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https://gitlab.xiph.org/xiph/icecast-server.git
synced 2024-11-03 04:17:17 -05:00
Implement EBML-aware parser.
* Loop over elements in input buffer. * Most are literally copied with their contents without inspection into the header or data buffers as appropriate. * Some only copy the element header, to allow inspecting children elements. * Cluster elements are identified and used as sync points. No probing is done for keyframes *yet*
This commit is contained in:
Joseph Wallace
parent
50c4984c78
commit
def5a4cf6c
@ -47,6 +47,14 @@ typedef enum ebml_read_mode {
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EBML_STATE_READING_CLUSTERS
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} ebml_read_mode;
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typedef enum ebml_parsing_state {
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EBML_STATE_PARSING_HEADER = 0,
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EBML_STATE_COPYING_TO_HEADER,
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EBML_STATE_START_CLUSTER,
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EBML_STATE_PARSING_CLUSTERS,
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EBML_STATE_COPYING_TO_DATA
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} ebml_parsing_state;
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typedef enum ebml_chunk_type {
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EBML_CHUNK_HEADER = 0,
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EBML_CHUNK_CLUSTER_START,
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@ -65,8 +73,9 @@ struct ebml_client_data_st {
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struct ebml_st {
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ebml_read_mode output_state;
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ebml_parsing_state parse_state;
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unsigned long long copy_len;
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char *cluster_id;
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int cluster_start;
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int position;
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@ -333,11 +342,9 @@ static ebml_t *ebml_create()
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ebml->output_state = EBML_STATE_READING_HEADER;
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ebml->header = calloc(1, EBML_HEADER_MAX_SIZE);
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ebml->buffer = calloc(1, EBML_SLICE_SIZE * 4);
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ebml->buffer = calloc(1, EBML_SLICE_SIZE);
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ebml->input_buffer = calloc(1, EBML_SLICE_SIZE);
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ebml->cluster_id = "\x1F\x43\xB6\x75";
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ebml->cluster_start = -1;
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return ebml;
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@ -487,65 +494,154 @@ static unsigned char *ebml_get_write_buffer(ebml_t *ebml, int *bytes)
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*/
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static int ebml_wrote(ebml_t *ebml, int len)
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{
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int processing = 1;
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int cursor = 0;
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int to_copy;
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unsigned char *end_of_buffer;
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int b;
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int tag_length;
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unsigned long long payload_length;
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int copy_state;
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if (ebml->header_size == 0) {
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/* Still reading header */
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if ((ebml->header_position + len) > EBML_HEADER_MAX_SIZE) {
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ICECAST_LOG_ERROR("EBML Header too large, failing");
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return -1;
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}
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/*
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ICECAST_LOG_DEBUG("EBML: Adding to header, ofset is %d size is %d adding %d",
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ebml->header_size, ebml->header_position, len);
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*/
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memcpy(ebml->header + ebml->header_position, ebml->input_buffer, len);
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ebml->header_position += len;
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} else {
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/* Header's already been determined, read into data buffer */
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memcpy(ebml->buffer + ebml->position, ebml->input_buffer, len);
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}
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for (b = 0; b <= len - 4; b++)
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{
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/* Scan for cluster start marker.
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* False positives are possible, but unlikely, and only
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* permanently corrupt a stream if they occur while scanning
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* the initial header. Else, a client can reconnect in a few
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* seconds and get a real sync point.
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*/
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if (!memcmp(ebml->input_buffer + b, ebml->cluster_id, 4))
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{
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/*
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ICECAST_LOG_DEBUG("EBML: found cluster");
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*/
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if (ebml->header_size == 0)
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{
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/* We were looking for the header end; now we've found it */
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ebml->header_size = ebml->header_position - len + b;
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char *segment_id = "\x18\x53\x80\x67";
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char *cluster_id = "\x1F\x43\xB6\x75";
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ebml->input_position += len;
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end_of_buffer = ebml->input_buffer + ebml->input_position;
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while (processing) {
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/*ICECAST_LOG_DEBUG("Parse State: %i", ebml->parse_state);*/
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switch (ebml->parse_state) {
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case EBML_STATE_PARSING_HEADER:
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case EBML_STATE_PARSING_CLUSTERS:
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/* Shift data after the header into the data buffer */
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memcpy(ebml->buffer, ebml->input_buffer + b, len - b);
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ebml->position = len - b;
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if (ebml->parse_state == EBML_STATE_PARSING_HEADER) {
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copy_state = EBML_STATE_COPYING_TO_HEADER;
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} else {
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copy_state = EBML_STATE_COPYING_TO_DATA;
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}
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/* Mark the start of the data as the first sync point */
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ebml->cluster_start = 0;
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return len;
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} else {
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/* We've located a sync point in the data stream */
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ebml->cluster_start = ebml->position + b;
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}
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tag_length = ebml_parse_tag(ebml->input_buffer + cursor,
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end_of_buffer, &payload_length);
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if (tag_length > 0) {
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if (payload_length == EBML_UNKNOWN) {
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/* Parse all children for tags we can't skip */
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payload_length = 0;
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}
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if (!memcmp(ebml->input_buffer + cursor, cluster_id, 4)) {
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/* Found a cluster */
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ebml->parse_state = EBML_STATE_START_CLUSTER;
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} else if (!memcmp(ebml->input_buffer + cursor, segment_id, 4)) {
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/* Segment tag, copy tag to buffer but parse children */
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ebml->copy_len = tag_length;
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ebml->parse_state = copy_state;
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} else {
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/* Non-cluster tag, copy it & children into buffer */
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ebml->copy_len = tag_length + payload_length;
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ebml->parse_state = copy_state;
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}
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} else if (tag_length == 0) {
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/* Wait for more data */
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/* ICECAST_LOG_DEBUG("Wait"); */
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processing = 0;
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} else if (tag_length < 0) {
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/* Parse error */
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/* ICECAST_LOG_DEBUG("Stop"); */
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return -1;
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}
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break;
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case EBML_STATE_START_CLUSTER:
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/* found a cluster; wait to process it until
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* any previous cluster tag has been flushed
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* from the read buffer, so as to not lose the
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* sync point.
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*/
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if (ebml->cluster_start >= 0) {
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processing = 0;
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} else {
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tag_length = ebml_parse_tag(ebml->input_buffer + cursor,
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end_of_buffer, &payload_length);
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/* The header has been fully read by now, publish its size. */
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ebml->header_size = ebml->header_position;
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/* Mark this sync point */
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ebml->cluster_start = ebml->position;
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/* Copy cluster tag to read buffer */
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ebml->copy_len = tag_length;
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ebml->parse_state = EBML_STATE_COPYING_TO_DATA;
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}
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break;
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case EBML_STATE_COPYING_TO_HEADER:
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case EBML_STATE_COPYING_TO_DATA:
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to_copy = ebml->input_position - cursor;
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if (to_copy > ebml->copy_len) {
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to_copy = ebml->copy_len;
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}
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if (ebml->parse_state == EBML_STATE_COPYING_TO_HEADER) {
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if ((ebml->header_position + to_copy) > EBML_HEADER_MAX_SIZE) {
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ICECAST_LOG_ERROR("EBML Header too large, failing");
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return -1;
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}
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memcpy(ebml->header + ebml->header_position, ebml->input_buffer + cursor, to_copy);
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ebml->header_position += to_copy;
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} else if (ebml->parse_state == EBML_STATE_COPYING_TO_DATA) {
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if ((ebml->position + to_copy) > EBML_SLICE_SIZE) {
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to_copy = EBML_SLICE_SIZE - ebml->position;
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}
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memcpy(ebml->buffer + ebml->position, ebml->input_buffer + cursor, to_copy);
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ebml->position += to_copy;
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}
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/* ICECAST_LOG_DEBUG("Copied %i of %hhu", to_copy, ebml->copy_len); */
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cursor += to_copy;
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ebml->copy_len -= to_copy;
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if (ebml->copy_len == 0) {
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/* resume parsing */
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if (ebml->parse_state == EBML_STATE_COPYING_TO_HEADER) {
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ebml->parse_state = EBML_STATE_PARSING_HEADER;
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} else {
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ebml->parse_state = EBML_STATE_PARSING_CLUSTERS;
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}
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} else {
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/* wait for more data */
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processing = 0;
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}
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break;
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default:
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processing = 0;
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}
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}
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ebml->position += len;
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/* Shift unprocessed data down to the start of the buffer */
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memmove(ebml->input_buffer, ebml->input_buffer + cursor, ebml->input_position - cursor);
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ebml->input_position -= cursor;
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return len;
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}
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/* Try to parse an EBML tag at the given location, returning the
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