/* ****************************************************************** * hist : Histogram functions * part of Finite State Entropy project * Copyright (c) 2013-2020, Yann Collet, Facebook, Inc. * * You can contact the author at : * - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy * - Public forum : https://groups.google.com/forum/#!forum/lz4c * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses. ****************************************************************** */ /* --- dependencies --- */ #include <stddef.h> /* size_t */ /* --- simple histogram functions --- */ /*! HIST_count(): * Provides the precise count of each byte within a table 'count'. * 'count' is a table of unsigned int, of minimum size (*maxSymbolValuePtr+1). * Updates *maxSymbolValuePtr with actual largest symbol value detected. * @return : count of the most frequent symbol (which isn't identified). * or an error code, which can be tested using HIST_isError(). * note : if return == srcSize, there is only one symbol. */ size_t HIST_count(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize); unsigned HIST_isError(size_t code); /**< tells if a return value is an error code */ /* --- advanced histogram functions --- */ #define HIST_WKSP_SIZE_U32 1024 #define HIST_WKSP_SIZE (HIST_WKSP_SIZE_U32 * sizeof(unsigned)) /** HIST_count_wksp() : * Same as HIST_count(), but using an externally provided scratch buffer. * Benefit is this function will use very little stack space. * `workSpace` is a writable buffer which must be 4-bytes aligned, * `workSpaceSize` must be >= HIST_WKSP_SIZE */ size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, void* workSpace, size_t workSpaceSize); /** HIST_countFast() : * same as HIST_count(), but blindly trusts that all byte values within src are <= *maxSymbolValuePtr. * This function is unsafe, and will segfault if any value within `src` is `> *maxSymbolValuePtr` */ size_t HIST_countFast(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize); /** HIST_countFast_wksp() : * Same as HIST_countFast(), but using an externally provided scratch buffer. * `workSpace` is a writable buffer which must be 4-bytes aligned, * `workSpaceSize` must be >= HIST_WKSP_SIZE */ size_t HIST_countFast_wksp(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, void* workSpace, size_t workSpaceSize); /*! HIST_count_simple() : * Same as HIST_countFast(), this function is unsafe, * and will segfault if any value within `src` is `> *maxSymbolValuePtr`. * It is also a bit slower for large inputs. * However, it does not need any additional memory (not even on stack). * @return : count of the most frequent symbol. * Note this function doesn't produce any error (i.e. it must succeed). */ unsigned HIST_count_simple(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize); |