ref: 985b2457cda207c2c65edeb647aedbb6e92dac46
dir: /sys/src/cmd/audio/libFLAC/bitmath.c/
/* libFLAC - Free Lossless Audio Codec library
* Copyright (C) 2001,2002,2003,2004 Josh Coalson
*
* 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.
*
* - Neither the name of the Xiph.org Foundation nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* 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 FOUNDATION 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.
*/
#include "private/bitmath.h"
#include "FLAC/assert.h"
/* An example of what FLAC__bitmath_ilog2() computes:
*
* ilog2( 0) = assertion failure
* ilog2( 1) = 0
* ilog2( 2) = 1
* ilog2( 3) = 1
* ilog2( 4) = 2
* ilog2( 5) = 2
* ilog2( 6) = 2
* ilog2( 7) = 2
* ilog2( 8) = 3
* ilog2( 9) = 3
* ilog2(10) = 3
* ilog2(11) = 3
* ilog2(12) = 3
* ilog2(13) = 3
* ilog2(14) = 3
* ilog2(15) = 3
* ilog2(16) = 4
* ilog2(17) = 4
* ilog2(18) = 4
*/
unsigned FLAC__bitmath_ilog2(unsigned v)
{
unsigned l = 0;
FLAC__ASSERT(v > 0);
while(v >>= 1)
l++;
return l;
}
/* An example of what FLAC__bitmath_silog2() computes:
*
* silog2(-10) = 5
* silog2(- 9) = 5
* silog2(- 8) = 4
* silog2(- 7) = 4
* silog2(- 6) = 4
* silog2(- 5) = 4
* silog2(- 4) = 3
* silog2(- 3) = 3
* silog2(- 2) = 2
* silog2(- 1) = 2
* silog2( 0) = 0
* silog2( 1) = 2
* silog2( 2) = 3
* silog2( 3) = 3
* silog2( 4) = 4
* silog2( 5) = 4
* silog2( 6) = 4
* silog2( 7) = 4
* silog2( 8) = 5
* silog2( 9) = 5
* silog2( 10) = 5
*/
unsigned FLAC__bitmath_silog2(int v)
{
while(1) {
if(v == 0) {
return 0;
}
else if(v > 0) {
unsigned l = 0;
while(v) {
l++;
v >>= 1;
}
return l+1;
}
else if(v == -1) {
return 2;
}
else {
v++;
v = -v;
}
}
}
unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v)
{
while(1) {
if(v == 0) {
return 0;
}
else if(v > 0) {
unsigned l = 0;
while(v) {
l++;
v >>= 1;
}
return l+1;
}
else if(v == -1) {
return 2;
}
else {
v++;
v = -v;
}
}
}