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bundle2: extract logic for seeking bundle2 part into own class...
bundle2: extract logic for seeking bundle2 part into own class Currently, unbundlepart classes support bi-directional seeking. Most consumers of unbundlepart only ever seek forward - typically as part of moving to the end of the bundle part so they can move on to the next one. But regardless of the actual usage of the part, instances maintain an index mapping offsets within the underlying raw payload to offsets within the decoded payload. Maintaining the mapping of offset data can be expensive in terms of memory use. Furthermore, many bundle2 consumers don't have access to an underlying seekable stream. This includes all compressed bundles. So maintaining offset data when the underlying stream can't be seeked anyway is wasteful. And since many bundle2 streams can't be seeked, it seems like a bad idea to expose a seek API in bundle2 parts by default. If you provide them, people will attempt to use them. Seekable bundle2 parts should be the exception, not the rule. This commit starts the process dividing unbundlepart into 2 classes: a base class that supports linear, one-time reads and a child class that supports bi-directional seeking. In this first commit, we split various methods and attributes out into a new "seekableunbundlepart" class. Previous instantiators of "unbundlepart" now instantiate "seekableunbundlepart." This preserves backwards compatibility. The coupling between the classes is still tight: "unbundlepart" cannot be used on its own. This will be addressed in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D1386
Gregory Szorc - - Load All Authors

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zdict.h
201 lines | 10.5 KiB | text/x-c | CLexer
/ contrib / python-zstandard / zstd / dictBuilder / zdict.h
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/**
* 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 DICTBUILDER_H_001
#define DICTBUILDER_H_001
#if defined (__cplusplus)
extern "C" {
#endif
/*====== Dependencies ======*/
#include <stddef.h> /* size_t */
/* ===== ZDICTLIB_API : control library symbols visibility ===== */
#if defined(__GNUC__) && (__GNUC__ >= 4)
# define ZDICTLIB_VISIBILITY __attribute__ ((visibility ("default")))
#else
# define ZDICTLIB_VISIBILITY
#endif
#if defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
# define ZDICTLIB_API __declspec(dllexport) ZDICTLIB_VISIBILITY
#elif defined(ZSTD_DLL_IMPORT) && (ZSTD_DLL_IMPORT==1)
# define ZDICTLIB_API __declspec(dllimport) ZDICTLIB_VISIBILITY /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
#else
# define ZDICTLIB_API ZDICTLIB_VISIBILITY
#endif
/*! ZDICT_trainFromBuffer() :
Train a dictionary from an array of samples.
Samples must be stored concatenated in a single flat buffer `samplesBuffer`,
supplied with an array of sizes `samplesSizes`, providing the size of each sample, in order.
The resulting dictionary will be saved into `dictBuffer`.
@return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
or an error code, which can be tested with ZDICT_isError().
Tips : In general, a reasonable dictionary has a size of ~ 100 KB.
It's obviously possible to target smaller or larger ones, just by specifying different `dictBufferCapacity`.
In general, it's recommended to provide a few thousands samples, but this can vary a lot.
It's recommended that total size of all samples be about ~x100 times the target size of dictionary.
*/
ZDICTLIB_API size_t ZDICT_trainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples);
/*====== Helper functions ======*/
ZDICTLIB_API unsigned ZDICT_getDictID(const void* dictBuffer, size_t dictSize); /**< extracts dictID; @return zero if error (not a valid dictionary) */
ZDICTLIB_API unsigned ZDICT_isError(size_t errorCode);
ZDICTLIB_API const char* ZDICT_getErrorName(size_t errorCode);
#ifdef ZDICT_STATIC_LINKING_ONLY
/* ====================================================================================
* The definitions in this section are considered experimental.
* They should never be used with a dynamic library, as they may change in the future.
* They are provided for advanced usages.
* Use them only in association with static linking.
* ==================================================================================== */
typedef struct {
unsigned selectivityLevel; /* 0 means default; larger => select more => larger dictionary */
int compressionLevel; /* 0 means default; target a specific zstd compression level */
unsigned notificationLevel; /* Write to stderr; 0 = none (default); 1 = errors; 2 = progression; 3 = details; 4 = debug; */
unsigned dictID; /* 0 means auto mode (32-bits random value); other : force dictID value */
unsigned reserved[2]; /* reserved space for future parameters */
} ZDICT_params_t;
/*! ZDICT_trainFromBuffer_advanced() :
Same as ZDICT_trainFromBuffer() with control over more parameters.
`parameters` is optional and can be provided with values set to 0 to mean "default".
@return : size of dictionary stored into `dictBuffer` (<= `dictBufferSize`),
or an error code, which can be tested by ZDICT_isError().
note : ZDICT_trainFromBuffer_advanced() will send notifications into stderr if instructed to, using notificationLevel>0.
*/
ZDICTLIB_API size_t ZDICT_trainFromBuffer_advanced(void* dictBuffer, size_t dictBufferCapacity,
const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
ZDICT_params_t parameters);
/*! COVER_params_t :
For all values 0 means default.
kMin and d are the only required parameters.
*/
typedef struct {
unsigned k; /* Segment size : constraint: 0 < k : Reasonable range [16, 2048+] */
unsigned d; /* dmer size : constraint: 0 < d <= k : Reasonable range [6, 16] */
unsigned steps; /* Number of steps : Only used for optimization : 0 means default (32) : Higher means more parameters checked */
unsigned nbThreads; /* Number of threads : constraint: 0 < nbThreads : 1 means single-threaded : Only used for optimization : Ignored if ZSTD_MULTITHREAD is not defined */
unsigned notificationLevel; /* Write to stderr; 0 = none (default); 1 = errors; 2 = progression; 3 = details; 4 = debug; */
unsigned dictID; /* 0 means auto mode (32-bits random value); other : force dictID value */
int compressionLevel; /* 0 means default; target a specific zstd compression level */
} COVER_params_t;
/*! COVER_trainFromBuffer() :
Train a dictionary from an array of samples using the COVER algorithm.
Samples must be stored concatenated in a single flat buffer `samplesBuffer`,
supplied with an array of sizes `samplesSizes`, providing the size of each sample, in order.
The resulting dictionary will be saved into `dictBuffer`.
@return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
or an error code, which can be tested with ZDICT_isError().
Note : COVER_trainFromBuffer() requires about 9 bytes of memory for each input byte.
Tips : In general, a reasonable dictionary has a size of ~ 100 KB.
It's obviously possible to target smaller or larger ones, just by specifying different `dictBufferCapacity`.
In general, it's recommended to provide a few thousands samples, but this can vary a lot.
It's recommended that total size of all samples be about ~x100 times the target size of dictionary.
*/
ZDICTLIB_API size_t COVER_trainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
COVER_params_t parameters);
/*! COVER_optimizeTrainFromBuffer() :
The same requirements as above hold for all the parameters except `parameters`.
This function tries many parameter combinations and picks the best parameters.
`*parameters` is filled with the best parameters found, and the dictionary
constructed with those parameters is stored in `dictBuffer`.
All of the parameters d, k, steps are optional.
If d is non-zero then we don't check multiple values of d, otherwise we check d = {6, 8, 10, 12, 14, 16}.
if steps is zero it defaults to its default value.
If k is non-zero then we don't check multiple values of k, otherwise we check steps values in [16, 2048].
@return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
or an error code, which can be tested with ZDICT_isError().
On success `*parameters` contains the parameters selected.
Note : COVER_optimizeTrainFromBuffer() requires about 8 bytes of memory for each input byte and additionally another 5 bytes of memory for each byte of memory for each thread.
*/
ZDICTLIB_API size_t COVER_optimizeTrainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
const void* samplesBuffer, const size_t *samplesSizes, unsigned nbSamples,
COVER_params_t *parameters);
/*! ZDICT_finalizeDictionary() :
Given a custom content as a basis for dictionary, and a set of samples,
finalize dictionary by adding headers and statistics.
Samples must be stored concatenated in a flat buffer `samplesBuffer`,
supplied with an array of sizes `samplesSizes`, providing the size of each sample in order.
dictContentSize must be > ZDICT_CONTENTSIZE_MIN bytes.
maxDictSize must be >= dictContentSize, and must be > ZDICT_DICTSIZE_MIN bytes.
@return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`),
or an error code, which can be tested by ZDICT_isError().
note : ZDICT_finalizeDictionary() will push notifications into stderr if instructed to, using notificationLevel>0.
note 2 : dictBuffer and customDictContent can overlap
*/
#define ZDICT_CONTENTSIZE_MIN 256
#define ZDICT_DICTSIZE_MIN 512
ZDICTLIB_API size_t ZDICT_finalizeDictionary(void* dictBuffer, size_t dictBufferCapacity,
const void* customDictContent, size_t dictContentSize,
const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
ZDICT_params_t parameters);
/* Deprecation warnings */
/* It is generally possible to disable deprecation warnings from compiler,
for example with -Wno-deprecated-declarations for gcc
or _CRT_SECURE_NO_WARNINGS in Visual.
Otherwise, it's also possible to manually define ZDICT_DISABLE_DEPRECATE_WARNINGS */
#ifdef ZDICT_DISABLE_DEPRECATE_WARNINGS
# define ZDICT_DEPRECATED(message) ZDICTLIB_API /* disable deprecation warnings */
#else
# define ZDICT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
# if defined (__cplusplus) && (__cplusplus >= 201402) /* C++14 or greater */
# define ZDICT_DEPRECATED(message) ZDICTLIB_API [[deprecated(message)]]
# elif (ZDICT_GCC_VERSION >= 405) || defined(__clang__)
# define ZDICT_DEPRECATED(message) ZDICTLIB_API __attribute__((deprecated(message)))
# elif (ZDICT_GCC_VERSION >= 301)
# define ZDICT_DEPRECATED(message) ZDICTLIB_API __attribute__((deprecated))
# elif defined(_MSC_VER)
# define ZDICT_DEPRECATED(message) ZDICTLIB_API __declspec(deprecated(message))
# else
# pragma message("WARNING: You need to implement ZDICT_DEPRECATED for this compiler")
# define ZDICT_DEPRECATED(message) ZDICTLIB_API
# endif
#endif /* ZDICT_DISABLE_DEPRECATE_WARNINGS */
ZDICT_DEPRECATED("use ZDICT_finalizeDictionary() instead")
size_t ZDICT_addEntropyTablesFromBuffer(void* dictBuffer, size_t dictContentSize, size_t dictBufferCapacity,
const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples);
#endif /* ZDICT_STATIC_LINKING_ONLY */
#if defined (__cplusplus)
}
#endif
#endif /* DICTBUILDER_H_001 */