X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=dehuff.c;h=5574e27184b8de5961b01f1f76cbf0e27688c89b;hb=4adcb962d555cba7af8e1de42d203f03d28d81a5;hp=af16b512a83c0f796fd24ff8a499e15fe3719817;hpb=8a495c6c9b595e9f188ef703d71fa868cbb1605d;p=fjl

diff --git a/dehuff.c b/dehuff.c
index af16b51..5574e27 100644
--- a/dehuff.c
+++ b/dehuff.c
@@ -114,11 +114,53 @@ void read_huffman_tables(huffman_tables_t* dst, input_func_t* input_func, void*
 				for (unsigned elem = prefix_min; elem < prefix_max; ++elem) {
 					assert(tbl->lookup_table_codes[elem] == DEHUF_SLOW_PATH);
 					assert(tbl->lookup_table_length[elem] == DEHUF_SLOW_PATH);
-					tbl->lookup_table_codes[elem] = k;
+					tbl->lookup_table_codes[elem] = tbl->codes[k];
 					tbl->lookup_table_length[elem] = length;
 				}
 			}
 		}	
+		
+		// Generate the AC lookup tables.
+		for (unsigned i = 0; i < DEHUF_AC_TABLE_SIZE; ++i) {
+			tbl->ac_table_codes[i] = AC_DEHUF_SLOW_PATH;
+
+			int lookup = i >> (DEHUF_AC_TABLE_BITS - DEHUF_TABLE_BITS);
+			int rs = tbl->lookup_table_codes[lookup];
+			unsigned length = tbl->lookup_table_length[lookup];
+			if (rs == DEHUF_SLOW_PATH) {
+				// Not enough bits to decode even the length.
+				continue;
+			}
+			if (rs == 0x00) {
+				// End of block.
+				tbl->ac_table_codes[i] = 0;
+				tbl->ac_table_length[i] = length;
+				tbl->ac_table_skip[i] = 64;
+				continue;
+			}
+			if (rs == 0xf0) {
+				// 16 zero coefficients.
+				tbl->ac_table_codes[i] = 0;
+				tbl->ac_table_length[i] = length;
+				tbl->ac_table_skip[i] = 16;
+				continue;
+			}
+			
+			unsigned r = rs >> 4;
+			unsigned s = rs & 0xf;
+			if (s > DEHUF_AC_TABLE_BITS - length) {
+				// Not enough bits to decode this coefficient.
+				continue;
+			}
+
+			unsigned bits = (i >> (DEHUF_AC_TABLE_BITS - length - s)) & ((1 << s) - 1);
+
+			tbl->ac_table_codes[i] = extend(bits, s);
+			tbl->ac_table_length[i] = length + s;
+			tbl->ac_table_skip[i] = r + 1;
+
+			assert(tbl->ac_table_length[i] <= DEHUF_AC_TABLE_BITS);
+		}	
 	}
 
 	free(buf);