Fix some errors/warnings in driver.c.

[fjl] / driver.c

diff --git a/driver.c b/driver.c
index 04e236912ca45d56bc4f1a34f16b3c04185112d9..6dcc8b3da676161ecd60e05898a27ebe3d19bf3f 100644 (file)
--- a/driver.c
+++ b/driver.c
@@ -15,10 +15,12 @@ struct jpeg_image {
        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) 
@@ -103,13 +105,59 @@ void read_sof(struct byte_source* source, struct jpeg_image* image)
 
                unsigned width = image->num_blocks_horizontal * image->hsample[c] * DCTSIZE;
                unsigned height = image->num_blocks_vertical * image->vsample[c] * DCTSIZE;
+               image->stride[c] = width;
                image->pixel_data[c] = (uint8_t*)malloc(width * height);
                assert(image->pixel_data[c] != NULL);
+               image->pixel_write_pointer[c] = image->pixel_data[c];
 
                fprintf(stderr, "Component %u: allocating %d x %d\n", c, width, height);
        }
 }
 
+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);
+               unsigned lookup = peek_bits(bits, DEHUF_AC_TABLE_BITS);
+               int code = tbl->ac_table_codes[lookup];
+
+               if (__builtin_expect(code == AC_DEHUF_SLOW_PATH, 0)) {
+                       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;
+                       }
+
+                       coeff[unzigzag[i]] = extend(read_bits(bits, s), s);
+               } else {
+                       unsigned length = tbl->ac_table_length[lookup];
+                       int r = tbl->ac_table_skip[lookup];
+                       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;
+                       }
+                       coeff[unzigzag[i]] = code;
+               }
+       }
+}
+
 void read_scan(struct byte_source* source, struct jpeg_image* image, huffman_tables_t* tables)
 {
        unsigned len = read_uint16(byte_source_input_func, source);
@@ -154,11 +202,12 @@ void read_scan(struct byte_source* source, struct jpeg_image* image, huffman_tab
        while (!bits.source_eof) {
                for (unsigned c = 0; c < num_components; ++c) {
                        unsigned cn = component_num[c];
-                       unsigned stride = image->num_blocks_horizontal * image->hsample[cn] * DCTSIZE;
                        assert(image->idct_data[image->qtable[cn]] != NULL);
-                       
-                       for (unsigned local_yb = 0; local_yb < image->vsample[cn]; ++local_yb) {
-                               for (unsigned local_xb = 0; local_xb < image->hsample[cn]; ++local_xb) {
+
+                       uint8_t* pixel_write_pointer_y = image->pixel_write_pointer[cn];
+                       for (unsigned local_yb = 0; local_yb < image->vsample[cn]; ++local_yb, pixel_write_pointer_y += image->stride[cn] * DCTSIZE) {
+                               uint8_t* pixel_write_pointer = pixel_write_pointer_y;
+                               for (unsigned local_xb = 0; local_xb < image->hsample[cn]; ++local_xb, pixel_write_pointer += DCTSIZE) {
                                        const struct huffman_table* dc_table = &((*tables)[DC_CLASS][dc_huffman_table[c]]);
                                        const struct huffman_table* ac_table = &((*tables)[AC_CLASS][ac_huffman_table[c]]);
 
@@ -169,44 +218,28 @@ void read_scan(struct byte_source* source, struct jpeg_image* image, huffman_tab
                                        
                                        int16_t coeff[DCTSIZE2] = { 0 };
                                        coeff[0] = last_dc[c];
+                                       decode_ac_coefficients(ac_table, &bits, coeff);
 
-                                       // decode AC components
-                                       for (unsigned i = 1; i < DCTSIZE2; ++i) {
-                                               unsigned rs = read_huffman_symbol(ac_table, &bits);
-                                               unsigned r = rs >> 4;
-                                               unsigned s = rs & 0xf;
-
-                                               if (rs == 0x00) {
-                                                       /* end of block */
-                                                       break;
-                                               }
-                                               if (rs == 0xf0) {
-                                                       /* 16 zero coefficients */
-                                                       i += 15;
-                                                       continue;
-                                               }
-                                               i += r;
-
-                                               possibly_refill(&bits, s);
-                                               coeff[unzigzag[i]] = extend(read_bits(&bits, s), s);
-                                       }
-                       
                                        uint8_t pixdata[DCTSIZE2];      
                                        idct_choice(coeff, image->idct_data[image->qtable[cn]], pixdata);
 
-                                       unsigned real_x = (mcu_x * image->hsample[cn] + local_xb) * DCTSIZE;
-                                       unsigned real_y = (mcu_y * image->vsample[cn] + local_yb) * DCTSIZE;
-                                       uint8_t* dest_pixdata = image->pixel_data[cn] + real_y * stride + real_x;
-                                       for (unsigned y = 0; y < DCTSIZE; ++y, dest_pixdata += stride) {
+                                       uint8_t* dest_pixdata = pixel_write_pointer;
+                                       for (unsigned y = 0; y < DCTSIZE; ++y, dest_pixdata += image->stride[cn]) {
                                                memcpy(dest_pixdata, pixdata + y * DCTSIZE, DCTSIZE);
                                        }
                                }
                        }
+                       image->pixel_write_pointer[cn] += DCTSIZE * image->hsample[cn];
                }
-               
+       
                if (++mcu_x == image->num_blocks_horizontal) {
                        ++mcu_y;
                        mcu_x = 0;
+               
+                       for (unsigned c = 0; c < num_components; ++c) {
+                               unsigned cn = component_num[c];
+                               image->pixel_write_pointer[cn] += (image->vsample[cn] * DCTSIZE - 1) * image->stride[cn];
+                       }
 
                        // Some debug code.
                        const int c = 1;