libavutil/intmath.h
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00001 /*
00002  * Copyright (c) 2010 Mans Rullgard <mans@mansr.com>
00003  *
00004  * This file is part of Libav.
00005  *
00006  * Libav is free software; you can redistribute it and/or
00007  * modify it under the terms of the GNU Lesser General Public
00008  * License as published by the Free Software Foundation; either
00009  * version 2.1 of the License, or (at your option) any later version.
00010  *
00011  * Libav is distributed in the hope that it will be useful,
00012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014  * Lesser General Public License for more details.
00015  *
00016  * You should have received a copy of the GNU Lesser General Public
00017  * License along with Libav; if not, write to the Free Software
00018  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00019  */
00020 
00021 #ifndef AVUTIL_INTMATH_H
00022 #define AVUTIL_INTMATH_H
00023 
00024 #include <stdint.h>
00025 #include "config.h"
00026 #include "attributes.h"
00027 
00033 extern const uint32_t ff_inverse[257];
00034 
00035 #if   ARCH_ARM
00036 #   include "arm/intmath.h"
00037 #elif ARCH_X86
00038 #   include "x86/intmath.h"
00039 #endif
00040 
00041 #if HAVE_FAST_CLZ && AV_GCC_VERSION_AT_LEAST(3,4)
00042 
00043 #ifndef av_log2
00044 #   define av_log2(x) (31 - __builtin_clz((x)|1))
00045 #   ifndef av_log2_16bit
00046 #      define av_log2_16bit av_log2
00047 #   endif
00048 #endif /* av_log2 */
00049 
00050 #endif /* AV_GCC_VERSION_AT_LEAST(3,4) */
00051 
00052 #ifndef FASTDIV
00053 #   if CONFIG_FASTDIV
00054 #       define FASTDIV(a,b) ((uint32_t)((((uint64_t)a) * ff_inverse[b]) >> 32))
00055 #   else
00056 #       define FASTDIV(a,b) ((a) / (b))
00057 #   endif
00058 #endif /* FASTDIV */
00059 
00060 #include "common.h"
00061 
00062 extern const uint8_t ff_sqrt_tab[256];
00063 
00064 static inline av_const unsigned int ff_sqrt(unsigned int a)
00065 {
00066     unsigned int b;
00067 
00068     if (a < 255) return (ff_sqrt_tab[a + 1] - 1) >> 4;
00069     else if (a < (1 << 12)) b = ff_sqrt_tab[a >> 4] >> 2;
00070 #if !CONFIG_SMALL
00071     else if (a < (1 << 14)) b = ff_sqrt_tab[a >> 6] >> 1;
00072     else if (a < (1 << 16)) b = ff_sqrt_tab[a >> 8]   ;
00073 #endif
00074     else {
00075         int s = av_log2_16bit(a >> 16) >> 1;
00076         unsigned int c = a >> (s + 2);
00077         b = ff_sqrt_tab[c >> (s + 8)];
00078         b = FASTDIV(c,b) + (b << s);
00079     }
00080 
00081     return b - (a < b * b);
00082 }
00083 
00087 #endif /* AVUTIL_INTMATH_H */