The Tor Browser / file comparison
comparison: media/libopus/celt/entcode.c
media/libopus/celt/entcode.c
- branch
- TOR_BUG_9701
- changeset 10
- ac0c01689b40
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| -1:000000000000 | 0:095ed28d8a74 |
|---|---|
| 1 /* Copyright (c) 2001-2011 Timothy B. Terriberry | |
| 2 */ | |
| 3 /* | |
| 4 Redistribution and use in source and binary forms, with or without | |
| 5 modification, are permitted provided that the following conditions | |
| 6 are met: | |
| 7 | |
| 8 - Redistributions of source code must retain the above copyright | |
| 9 notice, this list of conditions and the following disclaimer. | |
| 10 | |
| 11 - Redistributions in binary form must reproduce the above copyright | |
| 12 notice, this list of conditions and the following disclaimer in the | |
| 13 documentation and/or other materials provided with the distribution. | |
| 14 | |
| 15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| 16 ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| 17 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| 18 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER | |
| 19 OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
| 20 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
| 21 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
| 22 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
| 23 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | |
| 24 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | |
| 25 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 26 */ | |
| 27 | |
| 28 #ifdef HAVE_CONFIG_H | |
| 29 #include "config.h" | |
| 30 #endif | |
| 31 | |
| 32 #include "entcode.h" | |
| 33 #include "arch.h" | |
| 34 | |
| 35 #if !defined(EC_CLZ) | |
| 36 /*This is a fallback for systems where we don't know how to access | |
| 37 a BSR or CLZ instruction (see ecintrin.h). | |
| 38 If you are optimizing Opus on a new platform and it has a native CLZ or | |
| 39 BZR (e.g. cell, MIPS, x86, etc) then making it available to Opus will be | |
| 40 an easy performance win.*/ | |
| 41 int ec_ilog(opus_uint32 _v){ | |
| 42 /*On a Pentium M, this branchless version tested as the fastest on | |
| 43 1,000,000,000 random 32-bit integers, edging out a similar version with | |
| 44 branches, and a 256-entry LUT version.*/ | |
| 45 int ret; | |
| 46 int m; | |
| 47 ret=!!_v; | |
| 48 m=!!(_v&0xFFFF0000)<<4; | |
| 49 _v>>=m; | |
| 50 ret|=m; | |
| 51 m=!!(_v&0xFF00)<<3; | |
| 52 _v>>=m; | |
| 53 ret|=m; | |
| 54 m=!!(_v&0xF0)<<2; | |
| 55 _v>>=m; | |
| 56 ret|=m; | |
| 57 m=!!(_v&0xC)<<1; | |
| 58 _v>>=m; | |
| 59 ret|=m; | |
| 60 ret+=!!(_v&0x2); | |
| 61 return ret; | |
| 62 } | |
| 63 #endif | |
| 64 | |
| 65 opus_uint32 ec_tell_frac(ec_ctx *_this){ | |
| 66 opus_uint32 nbits; | |
| 67 opus_uint32 r; | |
| 68 int l; | |
| 69 int i; | |
| 70 /*To handle the non-integral number of bits still left in the encoder/decoder | |
| 71 state, we compute the worst-case number of bits of val that must be | |
| 72 encoded to ensure that the value is inside the range for any possible | |
| 73 subsequent bits. | |
| 74 The computation here is independent of val itself (the decoder does not | |
| 75 even track that value), even though the real number of bits used after | |
| 76 ec_enc_done() may be 1 smaller if rng is a power of two and the | |
| 77 corresponding trailing bits of val are all zeros. | |
| 78 If we did try to track that special case, then coding a value with a | |
| 79 probability of 1/(1<<n) might sometimes appear to use more than n bits. | |
| 80 This may help explain the surprising result that a newly initialized | |
| 81 encoder or decoder claims to have used 1 bit.*/ | |
| 82 nbits=_this->nbits_total<<BITRES; | |
| 83 l=EC_ILOG(_this->rng); | |
| 84 r=_this->rng>>(l-16); | |
| 85 for(i=BITRES;i-->0;){ | |
| 86 int b; | |
| 87 r=r*r>>15; | |
| 88 b=(int)(r>>16); | |
| 89 l=l<<1|b; | |
| 90 r>>=b; | |
| 91 } | |
| 92 return nbits-l; | |
| 93 } |
