mpv/libmpdemux/ebml.c

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/*
* native ebml reader for the Matroska demuxer
* Written by Aurelien Jacobs <aurel@gnuage.org>
* Based on the one written by Ronald Bultje for gstreamer
* Licence: GPL
*/
#include "config.h"
#ifdef HAVE_MATROSKA
#include <stdlib.h>
#include "stream.h"
#include "ebml.h"
/*
* Read: the element content data ID.
* Return: the ID.
*/
uint32_t
ebml_read_id (stream_t *s, int *length)
{
int i, len_mask = 0x80;
uint32_t id;
for (i=0, id=stream_read_char (s); i<4 && !(id & len_mask); i++)
len_mask >>= 1;
if (i >= 4)
return EBML_ID_INVALID;
if (length)
*length = i + 1;
while (i--)
id = (id << 8) | stream_read_char (s);
return id;
}
/*
* Read a variable length unsigned int.
*/
uint64_t
ebml_read_vlen_uint (uint8_t *buffer, int *length)
{
int i, j, num_ffs = 0, len_mask = 0x80;
uint64_t num;
for (i=0, num=*buffer++; i<8 && !(num & len_mask); i++)
len_mask >>= 1;
if (i >= 8)
return EBML_UINT_INVALID;
j = i+1;
if (length)
*length = j;
if (((int)num &= (len_mask - 1)) == len_mask - 1)
num_ffs++;
while (i--)
{
num = (num << 8) | *buffer++;
if ((num & 0xFF) == 0xFF)
num_ffs++;
}
if (j == num_ffs)
return EBML_UINT_INVALID;
return num;
}
/*
* Read a variable length signed int.
*/
int64_t
ebml_read_vlen_int (uint8_t *buffer, int *length)
{
uint64_t unum;
int l;
/* read as unsigned number first */
unum = ebml_read_vlen_uint (buffer, &l);
if (unum == EBML_UINT_INVALID)
return EBML_INT_INVALID;
if (length)
*length = l;
return unum - ((1 << ((7 * l) - 1)) - 1);
}
/*
* Read: element content length.
*/
uint64_t
ebml_read_length (stream_t *s, int *length)
{
int i, j, num_ffs = 0, len_mask = 0x80;
uint64_t len;
for (i=0, len=stream_read_char (s); i<8 && !(len & len_mask); i++)
len_mask >>= 1;
if (i >= 8)
return EBML_UINT_INVALID;
j = i+1;
if (length)
*length = j;
if (((int)len &= (len_mask - 1)) == len_mask - 1)
num_ffs++;
while (i--)
{
len = (len << 8) | stream_read_char (s);
if ((len & 0xFF) == 0xFF)
num_ffs++;
}
if (j == num_ffs)
return EBML_UINT_INVALID;
return len;
}
/*
* Read the next element as an unsigned int.
*/
uint64_t
ebml_read_uint (stream_t *s, uint64_t *length)
{
uint64_t len, value = 0;
int l;
len = ebml_read_length (s, &l);
if (len == EBML_UINT_INVALID || len < 1 || len > 8)
return EBML_UINT_INVALID;
if (length)
*length = len + l;
while (len--)
value = (value << 8) | stream_read_char (s);
return value;
}
/*
* Read the next element as a signed int.
*/
int64_t
ebml_read_int (stream_t *s, uint64_t *length)
{
int64_t value = 0;
uint64_t len;
int l;
len = ebml_read_length (s, &l);
if (len == EBML_UINT_INVALID || len < 1 || len > 8)
return EBML_INT_INVALID;
if (length)
*length = len + l;
len--;
l = stream_read_char (s);
if (l & 0x80)
value = -1;
value = (value << 8) | l;
while (len--)
value = (value << 8) | stream_read_char (s);
return value;
}
/*
* Read the next element as a float.
*/
long double
ebml_read_float (stream_t *s, uint64_t *length)
{
long double value;
uint64_t len;
int l;
len = ebml_read_length (s, &l);
switch (len)
{
case 4:
{
uint32_t i;
float *f;
#ifndef WORDS_BIGENDIAN
i = stream_read_dword (s);
#else
i = stream_read_dword_le (s);
#endif
f = (float *) (void *) &i;
value = *f;
break;
}
case 8:
{
uint64_t i;
double *d;
#ifndef WORDS_BIGENDIAN
i = stream_read_qword (s);
#else
i = stream_read_qword_le (s);
#endif
d = (double *) (void *) &i;
value = *d;
break;
}
case 10:
{
uint8_t data[10];
#ifdef WORDS_BIGENDIAN
int i = 10;
#endif
if (stream_read (s, data, 10) != 10)
return EBML_FLOAT_INVALID;
#ifndef WORDS_BIGENDIAN
value = * (long double *) data;
#else
while (i--)
((uint8_t *) &value)[i] = data[9 - i];
#endif
break;
}
default:
return EBML_FLOAT_INVALID;
}
if (length)
*length = len + l;
return value;
}
/*
* Read the next element as an ASCII string.
*/
char *
ebml_read_ascii (stream_t *s, uint64_t *length)
{
uint64_t len;
char *str;
int l;
len = ebml_read_length (s, &l);
if (len == EBML_UINT_INVALID)
return NULL;
if (length)
*length = len + l;
str = (char *) malloc (len+1);
if (stream_read(s, str, len) != (int) len)
{
free (str);
return NULL;
}
str[len] = '\0';
return str;
}
/*
* Read the next element as a UTF-8 string.
*/
char *
ebml_read_utf8 (stream_t *s, uint64_t *length)
{
return ebml_read_ascii (s, length);
}
/*
* Skip the next element.
*/
int
ebml_read_skip (stream_t *s, uint64_t *length)
{
uint64_t len;
int l;
len = ebml_read_length (s, &l);
if (len == EBML_UINT_INVALID)
return 1;
if (length)
*length = len + l;
stream_skip(s, len);
return 0;
}
/*
* Read the next element, but only the header. The contents
* are supposed to be sub-elements which can be read separately.
*/
uint32_t
ebml_read_master (stream_t *s, uint64_t *length)
{
uint64_t len;
uint32_t id;
id = ebml_read_id (s, NULL);
if (id == EBML_ID_INVALID)
return id;
len = ebml_read_length (s, NULL);
if (len == EBML_UINT_INVALID)
return EBML_ID_INVALID;
if (length)
*length = len;
return id;
}
/*
* Read an EBML header.
*/
char *
ebml_read_header (stream_t *s, int *version)
{
uint64_t length, l, num;
uint32_t id;
char *str = NULL;
if (ebml_read_master (s, &length) != EBML_ID_HEADER)
return 0;
if (version)
*version = 1;
while (length > 0)
{
id = ebml_read_id (s, NULL);
if (id == EBML_ID_INVALID)
return NULL;
length -= 2;
switch (id)
{
/* is our read version uptodate? */
case EBML_ID_EBMLREADVERSION:
num = ebml_read_uint (s, &l);
if (num != EBML_VERSION)
return NULL;
break;
/* we only handle 8 byte lengths at max */
case EBML_ID_EBMLMAXSIZELENGTH:
num = ebml_read_uint (s, &l);
if (num != sizeof (uint64_t))
return NULL;
break;
/* we handle 4 byte IDs at max */
case EBML_ID_EBMLMAXIDLENGTH:
num = ebml_read_uint (s, &l);
if (num != sizeof (uint32_t))
return NULL;
break;
case EBML_ID_DOCTYPE:
str = ebml_read_ascii (s, &l);
if (str == NULL)
return NULL;
break;
case EBML_ID_DOCTYPEREADVERSION:
num = ebml_read_uint (s, &l);
if (num == EBML_UINT_INVALID)
return NULL;
if (version)
*version = num;
break;
/* we ignore these two, they don't tell us anything we care about */
case EBML_ID_VOID:
case EBML_ID_EBMLVERSION:
case EBML_ID_DOCTYPEVERSION:
default:
if (ebml_read_skip (s, &l))
return NULL;
break;
}
length -= l;
}
return str;
}
#endif /* HAVE_MATROSKA */