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avformat/aviobuf: add ffio_read_leb() and ffio_write_leb()

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Signed-off-by: James Almer <jamrial@gmail.com>
This commit is contained in:
James Almer 2023-11-25 11:07:34 -03:00
parent 0cc0d8c0b5
commit 7f9308380f
2 changed files with 43 additions and 0 deletions
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10
libavformat/avio_internal.h
View File

@ -146,6 +146,16 @@ int ffio_rewind_with_probe_data(AVIOContext *s, unsigned char **buf, int buf_siz
uint64_t ffio_read_varlen(AVIOContext *bc);
/**
* Read a unsigned integer coded as a variable number of up to eight
* little-endian bytes, where the MSB in a byte signals another byte
* must be read.
* All coded bytes are read, but values > UINT_MAX are truncated.
*/
unsigned int ffio_read_leb(AVIOContext *s);
void ffio_write_leb(AVIOContext *s, unsigned val);
/**
* Read size bytes from AVIOContext into buf.
* Check that exactly size bytes have been read.

33
libavformat/aviobuf.c
View File

@ -971,6 +971,39 @@ uint64_t ffio_read_varlen(AVIOContext *bc){
return val;
}
unsigned int ffio_read_leb(AVIOContext *s) {
int more, i = 0;
unsigned leb = 0;
do {
int byte = avio_r8(s);
unsigned bits = byte & 0x7f;
more = byte & 0x80;
if (i <= 4)
leb |= bits << (i * 7);
if (++i == 8)
break;
} while (more);
return leb;
}
void ffio_write_leb(AVIOContext *s, unsigned val)
{
int len;
uint8_t byte;
len = (av_log2(val) + 7) / 7;
for (int i = 0; i < len; i++) {
byte = val >> (7 * i) & 0x7f;
if (i < len - 1)
byte |= 0x80;
avio_w8(s, byte);
}
}
int ffio_fdopen(AVIOContext **s, URLContext *h)
{
uint8_t *buffer = NULL;