Multiplier-free entropy coder

libentcode/bitrdec.h

@@ -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