f13fea7b53
Updated broken paper URLs. Cleaned up non-multiply-free range coder documentation (e.g., stop claiming it's multiply-free).
72 lines
1.2 KiB
C
72 lines
1.2 KiB
C
#include "entcode.h"
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void ec_byte_reset(ec_byte_buffer *_b){
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_b->ptr=_b->buf;
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}
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long ec_byte_bytes(ec_byte_buffer *_b){
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return _b->ptr-_b->buf;
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}
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unsigned char *ec_byte_get_buffer(ec_byte_buffer *_b){
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return _b->buf;
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}
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int ec_ilog(ec_uint32 _v){
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#if defined(EC_CLZ)
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return EC_CLZ0-EC_CLZ(_v)&-!!_v;
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#else
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/*On a Pentium M, this branchless version tested as the fastest on
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1,000,000,000 random 32-bit integers, edging out a similar version with
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branches, and a 256-entry LUT version.*/
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int ret;
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int m;
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ret=!!_v;
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m=!!(_v&0xFFFF0000)<<4;
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_v>>=m;
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ret|=m;
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m=!!(_v&0xFF00)<<3;
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_v>>=m;
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ret|=m;
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m=!!(_v&0xF0)<<2;
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_v>>=m;
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ret|=m;
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m=!!(_v&0xC)<<1;
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_v>>=m;
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ret|=m;
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ret+=!!(_v&0x2);
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return ret;
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#endif
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}
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int ec_ilog64(ec_uint64 _v){
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#if defined(EC_CLZ64)
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return EC_CLZ64_0-EC_CLZ64(_v)&-!!_v;
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#else
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ec_uint32 v;
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int ret;
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int m;
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ret=!!_v;
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m=!!(_v&0xFFFFFFFF00000000)<<5;
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v=(ec_uint32)(_v>>m);
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ret|=m;
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m=!!(v&0xFFFF0000)<<4;
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v>>=m;
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ret|=m;
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m=!!(v&0xFF00)<<3;
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v>>=m;
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ret|=m;
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m=!!(v&0xF0)<<2;
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v>>=m;
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ret|=m;
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m=!!(v&0xC)<<1;
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v>>=m;
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ret|=m;
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ret+=!!(v&0x2);
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return ret;
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#endif
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}
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