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145 lines
3.4 KiB
C
145 lines
3.4 KiB
C
/* libFLAC - Free Lossless Audio Codec library
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* Copyright (C) 2001,2002,2003,2004,2005 Josh Coalson
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*
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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
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* are met:
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*
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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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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* - Neither the name of the Xiph.org Foundation nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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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 FOUNDATION OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "private/bitmath.h"
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#include "FLAC/assert.h"
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/* An example of what FLAC__bitmath_ilog2() computes:
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*
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* ilog2( 0) = assertion failure
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* ilog2( 1) = 0
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* ilog2( 2) = 1
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* ilog2( 3) = 1
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* ilog2( 4) = 2
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* ilog2( 5) = 2
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* ilog2( 6) = 2
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* ilog2( 7) = 2
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* ilog2( 8) = 3
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* ilog2( 9) = 3
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* ilog2(10) = 3
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* ilog2(11) = 3
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* ilog2(12) = 3
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* ilog2(13) = 3
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* ilog2(14) = 3
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* ilog2(15) = 3
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* ilog2(16) = 4
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* ilog2(17) = 4
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* ilog2(18) = 4
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*/
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unsigned FLAC__bitmath_ilog2(FLAC__uint32 v)
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{
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unsigned l = 0;
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FLAC__ASSERT(v > 0);
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while(v >>= 1)
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l++;
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return l;
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}
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unsigned FLAC__bitmath_ilog2_wide(FLAC__uint64 v)
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{
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unsigned l = 0;
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FLAC__ASSERT(v > 0);
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while(v >>= 1)
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l++;
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return l;
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}
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/* An example of what FLAC__bitmath_silog2() computes:
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*
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* silog2(-10) = 5
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* silog2(- 9) = 5
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* silog2(- 8) = 4
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* silog2(- 7) = 4
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* silog2(- 6) = 4
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* silog2(- 5) = 4
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* silog2(- 4) = 3
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* silog2(- 3) = 3
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* silog2(- 2) = 2
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* silog2(- 1) = 2
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* silog2( 0) = 0
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* silog2( 1) = 2
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* silog2( 2) = 3
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* silog2( 3) = 3
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* silog2( 4) = 4
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* silog2( 5) = 4
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* silog2( 6) = 4
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* silog2( 7) = 4
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* silog2( 8) = 5
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* silog2( 9) = 5
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* silog2( 10) = 5
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*/
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unsigned FLAC__bitmath_silog2(int v)
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{
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while(1) {
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if(v == 0) {
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return 0;
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}
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else if(v > 0) {
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unsigned l = 0;
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while(v) {
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l++;
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v >>= 1;
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}
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return l+1;
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}
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else if(v == -1) {
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return 2;
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}
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else {
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v++;
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v = -v;
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}
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}
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}
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unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v)
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{
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while(1) {
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if(v == 0) {
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return 0;
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}
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else if(v > 0) {
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unsigned l = 0;
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while(v) {
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l++;
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v >>= 1;
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}
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return l+1;
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}
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else if(v == -1) {
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return 2;
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}
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else {
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v++;
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v = -v;
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}
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}
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}
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