Changeset 76 for mppenc/branches/r2d/libmpcenc/huffsv7.c

Timestamp:

10/17/06 13:52:34 (18 years ago)

Author:

r2d

Message:

• removed tools.c

File:

• mppenc/branches/r2d/libmpcenc/huffsv7.c (modified) (1 diff)

mppenc/branches/r2d/libmpcenc/huffsv7.c

@@ -332 +332 @@
 #endif
 
-
-// FIXME : remove the functions from tools.c
-void Make_HuffTable ( Huffman_t* dst, const HuffSrc_t* src, mpc_size_t len );
-void Resort_HuffTable ( Huffman_t* const Table, const mpc_size_t elements, mpc_int_t offset );
-void Make_LookupTable ( mpc_uint8_t* LUT, mpc_size_t LUT_len, const Huffman_t* const Table, const mpc_size_t elements );
+/*
+ *  Fills out the items Code and Length (but not Value) of a Huffman table
+ *  from a bit packed Huffman table 'src'. Table is not sorted, so this is
+ *  the table which is suitable for an encoder. Be careful: To get a table
+ *  usable for a decoder you must use Resort_HuffTable() after this
+ *  function. It's a little bit dangerous to divide the functionality, maybe
+ *  there is a more secure and handy solution to this problem.
+ */
+
+void Make_HuffTable ( Huffman_t* dst, const HuffSrc_t* src, mpc_size_t len )
+{
+        mpc_size_t  i;
+
+        for ( i = 0; i < len; i++,src++,dst++ ) {
+                dst->Code   = src->Code  ;
+                dst->Length = src->Length;
+        }
+}
+
+
+/*
+ *  Generates a Lookup table for quick Huffman decoding. This table must
+ *  have a size of a power of 2. Input is the pre-sorted Huffman table,
+ *  sorted by Resort_HuffTable() and its length, and the length of the
+ *  lookup table. Output is the Lookup table. It can be used for table based
+ *  decoding (Huffman_decode_fastest) which fully decodes by means of the
+ *  LUT. This is only handy for small huffman codes up to 9...10 bit
+ *  maximum length. For longer codes partial lookup is possible with
+ *  Huffman_decode_faster() which first estimates possible codes by means
+ *  of LUT and then searches the exact code like the tableless version
+ *  Huffman_decode().
+ */
+
+void Make_LookupTable ( mpc_uint8_t* LUT,
+                                                mpc_size_t LUT_len,
+                                                const Huffman_t* const Table,
+                                                const mpc_size_t elements )
+{
+        mpc_size_t    i;
+        mpc_size_t    idx  = elements;
+        mpc_uint32_t  dval = (mpc_uint32_t)0x80000000L / LUT_len * 2;
+        mpc_uint32_t  val  = dval - 1;
+
+        for ( i = 0; i < LUT_len; i++, val += dval ) {
+                while ( idx > 0  &&  val >= Table[idx-1].Code )
+                        idx--;
+                *LUT++ = (mpc_uint8_t)idx;
+        }
+
+        return;
+}
 
 #define MAKE(d,s)     Make_HuffTable   ( (d), (s), sizeof(s)/sizeof(*(s)) )
-#define SORT(x,o)     Resort_HuffTable ( (x), sizeof(x)/sizeof(*(x)), -(Int)(o) )
 #define LOOKUP(x,q)   Make_LookupTable ( (q), sizeof(q), (x), sizeof(x)/sizeof(*(x)) )