Support HLS MPEG2 TS with SAMPLE-AES encryption.

media/formats/mp2t/ts_section_cets_pssh.cc

+// Copyright 2015 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_cets_pssh.h"
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+#include "media/formats/mp2t/mp2t_common.h"
+
+namespace media {
+namespace mp2t {
+
+TsSectionCetsPssh::TsSectionCetsPssh(
+    const RegisterPsshBoxesCb& register_pssh_boxes_cb)
+    : register_pssh_boxes_cb_(register_pssh_boxes_cb) {}
+
+TsSectionCetsPssh::~TsSectionCetsPssh() {}
+
+bool TsSectionCetsPssh::Parse(bool payload_unit_start_indicator,
+                              const uint8_t* buf,
+                              int size) {
+  DCHECK(buf);
+  // Ignore if doesn't contain PUSI.
+  if (!payload_unit_start_indicator)
+    return false;
+  // TODO(dougsteed). This initial implementation requires the entire CETS-PSSH
+  // to fit in one TS packet, so we know that the box length will fit in one
+  // byte.
+  BitReader bit_reader(buf, size);
+  bool md5_flag;
+  RCHECK(bit_reader.ReadFlag(&md5_flag) && !md5_flag);
+  RCHECK(bit_reader.SkipBits(31));
+  int box_length_bits = bit_reader.bits_available();
+  std::string pssh;
+  RCHECK(bit_reader.ReadString(box_length_bits, &pssh));
+  // Now check that the first 4 bytes are of the form {0x00, 0x00, 0x00, X},
+  // where X is the box length in bytes.
+  RCHECK(pssh[0] == 0x00 && pssh[1] == 0x00 && pssh[2] == 0x00);
+  uint8_t declared_box_bytes = static_cast<uint8_t>(pssh[3]);
+  RCHECK(declared_box_bytes <= box_length_bits * 8);
+  pssh.resize(declared_box_bytes);
+  register_pssh_boxes_cb_.Run(std::vector<uint8_t>(pssh.begin(), pssh.end()));
+  return true;
+}
+
+void TsSectionCetsPssh::Flush() {
+  // No pending state.
+}
+
+void TsSectionCetsPssh::Reset() {
+  // No state to clean up.
+}
+
+}  // namespace mp2t
+}  // namespace media