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jpeg: malloc-less implementation

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This commit is contained in:
K. Lange 2018-12-05 18:12:11 +09:00
parent 0ddc8c15a1
commit 6f33b2ff97
1 changed files with 24 additions and 68 deletions
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92
lib/jpeg.c
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@ -104,59 +104,16 @@ static int xy_to_lin(int x, int y) {
struct huffman_table {
uint8_t lengths[16];
uint8_t * elements;
uint8_t elements[256];
} huffman_tables[256] = {0};
struct stream {
uint8_t * data;
FILE * file;
uint8_t byte;
int have;
int pos;
};
static struct stream * read_stream(FILE * f, int len) {
uint8_t *out = malloc(image_width * image_height * 3);
int size = image_width * image_height * 3;
int off = 0;
uint8_t data[2];
fread(&data, 2, 1, f);
int i = 0;
while (1) {
if (data[0] == 0xFF) {
if (data[1] != 0) {
fseek(f, -2, SEEK_CUR);
break;
}
out[off] = data[0];
off++;
i+= 2;
fread(&data, 2, 1, f);
} else {
out[off] = data[0];
off++;
i++;
data[0] = data[1];
fread(&data[1], 1, 1, f);
}
if (off >= size-1) {
size *= 2;
TRACE("upping size to %d", size);
out = realloc(out, size);
TRACE("done");
}
}
struct stream * st = malloc(sizeof(struct stream));
st->pos = 0;
st->data = out;
return st;
}
static void define_quant_table(FILE * f, int len) {
TRACE("Defining quant table");
@ -238,17 +195,15 @@ static void define_huffman_table(FILE * f, int len) {
required += lengths[i];
}
uint8_t * elements = malloc(sizeof(uint8_t) * required);
int o = 0;
for (int i = 0; i < 16; ++i) {
int l = lengths[i];
fread(&elements[o], l, 1, f);
fread(&huffman_tables[hdr].elements[o], l, 1, f);
o += l;
len -= l;
}
memcpy(huffman_tables[hdr].lengths, lengths, 16);
huffman_tables[hdr].elements = elements;
}
if (len > 0) {
@ -286,7 +241,22 @@ static void add_zigzag(struct idct * self, int zi, int coeff) {
}
static int get_bit(struct stream * st) {
uint8_t b = st->data[st->pos >> 3];
while ((st->pos >> 3) >= st->have) {
int t = fgetc(st->file);
if (t < 0) {
st->byte = 0;
} else {
st->byte = t;
}
if (st->byte == 0xFF) {
int tmp = fgetc(st->file);
if (tmp != 0) {
st->byte = 0;
}
}
st->have++;
}
uint8_t b = st->byte;
int s = 7 - (st->pos & 0x7);
st->pos += 1;
return (b >> s) & 1;
@ -375,7 +345,9 @@ static void start_of_scan(FILE * f, int len) {
/* Skip header */
fseek(f, len, SEEK_CUR);
struct stream * st = read_stream(f, len);
struct stream _st = {0};
_st.file = f;
struct stream * st = &_st;
TRACE("read stream, continuing...");
@ -403,13 +375,6 @@ static void start_of_scan(FILE * f, int len) {
}
TRACE("done");
TRACE("Freeing stream data");
free(st->data);
free(st);
TRACE("done done");
TRACE("returning");
}
int load_sprite_jpg(sprite_t * tsprite, char * filename) {
@ -460,14 +425,5 @@ int load_sprite_jpg(sprite_t * tsprite, char * filename) {
}
}
TRACE("freeing huffman tables");
for (int i = 0; i < 256; ++i) {
if (huffman_tables[i].elements) {
free(huffman_tables[i].elements);
huffman_tables[i].elements = 0;
}
}
return 0;
}