bitmath.c

00001 /* libFLAC - Free Lossless Audio Codec library
00002  * Copyright (C) 2001-2009  Josh Coalson
00003  * Copyright (C) 2011-2014  Xiph.Org Foundation
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions
00007  * are met:
00008  *
00009  * - Redistributions of source code must retain the above copyright
00010  * notice, this list of conditions and the following disclaimer.
00011  *
00012  * - Redistributions in binary form must reproduce the above copyright
00013  * notice, this list of conditions and the following disclaimer in the
00014  * documentation and/or other materials provided with the distribution.
00015  *
00016  * - Neither the name of the Xiph.org Foundation nor the names of its
00017  * contributors may be used to endorse or promote products derived from
00018  * this software without specific prior written permission.
00019  *
00020  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00021  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00022  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
00023  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
00024  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00025  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
00026  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
00027  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
00028  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00029  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00030  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00031  */
00032 
00033 #ifdef HAVE_CONFIG_H
00034 #  include <config.h>
00035 #endif
00036 
00037 #include "private/bitmath.h"
00038 
00039 /* An example of what FLAC__bitmath_silog2() computes:
00040  *
00041  * silog2(-10) = 5
00042  * silog2(- 9) = 5
00043  * silog2(- 8) = 4
00044  * silog2(- 7) = 4
00045  * silog2(- 6) = 4
00046  * silog2(- 5) = 4
00047  * silog2(- 4) = 3
00048  * silog2(- 3) = 3
00049  * silog2(- 2) = 2
00050  * silog2(- 1) = 2
00051  * silog2(  0) = 0
00052  * silog2(  1) = 2
00053  * silog2(  2) = 3
00054  * silog2(  3) = 3
00055  * silog2(  4) = 4
00056  * silog2(  5) = 4
00057  * silog2(  6) = 4
00058  * silog2(  7) = 4
00059  * silog2(  8) = 5
00060  * silog2(  9) = 5
00061  * silog2( 10) = 5
00062  */
00063 unsigned FLAC__bitmath_silog2(int v)
00064 {
00065     while(1) {
00066         if(v == 0) {
00067             return 0;
00068         }
00069         else if(v > 0) {
00070             unsigned l = 0;
00071             while(v) {
00072                 l++;
00073                 v >>= 1;
00074             }
00075             return l+1;
00076         }
00077         else if(v == -1) {
00078             return 2;
00079         }
00080         else {
00081             v++;
00082             v = -v;
00083         }
00084     }
00085 }
00086 
00087 unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v)
00088 {
00089     while(1) {
00090         if(v == 0) {
00091             return 0;
00092         }
00093         else if(v > 0) {
00094             unsigned l = 0;
00095             while(v) {
00096                 l++;
00097                 v >>= 1;
00098             }
00099             return l+1;
00100         }
00101         else if(v == -1) {
00102             return 2;
00103         }
00104         else {
00105             v++;
00106             v = -v;
00107         }
00108     }
00109 }