hist.h
92 lines
| 4.2 KiB
| text/x-c
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CLexer
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r40157 | /* ****************************************************************** | ||
hist : Histogram functions | ||||
part of Finite State Entropy project | ||||
Copyright (C) 2013-present, Yann Collet. | ||||
BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php) | ||||
Redistribution and use in source and binary forms, with or without | ||||
modification, are permitted provided that the following conditions are | ||||
met: | ||||
* Redistributions of source code must retain the above copyright | ||||
notice, this list of conditions and the following disclaimer. | ||||
* Redistributions in binary form must reproduce the above | ||||
copyright notice, this list of conditions and the following disclaimer | ||||
in the documentation and/or other materials provided with the | ||||
distribution. | ||||
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | ||||
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | ||||
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | ||||
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | ||||
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | ||||
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | ||||
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | ||||
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | ||||
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | ||||
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | ||||
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | ||||
You can contact the author at : | ||||
- FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy | ||||
- Public forum : https://groups.google.com/forum/#!forum/lz4c | ||||
****************************************************************** */ | ||||
/* --- 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 | ||||
/** 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` must be a table of unsigned of size >= HIST_WKSP_SIZE_U32 | ||||
*/ | ||||
size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr, | ||||
const void* src, size_t srcSize, | ||||
unsigned* workSpace); | ||||
/** 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` must be a table of unsigned of size >= HIST_WKSP_SIZE_U32 | ||||
*/ | ||||
size_t HIST_countFast_wksp(unsigned* count, unsigned* maxSymbolValuePtr, | ||||
const void* src, size_t srcSize, | ||||
unsigned* workSpace); | ||||
/*! 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); | ||||