[xiph-commits] r13216 - in trunk/ghost: . libentcode

jm at svn.xiph.org jm at svn.xiph.org
Tue Jul 3 22:09:19 PDT 2007


Author: jm
Date: 2007-07-03 22:09:19 -0700 (Tue, 03 Jul 2007)
New Revision: 13216

Added:
   trunk/ghost/libentcode/
   trunk/ghost/libentcode/LICENSE
   trunk/ghost/libentcode/bitrdec.c
   trunk/ghost/libentcode/bitrdec.h
   trunk/ghost/libentcode/bitree.c
   trunk/ghost/libentcode/bitree.h
   trunk/ghost/libentcode/bitrenc.c
   trunk/ghost/libentcode/bitrenc.h
   trunk/ghost/libentcode/ecintrin.h
   trunk/ghost/libentcode/ectest.c
   trunk/ghost/libentcode/entcode.c
   trunk/ghost/libentcode/entcode.h
   trunk/ghost/libentcode/entdec.c
   trunk/ghost/libentcode/entdec.h
   trunk/ghost/libentcode/entenc.c
   trunk/ghost/libentcode/entenc.h
   trunk/ghost/libentcode/mfrngcod.h
   trunk/ghost/libentcode/mfrngdec.c
   trunk/ghost/libentcode/mfrngenc.c
   trunk/ghost/libentcode/probdec.c
   trunk/ghost/libentcode/probdec.h
   trunk/ghost/libentcode/probenc.c
   trunk/ghost/libentcode/probenc.h
   trunk/ghost/libentcode/probmod.c
   trunk/ghost/libentcode/probmod.h
   trunk/ghost/libentcode/rangedec.c
   trunk/ghost/libentcode/rangeenc.c
Log:
Timothy Terriberry's range coding code


Added: trunk/ghost/libentcode/LICENSE
===================================================================
--- trunk/ghost/libentcode/LICENSE	                        (rev 0)
+++ trunk/ghost/libentcode/LICENSE	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,27 @@
+Copyright (c) 2002-2007 Timothy B. Terriberry
+
+Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+- Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+- Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+- Neither the name of the Xiph.org Foundation nor the names of its contributors
+   may be used to endorse or promote products derived from this software
+   without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS''
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED.
+IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Added: trunk/ghost/libentcode/bitrdec.c
===================================================================
--- trunk/ghost/libentcode/bitrdec.c	                        (rev 0)
+++ trunk/ghost/libentcode/bitrdec.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,24 @@
+#include "bitree.h"
+
+int ec_bitree_find_and_update(unsigned *_this,int _sz,int _split,
+ unsigned _freq,unsigned *_fl,int _val){
+  int base;
+  int test;
+  int fl;
+  base=-1;
+  fl=0;
+  while(_split>0){
+    test=base+_split;
+    if(test<_sz){
+      if(_freq>=_this[test]){
+        _freq-=_this[test];
+        fl+=_this[test];
+        base=test;
+      }
+      else _this[test]+=_val;
+    }
+    _split>>=1;
+  }
+  *_fl=fl;
+  return base+1;
+}

Added: trunk/ghost/libentcode/bitrdec.h
===================================================================
--- trunk/ghost/libentcode/bitrdec.h	                        (rev 0)
+++ trunk/ghost/libentcode/bitrdec.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,22 @@
+#if !defined(_bitrenc_H)
+# define _bitredec_H (1)
+# include "bitree.h"
+
+/*Decoder-specific functions for Binary Indexed Trees.
+  See bitree.h for more detailed documentation.*/
+
+/*Gets the symbol that corresponds with a given frequency.
+  This is an omnibus function that also computes the cumulative frequency of
+   the symbols before the one returned, and updates the count of that symbol by
+   the given amount.
+  _sz:    The size of the table.
+  _split: The largest power of two less than OR EQUAL to the table size.
+  _freq:  A frequency in the range of one of the symbols in the alphabet.
+  _fl:    Returns the sum of the frequencies of the symbols less than that of
+           the returned symbol.
+  _val:   The amount to add to returned symbol's frequency.
+  Return: The smallest symbol whose cumulative frequency is greater than freq.*/
+int ec_bitree_find_and_update(unsigned *_this,int _sz,int _split,
+ unsigned _freq,unsigned *_fl,int _val);
+
+#endif

Added: trunk/ghost/libentcode/bitree.c
===================================================================
--- trunk/ghost/libentcode/bitree.c	                        (rev 0)
+++ trunk/ghost/libentcode/bitree.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,101 @@
+#include "bitree.h"
+
+void ec_bitree_to_counts(unsigned *_this,int _sz,int _split){
+  int p;
+  int q;
+  int s;
+  for(p=_split;p>1;p=q){
+    q=p>>1;
+    for(s=p-1;s<_sz;s+=p)_this[s]-=_this[s-q];
+  }
+}
+
+void ec_bitree_from_counts(unsigned *_this,int _sz){
+  int p;
+  int q;
+  int s;
+  for(q=1,p=2;p<=_sz;q=p,p=q<<1){
+    for(s=p-1;s<_sz;s+=p)_this[s]+=_this[s-q];
+  }
+}
+
+unsigned ec_bitree_get_cumul(const unsigned *_this,int _sym){
+  unsigned ret;
+  ret=0;
+  while(_sym>0){
+    ret+=_this[_sym-1];
+    _sym&=_sym-1;
+  }
+  return ret;
+}
+
+unsigned ec_bitree_get_freq(const unsigned *_this,int _sym){
+  unsigned ret;
+  int      p;
+  ret=_this[_sym];
+  p=_sym&_sym+1;
+  while(_sym!=p){
+    ret-=_this[_sym-1];
+    _sym&=_sym-1;
+  }
+  return ret;
+}
+
+#if 0
+/*Fenwick's approach to re-scaling the counts.
+  This tests to be twice as slow or more than the one below, even with inline
+   functions enabled, and without loop vectorization (which would make Moffat's
+   approach even faster).*/
+void ec_bitree_halve(unsigned *_this,int _sz,int _split){
+  int i;
+  for(i=_sz;i-->0;){
+    ec_bitree_update(_this,_sz,i,-(int)(ec_bitree_get_freq(_this,i)>>1));
+  }
+}
+#else
+/*Fenwick mentions that this approach is also possible, and this is what
+   Moffat uses.
+  Simply convert the tree into a simple array of counts, perform the halving,
+   and then convert it back.*/
+void ec_bitree_halve(unsigned *_this,int _sz,int _split){
+  int i;
+  ec_bitree_to_counts(_this,_sz,_split);
+  /*LOOP VECTORIZES.*/
+  for(i=0;i<_sz;i++)_this[i]-=_this[i]>>1;
+  ec_bitree_from_counts(_this,_sz);
+}
+#endif
+
+#if 0
+#include <stdio.h>
+/*Simple regression test code.
+  Compile with bitrenc.c and bitrdec.c as well.*/
+
+static void ec_bitree_print(unsigned *_this,int _sz){
+  int i;
+  for(i=0;i<_sz;i++)printf("%3i%c",_this[i],i+1<_sz?' ':'\n');
+}
+
+int main(void){
+  unsigned t[16]={0,8,4,9,2,10,5,11,1,12,6,13,3,14,7,15};
+  int      fl;
+  int      s;
+  int      i;
+  ec_bitree_print(t,16);
+  ec_bitree_from_counts(t,16);
+  ec_bitree_print(t,16);
+  for(i=0;i<=16;i++)printf("%3i%c",ec_bitree_get_cumul(t,i),i<16?' ':'\n');
+  for(i=0;i<t[15];i++){
+    s=ec_bitree_find_and_update(t,16,16,i,&fl,0);
+    printf("%3i: %i %3i\n",i,s,fl);
+  }
+  for(i=0;i<16;i++){
+    s=ec_bitree_find_and_update(t,16,ec_bitree_get_cumul(t,i),&fl,100);
+    ec_bitree_to_counts(t,16,16);
+    ec_bitree_print(t,16);
+    ec_bitree_from_counts(t,16);
+    ec_bitree_update(t,16,s,-100);
+  }
+  return 0;
+}
+#endif

Added: trunk/ghost/libentcode/bitree.h
===================================================================
--- trunk/ghost/libentcode/bitree.h	                        (rev 0)
+++ trunk/ghost/libentcode/bitree.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,84 @@
+/*Implements Binary Indexed Trees for cumulative probability tables, based
+   upon a combination of the techniques described in \cite{Fen93,Fen95,Mof99}.
+  This is a really, amazingly elegant data structure, that maintains
+   cumulative frequency tables in logarithmic time, using exactly the same
+   space as an ordinary frequency table.
+  In addition, the non-cumulative frequency can be retrieved in constant
+   amortized time (under 2 memory references per symbol on average).
+
+  We are dealing primarily with relatively small alphabets and are not sorting
+   symbols by frequency, and so we adopt Fenwick's tree organization strategy.
+  It's complexity has better constant factors, and although it is logarithmic
+   in n (the alphabet size) instead of s (the index of the symbol), the latter
+   is not expected to be appreciably smaller.
+  We modify it however, to remove the special cases surrounding the element 0,
+   which greatly streamlines the code.
+  Our scheme has the added benefit that for alphabet sizes that are a power of
+   2, the last element of the array is the total cumulative frequency count.
+
+  We choose Moffat's approach to halving the entire frequency table, which is
+   over twice as fast in practice as that suggested by Fenwick, even though
+   they have the same number of memory accesses.
+  We also adapt Moffat's suggestion for an omnibus decode function that updates
+   the count of the symbol being decoded while it is searching for it.
+  We also have it retain and return the cumulative frequency count needed to
+   update the arithmetic decoder.
+
+  See bitrenc.h and bitrdec.h for encoding- and decoding-specific functions.
+
+  @TECHREPORT{Fen93,
+   author     ="Peter Fenwick",
+   title      ="A new data structure for cumulative probability tables",
+   institution="The University of Auckland, Department of Computer Science",
+   year       =1993,
+   number     =88,
+   month      =May,
+   URL        ="http://www.cs.auckland.ac.nz/~peter-f/ftplink/TechRep88.ps"
+  }
+  @TECHREPORT{Fen95,
+   author     ="Peter Fenwick",
+   title      ="A new data structure for cumulative probability tables: an
+                improved frequency to symbol algorithm",
+   institution="The University of Auckland, Department of Computer Science",
+   year       =1995,
+   number     =110,
+   month      =Feb,
+   URL        ="http://www.cs.auckland.ac.nz/~peter-f/ftplink/TechRep110.ps"
+  }
+  @ARTICLE{Mof99,
+    author    ="Alistair Moffat",
+    title     ="An improved data structure for cumulative probability tables",
+    journal   ="Software Practice and Experience",
+    volume    =29,
+    number    =7,
+    pages     ="647--659",
+    year      =1999
+  }*/
+#if !defined(_bitree_H)
+# define _bitree_H (1)
+
+/*Converts an array of frequency counts to our cumulative tree representation.
+  _sz: The size of the table.*/
+void ec_bitree_from_counts(unsigned *_this,int _sz);
+
+/*Converts our cumulative tree representation to an array of frequency counts.
+  _sz:    The size of the table.
+  _split: The largest power of two less than OR EQUAL to the table size.*/
+void ec_bitree_to_counts(unsigned *_this,int _sz,int _split);
+
+/*Gets the cumulative frequency of the symbols less than the given one.
+  _sym: The symbol to obtain the cumulative frequency for.
+  Return: The sum of the frequencies of the symbols less than _sym.*/
+unsigned ec_bitree_get_cumul(const unsigned *_this,int _sym);
+
+/*Gets the frequency of a single symbol.
+  _sym: The symbol to obtain the frequency for.
+  Return: The frequency of _sym.*/
+unsigned ec_bitree_get_freq(const unsigned *_this,int _sym);
+
+/*Halves the frequency of each symbol, rounding up.
+  _sz: The size of the table.
+  _split: The largest power of two less than OR EQUAL to the table size.*/
+void ec_bitree_halve(unsigned *_this,int _sz,int _split);
+
+#endif

Added: trunk/ghost/libentcode/bitrenc.c
===================================================================
--- trunk/ghost/libentcode/bitrenc.c	                        (rev 0)
+++ trunk/ghost/libentcode/bitrenc.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,9 @@
+#include "bitrenc.h"
+
+void ec_bitree_update(unsigned *_this,int _sz,int _sym,int _val){
+  do{
+    _this[_sym]+=_val;
+    _sym+=_sym+1&-(_sym+1);
+  }
+  while(_sym<_sz);
+}

Added: trunk/ghost/libentcode/bitrenc.h
===================================================================
--- trunk/ghost/libentcode/bitrenc.h	                        (rev 0)
+++ trunk/ghost/libentcode/bitrenc.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,14 @@
+#if !defined(_bitrenc_H)
+# define _bitrenc_H (1)
+# include "bitree.h"
+
+/*Encoder-specific functions for Binary Indexed Trees.
+  See bitree.h for more detailed documentation.*/
+
+/*Updates the frequency of a given symbol.
+  _sz:  The size of the table.
+  _sym: The symbol to update.
+  _val: The amount to add to this symbol's frequency.*/
+void ec_bitree_update(unsigned *_this,int _sz,int _sym,int _val);
+
+#endif

Added: trunk/ghost/libentcode/ecintrin.h
===================================================================
--- trunk/ghost/libentcode/ecintrin.h	                        (rev 0)
+++ trunk/ghost/libentcode/ecintrin.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,71 @@
+/*Some common macros for potential platform-specific optimization.*/
+#include <math.h>
+#include <limits.h>
+#if !defined(_ecintrin_H)
+# define _ecintrin_H (1)
+
+/*Some specific platforms may have optimized intrinsic or inline assembly
+   versions of these functions which can substantially improve performance.
+  We define macros for them to allow easy incorporation of these non-ANSI
+   features.*/
+
+/*Note that we do not provide a macro for abs(), because it is provided as a
+   library function, which we assume is translated into an intrinsic to avoid
+   the function call overhead and then implemented in the smartest way for the
+   target platform.
+  With modern gcc (4.x), this is true: it uses cmov instructions if the
+   architecture supports it and branchless bit-twiddling if it does not (the
+   speed difference between the two approaches is not measurable).
+  Interestingly, the bit-twiddling method was patented in 2000 (US 6,073,150)
+   by Sun Microsystems, despite prior art dating back to at least 1996:
+   http://web.archive.org/web/19961201174141/www.x86.org/ftp/articles/pentopt/PENTOPT.TXT
+  On gcc 3.x, however, our assumption is not true, as abs() is translated to a
+   conditional jump, which is horrible on deeply piplined architectures (e.g.,
+   all consumer architectures for the past decade or more) when the sign cannot
+   be reliably predicted.*/
+
+/*Modern gcc (4.x) can compile the naive versions of min and max with cmov if
+   given an appropriate architecture, but the branchless bit-twiddling versions
+   are just as fast, and do not require any special target architecture.
+  Earlier gcc versions (3.x) compiled both code to the same assembly
+   instructions, because of the way they represented ((_b)>(_a)) internally.*/
+#define EC_MAXI(_a,_b)      ((_a)-((_a)-(_b)&-((_b)>(_a))))
+#define EC_MINI(_a,_b)      ((_a)+((_b)-(_a)&-((_b)<(_a))))
+/*This has a chance of compiling branchless, and is just as fast as the
+   bit-twiddling method, which is slightly less portable, since it relies on a
+   sign-extended rightshift, which is not guaranteed by ANSI (but present on
+   every relevant platform).*/
+#define EC_SIGNI(_a)        (((_a)>0)-((_a)<0))
+/*Slightly more portable than relying on a sign-extended right-shift (which is
+   not guaranteed by ANSI), and just as fast, since gcc (3.x and 4.x both)
+   compile it into the right-shift anyway.*/
+#define EC_SIGNMASK(_a)     (-((_a)<0))
+/*Clamps an integer into the given range.
+  If _a>_c, then the lower bound _a is respected over the upper bound _c (this
+   behavior is required to meet our documented API behavior).
+  _a: The lower bound.
+  _b: The value to clamp.
+  _c: The upper boud.*/
+#define EC_CLAMPI(_a,_b,_c) (EC_MAXI(_a,EC_MINI(_b,_c)))
+/*Count leading zeros.
+  This macro should only be used for implementing ec_ilog(), if it is defined.
+  All other code should use EC_ILOG() instead.*/
+#if __GNUC_PREREQ(3,4)
+# if INT_MAX>=2147483647
+#  define EC_CLZ0 sizeof(unsigned)*CHAR_BIT
+#  define EC_CLZ(_x) (__builtin_clz(_x))
+# elif LONG_MAX>=2147483647L
+#  define EC_CLZ0 sizeof(unsigned long)*CHAR_BIT
+#  define EC_CLZ(_x) (__builtin_clzl(_x))
+# endif
+#endif
+#if defined(EC_CLZ)
+/*Note that __builtin_clz is not defined when _x==0, according to the gcc
+   documentation (and that of the BSR instruction that implements it on x86),
+   so we have to special-case it.*/
+# define EC_ILOG(_x) (EC_CLZ0-EC_CLZ(_x)&-!!(_x))
+#else
+# define EC_ILOG(_x) (ec_ilog(_x))
+#endif
+
+#endif

Added: trunk/ghost/libentcode/ectest.c
===================================================================
--- trunk/ghost/libentcode/ectest.c	                        (rev 0)
+++ trunk/ghost/libentcode/ectest.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include "probenc.h"
+#include "probdec.h"
+
+int main(int _argc,char **_argv){
+  ec_byte_buffer buf;
+  ec_enc         enc;
+  ec_dec         dec;
+  ec_probmod     mod;
+  int            ft;
+  int            ftb;
+  int            sym;
+  int            sz;
+  int            s;
+  int            i;
+  /*Testing encoding of raw bit values.*/
+  ec_byte_writeinit(&buf);
+  ec_enc_init(&enc,&buf);
+  for(ft=0;ft<1024;ft++){
+    for(i=0;i<ft;i++){
+      ec_enc_uint(&enc,i,ft);
+    }
+  }
+  /*Testing encoding of raw bit values.*/
+  for(ftb=0;ftb<16;ftb++){
+    for(i=0;i<(1<<ftb);i++){
+      ec_enc_bits(&enc,i,ftb);
+    }
+  }
+  for(sz=1;sz<256;sz++){
+    ec_probmod_init_full(&mod,sz,1,sz+(sz>>1),NULL);
+    for(i=0;i<sz;i++){
+      s=((unsigned)(i*45678901+7))%sz;
+      ec_probmod_write(&mod,&enc,s);
+    }
+    ec_probmod_clear(&mod);
+  }
+  for(sz=11;sz<256;sz++){
+    ec_probmod_init_full(&mod,sz,1,sz+(sz>>1),NULL);
+    for(i=0;i<sz;i++){
+      s=((unsigned)(i*45678901+7))%sz;
+      ec_probmod_write_range(&mod,&enc,s,EC_MAXI(s-5,0),EC_MINI(s+6,sz));
+    }
+    ec_probmod_clear(&mod);
+  }
+  ec_enc_done(&enc);
+  fprintf(stderr,"Encoded to %li bytes.\n",(long)(buf.ptr-buf.buf));
+  ec_byte_readinit(&buf,ec_byte_get_buffer(&buf),ec_byte_bytes(&buf));
+  ec_dec_init(&dec,&buf);
+  for(ft=0;ft<1024;ft++){
+    for(i=0;i<ft;i++){
+      sym=ec_dec_uint(&dec,ft);
+      if(sym!=i){
+        fprintf(stderr,"Decoded %i instead of %i with ft of %i.\n",sym,i,ft);
+        return -1;
+      }
+    }
+  }
+  for(ftb=0;ftb<16;ftb++){
+    for(i=0;i<(1<<ftb);i++){
+      sym=ec_dec_bits(&dec,ftb);
+      if(sym!=i){
+        fprintf(stderr,"Decoded %i instead of %i with ftb of %i.\n",sym,i,ftb);
+        return -1;
+      }
+    }
+  }
+  for(sz=1;sz<256;sz++){
+    ec_probmod_init_full(&mod,sz,1,sz+(sz>>1),NULL);
+    for(i=0;i<sz;i++){
+      s=((unsigned)(i*45678901+7))%sz;
+      sym=ec_probmod_read(&mod,&dec);
+      if(sym!=s){
+        fprintf(stderr,"Decoded %i instead of %i with sz of %i.\n",sym,s,sz);
+        return -1;
+      }
+    }
+    ec_probmod_clear(&mod);
+  }
+  for(sz=11;sz<256;sz++){
+    ec_probmod_init_full(&mod,sz,1,sz+(sz>>1),NULL);
+    for(i=0;i<sz;i++){
+      s=((unsigned)(i*45678901+7))%sz;
+      sym=ec_probmod_read_range(&mod,&dec,EC_MAXI(s-5,0),EC_MINI(s+6,sz));
+      if(sym!=s){
+        fprintf(stderr,"Decoded %i instead of %i with sz of %i.\n",sym,s,sz);
+        return -1;
+      }
+    }
+    ec_probmod_clear(&mod);
+  }
+  ec_byte_writeclear(&buf);
+  fprintf(stderr,"All tests passed.\n");
+  return 0;
+}

Added: trunk/ghost/libentcode/entcode.c
===================================================================
--- trunk/ghost/libentcode/entcode.c	                        (rev 0)
+++ trunk/ghost/libentcode/entcode.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,44 @@
+#include "entcode.h"
+
+
+
+void ec_byte_reset(ec_byte_buffer *_b){
+  _b->ptr=_b->buf;
+}
+
+long ec_byte_bytes(ec_byte_buffer *_b){
+  return _b->ptr-_b->buf;
+}
+
+unsigned char *ec_byte_get_buffer(ec_byte_buffer *_b){
+  return _b->buf;
+}
+
+
+
+int ec_ilog(ec_uint32 _v){
+#if defined(EC_CLZ)
+  return EC_CLZ0-EC_CLZ(_v)&-!!_v;
+#else
+  /*On a Pentium M, this branchless version tested as the fastest on
+     1,000,000,000 random 32-bit integers, edging out a similar version with
+     branches, and a 256-entry LUT version.*/
+  int ret;
+  int m;
+  ret=!!_v;
+  m=!!(_v&0xFFFF0000)<<4;
+  _v>>=m;
+  ret|=m;
+  m=!!(_v&0xFF00)<<3;
+  _v>>=m;
+  ret|=m;
+  m=!!(_v&0xF0)<<2;
+  _v>>=m;
+  ret|=m;
+  m=!!(_v&0xC)<<1;
+  _v>>=m;
+  ret|=m;
+  ret+=!!(_v&0x2);
+  return ret;
+#endif
+}

Added: trunk/ghost/libentcode/entcode.h
===================================================================
--- trunk/ghost/libentcode/entcode.h	                        (rev 0)
+++ trunk/ghost/libentcode/entcode.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,49 @@
+#if !defined(_entcode_H)
+# define _entcode_H (1)
+# include <limits.h>
+# include "ecintrin.h"
+
+
+
+typedef unsigned ec_uint32;
+typedef struct ec_byte_buffer ec_byte_buffer;
+
+
+
+/*The number of bits to code at a time when coding bits directly.*/
+# define EC_UNIT_BITS  (8)
+/*The mask for the given bits.*/
+# define EC_UNIT_MASK  ((1U<<EC_UNIT_BITS)-1)
+
+
+
+/*Simple libogg1-style buffer.*/
+struct ec_byte_buffer{
+  unsigned char *buf;
+  unsigned char *ptr;
+  long           storage;
+};
+
+/*Encoding functions.*/
+void ec_byte_writeinit(ec_byte_buffer *_b);
+void ec_byte_writetrunc(ec_byte_buffer *_b,long _bytes);
+void ec_byte_write1(ec_byte_buffer *_b,unsigned _value);
+void ec_byte_write4(ec_byte_buffer *_b,ec_uint32 _value);
+void ec_byte_writecopy(ec_byte_buffer *_b,void *_source,long _bytes);
+void ec_byte_writeclear(ec_byte_buffer *_b);
+/*Decoding functions.*/
+void ec_byte_readinit(ec_byte_buffer *_b,unsigned char *_buf,long _bytes);
+int ec_byte_look1(ec_byte_buffer *_b);
+int ec_byte_look4(ec_byte_buffer *_b,ec_uint32 *_val);
+void ec_byte_adv1(ec_byte_buffer *_b);
+void ec_byte_adv4(ec_byte_buffer *_b);
+int ec_byte_read1(ec_byte_buffer *_b);
+int ec_byte_read4(ec_byte_buffer *_b,ec_uint32 *_val);
+/*Shared functions.*/
+void ec_byte_reset(ec_byte_buffer *_b);
+long ec_byte_bytes(ec_byte_buffer *_b);
+unsigned char *ec_byte_get_buffer(ec_byte_buffer *_b);
+
+int ec_ilog(ec_uint32 _v);
+
+#endif

Added: trunk/ghost/libentcode/entdec.c
===================================================================
--- trunk/ghost/libentcode/entdec.c	                        (rev 0)
+++ trunk/ghost/libentcode/entdec.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,123 @@
+#include <stddef.h>
+#include "entdec.h"
+
+
+
+void ec_byte_readinit(ec_byte_buffer *_b,unsigned char *_buf,long _bytes){
+  _b->buf=_b->ptr=_buf;
+  _b->storage=_bytes;
+}
+
+int ec_byte_look1(ec_byte_buffer *_b){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte>=_b->storage)return -1;
+  else return _b->ptr[0];
+}
+
+int ec_byte_look4(ec_byte_buffer *_b,ec_uint32 *_val){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte+4>_b->storage){
+    if(endbyte<_b->storage){
+      *_val=_b->ptr[0];
+      endbyte++;
+      if(endbyte<_b->storage){
+        *_val|=(ec_uint32)_b->ptr[1]<<8;
+        endbyte++;
+        if(endbyte<_b->storage)*_val|=(ec_uint32)_b->ptr[2]<<16;
+      }
+    }
+    return -1;
+  }
+  else{
+    *_val=_b->ptr[0];
+    *_val|=(ec_uint32)_b->ptr[1]<<8;
+    *_val|=(ec_uint32)_b->ptr[2]<<16;
+    *_val|=(ec_uint32)_b->ptr[3]<<24;
+  }
+  return 0;
+}
+
+void ec_byte_adv1(ec_byte_buffer *_b){
+  _b->ptr++;
+}
+
+void ec_byte_adv4(ec_byte_buffer *_b){
+  _b->ptr+=4;
+}
+
+int ec_byte_read1(ec_byte_buffer *_b){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte>=_b->storage)return -1;
+  else return *(_b->ptr++);
+}
+
+int ec_byte_read4(ec_byte_buffer *_b,ec_uint32 *_val){
+  unsigned char *end;
+  end=_b->buf+_b->storage;
+  if(_b->ptr+4>end){
+    if(_b->ptr<end){
+      *_val=*(_b->ptr++);
+      if(_b->ptr<end){
+        *_val|=(ec_uint32)*(_b->ptr++)<<8;
+        if(_b->ptr<end)*_val|=(ec_uint32)*(_b->ptr++)<<16;
+      }
+    }
+    return -1;
+  }
+  else{
+    *_val=(*_b->ptr++);
+    *_val|=(ec_uint32)*(_b->ptr++)<<8;
+    *_val|=(ec_uint32)*(_b->ptr++)<<16;
+    *_val|=(ec_uint32)*(_b->ptr++)<<24;
+  }
+  return 0;
+}
+
+
+
+ec_uint32 ec_dec_bits(ec_dec *_this,int _ftb){
+  ec_uint32 t;
+  unsigned  s;
+  unsigned  ft;
+  t=0;
+  while(_ftb>EC_UNIT_BITS){
+    s=ec_decode(_this,EC_UNIT_MASK+1);
+    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);
+  ec_dec_update(_this,s,s+1,ft);
+  t=t<<_ftb|s;
+  return t;
+}
+
+ec_uint32 ec_dec_uint(ec_dec *_this,ec_uint32 _ft){
+  ec_uint32 mask;
+  ec_uint32 ft;
+  ec_uint32 t;
+  unsigned  s;
+  int       ftb;
+  t=0;
+  _ft--;
+  ftb=EC_ILOG(_ft);
+  while(ftb>EC_UNIT_BITS){
+    ftb-=EC_UNIT_BITS;
+    ft=(_ft>>ftb)+1;
+    s=ec_decode(_this,ft);
+    ec_dec_update(_this,s,s+1,ft);
+    t=t<<EC_UNIT_BITS|s;
+    if(s<ft-1)return t<<ftb|ec_dec_bits(_this,ftb);
+    mask=((ec_uint32)1<<ftb)-1;
+    _ft=_ft&mask;
+  }
+  _ft++;
+  s=ec_decode(_this,_ft);
+  ec_dec_update(_this,s,s+1,_ft);
+  t=t<<ftb|s;
+  return t;
+}

Added: trunk/ghost/libentcode/entdec.h
===================================================================
--- trunk/ghost/libentcode/entdec.h	                        (rev 0)
+++ trunk/ghost/libentcode/entdec.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,74 @@
+#if !defined(_entdec_H)
+# define _entdec_H (1)
+# include "entcode.h"
+
+
+
+typedef struct ec_dec ec_dec;
+
+
+
+/*The entropy decoder.*/
+struct ec_dec{
+   /*The buffer to decode.*/
+   ec_byte_buffer *buf;
+   /*The remainder of a buffered input symbol.*/
+   int             rem;
+   /*The number of values in the current range.*/
+   ec_uint32       rng;
+   /*The difference between the input value and the lowest value in the current
+      range.*/
+   ec_uint32       dif;
+   /*Normalization factor.*/
+   ec_uint32       nrm;
+};
+
+
+/*Initializes the decoder.
+  _buf: The input buffer to use.
+  Return: 0 on success, or a negative value on error.*/
+void ec_dec_init(ec_dec *_this,ec_byte_buffer *_buf);
+/*Calculates the cumulative frequency for the next symbol.
+  This can then be fed into the probability model to determine what that
+   symbol is, and the additional frequency information required to advance to
+   the next symbol.
+  This function cannot be called more than once without a corresponding call to
+   ec_dec_update(), or decoding will not proceed correctly.
+  _ft: The total frequency of the symbols in the alphabet the next symbol was
+        encoded with.
+  Return: A cumulative frequency representing the encoded symbol.
+          If the cumulative frequency of all the symbols before the one that
+           was encoded was fl, and the cumulative frequency of all the symbols
+           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);
+/*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
+   intermediate calculations are performed.
+  _fl:  The cumulative frequency of all symbols that come before the symbol
+         decoded.
+  _fh:  The cumulative frequency of all symbols up to and including the symbol
+        Together with _fl, this defines the range [_fl,_fh) in which the value
+         returned above must fall.
+  _ft:  The total frequency of the symbols in the alphabet the symbol decoded
+         was encoded in.
+        This must be the same as passed to the preceding call to ec_decode().*/
+void ec_dec_update(ec_dec *_this,unsigned _fl,unsigned _fh,
+ unsigned _ft);
+/*Extracts a sequence of raw bits from the stream.
+  The bits must have been encoded with ec_enc_bits().
+  No call to ec_dec_update() is necessary after this call.
+  _ftb: The number of bits to extract.
+        This must be at least one, and no more than 32.
+  Return: The decoded bits.*/
+ec_uint32 ec_dec_bits(ec_dec *_this,int _ftb);
+/*Extracts a raw unsigned integer with a non-power-of-2 range from the stream.
+  The bits must have been encoded with ec_enc_uint().
+  No call to ec_dec_update() is necessary after this call.
+  _ft: The number of integers that can be decoded (one more than the max).
+       This must be at least one, and no more than 2**32-1.
+  Return: The decoded bits.*/
+ec_uint32 ec_dec_uint(ec_dec *_this,ec_uint32 _ft);
+
+#endif

Added: trunk/ghost/libentcode/entenc.c
===================================================================
--- trunk/ghost/libentcode/entenc.c	                        (rev 0)
+++ trunk/ghost/libentcode/entenc.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,98 @@
+#include <stdlib.h>
+#include <string.h>
+#include "entenc.h"
+
+
+
+#define EC_BUFFER_INCREMENT (256)
+
+void ec_byte_writeinit(ec_byte_buffer *_b){
+  _b->ptr=_b->buf=malloc(EC_BUFFER_INCREMENT);
+  _b->storage=EC_BUFFER_INCREMENT;
+}
+
+void ec_byte_writetrunc(ec_byte_buffer *_b,long _bytes){
+  _b->ptr=_b->buf+_bytes;
+}
+
+void ec_byte_write1(ec_byte_buffer *_b,unsigned _value){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte>=_b->storage){
+    _b->buf=realloc(_b->buf,_b->storage+EC_BUFFER_INCREMENT);
+    _b->storage+=EC_BUFFER_INCREMENT;
+    _b->ptr=_b->buf+endbyte;
+  }
+  *(_b->ptr++)=(unsigned char)_value;
+}
+
+void ec_byte_write4(ec_byte_buffer *_b,ec_uint32 _value){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte+4>_b->storage){
+    _b->buf=realloc(_b->buf,_b->storage+EC_BUFFER_INCREMENT);
+    _b->storage+=EC_BUFFER_INCREMENT;
+    _b->ptr=_b->buf+endbyte;
+  }
+  *(_b->ptr++)=(unsigned char)_value;
+  _value>>=8;
+  *(_b->ptr++)=(unsigned char)_value;
+  _value>>=8;
+  *(_b->ptr++)=(unsigned char)_value;
+  _value>>=8;
+  *(_b->ptr++)=(unsigned char)_value;
+}
+
+void ec_byte_writecopy(ec_byte_buffer *_b,void *_source,long _bytes){
+  ptrdiff_t endbyte;
+  endbyte=_b->ptr-_b->buf;
+  if(endbyte+_bytes>_b->storage){
+    _b->storage=endbyte+_bytes+EC_BUFFER_INCREMENT;
+    _b->buf=realloc(_b->buf,_b->storage);
+    _b->ptr=_b->buf+endbyte;
+  }
+  memmove(_b->ptr,_source,_bytes);
+  _b->ptr+=_bytes;
+}
+
+void ec_byte_writeclear(ec_byte_buffer *_b){
+  free(_b->buf);
+}
+
+
+
+void ec_enc_bits(ec_enc *_this,ec_uint32 _fl,int _ftb){
+  unsigned fl;
+  unsigned ft;
+  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);
+  }
+  ft=1<<_ftb;
+  fl=_fl&ft-1;
+  ec_encode(_this,fl,fl+1,ft);
+}
+
+void ec_enc_uint(ec_enc *_this,ec_uint32 _fl,ec_uint32 _ft){
+  ec_uint32 mask;
+  ec_uint32 ft;
+  unsigned  fl;
+  int       ftb;
+  _ft--;
+  ftb=EC_ILOG(_ft);
+  while(ftb>EC_UNIT_BITS){
+    ftb-=EC_UNIT_BITS;
+    ft=(_ft>>ftb)+1;
+    fl=(unsigned)(_fl>>ftb);
+    ec_encode(_this,fl,fl+1,ft);
+    if(fl<ft-1){
+      ec_enc_bits(_this,_fl,ftb);
+      return;
+    }
+    mask=((ec_uint32)1<<ftb)-1;
+    _fl=_fl&mask;
+    _ft=_ft&mask;
+  }
+  ec_encode(_this,_fl,_fl+1,_ft+1);
+}

Added: trunk/ghost/libentcode/entenc.h
===================================================================
--- trunk/ghost/libentcode/entenc.h	                        (rev 0)
+++ trunk/ghost/libentcode/entenc.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,57 @@
+#if !defined(_entenc_H)
+# define _entenc_H (1)
+# include <stddef.h>
+# include "entcode.h"
+
+
+
+typedef struct ec_enc ec_enc;
+
+
+
+/*The entropy encoder.*/
+struct ec_enc{
+   /*Buffered output.*/
+   ec_byte_buffer *buf;
+   /*A buffered output symbol, awaiting carry propagation.*/
+   int             rem;
+   /*Number of extra carry propogating symbols.*/
+   size_t          ext;
+   /*The number of values in the current range.*/
+   ec_uint32       rng;
+   /*The low end of the current range (inclusive).*/
+   ec_uint32       low;
+};
+
+
+/*Initializes the encoder.
+  _buf: The buffer to store output bytes in.
+        This must have already been initialized for writing and reset.*/
+void ec_enc_init(ec_enc *_this,ec_byte_buffer *_buf);
+/*Encodes a symbol given its frequency information.
+  The frequency information must be discernable by the decoder, assuming it
+   has read only the previous symbols from the stream.
+  It is allowable to change the frequency information, or even the entire
+   source alphabet, so long as the decoder can tell from the context of the
+   previously encoded information that it is supposed to do so as well.
+  _fl: The sum of the frequencies of symbols before the one to be encoded.
+  _fs: The frequency of the symbol to be encoded.
+  _ft: The sum of the frequencies of all the symbols*/
+void ec_encode(ec_enc *_this,unsigned _fl,unsigned _fs,unsigned _ft);
+/*Encodes a sequence of raw bits in the stream.
+  _fl:  The bits to encode.
+  _ftb: The number of bits to encode.
+        This must be at least one, and no more than 32.*/
+void ec_enc_bits(ec_enc *_this,ec_uint32 _fl,int _ftb);
+/*Encodes a raw unsigned integer in the stream.
+  _fl: The integer to encode.
+  _ft: The number of integers that can be encoded (one more than the max).
+       This must be at least one, and no more than 2**32-1.*/
+void ec_enc_uint(ec_enc *_this,ec_uint32 _fl,ec_uint32 _ft);
+
+/*Indicates that there are no more symbols to encode.
+  All reamining output bytes are flushed to the output buffer.
+  ec_enc_init() must be called before the encoder can be used again.*/
+void ec_enc_done(ec_enc *_this);
+
+#endif

Added: trunk/ghost/libentcode/mfrngcod.h
===================================================================
--- trunk/ghost/libentcode/mfrngcod.h	                        (rev 0)
+++ trunk/ghost/libentcode/mfrngcod.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,36 @@
+#if !defined(_mfrngcode_H)
+# define _mfrngcode_H (1)
+# include "entcode.h"
+
+/*Constants used by the entropy encoder/decoder.*/
+
+/*The number of bits to output at a time.*/
+# define EC_SYM_BITS   (8)
+/*The total number of bits in each of the state registers.*/
+# define EC_CODE_BITS  (32)
+/*The maximum symbol value.*/
+# define EC_SYM_MAX    ((1U<<EC_SYM_BITS)-1)
+/*Bits to shift by to move a symbol into the high-order position.*/
+# define EC_CODE_SHIFT (EC_CODE_BITS-EC_SYM_BITS-1)
+/*Carry bit of the high-order range symbol.*/
+# define EC_CODE_TOP   (1U<<EC_CODE_BITS-1)
+/*Low-order bit of the high-order range symbol.*/
+# define EC_CODE_BOT   (EC_CODE_TOP>>EC_SYM_BITS)
+/*Code for which propogating carries are possible.*/
+# define EC_CODE_CARRY (EC_SYM_MAX<<EC_CODE_SHIFT)
+/*The number of bits available for the last, partial symbol in the code field.*/
+# define EC_CODE_EXTRA ((EC_CODE_BITS-2)%EC_SYM_BITS+1)
+/*A mask for the bits available in the coding buffer.
+  This allows different platforms to use a variable with more bits, if it is
+   convenient.
+  We will only use EC_CODE_BITS of it.*/
+# define EC_CODE_MASK  ((1U<<EC_CODE_BITS-1)-1<<1|1)
+
+
+/*The non-zero symbol of the second possible reserved ending.
+  This must be the high-bit.*/
+# define EC_FOF_RSV1      (1<<EC_SYM_BITS-1)
+/*A mask for all the other bits.*/
+# define EC_FOF_RSV1_MASK (EC_FOF_RSV1-1)
+
+#endif

Added: trunk/ghost/libentcode/mfrngdec.c
===================================================================
--- trunk/ghost/libentcode/mfrngdec.c	                        (rev 0)
+++ trunk/ghost/libentcode/mfrngdec.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,260 @@
+#include <stddef.h>
+#include "entdec.h"
+#include "mfrngcod.h"
+
+
+
+/*A multiply-free range decoder.
+  This is an entropy decoder based upon \cite{Mar79}, which is itself a
+   rediscovery of the FIFO arithmetic code introduced by \cite{Pas76}.
+  It is very similar to arithmetic encoding, except that encoding is done with
+   digits in any base, instead of with bits, and so it is faster when using
+   larger bases (i.e.: a byte).
+  The author claims an average waste of $\frac{1}{2}\log_b(2b)$ bits, where $b$
+   is the base, longer than the theoretical optimum, but to my knowledge there
+   is no published justification for this claim.
+  This only seems true when using near-infinite precision arithmetic so that
+   the process is carried out with no rounding errors.
+
+  IBM (the author's employer) never sought to patent the idea, and to my
+   knowledge the algorithm is unencumbered by any patents, though its
+   performance is very competitive with proprietary arithmetic coding.
+  The two are based on very similar ideas, however.
+  An excellent description of implementation details is available at
+   http://www.arturocampos.com/ac_range.html
+  A recent work \cite{MNW98} which proposes several changes to arithmetic
+   encoding for efficiency actually re-discovers many of the principles
+   behind range encoding, and presents a good theoretical analysis of them.
+
+  The coder is made multiply-free by replacing the standard multiply/divide
+   used to partition the current interval according to the total frequency
+   count.
+  The new partition function scales the count so that it differs from the size
+   of the interval by no more than a factor of two and then assigns each symbol
+   one or two code words in the interval.
+  For details see \cite{SM98}.
+
+  This coder also handles the end of the stream in a slightly more graceful
+   fashion than most arithmetic or range coders.
+  Once the final symbol has been encoded, the coder selects the code word with
+   the shortest number of bits that still falls within the final interval.
+  This method is not novel.
+  Here, by the length of the code word, we refer to the number of bits until
+   its final 1.
+  Any trailing zeros may be discarded, since the encoder, once it runs out of
+   input, will pad its buffer with zeros.
+
+  But this means that no encoded stream would ever have any zero bytes at the
+   end.
+  Since there are some coded representations we cannot produce, it implies that
+   there is still some redundancy in the stream.
+  In this case, we can pick a special byte value, RSV1, and should the stream
+   end in a sequence of zeros, followed by the RSV1 byte, we can code the
+   zeros, and discard the RSV1 byte.
+  The decoder, knowing that the encoder would never produce a sequence of zeros
+   at the end, would then know to add in the RSV1 byte if it observed it.
+
+  Now, the encoder would never produce a stream that ended in a sequence of
+   zeros followed by a RSV1 byte.
+  So, if the stream ends in a non-empty sequence of zeros, followed by any
+   positive number of RSV1 bytes, the last RSV1 byte is discarded.
+  The decoder, if it encounters a stream that ends in non-empty sequence of
+   zeros followed by any non-negative number of RSV1 bytes, adds an additional
+   RSV1 byte to the stream.
+  With this strategy, every possible sequence of input bytes is transformed to
+   one that could actually be produced by the encoder.
+
+  The only question is what non-zero value to use for RSV1.
+  We select 0x80, since it has the nice property of producing the shortest
+   possible byte streams when using our strategy for selecting a number within
+   the final interval to encode.
+  Clearly if the shortest possible code word that falls within the interval has
+   its last one bit as the most significant bit of the final byte, and the
+   previous bytes were a non-empty sequence of zeros followed by a non-negative
+   number of 0x80 bytes, then the last byte would be discarded.
+  If the shortest code word is not so formed, then no other code word in the
+   interval would result in any more bytes being discarded.
+  Any longer code word would have an additional one bit somewhere, and so would
+   require at a minimum that that byte would be coded.
+  If the shortest code word has a 1 before the final one that is preventing the
+   stream from ending in a non-empty sequence of zeros followed by a
+   non-negative number of 0x80's, then there is no code word of the same length
+   which contains that bit as a zero.
+  If there were, then we could simply leave that bit a 1, and drop all the bits
+   after it without leaving the interval, thus producing a shorter code word.
+
+  In this case, RSV1 can only drop 1 bit off the final stream.
+  Other choices could lead to savings of up to 8 bits for particular streams,
+   but this would produce the odd situation that a stream with more non-zero
+   bits is actually encoded in fewer bytes.
+
+  @PHDTHESIS{Pas76,
+    author="Richard Clark Pasco",
+    title="Sorce coding algorithms for fast data compression",
+    school="Dept. of Electrical Engineering, Stanford University",
+    address="Stanford, CA",
+    month=May,
+    year=1976
+  }
+  @INPROCEEDINGS{Mar79,
+   author="Martin, G.N.N.",
+   title="Range encoding: an algorithm for removing redundancy from a digitised
+    message",
+   booktitle="Video & Data Recording Conference",
+   year=1979,
+   address="Southampton",
+   month=Jul
+  }
+  @ARTICLE{MNW98,
+   author="Alistair Moffat and Radford Neal and Ian H. Witten",
+   title="Arithmetic Coding Revisited",
+   journal="{ACM} Transactions on Information Systems",
+   year=1998,
+   volume=16,
+   number=3,
+   pages="256--294",
+   month=Jul,
+   URL="http://dev.acm.org/pubs/citations/journals/tois/1998-16-3/p256-moffat/"
+  }
+  @INPROCEEDINGS{SM98,
+   author="Lang Stuiver and Alistair Moffat",
+   title="Piecewise Integer Mapping for Arithmetic Coding",
+   booktitle="Proceedings of the {IEEE} Data Compression Conference",
+   pages="1--10",
+   address="Snowbird, UT",
+   month="Mar./Apr.",
+   year=1998
+  }*/
+
+
+
+/*Gets the next byte of input.
+  After all the bytes in the current packet have been consumed, and the extra
+   end code returned if needed, this function will continue to return zero each
+   time it is called.
+  Return: The next byte of input.*/
+static int ec_dec_in(ec_dec *_this){
+  int ret;
+  ret=ec_byte_read1(_this->buf);
+  if(ret<0){
+    unsigned char *buf;
+    long           bytes;
+    bytes=ec_byte_bytes(_this->buf);
+    buf=ec_byte_get_buffer(_this->buf);
+    /*Breaking abstraction: don't do this at home, kids.*/
+    if(_this->buf->storage==bytes){
+      ec_byte_adv1(_this->buf);
+      if(bytes>0){
+        unsigned char *p;
+        p=buf+bytes;
+        /*If we end in a string of 0 or more EC_FOF_RSV1 bytes preceded by a
+           zero, return an extra EC_FOF_RSV1 byte.*/
+        do p--;
+        while(p>buf&&p[0]==EC_FOF_RSV1);
+        if(!p[0])return EC_FOF_RSV1;
+      }
+    }
+    return 0;
+  }
+  else return ret;
+}
+
+/*Normalizes the contents of low and rng so that rng is contained in the
+   high-order symbol of low.*/
+static void ec_dec_normalize(ec_dec *_this){
+  /*If the range is too small, rescale it and input some bits.*/
+  while(_this->rng<=EC_CODE_BOT){
+    int sym;
+    _this->rng<<=EC_SYM_BITS;
+    /*Use up the remaining bits from our last symbol.*/
+    sym=_this->rem<<EC_CODE_EXTRA&EC_SYM_MAX;
+    /*Read the next value from the input.*/
+    _this->rem=ec_dec_in(_this);
+    /*Take the rest of the bits we need from this new symbol.*/
+    sym|=_this->rem>>EC_SYM_BITS-EC_CODE_EXTRA;
+    _this->dif=(_this->dif<<EC_SYM_BITS)+sym&EC_CODE_MASK;
+    /*dif can never be larger than EC_CODE_TOP.
+      This is equivalent to the slightly more readable:
+      if(_this->dif>EC_CODE_TOP)_this->dif-=EC_CODE_TOP;*/
+    _this->dif^=(_this->dif&_this->dif-1)&EC_CODE_TOP;
+  }
+}
+
+void ec_dec_init(ec_dec *_this,ec_byte_buffer *_buf){
+  _this->buf=_buf;
+  _this->rem=ec_dec_in(_this);
+  _this->rng=1U<<EC_CODE_EXTRA;
+  _this->dif=_this->rem>>EC_SYM_BITS-EC_CODE_EXTRA;
+  /*Normalize the interval.*/
+  ec_dec_normalize(_this);
+}
+
+unsigned ec_decode(ec_dec *_this,unsigned _ft){
+  unsigned d;
+  /*Step 1: Compute the normalization factor for the frequency counts.*/
+  _this->nrm=EC_ILOG(_this->rng)-EC_ILOG(_ft);
+  _ft<<=_this->nrm;
+  d=_ft>_this->rng;
+  _ft>>=d;
+  _this->nrm-=d;
+  /*Step 2: invert the partition function.*/
+  d=_this->rng-_ft;
+  return EC_MAXI((int)(_this->dif>>1),(int)(_this->dif-d))>>_this->nrm;
+  /*Step 3: The caller locates the range [fl,fh) containing the return value
+     and calls ec_dec_update().*/
+}
+
+void ec_dec_update(ec_dec *_this,unsigned _fl,unsigned _fh,unsigned _ft){
+  unsigned r;
+  unsigned s;
+  unsigned d;
+  /*Step 4: Evaluate the two partition function values.*/
+  _fl<<=_this->nrm;
+  _fh<<=_this->nrm;
+  _ft<<=_this->nrm;
+  d=_this->rng-_ft;
+  r=_fh+EC_MINI(_fh,d);
+  s=_fl+EC_MINI(_fl,d);
+  /*Step 5: Update the interval.*/
+  _this->rng=r-s;
+  _this->dif-=s;
+  /*Step 6: Normalize the interval.*/
+  ec_dec_normalize(_this);
+}
+
+#if 0
+int ec_dec_done(ec_dec *_this){
+  unsigned low;
+  int      ret;
+  /*Check to make sure we've used all the input bytes.
+    This ensures that no more ones would ever be inserted into the decoder.*/
+  if(_this->buf->ptr-ec_byte_get_buffer(_this->buf)<=
+   ec_byte_bytes(_this->buf)){
+    return 0;
+  }
+  /*We compute the smallest finitely odd fraction that fits inside the current
+     range, and write that to the stream.
+    This is guaranteed to yield the smallest possible encoding.*/
+  /*TODO: Fix this line, as it is wrong.
+    It doesn't seem worth being able to make this check to do an extra
+     subtraction for every symbol decoded.*/
+  low=/*What we want: _this->top-_this->rng; What we have:*/_this->dif
+  if(low){
+    unsigned end;
+    end=EC_CODE_TOP;
+    /*Ensure that the next free end is in the range.*/
+    if(end-low>=_this->rng){
+      unsigned msk;
+      msk=EC_CODE_TOP-1;
+      do{
+        msk>>=1;
+        end=(low+msk)&~msk|msk+1;
+      }
+      while(end-low>=_this->rng);
+    }
+    /*The remaining input should have been the next free end.*/
+    return end-low!=_this->dif;
+  }
+  return 1;
+}
+#endif

Added: trunk/ghost/libentcode/mfrngenc.c
===================================================================
--- trunk/ghost/libentcode/mfrngenc.c	                        (rev 0)
+++ trunk/ghost/libentcode/mfrngenc.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,164 @@
+#include <stddef.h>
+#include "entenc.h"
+#include "mfrngcod.h"
+
+
+
+/*A multiply-free range encoder.
+  See mfrngdec.c and the references for implementation details
+   \cite{Mar79,MNW98,SM98}.
+
+  @INPROCEEDINGS{Mar79,
+   author="Martin, G.N.N.",
+   title="Range encoding: an algorithm for removing redundancy from a digitised
+    message",
+   booktitle="Video \& Data Recording Conference",
+   year=1979,
+   address="Southampton",
+   month=Jul
+  }
+  @ARTICLE{MNW98,
+   author="Alistair Moffat and Radford Neal and Ian H. Witten",
+   title="Arithmetic Coding Revisited",
+   journal="{ACM} Transactions on Information Systems",
+   year=1998,
+   volume=16,
+   number=3,
+   pages="256--294",
+   month=Jul,
+   URL="http://dev.acm.org/pubs/citations/journals/tois/1998-16-3/p256-moffat/"
+  }
+  @INPROCEEDINGS{SM98,
+   author="Lang Stuiver and Alistair Moffat",
+   title="Piecewise Integer Mapping for Arithmetic Coding",
+   booktitle="Proceedings of the {IEEE} Data Compression Conference",
+   pages="1--10",
+   address="Snowbird, UT",
+   month="Mar./Apr.",
+   year=1998
+  }*/
+
+
+
+/*Outputs a symbol, with a carry bit.
+  If there is a potential to propogate a carry over several symbols, they are
+   buffered until it can be determined whether or not an actual carry will
+   occur.
+  If the counter for the buffered symbols overflows, then the range is
+   truncated to force a carry to occur, towards whichever side maximizes the
+   remaining range.*/
+static void ec_enc_carry_out(ec_enc *_this,int _c){
+  if(_c!=EC_SYM_MAX){
+    /*No further carry propogation possible, flush buffer.*/
+    int carry;
+    carry=_c>>EC_SYM_BITS;
+    /*Don't output a byte on the first write.
+      This compare should be taken care of by branch-prediction thereafter.*/
+    if(_this->rem>=0)ec_byte_write1(_this->buf,_this->rem+carry);
+    if(_this->ext>0){
+      unsigned sym;
+      sym=EC_SYM_MAX+carry&EC_SYM_MAX;
+      do ec_byte_write1(_this->buf,sym);
+      while(--(_this->ext)>0);
+    }
+    _this->rem=_c&EC_SYM_MAX;
+  }
+  else _this->ext++;
+}
+
+static void ec_enc_normalize(ec_enc *_this){
+  /*If the range is too small, output some bits and rescale it.*/
+  while(_this->rng<=EC_CODE_BOT){
+    ec_enc_carry_out(_this,(int)(_this->low>>EC_CODE_SHIFT));
+    /*Move the next-to-high-order symbol into the high-order position.*/
+    _this->low=_this->low<<EC_SYM_BITS&EC_CODE_TOP-1;
+    _this->rng<<=EC_SYM_BITS;
+  }
+}
+
+void ec_enc_init(ec_enc *_this,ec_byte_buffer *_buf){
+  _this->buf=_buf;
+  _this->rem=-1;
+  _this->ext=0;
+  _this->low=0;
+  _this->rng=EC_CODE_TOP;
+}
+
+void ec_encode(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _ft){
+  unsigned r;
+  unsigned s;
+  unsigned d;
+  int      nrm;
+  /*Step 1: we want ft in the range of [rng/2,rng).
+    The high-order bits of the rng and ft are computed via a logarithm.
+    This could also be done on some architectures with some custom assembly,
+     which would provide even more speed.*/
+  nrm=EC_ILOG(_this->rng)-EC_ILOG(_ft);
+  /*Having the same high order bit may be too much.
+    We may need to shift one less to ensure that ft is actually in the proper
+     range.*/
+  _ft<<=nrm;
+  d=_ft>_this->rng;
+  _ft>>=d;
+  nrm-=d;
+  /*We then scale everything by the computed power of 2.*/
+  _fl<<=nrm;
+  _fh<<=nrm;
+  /*Step 2: compute the two values of the partition function.
+    d is the splitting point of the interval [0,ft).*/
+  d=_this->rng-_ft;
+  r=_fh+EC_MINI(_fh,d);
+  s=_fl+EC_MINI(_fl,d);
+  /*Step 3: Update the end-point and range of the interval.*/
+  _this->low+=s;
+  _this->rng=r-s;
+  /*Step 4: Normalize the interval.*/
+  ec_enc_normalize(_this);
+}
+
+void ec_enc_done(ec_enc *_this){
+  /*We compute the integer in the current interval that has the largest number
+     of trailing zeros, and write that to the stream.
+    This is guaranteed to yield the smallest possible encoding.*/
+  if(_this->low){
+    unsigned end;
+    end=EC_CODE_TOP;
+    /*Ensure that the end value is in the range.*/
+    if(end-_this->low>=_this->rng){
+      unsigned msk;
+      msk=EC_CODE_TOP-1;
+      do{
+        msk>>=1;
+        end=(_this->low+msk)&~msk|msk+1;
+      }
+      while(end-_this->low>=_this->rng);
+    }
+    /*The remaining output is the next free end.*/
+    while(end){
+      ec_enc_carry_out(_this,end>>EC_CODE_SHIFT);
+      end=end<<EC_SYM_BITS&EC_CODE_TOP-1;
+    }
+  }
+  /*If we have a buffered byte...*/
+  if(_this->rem>=0){
+    unsigned char *p;
+    unsigned char *buf;
+    /*Flush it into the output buffer.*/
+    ec_enc_carry_out(_this,0);
+    /*We may be able to drop some redundant bytes from the end.*/
+    buf=ec_byte_get_buffer(_this->buf);
+    p=buf+ec_byte_bytes(_this->buf)-1;
+    /*Strip trailing zeros.*/
+    while(p>=buf&&!p[0])p--;
+    /*Strip one trailing EC_FOF_RSV1 byte if the buffer ends in a string of
+       consecutive EC_FOF_RSV1 bytes preceded by one (or more) zeros.*/
+    if(p>buf&&p[0]==EC_FOF_RSV1){
+      unsigned char *q;
+      q=p;
+      do q--;
+      while(q>buf&&q[0]==EC_FOF_RSV1);
+      if(!q[0])p--;
+    }
+    ec_byte_writetrunc(_this->buf,p+1-buf);
+  }
+}

Added: trunk/ghost/libentcode/probdec.c
===================================================================
--- trunk/ghost/libentcode/probdec.c	                        (rev 0)
+++ trunk/ghost/libentcode/probdec.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,59 @@
+#include <stdlib.h>
+#include <string.h>
+#include "probdec.h"
+#include "bitrdec.h"
+
+
+
+/*Gets the cumulative frequency count between _lo and _hi, as well as the
+   cumulative frequency count below _lo.*/
+static unsigned ec_probmod_get_total(ec_probmod *_this,unsigned *_fl,
+ unsigned _lo,unsigned _hi){
+  *_fl=ec_bitree_get_cumul(_this->bitree,_lo);
+  return ec_bitree_get_cumul(_this->bitree,_hi)-*_fl;
+}
+
+static int ec_probmod_find_and_update(ec_probmod *_this,ec_probsamp *_samp,
+ unsigned _freq){
+  int sym;
+  sym=ec_bitree_find_and_update(_this->bitree,_this->sz,_this->split,
+   _freq,&_samp->fl,_this->inc);
+  _samp->fs=ec_bitree_get_freq(_this->bitree,sym)-_this->inc;
+  _this->ft+=_this->inc;
+  if(_this->ft>_this->thresh){
+    ec_bitree_halve(_this->bitree,_this->sz,_this->split);
+    _this->ft=ec_bitree_get_cumul(_this->bitree,_this->sz);
+  }
+  return sym;
+}
+
+
+
+int ec_probmod_read(ec_probmod *_this,ec_dec *_dec){
+  ec_probsamp samp;
+  unsigned    freq;
+  int         sym;
+  samp.ft=_this->ft;
+  freq=ec_decode(_dec,samp.ft);
+  sym=ec_probmod_find_and_update(_this,&samp,freq);
+  ec_dec_update(_dec,samp.fl,samp.fl+samp.fs,samp.ft);
+  return sym;
+}
+
+int ec_probmod_read_range(ec_probmod *_this,ec_dec *_dec,int _lo,int _hi){
+  ec_probsamp samp;
+  unsigned    freq;
+  unsigned    base;
+  int         sz;
+  int         sym;
+  sz=_this->sz;
+  _lo=EC_MINI(_lo,sz);
+  _hi=EC_MINI(_hi,sz);
+  if(_hi<=_lo)return -1;
+  samp.ft=ec_probmod_get_total(_this,&base,_lo,_hi);
+  freq=ec_decode(_dec,samp.ft);
+  sym=ec_probmod_find_and_update(_this,&samp,freq+base);
+  samp.fl-=base;
+  ec_dec_update(_dec,samp.fl,samp.fl+samp.fs,samp.ft);
+  return sym;
+}

Added: trunk/ghost/libentcode/probdec.h
===================================================================
--- trunk/ghost/libentcode/probdec.h	                        (rev 0)
+++ trunk/ghost/libentcode/probdec.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,23 @@
+#if !defined(_probdec_H)
+# define _probdec_H (1)
+# include "probmod.h"
+# include "entdec.h"
+
+
+
+/*Decodes a single symbol using the given probability model and entropy
+   decoder.
+  Return: The decoded symbol.*/
+int ec_probmod_read(ec_probmod *_this,ec_dec *_dec);
+/*Decodes a single symbol using the given probability model and entropy
+   decoder, restricted to a given subrange of the available symbols.
+  This effectively sets the frequency counts of all the symbols outside this
+   range to zero, decodes the symbol, then restores the counts to their
+   original values, and updates the model.
+  _lo: The first legal symbol to decode.
+  _hi: One greater than the last legal symbol to decode.
+       This must be greater than _lo.
+  Return: The decoded symbol.*/
+int ec_probmod_read_range(ec_probmod *_this,ec_dec *_dec,int _lo,int _hi);
+
+#endif

Added: trunk/ghost/libentcode/probenc.c
===================================================================
--- trunk/ghost/libentcode/probenc.c	                        (rev 0)
+++ trunk/ghost/libentcode/probenc.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,50 @@
+#include <string.h>
+#include "probenc.h"
+#include "bitrenc.h"
+
+
+
+static void ec_probmod_samp_and_update(ec_probmod *_this,ec_probsamp *_samp,
+ unsigned _sym){
+  unsigned sz;
+  sz=_this->sz;
+  _samp->fs=ec_bitree_get_freq(_this->bitree,_sym);
+  _samp->fl=ec_bitree_get_cumul(_this->bitree,_sym);
+  _samp->ft=_this->ft;
+  ec_bitree_update(_this->bitree,sz,_sym,_this->inc);
+  _this->ft+=_this->inc;
+  if(_this->ft>_this->thresh){
+    ec_bitree_halve(_this->bitree,sz,_this->split);
+    _this->ft=ec_bitree_get_cumul(_this->bitree,sz);
+  }
+}
+
+static void ec_probmod_samp_and_update_range(ec_probmod *_this,
+ ec_probsamp *_samp,int _sym,int _lo,int _hi){
+  unsigned base;
+  int      sz;
+  sz=_this->sz;
+  base=ec_bitree_get_cumul(_this->bitree,_lo);
+  _samp->fs=ec_bitree_get_freq(_this->bitree,_sym);
+  _samp->fl=ec_bitree_get_cumul(_this->bitree,_sym)-base;
+  _samp->ft=ec_bitree_get_cumul(_this->bitree,_hi)-base;
+  ec_bitree_update(_this->bitree,sz,_sym,_this->inc);
+  _this->ft+=_this->inc;
+  if(_this->ft>_this->thresh){
+    ec_bitree_halve(_this->bitree,sz,_this->split);
+    _this->ft=ec_bitree_get_cumul(_this->bitree,sz);
+  }
+}
+
+void ec_probmod_write(ec_probmod *_this,ec_enc *_enc,int _sym){
+  ec_probsamp samp;
+  ec_probmod_samp_and_update(_this,&samp,_sym);
+  ec_encode(_enc,samp.fl,samp.fl+samp.fs,samp.ft);
+}
+
+void ec_probmod_write_range(ec_probmod *_this,ec_enc *_enc,int _sym,
+ int _lo,int _hi){
+  ec_probsamp samp;
+  ec_probmod_samp_and_update_range(_this,&samp,_sym,_lo,_hi);
+  ec_encode(_enc,samp.fl,samp.fl+samp.fs,samp.ft);
+}

Added: trunk/ghost/libentcode/probenc.h
===================================================================
--- trunk/ghost/libentcode/probenc.h	                        (rev 0)
+++ trunk/ghost/libentcode/probenc.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,23 @@
+#if !defined(_probenc_H)
+# define _probenc_H (1)
+# include "probmod.h"
+# include "entenc.h"
+
+/*Encodes a single symbol using the given probability model and entropy
+   encoder.
+  _sym: The symbol to encode.*/
+void ec_probmod_write(ec_probmod *_this,ec_enc *_enc,int _sym);
+/*Encodes a single symbol using the given probability model and entropy
+   encoder, restricted to a given subrange of the available symbols.
+  This effectively sets the frequency counts of all the symbols outside this
+   range to zero, encodes the symbol, then restores the counts to their
+   original values, and updates the models.
+  _sym: The symbol to encode.
+        The caller must ensure this falls in the range _lo<=_sym<_hi.
+  _lo:  The first legal symbol to encode.
+  _hi:  One greater than the last legal symbol to encode.
+        This must be greater than _lo.*/
+void ec_probmod_write_range(ec_probmod *_this,ec_enc *_enc,int _sym,
+ int _lo,int _hi);
+
+#endif

Added: trunk/ghost/libentcode/probmod.c
===================================================================
--- trunk/ghost/libentcode/probmod.c	                        (rev 0)
+++ trunk/ghost/libentcode/probmod.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,32 @@
+#include <stdlib.h>
+#include <string.h>
+#include "probmod.h"
+#include "bitree.h"
+
+void ec_probmod_init(ec_probmod *_this,unsigned _sz){
+  ec_probmod_init_full(_this,_sz,1U,1U<<23,NULL);
+}
+
+void ec_probmod_init_from_counts(ec_probmod *_this,unsigned _sz,
+ const unsigned *_counts){
+  ec_probmod_init_full(_this,_sz,1U,1U<<23,_counts);
+}
+
+void ec_probmod_init_full(ec_probmod *_this,unsigned _sz,unsigned _inc,
+ unsigned _thresh,const unsigned *_counts){
+  unsigned s;
+  _this->sz=_sz;
+  for(s=1;s<=_this->sz;s<<=1);
+  _this->split=s>>1;
+  _this->inc=_inc;
+  _this->thresh=_thresh;
+  _this->bitree=(unsigned *)malloc(_sz*sizeof(*_this->bitree));
+  if(_counts!=NULL)memcpy(_this->bitree,_counts,_sz*sizeof(*_this->bitree));
+  else for(s=0;s<_this->sz;s++)_this->bitree[s]=1;
+  ec_bitree_from_counts(_this->bitree,_sz);
+  _this->ft=ec_bitree_get_cumul(_this->bitree,_sz);
+}
+
+void ec_probmod_clear(ec_probmod *_this){
+  free(_this->bitree);
+}

Added: trunk/ghost/libentcode/probmod.h
===================================================================
--- trunk/ghost/libentcode/probmod.h	                        (rev 0)
+++ trunk/ghost/libentcode/probmod.h	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,73 @@
+#if !defined(_probmod_H)
+# define _probmod_H (1)
+# include "entcode.h"
+
+typedef struct ec_probsamp     ec_probsamp;
+typedef struct ec_probmod      ec_probmod;
+
+/*A sample from a probability distribution.
+  This is the information needed to encode a symbol or update the decoder
+   state.*/
+struct ec_probsamp{
+  /*The cumulative frequency of all symbols preceding this one in the
+     alphabet.*/
+  unsigned fl;
+  /*The frequency of the symbol coded.*/
+  unsigned fs;
+  /*The total frequency of all symbols in the alphabet.*/
+  unsigned ft;
+};
+
+
+/*A simple frequency-count probability model.*/
+struct ec_probmod{
+  /*The number of symbols in this context.*/
+  int       sz;
+  /*The largest power of two less than or equal to sz.*/
+  int       split;
+  /*The amount by which to increment the frequency count of an observed
+     symbol.*/
+  unsigned  inc;
+  /*The current total frequency count.*/
+  unsigned  ft;
+  /*The maximum total frequency count allowed before the counts are rescaled.
+    Note that this should be larger than (inc+1>>1)+sz-1, since at most one
+     rescaling is done per decoded symbol.
+    Otherwise, this threshold might be exceeded.
+    This must be less than 2**23 for a range coder, and 2**31 for an
+     arithmetic coder.*/
+  unsigned  thresh;
+  /*The binary indexed tree used to keep track of the frequency counts.*/
+  unsigned *bitree;
+};
+
+
+/*Initializes a probability model of the given size.
+  The amount to increment and all frequency counts are initialized to 1.
+  The rescaling threshold is initialized to 2**23.
+  _sz: The number of symbols in this context.*/
+void ec_probmod_init(ec_probmod *_this,unsigned _sz);
+/*Initializes a probability model of the given size.
+  The amount to increment is initialized to 1.
+  The rescaling threshold is initialized to 2**23.
+  _sz:     The number of symbols in this context.
+  _counts: The initial frequency count of each symbol.*/
+void ec_probmod_init_from_counts(ec_probmod *_this,unsigned _sz,
+ const unsigned *_counts);
+/*Initializes a probability model of the given size.
+  _sz:     The number of symbols in this context.
+  _inc:    The amount by which to increment the frequency count of an observed
+            symbol.
+  _thresh: The maximum total frequency count allowed before the counts are
+            rescaled.
+           See above for restrictions on this value.
+  _counts: The initial frequency count of each symbol, or NULL to initialize
+            each frequency count to 1.*/
+void ec_probmod_init_full(ec_probmod *_this,unsigned _sz,unsigned _inc,
+ unsigned _thresh,const unsigned *_counts);
+/*Frees all memory used by this probability model.*/
+void ec_probmod_clear(ec_probmod *_this);
+
+
+
+#endif

Added: trunk/ghost/libentcode/rangedec.c
===================================================================
--- trunk/ghost/libentcode/rangedec.c	                        (rev 0)
+++ trunk/ghost/libentcode/rangedec.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,243 @@
+#include <stddef.h>
+#include "entdec.h"
+#include "mfrngcod.h"
+
+
+
+/*A multiply-free range decoder.
+  This is an entropy decoder based upon \cite{Mar79}, which is itself a
+   rediscovery of the FIFO arithmetic code introduced by \cite{Pas76}.
+  It is very similar to arithmetic encoding, except that encoding is done with
+   digits in any base, instead of with bits, and so it is faster when using
+   larger bases (i.e.: a byte).
+  The author claims an average waste of $\frac{1}{2}\log_b(2b)$ bits, where $b$
+   is the base, longer than the theoretical optimum, but to my knowledge there
+   is no published justification for this claim.
+  This only seems true when using near-infinite precision arithmetic so that
+   the process is carried out with no rounding errors.
+
+  IBM (the author's employer) never sought to patent the idea, and to my
+   knowledge the algorithm is unencumbered by any patents, though its
+   performance is very competitive with proprietary arithmetic coding.
+  The two are based on very similar ideas, however.
+  An excellent description of implementation details is available at
+   http://www.arturocampos.com/ac_range.html
+  A recent work \cite{MNW98} which proposes several changes to arithmetic
+   encoding for efficiency actually re-discovers many of the principles
+   behind range encoding, and presents a good theoretical analysis of them.
+
+  The coder is made multiply-free by replacing the standard multiply/divide
+   used to partition the current interval according to the total frequency
+   count.
+  The new partition function scales the count so that it differs from the size
+   of the interval by no more than a factor of two and then assigns each symbol
+   one or two code words in the interval.
+  For details see \cite{SM98}.
+
+  This coder also handles the end of the stream in a slightly more graceful
+   fashion than most arithmetic or range coders.
+  Once the final symbol has been encoded, the coder selects the code word with
+   the shortest number of bits that still falls within the final interval.
+  This method is not novel.
+  Here, by the length of the code word, we refer to the number of bits until
+   its final 1.
+  Any trailing zeros may be discarded, since the encoder, once it runs out of
+   input, will pad its buffer with zeros.
+
+  But this means that no encoded stream would ever have any zero bytes at the
+   end.
+  Since there are some coded representations we cannot produce, it implies that
+   there is still some redundancy in the stream.
+  In this case, we can pick a special byte value, RSV1, and should the stream
+   end in a sequence of zeros, followed by the RSV1 byte, we can code the
+   zeros, and discard the RSV1 byte.
+  The decoder, knowing that the encoder would never produce a sequence of zeros
+   at the end, would then know to add in the RSV1 byte if it observed it.
+
+  Now, the encoder would never produce a stream that ended in a sequence of
+   zeros followed by a RSV1 byte.
+  So, if the stream ends in a non-empty sequence of zeros, followed by any
+   positive number of RSV1 bytes, the last RSV1 byte is discarded.
+  The decoder, if it encounters a stream that ends in non-empty sequence of
+   zeros followed by any non-negative number of RSV1 bytes, adds an additional
+   RSV1 byte to the stream.
+  With this strategy, every possible sequence of input bytes is transformed to
+   one that could actually be produced by the encoder.
+
+  The only question is what non-zero value to use for RSV1.
+  We select 0x80, since it has the nice property of producing the shortest
+   possible byte streams when using our strategy for selecting a number within
+   the final interval to encode.
+  Clearly if the shortest possible code word that falls within the interval has
+   its last one bit as the most significant bit of the final byte, and the
+   previous bytes were a non-empty sequence of zeros followed by a non-negative
+   number of 0x80 bytes, then the last byte would be discarded.
+  If the shortest code word is not so formed, then no other code word in the
+   interval would result in any more bytes being discarded.
+  Any longer code word would have an additional one bit somewhere, and so would
+   require at a minimum that that byte would be coded.
+  If the shortest code word has a 1 before the final one that is preventing the
+   stream from ending in a non-empty sequence of zeros followed by a
+   non-negative number of 0x80's, then there is no code word of the same length
+   which contains that bit as a zero.
+  If there were, then we could simply leave that bit a 1, and drop all the bits
+   after it without leaving the interval, thus producing a shorter code word.
+
+  In this case, RSV1 can only drop 1 bit off the final stream.
+  Other choices could lead to savings of up to 8 bits for particular streams,
+   but this would produce the odd situation that a stream with more non-zero
+   bits is actually encoded in fewer bytes.
+
+  @PHDTHESIS{Pas76,
+    author="Richard Clark Pasco",
+    title="Sorce coding algorithms for fast data compression",
+    school="Dept. of Electrical Engineering, Stanford University",
+    address="Stanford, CA",
+    month=May,
+    year=1976
+  }
+  @INPROCEEDINGS{Mar79,
+   author="Martin, G.N.N.",
+   title="Range encoding: an algorithm for removing redundancy from a digitised
+    message",
+   booktitle="Video & Data Recording Conference",
+   year=1979,
+   address="Southampton",
+   month=Jul
+  }
+  @ARTICLE{MNW98,
+   author="Alistair Moffat and Radford Neal and Ian H. Witten",
+   title="Arithmetic Coding Revisited",
+   journal="{ACM} Transactions on Information Systems",
+   year=1998,
+   volume=16,
+   number=3,
+   pages="256--294",
+   month=Jul,
+   URL="http://dev.acm.org/pubs/citations/journals/tois/1998-16-3/p256-moffat/"
+  }
+  @INPROCEEDINGS{SM98,
+   author="Lang Stuiver and Alistair Moffat",
+   title="Piecewise Integer Mapping for Arithmetic Coding",
+   booktitle="Proceedings of the {IEEE} Data Compression Conference",
+   pages="1--10",
+   address="Snowbird, UT",
+   month="Mar./Apr.",
+   year=1998
+  }*/
+
+
+
+/*Gets the next byte of input.
+  After all the bytes in the current packet have been consumed, and the extra
+   end code returned if needed, this function will continue to return zero each
+   time it is called.
+  Return: The next byte of input.*/
+static int ec_dec_in(ec_dec *_this){
+  int ret;
+  ret=ec_byte_read1(_this->buf);
+  if(ret<0){
+    unsigned char *buf;
+    long           bytes;
+    bytes=ec_byte_bytes(_this->buf);
+    buf=ec_byte_get_buffer(_this->buf);
+    /*Breaking abstraction: don't do this at home, kids.*/
+    if(_this->buf->storage==bytes){
+      ec_byte_adv1(_this->buf);
+      if(bytes>0){
+        unsigned char *p;
+        p=buf+bytes;
+        /*If we end in a string of 0 or more EC_FOF_RSV1 bytes preceded by a
+           zero, return an extra EC_FOF_RSV1 byte.*/
+        do p--;
+        while(p>buf&&p[0]==EC_FOF_RSV1);
+        if(!p[0])return EC_FOF_RSV1;
+      }
+    }
+    return 0;
+  }
+  else return ret;
+}
+
+/*Normalizes the contents of low and rng so that rng is contained in the
+   high-order symbol of low.*/
+static void ec_dec_normalize(ec_dec *_this){
+  /*If the range is too small, rescale it and input some bits.*/
+  while(_this->rng<=EC_CODE_BOT){
+    int sym;
+    _this->rng<<=EC_SYM_BITS;
+    /*Use up the remaining bits from our last symbol.*/
+    sym=_this->rem<<EC_CODE_EXTRA&EC_SYM_MAX;
+    /*Read the next value from the input.*/
+    _this->rem=ec_dec_in(_this);
+    /*Take the rest of the bits we need from this new symbol.*/
+    sym|=_this->rem>>EC_SYM_BITS-EC_CODE_EXTRA;
+    _this->dif=(_this->dif<<EC_SYM_BITS)-sym&EC_CODE_MASK;
+    /*dif can never be larger than EC_CODE_TOP.
+      This is equivalent to the slightly more readable:
+      if(_this->dif>EC_CODE_TOP)_this->dif-=EC_CODE_TOP;*/
+    _this->dif^=(_this->dif&_this->dif-1)&EC_CODE_TOP;
+  }
+}
+
+void ec_dec_init(ec_dec *_this,ec_byte_buffer *_buf){
+  _this->buf=_buf;
+  _this->rem=ec_dec_in(_this);
+  _this->rng=1U<<EC_CODE_EXTRA;
+  _this->dif=_this->rng-(_this->rem>>EC_SYM_BITS-EC_CODE_EXTRA);
+  /*Normalize the interval.*/
+  ec_dec_normalize(_this);
+}
+
+
+unsigned ec_decode(ec_dec *_this,unsigned _ft){
+  unsigned s;
+  _this->nrm=_this->rng/_ft;
+  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);
+  _this->dif-=s;
+  _this->rng=_fl>0?_this->nrm*(_fh-_fl):_this->rng-s;
+  ec_dec_normalize(_this);
+}
+
+#if 0
+int ec_dec_done(ec_dec *_this){
+  unsigned low;
+  int      ret;
+  /*Check to make sure we've used all the input bytes.
+    This ensures that no more ones would ever be inserted into the decoder.*/
+  if(_this->buf->ptr-ec_byte_get_buffer(_this->buf)<=
+   ec_byte_bytes(_this->buf)){
+    return 0;
+  }
+  /*We compute the smallest finitely odd fraction that fits inside the current
+     range, and write that to the stream.
+    This is guaranteed to yield the smallest possible encoding.*/
+  /*TODO: Fix this line, as it is wrong.
+    It doesn't seem worth being able to make this check to do an extra
+     subtraction for every symbol decoded.*/
+  low=/*What we want: _this->top-_this->rng; What we have:*/_this->dif
+  if(low){
+    unsigned end;
+    end=EC_CODE_TOP;
+    /*Ensure that the next free end is in the range.*/
+    if(end-low>=_this->rng){
+      unsigned msk;
+      msk=EC_CODE_TOP-1;
+      do{
+        msk>>=1;
+        end=(low+msk)&~msk|msk+1;
+      }
+      while(end-low>=_this->rng);
+    }
+    /*The remaining input should have been the next free end.*/
+    return end-low!=_this->dif;
+  }
+  return 1;
+}
+#endif

Added: trunk/ghost/libentcode/rangeenc.c
===================================================================
--- trunk/ghost/libentcode/rangeenc.c	                        (rev 0)
+++ trunk/ghost/libentcode/rangeenc.c	2007-07-04 05:09:19 UTC (rev 13216)
@@ -0,0 +1,145 @@
+#include <stddef.h>
+#include "entenc.h"
+#include "mfrngcod.h"
+
+
+
+/*A multiply-free range encoder.
+  See mfrngdec.c and the references for implementation details
+   \cite{Mar79,MNW98,SM98}.
+
+  @INPROCEEDINGS{Mar79,
+   author="Martin, G.N.N.",
+   title="Range encoding: an algorithm for removing redundancy from a digitised
+    message",
+   booktitle="Video \& Data Recording Conference",
+   year=1979,
+   address="Southampton",
+   month=Jul
+  }
+  @ARTICLE{MNW98,
+   author="Alistair Moffat and Radford Neal and Ian H. Witten",
+   title="Arithmetic Coding Revisited",
+   journal="{ACM} Transactions on Information Systems",
+   year=1998,
+   volume=16,
+   number=3,
+   pages="256--294",
+   month=Jul,
+   URL="http://dev.acm.org/pubs/citations/journals/tois/1998-16-3/p256-moffat/"
+  }
+  @INPROCEEDINGS{SM98,
+   author="Lang Stuiver and Alistair Moffat",
+   title="Piecewise Integer Mapping for Arithmetic Coding",
+   booktitle="Proceedings of the {IEEE} Data Compression Conference",
+   pages="1--10",
+   address="Snowbird, UT",
+   month="Mar./Apr.",
+   year=1998
+  }*/
+
+
+
+/*Outputs a symbol, with a carry bit.
+  If there is a potential to propogate a carry over several symbols, they are
+   buffered until it can be determined whether or not an actual carry will
+   occur.
+  If the counter for the buffered symbols overflows, then the range is
+   truncated to force a carry to occur, towards whichever side maximizes the
+   remaining range.*/
+static void ec_enc_carry_out(ec_enc *_this,int _c){
+  if(_c!=EC_SYM_MAX){
+    /*No further carry propogation possible, flush buffer.*/
+    int carry;
+    carry=_c>>EC_SYM_BITS;
+    /*Don't output a byte on the first write.
+      This compare should be taken care of by branch-prediction thereafter.*/
+    if(_this->rem>=0)ec_byte_write1(_this->buf,_this->rem+carry);
+    if(_this->ext>0){
+      unsigned sym;
+      sym=EC_SYM_MAX+carry&EC_SYM_MAX;
+      do ec_byte_write1(_this->buf,sym);
+      while(--(_this->ext)>0);
+    }
+    _this->rem=_c&EC_SYM_MAX;
+  }
+  else _this->ext++;
+}
+
+static void ec_enc_normalize(ec_enc *_this){
+  /*If the range is too small, output some bits and rescale it.*/
+  while(_this->rng<=EC_CODE_BOT){
+    ec_enc_carry_out(_this,(int)(_this->low>>EC_CODE_SHIFT));
+    /*Move the next-to-high-order symbol into the high-order position.*/
+    _this->low=_this->low<<EC_SYM_BITS&EC_CODE_TOP-1;
+    _this->rng<<=EC_SYM_BITS;
+  }
+}
+
+void ec_enc_init(ec_enc *_this,ec_byte_buffer *_buf){
+  _this->buf=_buf;
+  _this->rem=-1;
+  _this->ext=0;
+  _this->low=0;
+  _this->rng=EC_CODE_TOP;
+}
+
+void ec_encode(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _ft){
+  unsigned r;
+  unsigned s;
+  r=_this->rng/_ft;
+  if(_fl>0){
+    s=r*(_ft-_fl);
+    _this->low+=_this->rng-s;
+    _this->rng=r*(_fh-_fl);
+  }
+  else _this->rng-=r*(_ft-_fh);
+  ec_enc_normalize(_this);
+}
+
+void ec_enc_done(ec_enc *_this){
+  /*We compute the integer in the current interval that has the largest number
+     of trailing zeros, and write that to the stream.
+    This is guaranteed to yield the smallest possible encoding.*/
+  if(_this->low){
+    unsigned end;
+    end=EC_CODE_TOP;
+    /*Ensure that the end value is in the range.*/
+    if(end-_this->low>=_this->rng){
+      unsigned msk;
+      msk=EC_CODE_TOP-1;
+      do{
+        msk>>=1;
+        end=(_this->low+msk)&~msk|msk+1;
+      }
+      while(end-_this->low>=_this->rng);
+    }
+    /*The remaining output is the next free end.*/
+    while(end){
+      ec_enc_carry_out(_this,end>>EC_CODE_SHIFT);
+      end=end<<EC_SYM_BITS&EC_CODE_TOP-1;
+    }
+  }
+  /*If we have a buffered byte...*/
+  if(_this->rem>=0){
+    unsigned char *p;
+    unsigned char *buf;
+    /*Flush it into the output buffer.*/
+    ec_enc_carry_out(_this,0);
+    /*We may be able to drop some redundant bytes from the end.*/
+    buf=ec_byte_get_buffer(_this->buf);
+    p=buf+ec_byte_bytes(_this->buf)-1;
+    /*Strip trailing zeros.*/
+    while(p>=buf&&!p[0])p--;
+    /*Strip one trailing EC_FOF_RSV1 byte if the buffer ends in a string of
+       consecutive EC_FOF_RSV1 bytes preceded by one (or more) zeros.*/
+    if(p>buf&&p[0]==EC_FOF_RSV1){
+      unsigned char *q;
+      q=p;
+      do q--;
+      while(q>buf&&q[0]==EC_FOF_RSV1);
+      if(!q[0])p--;
+    }
+    ec_byte_writetrunc(_this->buf,p+1-buf);
+  }
+}



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