libmpdemux/ebml.c

   1 /*
   2  * native ebml reader for the Matroska demuxer
   3  * Written by Aurelien Jacobs <aurel@gnuage.org>
   4  * Based on the one written by Ronald Bultje for gstreamer
   5  * Licence: GPL
   6  */
   7
   8 #include "config.h"
   9
  10 #include <stdlib.h>
  11
  12 #include "stream.h"
  13 #include "ebml.h"
  14 #include "libavutil/common.h"
  15 #include "mpbswap.h"
  16 #include "libavutil/intfloat_readwrite.h"
  17
  18
  19 #ifndef SIZE_MAX
  20 #define SIZE_MAX ((size_t)-1)
  21 #endif
  22
  23 /*
  24  * Read: the element content data ID.
  25  * Return: the ID.
  26  */
  27 uint32_t
  28 ebml_read_id (stream_t *s, int *length)
  29 {
  30   int i, len_mask = 0x80;
  31   uint32_t id;
  32
  33   for (i=0, id=stream_read_char (s); i<4 && !(id & len_mask); i++)
  34     len_mask >>= 1;
  35   if (i >= 4)
  36     return EBML_ID_INVALID;
  37   if (length)
  38     *length = i + 1;
  39   while (i--)
  40     id = (id << 8) | stream_read_char (s);
  41   return id;
  42 }
  43
  44 /*
  45  * Read a variable length unsigned int.
  46  */
  47 uint64_t
  48 ebml_read_vlen_uint (uint8_t *buffer, int *length)
  49 {
  50   int i, j, num_ffs = 0, len_mask = 0x80;
  51   uint64_t num;
  52
  53   for (i=0, num=*buffer++; i<8 && !(num & len_mask); i++)
  54     len_mask >>= 1;
  55   if (i >= 8)
  56     return EBML_UINT_INVALID;
  57   j = i+1;
  58   if (length)
  59     *length = j;
  60   if ((int)(num &= (len_mask - 1)) == len_mask - 1)
  61     num_ffs++;
  62   while (i--)
  63     {
  64       num = (num << 8) | *buffer++;
  65       if ((num & 0xFF) == 0xFF)
  66         num_ffs++;
  67     }
  68   if (j == num_ffs)
  69     return EBML_UINT_INVALID;
  70   return num;
  71 }
  72
  73 /*
  74  * Read a variable length signed int.
  75  */
  76 int64_t
  77 ebml_read_vlen_int (uint8_t *buffer, int *length)
  78 {
  79   uint64_t unum;
  80   int l;
  81
  82   /* read as unsigned number first */
  83   unum = ebml_read_vlen_uint (buffer, &l);
  84   if (unum == EBML_UINT_INVALID)
  85     return EBML_INT_INVALID;
  86   if (length)
  87     *length = l;
  88
  89   return unum - ((1 << ((7 * l) - 1)) - 1);
  90 }
  91
  92 /*
  93  * Read: element content length.
  94  */
  95 uint64_t
  96 ebml_read_length (stream_t *s, int *length)
  97 {
  98   int i, j, num_ffs = 0, len_mask = 0x80;
  99   uint64_t len;
 100
 101   for (i=0, len=stream_read_char (s); i<8 && !(len & len_mask); i++)
 102     len_mask >>= 1;
 103   if (i >= 8)
 104     return EBML_UINT_INVALID;
 105   j = i+1;
 106   if (length)
 107     *length = j;
 108   if ((int)(len &= (len_mask - 1)) == len_mask - 1)
 109     num_ffs++;
 110   while (i--)
 111     {
 112       len = (len << 8) | stream_read_char (s);
 113       if ((len & 0xFF) == 0xFF)
 114         num_ffs++;
 115     }
 116   if (j == num_ffs)
 117     return EBML_UINT_INVALID;
 118   return len;
 119 }
 120
 121 /*
 122  * Read the next element as an unsigned int.
 123  */
 124 uint64_t
 125 ebml_read_uint (stream_t *s, uint64_t *length)
 126 {
 127   uint64_t len, value = 0;
 128   int l;
 129
 130   len = ebml_read_length (s, &l);
 131   if (len == EBML_UINT_INVALID || len < 1 || len > 8)
 132     return EBML_UINT_INVALID;
 133   if (length)
 134     *length = len + l;
 135
 136   while (len--)
 137     value = (value << 8) | stream_read_char (s);
 138
 139   return value;
 140 }
 141
 142 /*
 143  * Read the next element as a signed int.
 144  */
 145 int64_t
 146 ebml_read_int (stream_t *s, uint64_t *length)
 147 {
 148   int64_t value = 0;
 149   uint64_t len;
 150   int l;
 151
 152   len = ebml_read_length (s, &l);
 153   if (len == EBML_UINT_INVALID || len < 1 || len > 8)
 154     return EBML_INT_INVALID;
 155   if (length)
 156     *length = len + l;
 157
 158   len--;
 159   l = stream_read_char (s);
 160   if (l & 0x80)
 161     value = -1;
 162   value = (value << 8) | l;
 163   while (len--)
 164     value = (value << 8) | stream_read_char (s);
 165
 166   return value;
 167 }
 168
 169 /*
 170  * Read the next element as a float.
 171  */
 172 long double
 173 ebml_read_float (stream_t *s, uint64_t *length)
 174 {
 175   long double value;
 176   uint64_t len;
 177   int l;
 178
 179   len = ebml_read_length (s, &l);
 180   switch (len)
 181     {
 182     case 4:
 183         value = av_int2flt(stream_read_dword(s));
 184         break;
 185
 186     case 8:
 187         value = av_int2dbl(stream_read_qword(s));
 188         break;
 189
 190     default:
 191       return EBML_FLOAT_INVALID;
 192     }
 193
 194   if (length)
 195     *length = len + l;
 196
 197   return value;
 198 }
 199
 200 /*
 201  * Read the next element as an ASCII string.
 202  */
 203 char *
 204 ebml_read_ascii (stream_t *s, uint64_t *length)
 205 {
 206   uint64_t len;
 207   char *str;
 208   int l;
 209
 210   len = ebml_read_length (s, &l);
 211   if (len == EBML_UINT_INVALID)
 212     return NULL;
 213   if (len > SIZE_MAX - 1)
 214     return NULL;
 215   if (length)
 216     *length = len + l;
 217
 218   str = (char *) malloc (len+1);
 219   if (stream_read(s, str, len) != (int) len)
 220     {
 221       free (str);
 222       return NULL;
 223     }
 224   str[len] = '\0';
 225
 226   return str;
 227 }
 228
 229 /*
 230  * Read the next element as a UTF-8 string.
 231  */
 232 char *
 233 ebml_read_utf8 (stream_t *s, uint64_t *length)
 234 {
 235   return ebml_read_ascii (s, length);
 236 }
 237
 238 /*
 239  * Skip the next element.
 240  */
 241 int
 242 ebml_read_skip (stream_t *s, uint64_t *length)
 243 {
 244   uint64_t len;
 245   int l;
 246
 247   len = ebml_read_length (s, &l);
 248   if (len == EBML_UINT_INVALID)
 249     return 1;
 250   if (length)
 251     *length = len + l;
 252
 253   stream_skip(s, len);
 254
 255   return 0;
 256 }
 257
 258 /*
 259  * Read the next element, but only the header. The contents
 260  * are supposed to be sub-elements which can be read separately.
 261  */
 262 uint32_t
 263 ebml_read_master (stream_t *s, uint64_t *length)
 264 {
 265   uint64_t len;
 266   uint32_t id;
 267
 268   id = ebml_read_id (s, NULL);
 269   if (id == EBML_ID_INVALID)
 270     return id;
 271
 272   len = ebml_read_length (s, NULL);
 273   if (len == EBML_UINT_INVALID)
 274     return EBML_ID_INVALID;
 275   if (length)
 276     *length = len;
 277
 278   return id;
 279 }
 280
 281
 282 /*
 283  * Read an EBML header.
 284  */
 285 char *
 286 ebml_read_header (stream_t *s, int *version)
 287 {
 288   uint64_t length, l, num;
 289   uint32_t id;
 290   char *str = NULL;
 291
 292   if (ebml_read_master (s, &length) != EBML_ID_HEADER)
 293     return 0;
 294
 295   if (version)
 296     *version = 1;
 297
 298   while (length > 0)
 299     {
 300       id = ebml_read_id (s, NULL);
 301       if (id == EBML_ID_INVALID)
 302         return NULL;
 303       length -= 2;
 304
 305       switch (id)
 306         {
 307           /* is our read version uptodate? */
 308         case EBML_ID_EBMLREADVERSION:
 309           num = ebml_read_uint (s, &l);
 310           if (num != EBML_VERSION)
 311             return NULL;
 312           break;
 313
 314           /* we only handle 8 byte lengths at max */
 315         case EBML_ID_EBMLMAXSIZELENGTH:
 316           num = ebml_read_uint (s, &l);
 317           if (num != sizeof (uint64_t))
 318             return NULL;
 319           break;
 320
 321           /* we handle 4 byte IDs at max */
 322         case EBML_ID_EBMLMAXIDLENGTH:
 323           num = ebml_read_uint (s, &l);
 324           if (num != sizeof (uint32_t))
 325             return NULL;
 326           break;
 327
 328         case EBML_ID_DOCTYPE:
 329           str = ebml_read_ascii (s, &l);
 330           if (str == NULL)
 331             return NULL;
 332           break;
 333
 334         case EBML_ID_DOCTYPEREADVERSION:
 335           num = ebml_read_uint (s, &l);
 336           if (num == EBML_UINT_INVALID)
 337             return NULL;
 338           if (version)
 339             *version = num;
 340           break;
 341
 342           /* we ignore these two, they don't tell us anything we care about */
 343         case EBML_ID_VOID:
 344         case EBML_ID_EBMLVERSION:
 345         case EBML_ID_DOCTYPEVERSION:
 346         default:
 347           if (ebml_read_skip (s, &l))
 348             return NULL;
 349           break;
 350         }
 351       length -= l;
 352     }
 353
 354   return str;
 355 }