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Tolerate chunks in between APNG chunks #11

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198 changes: 72 additions & 126 deletions YYImage/YYImageCoder.m
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Original file line number Diff line number Diff line change
Expand Up @@ -318,82 +318,6 @@ static double yy_png_delay_to_seconds(uint16_t num, uint16_t den) {
}
}

static bool yy_png_validate_animation_chunk_order(yy_png_chunk_info *chunks, /* input */
uint32_t chunk_num, /* input */
uint32_t *first_idat_index, /* output */
bool *first_frame_is_cover /* output */) {
/*
PNG at least contains 3 chunks: IHDR, IDAT, IEND.
`IHDR` must appear first.
`IDAT` must appear consecutively.
`IEND` must appear end.

APNG must contains one `acTL` and at least one 'fcTL' and `fdAT`.
`fdAT` must appear consecutively.
`fcTL` must appear before `IDAT` or `fdAT`.
*/
if (chunk_num <= 2) return false;
if (chunks->fourcc != YY_FOUR_CC('I', 'H', 'D', 'R')) return false;
if ((chunks + chunk_num - 1)->fourcc != YY_FOUR_CC('I', 'E', 'N', 'D')) return false;

uint32_t prev_fourcc = 0;
uint32_t IHDR_num = 0;
uint32_t IDAT_num = 0;
uint32_t acTL_num = 0;
uint32_t fcTL_num = 0;
uint32_t first_IDAT = 0;
bool first_frame_cover = false;
for (uint32_t i = 0; i < chunk_num; i++) {
yy_png_chunk_info *chunk = chunks + i;
switch (chunk->fourcc) {
case YY_FOUR_CC('I', 'H', 'D', 'R'): { // png header
if (i != 0) return false;
if (IHDR_num > 0) return false;
IHDR_num++;
} break;
case YY_FOUR_CC('I', 'D', 'A', 'T'): { // png data
if (prev_fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
if (IDAT_num == 0)
first_IDAT = i;
else
return false;
}
IDAT_num++;
} break;
case YY_FOUR_CC('a', 'c', 'T', 'L'): { // apng control
if (acTL_num > 0) return false;
acTL_num++;
} break;
case YY_FOUR_CC('f', 'c', 'T', 'L'): { // apng frame control
if (i + 1 == chunk_num) return false;
if ((chunk + 1)->fourcc != YY_FOUR_CC('f', 'd', 'A', 'T') &&
(chunk + 1)->fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
return false;
}
if (fcTL_num == 0) {
if ((chunk + 1)->fourcc == YY_FOUR_CC('I', 'D', 'A', 'T')) {
first_frame_cover = true;
}
}
fcTL_num++;
} break;
case YY_FOUR_CC('f', 'd', 'A', 'T'): { // apng data
if (prev_fourcc != YY_FOUR_CC('f', 'd', 'A', 'T') && prev_fourcc != YY_FOUR_CC('f', 'c', 'T', 'L')) {
return false;
}
} break;
}
prev_fourcc = chunk->fourcc;
}
if (IHDR_num != 1) return false;
if (IDAT_num == 0) return false;
if (acTL_num != 1) return false;
if (fcTL_num < acTL_num) return false;
*first_idat_index = first_IDAT;
*first_frame_is_cover = first_frame_cover;
return true;
}

static void yy_png_info_release(yy_png_info *info) {
if (info) {
if (info->chunks) free(info->chunks);
Expand All @@ -419,6 +343,7 @@ static void yy_png_info_release(yy_png_info *info) {
uint32_t chunk_realloc_num = 16;
yy_png_chunk_info *chunks = malloc(sizeof(yy_png_chunk_info) * chunk_realloc_num);
if (!chunks) return NULL;
yy_png_info *info = NULL;

// parse png chunks
uint32_t offset = 8;
Expand All @@ -429,34 +354,42 @@ static void yy_png_info_release(yy_png_info *info) {
int32_t apng_frame_index = 0;
int32_t apng_frame_number = -1;
bool apng_chunk_error = false;
bool first_frame_is_cover = false;
bool encountered_fdAT = false;
uint32_t first_IDAT_index = 0;
do {
if (chunk_num >= chunk_capacity) {
yy_png_chunk_info *new_chunks = realloc(chunks, sizeof(yy_png_chunk_info) * (chunk_capacity + chunk_realloc_num));
if (!new_chunks) {
free(chunks);
return NULL;
}
if (!new_chunks) goto fail;
chunks = new_chunks;
chunk_capacity += chunk_realloc_num;
}
yy_png_chunk_info *chunk = chunks + chunk_num;
const uint8_t *chunk_data = data + offset;
chunk->offset = offset;
chunk->length = yy_swap_endian_uint32(*((uint32_t *)chunk_data));
if ((uint64_t)chunk->offset + (uint64_t)chunk->length + 12 > length) {
free(chunks);
return NULL;
}
if ((uint64_t)chunk->offset + (uint64_t)chunk->length + 12 > length) goto fail;

chunk->fourcc = *((uint32_t *)(chunk_data + 4));
if ((uint64_t)chunk->offset + 4 + chunk->length + 4 > (uint64_t)length) break;
chunk->crc32 = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8 + chunk->length)));
chunk_num++;
offset += 12 + chunk->length;

if (chunk_num == 0 && chunk->fourcc != YY_FOUR_CC('I', 'H', 'D', 'R') ||
offset == length && chunk->fourcc != YY_FOUR_CC('I', 'E', 'N', 'D')) {
goto fail;
}
if (chunk->fourcc == YY_FOUR_CC('t', 'E', 'X', 't') ||
chunk->fourcc == YY_FOUR_CC('z', 'T', 'X', 't') ||
chunk->fourcc == YY_FOUR_CC('i', 'T', 'X', 't') ||
chunk->fourcc == YY_FOUR_CC('t', 'I', 'M', 'E') ||
chunk->fourcc == YY_FOUR_CC('e', 'X', 'I', 'f')) {
continue;
}
chunk_num++;

switch (chunk->fourcc) {
case YY_FOUR_CC('a', 'c', 'T', 'L') : {
if (chunk->length == 8) {
if (apng_frame_number == -1 && first_IDAT_index == 0 && chunk->length == 8) {
apng_frame_number = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8)));
apng_loop_num = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 12)));
} else {
Expand All @@ -466,11 +399,17 @@ case YY_FOUR_CC('a', 'c', 'T', 'L') : {
case YY_FOUR_CC('f', 'c', 'T', 'L') :
case YY_FOUR_CC('f', 'd', 'A', 'T') : {
if (chunk->fourcc == YY_FOUR_CC('f', 'c', 'T', 'L')) {
if (chunk->length != 26) {
apng_chunk_error = true;
} else {
if ((apng_frame_index > 0 ? encountered_fdAT : 1) && chunk->length == 26) {
apng_frame_index++;
encountered_fdAT = false;
} else {
apng_chunk_error = true;
}
} else if (apng_sequence_index == -1 || first_IDAT_index == 0 ||
(apng_sequence_index == 0 && first_frame_is_cover)) {
apng_chunk_error = true;
} else {
encountered_fdAT = true;
}
if (chunk->length > 4) {
uint32_t sequence = yy_swap_endian_uint32(*((uint32_t *)(chunk_data + 8)));
Expand All @@ -482,64 +421,60 @@ case YY_FOUR_CC('f', 'd', 'A', 'T') : {
} else {
apng_chunk_error = true;
}
if (apng_sequence_index == 0 && first_IDAT_index == 0) {
first_frame_is_cover = true;
}
} break;
case YY_FOUR_CC('I', 'D', 'A', 'T') : {
if (first_IDAT_index == 0) {
first_IDAT_index = chunk_num - 1;
} else if ((chunk - 1)->fourcc != YY_FOUR_CC('I', 'D', 'A', 'T')) {
goto fail;
}
encountered_fdAT = true;
} break;
case YY_FOUR_CC('I', 'H', 'D', 'R') : {
if (chunk->length != 13 || chunk_num != 1) goto fail;
} break;
case YY_FOUR_CC('I', 'E', 'N', 'D') : {
if (chunk->length != 0) goto fail;
offset = length; // end, break do-while loop
} break;
}
} while (offset + 12 <= length);

if (chunk_num < 3 ||
chunks->fourcc != YY_FOUR_CC('I', 'H', 'D', 'R') ||
chunks->length != 13) {
free(chunks);
return NULL;
}
if (first_IDAT_index == 0 || offset != length) goto fail;
if (!encountered_fdAT) apng_chunk_error = true;

// png info
yy_png_info *info = calloc(1, sizeof(yy_png_info));
if (!info) {
free(chunks);
return NULL;
}
info = calloc(1, sizeof(yy_png_info));
if (!info) goto fail;
info->chunks = chunks;
info->chunk_num = chunk_num;
yy_png_chunk_IHDR_read(&info->header, data + chunks->offset + 8);

// apng info
if (!apng_chunk_error && apng_frame_number == apng_frame_index && apng_frame_number >= 1) {
bool first_frame_is_cover = false;
uint32_t first_IDAT_index = 0;
if (!yy_png_validate_animation_chunk_order(info->chunks, info->chunk_num, &first_IDAT_index, &first_frame_is_cover)) {
return info; // ignore apng chunk
}

info->apng_loop_num = apng_loop_num;
info->apng_frame_num = apng_frame_number;
info->apng_first_frame_is_cover = first_frame_is_cover;
info->apng_shared_insert_index = first_IDAT_index;
info->apng_frames = calloc(apng_frame_number, sizeof(yy_png_frame_info));
if (!info->apng_frames) {
yy_png_info_release(info);
return NULL;
}
if (!info->apng_frames) goto fail;
info->apng_shared_chunk_indexs = calloc(info->chunk_num, sizeof(uint32_t));
if (!info->apng_shared_chunk_indexs) {
yy_png_info_release(info);
return NULL;
}
if (!info->apng_shared_chunk_indexs) goto fail;

int32_t frame_index = -1;
uint32_t *shared_chunk_index = info->apng_shared_chunk_indexs;
for (int32_t i = 0; i < info->chunk_num; i++) {
yy_png_chunk_info *chunk = info->chunks + i;
switch (chunk->fourcc) {
case YY_FOUR_CC('I', 'D', 'A', 'T'): {
if (info->apng_shared_insert_index == 0) {
info->apng_shared_insert_index = i;
}
if (first_frame_is_cover) {
yy_png_frame_info *frame = info->apng_frames + frame_index;
if (frame->chunk_index == 0) {
frame->chunk_index = i;
}
frame->chunk_num++;
frame->chunk_size += chunk->length + 12;
}
Expand All @@ -549,24 +484,33 @@ case YY_FOUR_CC('a', 'c', 'T', 'L'): {
case YY_FOUR_CC('f', 'c', 'T', 'L'): {
frame_index++;
yy_png_frame_info *frame = info->apng_frames + frame_index;
frame->chunk_index = i + 1;
yy_png_chunk_fcTL_read(&frame->frame_control, data + chunk->offset + 8);
} break;
case YY_FOUR_CC('f', 'd', 'A', 'T'): {
yy_png_frame_info *frame = info->apng_frames + frame_index;
if (frame->chunk_index == 0) {
frame->chunk_index = i;
}
frame->chunk_num++;
frame->chunk_size += chunk->length + 12;
} break;
default: {
*shared_chunk_index = i;
shared_chunk_index++;
info->apng_shared_chunk_size += chunk->length + 12;
info->apng_shared_chunk_num++;
if (i < first_IDAT_index || i == info->chunk_num - 1) {
*shared_chunk_index = i;
shared_chunk_index++;
info->apng_shared_chunk_size += chunk->length + 12;
info->apng_shared_chunk_num++;
}
} break;
}
}
}
return info;

fail:
if (info) yy_png_info_release(info);
else if (chunks) free(chunks);
return NULL;
}

/**
Expand Down Expand Up @@ -604,18 +548,20 @@ case YY_FOUR_CC('f', 'd', 'A', 'T'): {

if (shared_chunk_index >= info->apng_shared_insert_index && !inserted) { // replace IDAT with fdAT
inserted = true;
for (uint32_t c = 0; c < frame_info->chunk_num; c++) {
yy_png_chunk_info *insert_chunk_info = info->chunks + frame_info->chunk_index + c;
yy_png_chunk_info *insert_chunk_info = info->chunks + frame_info->chunk_index;
for (uint32_t c = frame_info->chunk_num; c > 0; insert_chunk_info++) {
if (insert_chunk_info->fourcc == YY_FOUR_CC('f', 'd', 'A', 'T')) {
*((uint32_t *)(frame_data + data_offset)) = yy_swap_endian_uint32(insert_chunk_info->length - 4);
*((uint32_t *)(frame_data + data_offset + 4)) = YY_FOUR_CC('I', 'D', 'A', 'T');
memcpy(frame_data + data_offset + 8, data + insert_chunk_info->offset + 12, insert_chunk_info->length - 4);
uint32_t crc = (uint32_t)crc32(0, frame_data + data_offset + 4, insert_chunk_info->length);
*((uint32_t *)(frame_data + data_offset + insert_chunk_info->length + 4)) = yy_swap_endian_uint32(crc);
data_offset += insert_chunk_info->length + 8;
} else { // IDAT
c--;
} else if (insert_chunk_info->fourcc == YY_FOUR_CC('I', 'D', 'A', 'T')) {
memcpy(frame_data + data_offset, data + insert_chunk_info->offset, insert_chunk_info->length + 12);
data_offset += insert_chunk_info->length + 12;
c--;
}
}
}
Expand Down