| /* libFLAC - Free Lossless Audio Codec library |
| * Copyright (C) 2001,2002 Josh Coalson |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Library General Public |
| * License as published by the Free Software Foundation; either |
| * version 2 of the License, or (at your option) any later version. |
| * |
| * This library is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Library General Public License for more details. |
| * |
| * You should have received a copy of the GNU Library General Public |
| * License along with this library; if not, write to the |
| * Free Software Foundation, Inc., 59 Temple Place - Suite 330, |
| * Boston, MA 02111-1307, USA. |
| */ |
| |
| #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; |
| } |
| } |
| } |