Multiplier-free entropy coder

libentcode/entcode.c

@@ -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
+}