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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/formats/mp2t/ts_section_psi.h"
#include "base/basictypes.h"
#include "base/logging.h"
#include "media/base/bit_reader.h"
#include "media/formats/mp2t/mp2t_common.h"
static bool IsCrcValid(const uint8* buf, int size) {
uint32 crc = 0xffffffffu;
const uint32 kCrcPoly = 0x4c11db7;
for (int k = 0; k < size; k++) {
int nbits = 8;
uint32 data_msb_aligned = buf[k];
data_msb_aligned <<= (32 - nbits);
while (nbits > 0) {
if ((data_msb_aligned ^ crc) & 0x80000000) {
crc <<= 1;
crc ^= kCrcPoly;
} else {
crc <<= 1;
}
data_msb_aligned <<= 1;
nbits--;
}
}
return (crc == 0);
}
namespace media {
namespace mp2t {
TsSectionPsi::TsSectionPsi()
: wait_for_pusi_(true),
leading_bytes_to_discard_(0) {
}
TsSectionPsi::~TsSectionPsi() {
}
bool TsSectionPsi::Parse(bool payload_unit_start_indicator,
const uint8* buf, int size) {
// Ignore partial PSI.
if (wait_for_pusi_ && !payload_unit_start_indicator)
return true;
if (payload_unit_start_indicator) {
// Reset the state of the PSI section.
ResetPsiState();
// Update the state.
wait_for_pusi_ = false;
DCHECK_GE(size, 1);
int pointer_field = buf[0];
leading_bytes_to_discard_ = pointer_field;
buf++;
size--;
}
// Discard some leading bytes if needed.
if (leading_bytes_to_discard_ > 0) {
int nbytes_to_discard = std::min(leading_bytes_to_discard_, size);
buf += nbytes_to_discard;
size -= nbytes_to_discard;
leading_bytes_to_discard_ -= nbytes_to_discard;
}
if (size == 0)
return true;
// Add the data to the parser state.
psi_byte_queue_.Push(buf, size);
int raw_psi_size;
const uint8* raw_psi;
psi_byte_queue_.Peek(&raw_psi, &raw_psi_size);
// Check whether we have enough data to start parsing.
if (raw_psi_size < 3)
return true;
int section_length =
((static_cast<int>(raw_psi[1]) << 8) |
(static_cast<int>(raw_psi[2]))) & 0xfff;
if (section_length >= 1021)
return false;
int psi_length = section_length + 3;
if (raw_psi_size < psi_length) {
// Don't throw an error when there is not enough data,
// just wait for more data to come.
return true;
}
// There should not be any trailing bytes after a PMT.
// Instead, the pointer field should be used to stuff bytes.
DVLOG_IF(1, raw_psi_size > psi_length)
<< "Trailing bytes after a PSI section: "
<< psi_length << " vs " << raw_psi_size;
// Verify the CRC.
RCHECK(IsCrcValid(raw_psi, psi_length));
// Parse the PSI section.
BitReader bit_reader(raw_psi, raw_psi_size);
bool status = ParsePsiSection(&bit_reader);
if (status)
ResetPsiState();
return status;
}
void TsSectionPsi::Flush() {
}
void TsSectionPsi::Reset() {
ResetPsiSection();
ResetPsiState();
}
void TsSectionPsi::ResetPsiState() {
wait_for_pusi_ = true;
psi_byte_queue_.Reset();
leading_bytes_to_discard_ = 0;
}
} // namespace mp2t
} // namespace media
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