static vint_c
read_id(int64_t end_pos) {
try {
int64_t pos = g_in->getFilePointer();
int mask = 0x80;
int id_len = 1;
if (pos >= end_pos)
throw id_error_c(id_error_c::end_of_scope);
unsigned char first_byte = g_in->read_uint8();
while (0 != mask) {
if (0 != (first_byte & mask))
break;
mask >>= 1;
id_len++;
}
if (0 == mask)
throw id_error_c(id_error_c::first_byte_is_zero);
if (4 < id_len)
throw id_error_c(id_error_c::longer_than_four_bytes);
if ((pos + id_len) > end_pos)
throw id_error_c(id_error_c::end_of_scope);
uint32_t id = first_byte;
int i;
for (i = 1; i < id_len; ++i) {
id <<= 8;
id |= g_in->read_uint8();
}
return vint_c(id, id_len);
} catch (mtx::exception &error) {
throw id_error_c(id_error_c::end_of_file);
}
}
static vint_c
read_size(int64_t end_pos) {
try {
int64_t pos = g_in->getFilePointer();
int mask = 0x80;
int size_len = 1;
if (pos >= end_pos)
throw size_error_c(size_error_c::end_of_scope);
unsigned char first_byte = g_in->read_uint8();
while (0 != mask) {
if (0 != (first_byte & mask))
break;
mask >>= 1;
size_len++;
}
if ((pos + size_len) > end_pos)
throw size_error_c(size_error_c::end_of_scope);
int64_t size = first_byte & ~mask;
int i;
for (i = 1; i < size_len; ++i) {
size <<= 8;
size |= g_in->read_uint8();
}
return vint_c(size, size_len);
} catch (mtx::exception &error) {
throw size_error_c(size_error_c::end_of_file);
}
}
EbmlElement *
kax_file_c::resync_to_level1_element_internal(uint32_t wanted_id) {
if (m_segment_end && (m_in->getFilePointer() >= m_segment_end))
return nullptr;
m_resynced = true;
m_resync_start_pos = m_in->getFilePointer();
uint32_t actual_id = m_in->read_uint32_be();
int64_t start_time = mtx::sys::get_current_time_millis();
bool is_cluster_id = !wanted_id || (EBML_ID_VALUE(EBML_ID(KaxCluster)) == wanted_id); // 0 means: any level 1 element will do
mxinfo(boost::format(Y("%1%: Error in the Matroska file structure at position %2%. Resyncing to the next level 1 element.\n"))
% m_in->get_file_name() % m_resync_start_pos);
if (is_cluster_id && (-1 != m_last_timecode)) {
mxinfo(boost::format(Y("The last timecode processed before the error was encountered was %1%.\n")) % format_timecode(m_last_timecode));
m_last_timecode = -1;
}
if (m_debug_resync)
mxinfo(boost::format("kax_file::resync_to_level1_element(): starting at %1% potential ID %|2$08x|\n") % m_resync_start_pos % actual_id);
while (m_in->getFilePointer() < m_file_size) {
int64_t now = mtx::sys::get_current_time_millis();
if ((now - start_time) >= 10000) {
mxinfo(boost::format("Still resyncing at position %1%.\n") % m_in->getFilePointer());
start_time = now;
}
actual_id = (actual_id << 8) | m_in->read_uint8();
if ( ((0 != wanted_id) && (wanted_id != actual_id))
|| ((0 == wanted_id) && !is_level1_element_id(vint_c(actual_id, 4))))
continue;
uint64_t current_start_pos = m_in->getFilePointer() - 4;
uint64_t element_pos = current_start_pos;
unsigned int num_headers = 1;
bool valid_unknown_size = false;
if (m_debug_resync)
mxinfo(boost::format("kax_file::resync_to_level1_element(): byte-for-byte search, found level 1 ID %|2$x| at %1%\n") % current_start_pos % actual_id);
try {
unsigned int idx;
for (idx = 0; 3 > idx; ++idx) {
vint_c length = vint_c::read(m_in);
if (m_debug_resync)
mxinfo(boost::format("kax_file::resync_to_level1_element(): read ebml length %1%/%2% valid? %3% unknown? %4%\n")
% length.m_value % length.m_coded_size % length.is_valid() % length.is_unknown());
if (length.is_unknown()) {
valid_unknown_size = true;
break;
}
if ( !length.is_valid()
|| ((element_pos + length.m_value + length.m_coded_size + 2 * 4) >= m_file_size)
|| !m_in->setFilePointer2(element_pos + 4 + length.m_value + length.m_coded_size, seek_beginning))
break;
element_pos = m_in->getFilePointer();
uint32_t next_id = m_in->read_uint32_be();
if (m_debug_resync)
mxinfo(boost::format("kax_file::resync_to_level1_element(): next ID is %|1$x| at %2%\n") % next_id % element_pos);
if ( ((0 != wanted_id) && (wanted_id != next_id))
|| ((0 == wanted_id) && !is_level1_element_id(vint_c(next_id, 4))))
break;
++num_headers;
}
} catch (...) {
}
if ((4 == num_headers) || valid_unknown_size) {
mxinfo(boost::format(Y("Resyncing successful at position %1%.\n")) % current_start_pos);
m_in->setFilePointer(current_start_pos, seek_beginning);
return read_next_level1_element(wanted_id, is_cluster_id);
}
m_in->setFilePointer(current_start_pos + 4, seek_beginning);
}
mxinfo(Y("Resync failed: no valid Matroska level 1 element found.\n"));
return nullptr;
}
