static void
flacdec_read_vorbis_comment(BitstreamReader *comment,
unsigned channel_count,
int *channel_mask)
{
struct bs_buffer *line = buf_new();
unsigned line_len;
unsigned total_lines;
const char mask_prefix[] =
"WAVEFORMATEXTENSIBLE_CHANNEL_MASK=";
if (!setjmp(*br_try(comment))) {
/*skip over vendor string*/
line_len = comment->read(comment, 32);
comment->skip_bytes(comment, line_len);
/*walk through all entries in the comment*/
for (total_lines = comment->read(comment, 32);
total_lines > 0;
total_lines--) {
const char *s;
/*populate entry one character at a time
(this avoids allocating a big chunk of space
if the length field is something way too large)*/
buf_reset(line);
for (line_len = comment->read(comment, 32);
line_len > 0;
line_len--) {
buf_putc(
toupper((int)comment->read(comment, 8)),
line);
}
buf_putc(0, line); /*NULL terminator*/
s = (const char *)buf_window_start(line);
/*if line starts with mask prefix*/
if (strstr(s, mask_prefix) == s) {
/*convert rest of line to base-16 integer*/
unsigned mask = (unsigned)strtoul(
s + strlen(mask_prefix), NULL, 16);
/*and populate mask field if its number of channel bits
matches the stream's channel count*/
if (channel_bits(mask) == channel_count) {
*channel_mask = mask;
}
}
}
br_etry(comment);
} else {
/*read error in VORBIS_COMMENT
(probably invalid length field somewhere)*/
br_etry(comment);
}
buf_close(line);
}
unsigned
buf_read(struct bs_buffer *stream, uint8_t *data, unsigned data_size)
{
const buf_size_t to_read = MIN(data_size, buf_window_size(stream));
memcpy(data, buf_window_start(stream), to_read);
stream->window_start += to_read;
return to_read;
}
void
buf_resize(struct bs_buffer *stream, unsigned additional_bytes)
{
/*only perform resize if space actually needed*/
if (additional_bytes > buf_unused_size(stream)) {
if (stream->window_start > 0) {
/*shift window down before extending buffer to add more space*/
if (buf_window_size(stream)) {
memmove(stream->data,
buf_window_start(stream),
buf_window_size(stream));
}
stream->window_end -= stream->window_start;
stream->window_start = 0;
}
while (additional_bytes > buf_unused_size(stream)) {
stream->data_size *= 2;
}
stream->data = realloc(stream->data, stream->data_size);
}
}
