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Don't run past the padding of the byte stream when decoding; re #4

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This commit is contained in:
Dominic Szablewski 2021-11-24 22:09:08 +01:00
parent de17b3c2c1
commit e969322d00
1 changed files with 9 additions and 4 deletions
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13
qoi.h
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@ -145,6 +145,10 @@ QOI_COLOR {
u8 a; // alpha value if has_a == 1: 0..255 u8 a; // alpha value if has_a == 1: 0..255
} }
The byte stream is padded with 4 zero bytes. Size the longest chunk we can
encounter is 5 bytes (QOI_COLOR with RGBA set), with this padding we just have
to check for an overrun once per decode loop iteration.
*/ */
@ -231,6 +235,7 @@ void *qoi_decode(const void *data, int size, int *out_w, int *out_h, int channel
#define QOI_MASK_4 0xf0 // 11110000 #define QOI_MASK_4 0xf0 // 11110000
#define QOI_COLOR_HASH(C) (C.rgba.r ^ C.rgba.g ^ C.rgba.b ^ C.rgba.a) #define QOI_COLOR_HASH(C) (C.rgba.r ^ C.rgba.g ^ C.rgba.b ^ C.rgba.a)
#define QOI_PADDING 4
typedef union { typedef union {
struct { unsigned char r, g, b, a; } rgba; struct { unsigned char r, g, b, a; } rgba;
@ -362,7 +367,7 @@ void *qoi_encode(const void *data, int w, int h, int channels, int *out_len) {
px_prev = px; px_prev = px;
} }
for (int i = 0; i < 4; i++) { for (int i = 0; i < QOI_PADDING; i++) {
bytes[p++] = 0; bytes[p++] = 0;
} }
@ -394,16 +399,16 @@ void *qoi_decode(const void *data, int size, int *out_w, int *out_h, int channel
const unsigned char *bytes = (const unsigned char *)data + sizeof(qoi_header_t); const unsigned char *bytes = (const unsigned char *)data + sizeof(qoi_header_t);
int data_len = header->size; int data_len = header->size - QOI_PADDING;
qoi_rgba_t px = {.rgba = {.r = 0, .g = 0, .b = 0, .a = 255}}; qoi_rgba_t px = {.rgba = {.r = 0, .g = 0, .b = 0, .a = 255}};
qoi_rgba_t index[64] = {0}; qoi_rgba_t index[64] = {0};
int run = 0; int run = 0;
for (int px_pos = 0, p = 0; px_pos < px_len && p < data_len; px_pos += channels) { for (int px_pos = 0, p = 0; px_pos < px_len; px_pos += channels) {
if (run > 0) { if (run > 0) {
run--; run--;
} }
else { else if (p < data_len) {
int b1 = bytes[p++]; int b1 = bytes[p++];
if ((b1 & QOI_MASK_2) == QOI_INDEX) { if ((b1 & QOI_MASK_2) == QOI_INDEX) {