT; if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;
/* invalidate tiny dictionaries */ /* invalidate tiny dictionaries */
if ( (streamPtr->dictSize-1 < 4-1) /* intentional underflow */ if ( (streamPtr->dictSize-1 < 4-1) /* intentional underflow */

3
lib/lz4.h
View File

@ -186,7 +186,8 @@ LZ4LIB_API int LZ4_compressBound(int inputSize);
The larger the acceleration value, the faster the algorithm, but also the lesser the compression. The larger the acceleration value, the faster the algorithm, but also the lesser the compression.
It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed. It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed.
An acceleration value of "1" is the same as regular LZ4_compress_default() An acceleration value of "1" is the same as regular LZ4_compress_default()
Values <= 0 will be replaced by ACCELERATION_DEFAULT (currently == 1, see lz4.c). Values <= 0 will be replaced by LZ4_ACCELERATION_DEFAULT (currently == 1, see lz4.c).
Values > LZ4_ACCELERATION_MAX will be replaced by LZ4_ACCELERATION_MAX (currently == 65537, see lz4.c).
*/ */
LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration); LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);