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Change padding bytes to a unique stream-end marker; #89

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This commit is contained in:
Dominic Szablewski 2021-12-16 20:50:19 +01:00
parent bf6951036d
commit 3a62cabad2
1 changed files with 13 additions and 9 deletions
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22
qoi.h
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@ -83,8 +83,8 @@ implementation you can define QOI_ZEROARR before including this library.
-- Data Format -- Data Format
A QOI file has a 14 byte header, followed by any number of data "chunks" and 8 A QOI file has a 14 byte header, followed by any number of data "chunks" and an
zero-bytes to mark the end of the data stream. 8-byte end marker.
struct qoi_header_t { struct qoi_header_t {
char magic[4]; // magic bytes "qoif" char magic[4]; // magic bytes "qoif"
@ -120,7 +120,7 @@ values encoded in these data bits have the most significant bit on the left.
The 8-bit tags have precedence over the 2-bit tags. A decoder must check for the The 8-bit tags have precedence over the 2-bit tags. A decoder must check for the
presence of an 8-bit tag first. presence of an 8-bit tag first.
The byte stream is padded with 8 zero-bytes at the end. The byte stream's end is marked with 7 0x00 bytes followed a single 0x01 byte.
The possible chunks are: The possible chunks are:
@ -135,6 +135,9 @@ The possible chunks are:
2-bit tag b00 2-bit tag b00
6-bit index into the color index array: 0..63 6-bit index into the color index array: 0..63
A valid encoder must not issue 7 or more consecutive QOI_OP_INDEX chunks to the
index 0, to avoid confusion with the 8 byte end marker.
.- QOI_OP_DIFF -----------. .- QOI_OP_DIFF -----------.
| Byte[0] | | Byte[0] |
@ -342,7 +345,6 @@ Implementation */
(((unsigned int)'q') << 24 | ((unsigned int)'o') << 16 | \ (((unsigned int)'q') << 24 | ((unsigned int)'o') << 16 | \
((unsigned int)'i') << 8 | ((unsigned int)'f')) ((unsigned int)'i') << 8 | ((unsigned int)'f'))
#define QOI_HEADER_SIZE 14 #define QOI_HEADER_SIZE 14
#define QOI_PADDING 8
/* 2GB is the max file size that this implementation can safely handle. We guard /* 2GB is the max file size that this implementation can safely handle. We guard
against anything larger than that, assuming the worst case with 5 bytes per against anything larger than that, assuming the worst case with 5 bytes per
@ -355,6 +357,8 @@ typedef union {
unsigned int v; unsigned int v;
} qoi_rgba_t; } qoi_rgba_t;
static const unsigned char qoi_padding[8] = {0,0,0,0,0,0,0,1};
void qoi_write_32(unsigned char *bytes, int *p, unsigned int v) { void qoi_write_32(unsigned char *bytes, int *p, unsigned int v) {
bytes[(*p)++] = (0xff000000 & v) >> 24; bytes[(*p)++] = (0xff000000 & v) >> 24;
bytes[(*p)++] = (0x00ff0000 & v) >> 16; bytes[(*p)++] = (0x00ff0000 & v) >> 16;
@ -390,7 +394,7 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
max_size = max_size =
desc->width * desc->height * (desc->channels + 1) + desc->width * desc->height * (desc->channels + 1) +
QOI_HEADER_SIZE + QOI_PADDING; QOI_HEADER_SIZE + sizeof(qoi_padding);
p = 0; p = 0;
bytes = (unsigned char *) QOI_MALLOC(max_size); bytes = (unsigned char *) QOI_MALLOC(max_size);
@ -495,8 +499,8 @@ void *qoi_encode(const void *data, const qoi_desc *desc, int *out_len) {
px_prev = px; px_prev = px;
} }
for (i = 0; i < QOI_PADDING; i++) { for (i = 0; i < sizeof(qoi_padding); i++) {
bytes[p++] = 0; bytes[p++] = qoi_padding[i];
} }
*out_len = p; *out_len = p;
@ -515,7 +519,7 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) {
if ( if (
data == NULL || desc == NULL || data == NULL || desc == NULL ||
(channels != 0 && channels != 3 && channels != 4) || (channels != 0 && channels != 3 && channels != 4) ||
size < QOI_HEADER_SIZE + QOI_PADDING size < QOI_HEADER_SIZE + sizeof(qoi_padding)
) { ) {
return NULL; return NULL;
} }
@ -554,7 +558,7 @@ void *qoi_decode(const void *data, int size, qoi_desc *desc, int channels) {
px.rgba.b = 0; px.rgba.b = 0;
px.rgba.a = 255; px.rgba.a = 255;
chunks_len = size - QOI_PADDING; chunks_len = size - sizeof(qoi_padding);
for (px_pos = 0; px_pos < px_len; px_pos += channels) { for (px_pos = 0; px_pos < px_len; px_pos += channels) {
if (run > 0) { if (run > 0) {
run--; run--;