diff options
Diffstat (limited to 'libavutil/adler32.c')
-rw-r--r-- | libavutil/adler32.c | 55 |
1 files changed, 49 insertions, 6 deletions
diff --git a/libavutil/adler32.c b/libavutil/adler32.c index 7f5afdbc40..579d022978 100644 --- a/libavutil/adler32.c +++ b/libavutil/adler32.c @@ -21,8 +21,19 @@ * 3. This notice may not be removed or altered from any source distribution. */ +/** + * @file + * Computes the Adler-32 checksum of a data stream + * + * This is a modified version based on adler32.c from the zlib library. + * @author Mark Adler + * @ingroup lavu_adler32 + */ + #include "config.h" #include "adler32.h" +#include "common.h" +#include "intreadwrite.h" #define BASE 65521L /* largest prime smaller than 65536 */ @@ -37,16 +48,46 @@ unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf, unsigned long s2 = adler >> 16; while (len > 0) { -#if CONFIG_SMALL +#if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL + unsigned len2 = FFMIN((len-1) & ~7, 23*8); + if (len2) { + uint64_t a1= 0; + uint64_t a2= 0; + uint64_t b1= 0; + uint64_t b2= 0; + len -= len2; + s2 += s1*len2; + while (len2 >= 8) { + uint64_t v = AV_RN64(buf); + a2 += a1; + b2 += b1; + a1 += v &0x00FF00FF00FF00FF; + b1 += (v>>8)&0x00FF00FF00FF00FF; + len2 -= 8; + buf+=8; + } + + //We combine the 8 interleaved adler32 checksums without overflows + //Decreasing the number of iterations would allow below code to be + //simplified but would likely be slower due to the fewer iterations + //of the inner loop + s1 += ((a1+b1)*0x1000100010001)>>48; + s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32) +#if HAVE_BIGENDIAN + + 2*((b1*0x1000200030004)>>48) + + ((a1*0x1000100010001)>>48) + + 2*((a1*0x0000100020003)>>48); +#else + + 2*((a1*0x4000300020001)>>48) + + ((b1*0x1000100010001)>>48) + + 2*((b1*0x3000200010000)>>48); +#endif + } +#else while (len > 4 && s2 < (1U << 31)) { DO4(buf); len -= 4; } -#else - while (len > 16 && s2 < (1U << 31)) { - DO16(buf); - len -= 16; - } #endif DO1(buf); len--; s1 %= BASE; @@ -56,6 +97,7 @@ unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf, } #ifdef TEST +// LCOV_EXCL_START #include <string.h> #include "log.h" #include "timer.h" @@ -86,4 +128,5 @@ int main(int argc, char **argv) av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum); return checksum == 0x50e6e508 ? 0 : 1; } +// LCOV_EXCL_STOP #endif |