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      1 /* libFLAC - Free Lossless Audio Codec library
      2  * Copyright (C) 2001-2009  Josh Coalson
      3  * Copyright (C) 2011-2014  Xiph.Org Foundation
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *
      9  * - Redistributions of source code must retain the above copyright
     10  * notice, this list of conditions and the following disclaimer.
     11  *
     12  * - Redistributions in binary form must reproduce the above copyright
     13  * notice, this list of conditions and the following disclaimer in the
     14  * documentation and/or other materials provided with the distribution.
     15  *
     16  * - Neither the name of the Xiph.org Foundation nor the names of its
     17  * contributors may be used to endorse or promote products derived from
     18  * this software without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     23  * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
     24  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     26  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     27  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     28  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     29  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     30  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     31  */
     32 
     33 #ifdef HAVE_CONFIG_H
     34 #  include <config.h>
     35 #endif
     36 
     37 #include "private/bitmath.h"
     38 
     39 /* An example of what FLAC__bitmath_silog2() computes:
     40  *
     41  * silog2(-10) = 5
     42  * silog2(- 9) = 5
     43  * silog2(- 8) = 4
     44  * silog2(- 7) = 4
     45  * silog2(- 6) = 4
     46  * silog2(- 5) = 4
     47  * silog2(- 4) = 3
     48  * silog2(- 3) = 3
     49  * silog2(- 2) = 2
     50  * silog2(- 1) = 2
     51  * silog2(  0) = 0
     52  * silog2(  1) = 2
     53  * silog2(  2) = 3
     54  * silog2(  3) = 3
     55  * silog2(  4) = 4
     56  * silog2(  5) = 4
     57  * silog2(  6) = 4
     58  * silog2(  7) = 4
     59  * silog2(  8) = 5
     60  * silog2(  9) = 5
     61  * silog2( 10) = 5
     62  */
     63 unsigned FLAC__bitmath_silog2(int v)
     64 {
     65 	while(1) {
     66 		if(v == 0) {
     67 			return 0;
     68 		}
     69 		else if(v > 0) {
     70 			unsigned l = 0;
     71 			while(v) {
     72 				l++;
     73 				v >>= 1;
     74 			}
     75 			return l+1;
     76 		}
     77 		else if(v == -1) {
     78 			return 2;
     79 		}
     80 		else {
     81 			v++;
     82 			v = -v;
     83 		}
     84 	}
     85 }
     86 
     87 unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v)
     88 {
     89 	while(1) {
     90 		if(v == 0) {
     91 			return 0;
     92 		}
     93 		else if(v > 0) {
     94 			unsigned l = 0;
     95 			while(v) {
     96 				l++;
     97 				v >>= 1;
     98 			}
     99 			return l+1;
    100 		}
    101 		else if(v == -1) {
    102 			return 2;
    103 		}
    104 		else {
    105 			v++;
    106 			v = -v;
    107 		}
    108 	}
    109 }
    110