X-Git-Url: https://git.sesse.net/?p=fjl;a=blobdiff_plain;f=dehuff.h;h=c54f68a55bf38528c629131b7802e71c3b9eda5d;hp=2669034554c25fb16362ace9879f5fa280be9592;hb=HEAD;hpb=19a58db08afd149a862506936093423db756a2dc

diff --git a/dehuff.h b/dehuff.h
index 2669034..c54f68a 100644
--- a/dehuff.h
+++ b/dehuff.h
@@ -14,6 +14,13 @@
 #define DEHUF_TABLE_SIZE (1 << DEHUF_TABLE_BITS)
 static const int DEHUF_SLOW_PATH = -1;
 
+// About 98% of all AC coefficients (control byte + coefficient) are <= 10 bits
+// long; again, see codelen.txt. This will cost us about 6 kB of data to store
+// in L1 cache.
+#define DEHUF_AC_TABLE_BITS 10
+#define DEHUF_AC_TABLE_SIZE (1 << DEHUF_AC_TABLE_BITS)
+static const int AC_DEHUF_SLOW_PATH = 0xf0000000;
+
 struct huffman_table {
 	unsigned num_codes[17];     // BITS
 	unsigned char codes[256];   // HUFFVAL
@@ -33,6 +40,15 @@ struct huffman_table {
 	// the lookup tables is int to avoid extra zero extending. 
 	int lookup_table_codes[DEHUF_TABLE_SIZE]; 
 	int lookup_table_length[DEHUF_TABLE_SIZE]; 
+	
+	// Further lookup tables for decoding AC coefficients.
+	// (Generated but obviously not used for DC coefficients.)
+	// Maps from 10-bit lookahead values to the signed coeffient (_codes),
+	// number of bits to skip (_length) and the number of zero coefficients
+	// after this one (_skip).
+	int ac_table_codes[DEHUF_AC_TABLE_SIZE]; 
+	uint8_t ac_table_length[DEHUF_AC_TABLE_SIZE]; 
+	uint8_t ac_table_skip[DEHUF_AC_TABLE_SIZE]; 
 };
 
 enum coefficient_class {