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Move MKV element magic values into proper #define constants.

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This commit is contained in:
Joseph Wallace 2015-11-21 17:29:26 -05:00
parent d394a244f0
commit af238d9129
1 changed files with 30 additions and 17 deletions
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47
src/format_ebml.c
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@ -42,6 +42,27 @@
/* A value that no EBML var-int is allowed to take. */ /* A value that no EBML var-int is allowed to take. */
#define EBML_UNKNOWN ((unsigned long long) -1) #define EBML_UNKNOWN ((unsigned long long) -1)
/* The magic numbers for each element we are interested in.
* Defined here:
* http://www.matroska.org/technical/specs/index.html
* http://www.webmproject.org/docs/container/
*
* Some of the higher-level elements have 4-byte identifiers;
* The lower-level elements have 1-byte identifiers.
*/
#define UNCOMMON_MAGIC_LEN 4
#define SEGMENT_MAGIC "\x18\x53\x80\x67"
#define CLUSTER_MAGIC "\x1F\x43\xB6\x75"
#define TRACKS_MAGIC "\x16\x54\xAE\x6B"
#define COMMON_MAGIC_LEN 1
#define TRACK_ENTRY_MAGIC "\xAE"
#define TRACK_NUMBER_MAGIC "\xD7"
#define TRACK_TYPE_MAGIC "\x83"
#define SIMPLE_BLOCK_MAGIC "\xA3"
typedef enum ebml_read_mode { typedef enum ebml_read_mode {
EBML_STATE_READING_HEADER = 0, EBML_STATE_READING_HEADER = 0,
EBML_STATE_READING_CLUSTERS EBML_STATE_READING_CLUSTERS
@ -550,14 +571,6 @@ static int ebml_wrote(ebml_t *ebml, int len)
unsigned char flags; unsigned char flags;
int copy_state; int copy_state;
char *segment_id = "\x18\x53\x80\x67";
char *cluster_id = "\x1F\x43\xB6\x75";
char *tracks_id = "\x16\x54\xAE\x6B";
char *track_entry_id = "\xAE";
char *track_number_id = "\xD7";
char *track_type_id = "\x83";
char *simple_block_id = "\xA3";
ebml->input_position += len; ebml->input_position += len;
end_of_buffer = ebml->input_buffer + ebml->input_position; end_of_buffer = ebml->input_buffer + ebml->input_position;
@ -587,16 +600,16 @@ static int ebml_wrote(ebml_t *ebml, int len)
} }
/* Recognize tags of interest */ /* Recognize tags of interest */
if (tag_length > 4) { if (tag_length > UNCOMMON_MAGIC_LEN) {
if (!memcmp(ebml->input_buffer + cursor, cluster_id, 4)) { if (!memcmp(ebml->input_buffer + cursor, CLUSTER_MAGIC, UNCOMMON_MAGIC_LEN)) {
/* Found a Cluster */ /* Found a Cluster */
ebml->parse_state = EBML_STATE_START_CLUSTER; ebml->parse_state = EBML_STATE_START_CLUSTER;
break; break;
} else if (!memcmp(ebml->input_buffer + cursor, segment_id, 4)) { } else if (!memcmp(ebml->input_buffer + cursor, SEGMENT_MAGIC, UNCOMMON_MAGIC_LEN)) {
/* Parse all Segment children */ /* Parse all Segment children */
payload_length = 0; payload_length = 0;
} else if (!memcmp(ebml->input_buffer + cursor, tracks_id, 4)) { } else if (!memcmp(ebml->input_buffer + cursor, TRACKS_MAGIC, UNCOMMON_MAGIC_LEN)) {
/* Parse all Tracks children */ /* Parse all Tracks children */
payload_length = 0; payload_length = 0;
@ -604,8 +617,8 @@ static int ebml_wrote(ebml_t *ebml, int len)
} }
if (tag_length > 1) { if (tag_length > COMMON_MAGIC_LEN) {
if (!memcmp(ebml->input_buffer + cursor, simple_block_id, 1)) { if (!memcmp(ebml->input_buffer + cursor, SIMPLE_BLOCK_MAGIC, COMMON_MAGIC_LEN)) {
/* Probe SimpleBlock header for the keyframe status */ /* Probe SimpleBlock header for the keyframe status */
if (ebml->cluster_starts_with_keyframe == EBML_KEYFRAME_UNKNOWN) { if (ebml->cluster_starts_with_keyframe == EBML_KEYFRAME_UNKNOWN) {
track_number_length = ebml_parse_var_int(ebml->input_buffer + cursor + tag_length, track_number_length = ebml_parse_var_int(ebml->input_buffer + cursor + tag_length,
@ -640,13 +653,13 @@ static int ebml_wrote(ebml_t *ebml, int len)
} }
} else if (!memcmp(ebml->input_buffer + cursor, track_entry_id, 1)) { } else if (!memcmp(ebml->input_buffer + cursor, TRACK_ENTRY_MAGIC, COMMON_MAGIC_LEN)) {
/* Parse all TrackEntry children; reset the state */ /* Parse all TrackEntry children; reset the state */
payload_length = 0; payload_length = 0;
ebml->parsing_track_number = EBML_UNKNOWN; ebml->parsing_track_number = EBML_UNKNOWN;
ebml->parsing_track_is_video = 0; ebml->parsing_track_is_video = 0;
} else if (!memcmp(ebml->input_buffer + cursor, track_number_id, 1)) { } else if (!memcmp(ebml->input_buffer + cursor, TRACK_NUMBER_MAGIC, COMMON_MAGIC_LEN)) {
/* Probe TrackNumber for value */ /* Probe TrackNumber for value */
value_length = ebml_parse_sized_int(ebml->input_buffer + cursor + tag_length, value_length = ebml_parse_sized_int(ebml->input_buffer + cursor + tag_length,
end_of_buffer, payload_length, 0, &data_value); end_of_buffer, payload_length, 0, &data_value);
@ -661,7 +674,7 @@ static int ebml_wrote(ebml_t *ebml, int len)
ebml_check_track(ebml); ebml_check_track(ebml);
} }
} else if (!memcmp(ebml->input_buffer + cursor, track_type_id, 1)) { } else if (!memcmp(ebml->input_buffer + cursor, TRACK_TYPE_MAGIC, COMMON_MAGIC_LEN)) {
/* Probe TrackType for a video flag */ /* Probe TrackType for a video flag */
value_length = ebml_parse_sized_int(ebml->input_buffer + cursor + tag_length, value_length = ebml_parse_sized_int(ebml->input_buffer + cursor + tag_length,
end_of_buffer, payload_length, 0, &data_value); end_of_buffer, payload_length, 0, &data_value);