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bundle2: implement consume() API on unbundlepart...
bundle2: implement consume() API on unbundlepart We want bundle parts to not be seekable by default. That means eliminating the generic seek() method. A common pattern in bundle2.py is to seek to the end of the part data. This is mainly used by the part iteration code to ensure the underlying stream is advanced to the next bundle part. In this commit, we establish a dedicated API for consuming a bundle2 part data. We switch users of seek() to it. The old implementation of seek(0, os.SEEK_END) would effectively call self.read(). The new implementation calls self.read(32768) in a loop. The old implementation would therefore assemble a buffer to hold all remaining data being seeked over. For seeking over large bundle parts, this would involve a large allocation and a lot of overhead to collect intermediate data! This overhead can be seen in the results for `hg perfbundleread`: ! bundle2 iterparts() ! wall 10.891305 comb 10.820000 user 7.990000 sys 2.830000 (best of 3) ! wall 8.070791 comb 8.060000 user 7.180000 sys 0.880000 (best of 3) ! bundle2 part seek() ! wall 12.991478 comb 10.390000 user 7.720000 sys 2.670000 (best of 3) ! wall 10.370142 comb 10.350000 user 7.430000 sys 2.920000 (best of 3) Of course, skipping over large payload data isn't likely very common. So I doubt the performance wins will be observed in the wild. Differential Revision: https://phab.mercurial-scm.org/D1388

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zstdmt_compress.h
78 lines | 3.5 KiB | text/x-c | CLexer
/**
* Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#ifndef ZSTDMT_COMPRESS_H
#define ZSTDMT_COMPRESS_H
#if defined (__cplusplus)
extern "C" {
#endif
/* Note : All prototypes defined in this file shall be considered experimental.
* There is no guarantee of API continuity (yet) on any of these prototypes */
/* === Dependencies === */
#include <stddef.h> /* size_t */
#define ZSTD_STATIC_LINKING_ONLY /* ZSTD_parameters */
#include "zstd.h" /* ZSTD_inBuffer, ZSTD_outBuffer, ZSTDLIB_API */
/* === Simple one-pass functions === */
typedef struct ZSTDMT_CCtx_s ZSTDMT_CCtx;
ZSTDLIB_API ZSTDMT_CCtx* ZSTDMT_createCCtx(unsigned nbThreads);
ZSTDLIB_API size_t ZSTDMT_freeCCtx(ZSTDMT_CCtx* cctx);
ZSTDLIB_API size_t ZSTDMT_compressCCtx(ZSTDMT_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
int compressionLevel);
/* === Streaming functions === */
ZSTDLIB_API size_t ZSTDMT_initCStream(ZSTDMT_CCtx* mtctx, int compressionLevel);
ZSTDLIB_API size_t ZSTDMT_resetCStream(ZSTDMT_CCtx* mtctx, unsigned long long pledgedSrcSize); /**< pledgedSrcSize is optional and can be zero == unknown */
ZSTDLIB_API size_t ZSTDMT_compressStream(ZSTDMT_CCtx* mtctx, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
ZSTDLIB_API size_t ZSTDMT_flushStream(ZSTDMT_CCtx* mtctx, ZSTD_outBuffer* output); /**< @return : 0 == all flushed; >0 : still some data to be flushed; or an error code (ZSTD_isError()) */
ZSTDLIB_API size_t ZSTDMT_endStream(ZSTDMT_CCtx* mtctx, ZSTD_outBuffer* output); /**< @return : 0 == all flushed; >0 : still some data to be flushed; or an error code (ZSTD_isError()) */
/* === Advanced functions and parameters === */
#ifndef ZSTDMT_SECTION_SIZE_MIN
# define ZSTDMT_SECTION_SIZE_MIN (1U << 20) /* 1 MB - Minimum size of each compression job */
#endif
ZSTDLIB_API size_t ZSTDMT_initCStream_advanced(ZSTDMT_CCtx* mtctx, const void* dict, size_t dictSize, /**< dict can be released after init, a local copy is preserved within zcs */
ZSTD_parameters params, unsigned long long pledgedSrcSize); /**< pledgedSrcSize is optional and can be zero == unknown */
/* ZSDTMT_parameter :
* List of parameters that can be set using ZSTDMT_setMTCtxParameter() */
typedef enum {
ZSTDMT_p_sectionSize, /* size of input "section". Each section is compressed in parallel. 0 means default, which is dynamically determined within compression functions */
ZSTDMT_p_overlapSectionLog /* Log of overlapped section; 0 == no overlap, 6(default) == use 1/8th of window, >=9 == use full window */
} ZSDTMT_parameter;
/* ZSTDMT_setMTCtxParameter() :
* allow setting individual parameters, one at a time, among a list of enums defined in ZSTDMT_parameter.
* The function must be called typically after ZSTD_createCCtx().
* Parameters not explicitly reset by ZSTDMT_init*() remain the same in consecutive compression sessions.
* @return : 0, or an error code (which can be tested using ZSTD_isError()) */
ZSTDLIB_API size_t ZSTDMT_setMTCtxParameter(ZSTDMT_CCtx* mtctx, ZSDTMT_parameter parameter, unsigned value);
#if defined (__cplusplus)
}
#endif
#endif /* ZSTDMT_COMPRESS_H */