From 0f3bc4b6b42f4435143ed3f57a5e84274cb2d9b6 Mon Sep 17 00:00:00 2001
From: Kongqun Yang <kqyang@google.com>
Date: Fri, 22 Nov 2013 13:28:21 -0800
Subject: [PATCH] Implement base mp4 box objects: Box and FullBox.

Change-Id: Ic1acc0f7ec3999d5270609a8836dbbde7f0d1c0f
---
 media/mp4/box.cc | 63 ++++++++++++++++++++++++++++++++++++++++++++++++
 media/mp4/box.h  | 62 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 125 insertions(+)
 create mode 100644 media/mp4/box.cc
 create mode 100644 media/mp4/box.h

diff --git a/media/mp4/box.cc b/media/mp4/box.cc
new file mode 100644
index 0000000000..f8d27bf09b
--- /dev/null
+++ b/media/mp4/box.cc
@@ -0,0 +1,63 @@
+// Copyright (c) 2013 Google Inc. 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/mp4/box.h"
+
+#include "base/logging.h"
+#include "media/mp4/box_buffer.h"
+
+namespace media {
+namespace mp4 {
+
+Box::Box() : atom_size(0) {}
+Box::~Box() {}
+
+bool Box::Parse(BoxReader* reader) {
+  DCHECK(reader != NULL);
+  BoxBuffer buffer(reader);
+  return ReadWrite(&buffer);
+}
+
+void Box::Write(BufferWriter* writer) {
+  DCHECK(writer != NULL);
+  uint32 size = ComputeSize();
+  DCHECK_EQ(size, this->atom_size);
+
+  size_t buffer_size_before_write = writer->Size();
+  BoxBuffer buffer(writer);
+  CHECK(ReadWrite(&buffer));
+  DCHECK_EQ(this->atom_size, writer->Size() - buffer_size_before_write);
+}
+
+bool Box::ReadWrite(BoxBuffer* buffer) {
+  if (buffer->Reading()) {
+    // Skip for read mode, which is handled already in BoxReader.
+  } else {
+    CHECK(buffer->ReadWriteUInt32(&this->atom_size));
+    FourCC fourcc = BoxType();
+    CHECK(buffer->ReadWriteFourCC(&fourcc));
+  }
+  return true;
+}
+
+FullBox::FullBox() : version(0), flags(0) {}
+FullBox::~FullBox() {}
+
+bool FullBox::ReadWrite(BoxBuffer* buffer) {
+  RCHECK(Box::ReadWrite(buffer));
+
+  uint32 vflags;
+  if (buffer->Reading()) {
+    RCHECK(buffer->ReadWriteUInt32(&vflags));
+    this->version = vflags >> 24;
+    this->flags = vflags & 0x00FFFFFF;
+  } else {
+    vflags = (this->version << 24) | this->flags;
+    RCHECK(buffer->ReadWriteUInt32(&vflags));
+  }
+  return true;
+}
+
+}  // namespace mp4
+}  // namespace media
diff --git a/media/mp4/box.h b/media/mp4/box.h
new file mode 100644
index 0000000000..f8466dc155
--- /dev/null
+++ b/media/mp4/box.h
@@ -0,0 +1,62 @@
+// Copyright (c) 2013 Google Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_MP4_BOX_H_
+#define MEDIA_MP4_BOX_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "media/mp4/fourccs.h"
+
+namespace media {
+
+class BufferWriter;
+
+namespace mp4 {
+
+class BoxBuffer;
+class BoxReader;
+
+// Defines Box and FullBox, the two base ISO BMFF box objects as defined in
+// ISO 14496-12:2012 ISO BMFF section 4.2. All ISO BMFF compatible boxes
+// inherits either Box or FullBox.
+struct Box {
+ public:
+  Box();
+  virtual ~Box();
+  bool Parse(BoxReader* reader);
+  // Write the box to buffer.
+  // The function calls ComputeSize internally to compute box size.
+  void Write(BufferWriter* writer);
+  // Computer box size.
+  // The calculated size will be saved in |atom_size| for consumption later.
+  virtual uint32 ComputeSize() = 0;
+  virtual FourCC BoxType() const = 0;
+
+ protected:
+  friend class BoxBuffer;
+  // Read or write the mp4 box through BoxBuffer.
+  virtual bool ReadWrite(BoxBuffer* buffer);
+
+  // We don't support 64-bit atom size. 32-bit should be large enough for our
+  // current needs.
+  uint32 atom_size;
+};
+
+struct FullBox : Box {
+ public:
+  FullBox();
+  virtual ~FullBox();
+
+  uint8 version;
+  uint32 flags;
+
+ protected:
+  virtual bool ReadWrite(BoxBuffer* buffer) OVERRIDE;
+};
+
+}  // namespace mp4
+}  // namespace media
+
+#endif  // MEDIA_MP4_BOX_H_