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