1 /* Copyright (c) 2001-2011 Timothy B. Terriberry
2    Copyright (c) 2008-2009 Xiph.Org Foundation */
8    - Redistributions of source code must retain the above copyright
11    - Redistributions in binary form must reproduce the above copyright
40    rediscovery of the FIFO arithmetic code introduced by \cite{Pas76}.
47   This only seems true when using near-infinite precision arithmetic so that
53    encoding for efficiency actually re-discovers many of the principles
64     title="Source coding algorithms for fast data compression",
86    pages="256--294",
92   return _this->offs<_this->storage?_this->buf[_this->offs++]:0;  in ec_read_byte()
96   return _this->end_offs<_this->storage?  in ec_read_byte_from_end()
97    _this->buf[_this->storage-++(_this->end_offs)]:0;  in ec_read_byte_from_end()
101    high-order symbol.*/
104   while(_this->rng<=EC_CODE_BOT){  in ec_dec_normalize()
106     _this->nbits_total+=EC_SYM_BITS;  in ec_dec_normalize()
107     _this->rng<<=EC_SYM_BITS;  in ec_dec_normalize()
109     sym=_this->rem;  in ec_dec_normalize()
111     _this->rem=ec_read_byte(_this);  in ec_dec_normalize()
113     sym=(sym<<EC_SYM_BITS|_this->rem)>>(EC_SYM_BITS-EC_CODE_EXTRA);  in ec_dec_normalize()
115     _this->val=((_this->val<<EC_SYM_BITS)+(EC_SYM_MAX&~sym))&(EC_CODE_TOP-1);  in ec_dec_normalize()
120   _this->buf=_buf;  in ec_dec_init()
121   _this->storage=_storage;  in ec_dec_init()
122   _this->end_offs=0;  in ec_dec_init()
123   _this->end_window=0;  in ec_dec_init()
124   _this->nend_bits=0;  in ec_dec_init()
128   _this->nbits_total=EC_CODE_BITS+1  in ec_dec_init()
129    -((EC_CODE_BITS-EC_CODE_EXTRA)/EC_SYM_BITS)*EC_SYM_BITS;  in ec_dec_init()
130   _this->offs=0;  in ec_dec_init()
131   _this->rng=1U<<EC_CODE_EXTRA;  in ec_dec_init()
132   _this->rem=ec_read_byte(_this);  in ec_dec_init()
133   _this->val=_this->rng-1-(_this->rem>>(EC_SYM_BITS-EC_CODE_EXTRA));  in ec_dec_init()
134   _this->error=0;  in ec_dec_init()
141   _this->ext=celt_udiv(_this->rng,_ft);  in ec_decode()
142   s=(unsigned)(_this->val/_this->ext);  in ec_decode()
143   return _ft-EC_MINI(s+1,_ft);  in ec_decode()
148    _this->ext=_this->rng>>_bits;  in ec_decode_bin()
149    s=(unsigned)(_this->val/_this->ext);  in ec_decode_bin()
150    return (1U<<_bits)-EC_MINI(s+1U,1U<<_bits);  in ec_decode_bin()
155   s=IMUL32(_this->ext,_ft-_fh);  in ec_dec_update()
156   _this->val-=s;  in ec_dec_update()
157   _this->rng=_fl>0?IMUL32(_this->ext,_fh-_fl):_this->rng-s;  in ec_dec_update()
167   r=_this->rng;  in ec_dec_bit_logp()
168   d=_this->val;  in ec_dec_bit_logp()
171   if(!ret)_this->val=d-s;  in ec_dec_bit_logp()
172   _this->rng=ret?s:r-s;  in ec_dec_bit_logp()
183   s=_this->rng;  in ec_dec_icdf()
184   d=_this->val;  in ec_dec_icdf()
186   ret=-1;  in ec_dec_icdf()
192   _this->val=d-s;  in ec_dec_icdf()
193   _this->rng=t-s;  in ec_dec_icdf()
204   s=_this->rng;  in ec_dec_icdf16()
205   d=_this->val;  in ec_dec_icdf16()
207   ret=-1;  in ec_dec_icdf16()
213   _this->val=d-s;  in ec_dec_icdf16()
214   _this->rng=t-s;  in ec_dec_icdf16()
225   _ft--;  in ec_dec_uint()
229     ftb-=EC_UINT_BITS;  in ec_dec_uint()
235     _this->error=1;  in ec_dec_uint()
250   window=_this->end_window;  in ec_dec_bits()
251   available=_this->nend_bits;  in ec_dec_bits()
257     while(available<=EC_WINDOW_SIZE-EC_SYM_BITS);  in ec_dec_bits()
259   ret=(opus_uint32)window&(((opus_uint32)1<<_bits)-1U);  in ec_dec_bits()
261   available-=_bits;  in ec_dec_bits()
262   _this->end_window=window;  in ec_dec_bits()
263   _this->nend_bits=available;  in ec_dec_bits()
264   _this->nbits_total+=_bits;  in ec_dec_bits()