X-Git-Url: https://git.sesse.net/?p=fjl;a=blobdiff_plain;f=dehuff.c;h=5574e27184b8de5961b01f1f76cbf0e27688c89b;hp=8fd4c2072fce46cbe792295fc977a3e7f53b2deb;hb=HEAD;hpb=352c52d38c212a2aa93a9970731c9d7a2f8d4dac

diff --git a/dehuff.c b/dehuff.c
index 8fd4c20..5574e27 100644
--- a/dehuff.c
+++ b/dehuff.c
@@ -8,7 +8,7 @@
 
 void read_huffman_tables(huffman_tables_t* dst, input_func_t* input_func, void* userdata)
 {
-	size_t len = read_length(input_func, userdata);
+	size_t len = read_uint16(input_func, userdata);
 	assert(len > 2);
 	len -= 2;
 
@@ -32,7 +32,7 @@ void read_huffman_tables(huffman_tables_t* dst, input_func_t* input_func, void*
 			exit(1);
 		}
 
-		struct huffman_table* tbl = dst[table_class][table_dest];
+		struct huffman_table* tbl = &((*dst)[table_class][table_dest]);
 		if (len < 16) {
 			fprintf(stderr, "Short read for num_codes\n");
 			exit(1);
@@ -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);