Move some parts of the driver code into its own function.

[fjl] / driver.c

diff --git a/driver.c b/driver.c
index cda257e3c90ba023ed8b465eeedf2e1417768aff..c4f48ac6f9557df89fea22169f995bbb52c7994a 100644 (file)
--- a/driver.c
+++ b/driver.c
@@ -5,24 +5,11 @@
 #include "bytesource.h"
 #include "choice.h"
 #include "dehuff.h"
+#include "driver.h"
 #include "idct.h"
 #include "input.h"
 #include "zigzag.h"
 
-struct jpeg_image {
-       unsigned precision;
-       unsigned width, height;
-       unsigned num_components;
-       unsigned hsample[256], vsample[256], qtable[256];
-       unsigned max_hsample, max_vsample;
-       unsigned stride[256];
-       unsigned num_blocks_horizontal, num_blocks_vertical;
-       uint32_t qvalues[256][DCTSIZE2];
-       void* idct_data[256];
-       uint8_t* pixel_data[256];
-       uint8_t* pixel_write_pointer[256];
-};
-
 ssize_t stdio_read(void* userdata, uint8_t* buf, size_t count) 
 {
        return fread(buf, 1, count, (FILE*)userdata);
@@ -116,45 +103,33 @@ void read_sof(struct byte_source* source, struct jpeg_image* image)
 
 void decode_ac_coefficients(const struct huffman_table* tbl, struct bit_source* bits, int16_t* coeff)
 {
-       for (unsigned i = 1; i < DCTSIZE2; ++i) {
-               possibly_refill(bits, DEHUF_AC_TABLE_BITS);
+       possibly_refill(bits, DEHUF_AC_TABLE_BITS);
+       for (unsigned i = 0; i < DCTSIZE2 - 1; ) {
                unsigned lookup = peek_bits(bits, DEHUF_AC_TABLE_BITS);
                int code = tbl->ac_table_codes[lookup];
-               int length = tbl->ac_table_length[lookup];
-               int r = tbl->ac_table_skip[lookup];
-
-               assert(length == AC_DEHUF_SLOW_PATH || (length > 0 && length <= DEHUF_AC_TABLE_BITS));
+               unsigned length = tbl->ac_table_length[lookup];
+               unsigned r = tbl->ac_table_skip[lookup];
 
-               if (__builtin_expect(code == AC_DEHUF_SLOW_PATH, 0)) {
+               if (code == AC_DEHUF_SLOW_PATH) {
                        unsigned rs = read_huffman_symbol_no_refill(tbl, bits);
-                       unsigned r = rs >> 4;
-                       unsigned s = rs & 0xf;
-                       i += r;
-                       possibly_refill(bits, s);
-
                        if (rs == 0x00) {
-                               assert(code == AC_DEHUF_SLOW_PATH || code == AC_END_OF_BLOCK);
                                /* end of block */
                                break;
                        }
-                       if (rs == 0xf0) {
-                               assert(code == AC_DEHUF_SLOW_PATH || code == AC_SIXTEEN_ZEROS);
-                               /* 16 zero coefficients */
-                               continue;
-                       }
 
+                       unsigned r = rs >> 4;
+                       unsigned s = rs & 0xf;
+                       i += r + 1;
+                       possibly_refill(bits, s);
                        coeff[unzigzag[i]] = extend(read_bits(bits, s), s);
+                       possibly_refill(bits, DEHUF_AC_TABLE_BITS);
                } else {
-                       assert(r >= 0);
-                       i += r;
                        assert(bits->bits_available >= length);
                        read_bits(bits, length);
-                       if (code == AC_END_OF_BLOCK) {
-                               break;
-                       }
-                       if (code == AC_SIXTEEN_ZEROS) {
-                               continue;
-                       }
+                       possibly_refill(bits, DEHUF_AC_TABLE_BITS);
+
+                       assert(r >= 1);
+                       i += r;
                        coeff[unzigzag[i]] = code;
                }
        }
@@ -273,14 +248,12 @@ void skip_segment(struct byte_source* source)
        }
 }
        
-int main(void)
+void read_jpeg(struct jpeg_image* jpeg, FILE *input)
 {
-       struct jpeg_image jpeg;
-       memset(&jpeg, 0, sizeof(jpeg));
-       init_choices();
-
+       memset(jpeg, 0, sizeof(*jpeg));
+       
        struct byte_source source;
-       init_byte_source(&source, stdio_read, stdin);
+       init_byte_source(&source, stdio_read, input);
 
        huffman_tables_t tables;
 
@@ -318,11 +291,11 @@ int main(void)
                        break;
                case 0xdb:
                        /* DQT */
-                       read_dqt(&source, &jpeg);
+                       read_dqt(&source, jpeg);
                        break;
                case 0xc0:
                        /* SOF0 (baseline DCT, Huffman encoded) */
-                       read_sof(&source, &jpeg);
+                       read_sof(&source, jpeg);
                        break;
                case 0xd8:
                        /* SOI */
@@ -336,7 +309,7 @@ int main(void)
                        break;
                case 0xda:
                        /* SOS (start of scan) */
-                       read_scan(&source, &jpeg, &tables);
+                       read_scan(&source, jpeg, &tables);
                        break;
                default:
                        fprintf(stderr, "Error: Unknown marker 0x%02x\n", m2);
@@ -344,3 +317,11 @@ int main(void)
                }
        }
 }
+       
+int main(void)
+{
+       init_choices();
+
+       struct jpeg_image jpeg;
+       read_jpeg(&jpeg, stdin);
+}