203 lines
8.3 KiB
C
203 lines
8.3 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-present, Yann Collet.
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BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above
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copyright notice, this list of conditions and the following disclaimer
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in the documentation and/or other materials provided with the
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distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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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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/* --- dependencies --- */
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#include "mem.h" /* U32, BYTE, etc. */
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#include "debug.h" /* assert, DEBUGLOG */
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#include "error_private.h" /* ERROR */
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#include "hist.h"
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/* --- Error management --- */
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unsigned HIST_isError(size_t code) { return ERR_isError(code); }
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/*-**************************************************************
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* Histogram functions
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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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{
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const BYTE* ip = (const BYTE*)src;
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const BYTE* const end = ip + srcSize;
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unsigned maxSymbolValue = *maxSymbolValuePtr;
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unsigned largestCount=0;
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memset(count, 0, (maxSymbolValue+1) * sizeof(*count));
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if (srcSize==0) { *maxSymbolValuePtr = 0; return 0; }
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while (ip<end) {
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assert(*ip <= maxSymbolValue);
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count[*ip++]++;
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}
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while (!count[maxSymbolValue]) maxSymbolValue--;
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*maxSymbolValuePtr = maxSymbolValue;
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{ U32 s;
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for (s=0; s<=maxSymbolValue; s++)
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if (count[s] > largestCount) largestCount = count[s];
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}
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return largestCount;
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}
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typedef enum { trustInput, checkMaxSymbolValue } HIST_checkInput_e;
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/* HIST_count_parallel_wksp() :
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* store histogram into 4 intermediate tables, recombined at the end.
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* this design makes better use of OoO cpus,
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* and is noticeably faster when some values are heavily repeated.
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* But it needs some additional workspace for intermediate tables.
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* `workSpace` size must be a table of size >= HIST_WKSP_SIZE_U32.
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* @return : largest histogram frequency,
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* or an error code (notably when histogram would be larger than *maxSymbolValuePtr). */
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static size_t HIST_count_parallel_wksp(
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unsigned* count, unsigned* maxSymbolValuePtr,
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const void* source, size_t sourceSize,
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HIST_checkInput_e check,
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U32* const workSpace)
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{
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const BYTE* ip = (const BYTE*)source;
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const BYTE* const iend = ip+sourceSize;
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unsigned maxSymbolValue = *maxSymbolValuePtr;
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unsigned max=0;
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U32* const Counting1 = workSpace;
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U32* const Counting2 = Counting1 + 256;
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U32* const Counting3 = Counting2 + 256;
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U32* const Counting4 = Counting3 + 256;
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memset(workSpace, 0, 4*256*sizeof(unsigned));
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/* safety checks */
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if (!sourceSize) {
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memset(count, 0, maxSymbolValue + 1);
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*maxSymbolValuePtr = 0;
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return 0;
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}
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if (!maxSymbolValue) maxSymbolValue = 255; /* 0 == default */
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/* by stripes of 16 bytes */
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{ U32 cached = MEM_read32(ip); ip += 4;
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while (ip < iend-15) {
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U32 c = cached; cached = MEM_read32(ip); ip += 4;
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Counting1[(BYTE) c ]++;
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Counting2[(BYTE)(c>>8) ]++;
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Counting3[(BYTE)(c>>16)]++;
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Counting4[ c>>24 ]++;
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c = cached; cached = MEM_read32(ip); ip += 4;
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Counting1[(BYTE) c ]++;
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Counting2[(BYTE)(c>>8) ]++;
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Counting3[(BYTE)(c>>16)]++;
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Counting4[ c>>24 ]++;
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c = cached; cached = MEM_read32(ip); ip += 4;
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Counting1[(BYTE) c ]++;
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Counting2[(BYTE)(c>>8) ]++;
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Counting3[(BYTE)(c>>16)]++;
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Counting4[ c>>24 ]++;
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c = cached; cached = MEM_read32(ip); ip += 4;
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Counting1[(BYTE) c ]++;
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Counting2[(BYTE)(c>>8) ]++;
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Counting3[(BYTE)(c>>16)]++;
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Counting4[ c>>24 ]++;
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}
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ip-=4;
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}
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/* finish last symbols */
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while (ip<iend) Counting1[*ip++]++;
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if (check) { /* verify stats will fit into destination table */
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U32 s; for (s=255; s>maxSymbolValue; s--) {
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Counting1[s] += Counting2[s] + Counting3[s] + Counting4[s];
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if (Counting1[s]) return ERROR(maxSymbolValue_tooSmall);
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} }
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{ U32 s;
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if (maxSymbolValue > 255) maxSymbolValue = 255;
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for (s=0; s<=maxSymbolValue; s++) {
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count[s] = Counting1[s] + Counting2[s] + Counting3[s] + Counting4[s];
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if (count[s] > max) max = count[s];
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} }
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while (!count[maxSymbolValue]) maxSymbolValue--;
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*maxSymbolValuePtr = maxSymbolValue;
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return (size_t)max;
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}
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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* source, size_t sourceSize,
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void* workSpace, size_t workSpaceSize)
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{
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if (sourceSize < 1500) /* heuristic threshold */
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return HIST_count_simple(count, maxSymbolValuePtr, source, sourceSize);
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if ((size_t)workSpace & 3) return ERROR(GENERIC); /* must be aligned on 4-bytes boundaries */
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if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
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return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, trustInput, (U32*)workSpace);
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}
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/* fast variant (unsafe : won't check if src contains values beyond count[] limit) */
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size_t HIST_countFast(unsigned* count, unsigned* maxSymbolValuePtr,
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const void* source, size_t sourceSize)
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{
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unsigned tmpCounters[HIST_WKSP_SIZE_U32];
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return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, tmpCounters, sizeof(tmpCounters));
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}
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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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* `workSpace` size must be table of >= HIST_WKSP_SIZE_U32 unsigned */
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size_t HIST_count_wksp(unsigned* count, unsigned* maxSymbolValuePtr,
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const void* source, size_t sourceSize,
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void* workSpace, size_t workSpaceSize)
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{
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if ((size_t)workSpace & 3) return ERROR(GENERIC); /* must be aligned on 4-bytes boundaries */
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if (workSpaceSize < HIST_WKSP_SIZE) return ERROR(workSpace_tooSmall);
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if (*maxSymbolValuePtr < 255)
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return HIST_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, checkMaxSymbolValue, (U32*)workSpace);
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*maxSymbolValuePtr = 255;
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return HIST_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, workSpace, workSpaceSize);
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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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{
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unsigned tmpCounters[HIST_WKSP_SIZE_U32];
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return HIST_count_wksp(count, maxSymbolValuePtr, src, srcSize, tmpCounters, sizeof(tmpCounters));
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}
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