diff options
Diffstat (limited to 'lib/zstd.h')
| -rw-r--r-- | lib/zstd.h | 49 |
1 files changed, 32 insertions, 17 deletions
@@ -262,9 +262,9 @@ ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); /* accept NULL pointer * /*! ZSTD_compressCCtx() : * Same as ZSTD_compress(), using an explicit ZSTD_CCtx. - * Important : in order to behave similarly to `ZSTD_compress()`, - * this function compresses at requested compression level, - * __ignoring any other parameter__ . + * Important : in order to mirror `ZSTD_compress()` behavior, + * this function compresses at the requested compression level, + * __ignoring any other advanced parameter__ . * If any advanced parameter was set using the advanced API, * they will all be reset. Only `compressionLevel` remains. */ @@ -286,7 +286,7 @@ ZSTDLIB_API size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); /* accept NULL pointer * /*! ZSTD_decompressDCtx() : * Same as ZSTD_decompress(), * requires an allocated ZSTD_DCtx. - * Compatible with sticky parameters. + * Compatible with sticky parameters (see below). */ ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, @@ -302,12 +302,12 @@ ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, * using ZSTD_CCtx_set*() functions. * Pushed parameters are sticky : they are valid for next compressed frame, and any subsequent frame. * "sticky" parameters are applicable to `ZSTD_compress2()` and `ZSTD_compressStream*()` ! - * __They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()__ . + * __They do not apply to one-shot variants such as ZSTD_compressCCtx()__ . * * It's possible to reset all parameters to "default" using ZSTD_CCtx_reset(). * * This API supersedes all other "advanced" API entry points in the experimental section. - * In the future, we expect to remove from experimental API entry points which are redundant with this API. + * In the future, we expect to remove API entry points from experimental which are redundant with this API. */ @@ -390,16 +390,19 @@ typedef enum { * The higher the value of selected strategy, the more complex it is, * resulting in stronger and slower compression. * Special: value 0 means "use default strategy". */ - ZSTD_c_targetCBlockSize=130, /* Tries to fit compressed block size to be - * around targetCBlockSize. No target when - * targetCBlockSize == 0. There is no guarantee - * on compressed block size (default:0). - * Since the decoder has to buffer a complete - * block to begin decoding it, in low band- - * width streaming environments this may - * improve end-to-end latency. Bound by - * ZSTD_TARGETCBLOCKSIZE_MIN and - * ZSTD_TARGETCBLOCKSIZE_MAX. */ + + ZSTD_c_targetCBlockSize=130, /* v1.5.6+ + * Attempts to fit compressed block size into approximatively targetCBlockSize. + * Bound by ZSTD_TARGETCBLOCKSIZE_MIN and ZSTD_TARGETCBLOCKSIZE_MAX. + * Note that it's not a guarantee, just a convergence target (default:0). + * No target when targetCBlockSize == 0. + * This is helpful in low bandwidth streaming environments to improve end-to-end latency, + * when a client can make use of partial documents (a prominent example being Chrome). + * Note: this parameter is stable since v1.5.6. + * It was present as an experimental parameter in earlier versions, + * but it's not recommended using it with earlier library versions + * due to massive performance regressions. + */ /* LDM mode parameters */ ZSTD_c_enableLongDistanceMatching=160, /* Enable long distance matching. * This parameter is designed to improve compression ratio @@ -584,6 +587,7 @@ ZSTDLIB_API size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); /*! ZSTD_compress2() : * Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. + * (note that this entry point doesn't even expose a compression level parameter). * ZSTD_compress2() always starts a new frame. * Should cctx hold data from a previously unfinished frame, everything about it is forgotten. * - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() @@ -787,6 +791,11 @@ typedef enum { * only ZSTD_e_end or ZSTD_e_flush operations are allowed. * Before starting a new compression job, or changing compression parameters, * it is required to fully flush internal buffers. + * - note: if an operation ends with an error, it may leave @cctx in an undefined state. + * Therefore, it's UB to invoke ZSTD_compressStream2() of ZSTD_compressStream() on such a state. + * In order to be re-employed after an error, a state must be reset, + * which can be done explicitly (ZSTD_CCtx_reset()), + * or is sometimes implied by methods starting a new compression job (ZSTD_initCStream(), ZSTD_compressCCtx()) */ ZSTDLIB_API size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, ZSTD_outBuffer* output, @@ -900,6 +909,12 @@ ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds); * @return : 0 when a frame is completely decoded and fully flushed, * or an error code, which can be tested using ZSTD_isError(), * or any other value > 0, which means there is some decoding or flushing to do to complete current frame. + * + * Note: when an operation returns with an error code, the @zds state may be left in undefined state. + * It's UB to invoke `ZSTD_decompressStream()` on such a state. + * In order to re-use such a state, it must be first reset, + * which can be done explicitly (`ZSTD_DCtx_reset()`), + * or is implied for operations starting some new decompression job (`ZSTD_initDStream`, `ZSTD_decompressDCtx()`, `ZSTD_decompress_usingDict()`) */ ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); @@ -1250,7 +1265,7 @@ ZSTDLIB_API size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); #define ZSTD_LDM_HASHRATELOG_MAX (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN) /* Advanced parameter bounds */ -#define ZSTD_TARGETCBLOCKSIZE_MIN 64 +#define ZSTD_TARGETCBLOCKSIZE_MIN 1340 /* suitable to fit into an ethernet / wifi / 4G transport frame */ #define ZSTD_TARGETCBLOCKSIZE_MAX ZSTD_BLOCKSIZE_MAX #define ZSTD_SRCSIZEHINT_MIN 0 #define ZSTD_SRCSIZEHINT_MAX INT_MAX |