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Made a second version of ec_{en|de}code optimised for encoding bits (no div
required) and using it in ec_{en|de}c_bits()

--- a/libcelt/entdec.c

+++ b/libcelt/entdec.c

@@ -88,13 +88,13 @@

   unsigned  ft;

   t=0;

   while(_ftb>EC_UNIT_BITS){

-    s=ec_decode(_this,EC_UNIT_MASK+1);

+    s=ec_decode_bin(_this,EC_UNIT_BITS);

     ec_dec_update(_this,s,s+1,EC_UNIT_MASK+1);

     t=t<<EC_UNIT_BITS|s;

     _ftb-=EC_UNIT_BITS;

   }

   ft=1U<<_ftb;

-  s=ec_decode(_this,ft);

+  s=ec_decode_bin(_this,_ftb);

   ec_dec_update(_this,s,s+1,ft);

   t=t<<_ftb|s;

   return t;

--- a/libcelt/entdec.h

+++ b/libcelt/entdec.h

@@ -42,6 +42,7 @@

            up to and including the one encoded is fh, then the returned value

            will fall in the range [fl,fh).*/

 unsigned ec_decode(ec_dec *_this,unsigned _ft);

+unsigned ec_decode_bin(ec_dec *_this,unsigned bits);

 /*Advance the decoder past the next symbol using the frequency information the

    symbol was encoded with.

   Exactly one call to ec_decode() must have been made so that all necessary

--- a/libcelt/entenc.c

+++ b/libcelt/entenc.c

@@ -70,11 +70,11 @@

   while(_ftb>EC_UNIT_BITS){

     _ftb-=EC_UNIT_BITS;

     fl=(unsigned)(_fl>>_ftb)&EC_UNIT_MASK;

-    ec_encode(_this,fl,fl+1,EC_UNIT_MASK+1);

+    ec_encode_bin(_this,fl,fl+1,EC_UNIT_BITS);

   }

   ft=1<<_ftb;

   fl=(unsigned)_fl&ft-1;

-  ec_encode(_this,fl,fl+1,ft);

+  ec_encode_bin(_this,fl,fl+1,_ftb);

 }

 void ec_enc_bits64(ec_enc *_this,ec_uint64 _fl,int _ftb){

--- a/libcelt/entenc.h

+++ b/libcelt/entenc.h

@@ -42,6 +42,7 @@

         decoded value will fall.

   _ft: The sum of the frequencies of all the symbols*/

 void ec_encode(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _ft);

+void ec_encode_bin(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned bits);

 /*Encodes a sequence of raw bits in the stream.

   _fl:  The bits to encode.

   _ftb: The number of bits to encode.

--- a/libcelt/rangedec.c

+++ b/libcelt/rangedec.c

@@ -168,6 +168,15 @@

   return _ft-EC_MINI(s+1,_ft);

 }

+unsigned ec_decode_bin(ec_dec *_this,unsigned bits){

+   unsigned s;

+   ec_uint32 ft;

+   ft = (ec_uint32)1<<bits;

+   _this->nrm=_this->rng>>bits;

+   s=(unsigned)((_this->dif-1)/_this->nrm);

+   return ft-EC_MINI(s+1,ft);

+}

+

 void ec_dec_update(ec_dec *_this,unsigned _fl,unsigned _fh,unsigned _ft){

   ec_uint32 s;

   s=_this->nrm*(_ft-_fh);

--- a/libcelt/rangeenc.c

+++ b/libcelt/rangeenc.c

@@ -92,6 +92,18 @@

   ec_enc_normalize(_this);

 }

+void ec_encode_bin(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned bits){

+   ec_uint32 r, ft;

+   r=_this->rng>>bits;

+   ft = (ec_uint32)1<<bits;

+   if(_fl>0){

+      _this->low+=_this->rng-r*(ft-_fl);

+      _this->rng=r*(_fh-_fl);

+   }

+   else _this->rng-=r*(ft-_fh);

+   ec_enc_normalize(_this);

+}

+

 long ec_enc_tell(ec_enc *_this,int _b){

   ec_uint32 r;

   int       l;