text: // Copyright (c) 2012 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.
  
  #ifndef MEDIA_BASE_DECODER_BUFFER_H_
  #define MEDIA_BASE_DECODER_BUFFER_H_
  
  #include <stddef.h>
  #include <stdint.h>
  
  #include <memory>
  #include <string>
  #include <utility>
  
  #include "base/logging.h"
  #include "base/macros.h"
  #include "base/memory/aligned_memory.h"
  #include "base/memory/ref_counted.h"
  #include "base/memory/shared_memory_handle.h"
  #include "base/time/time.h"
  #include "build/build_config.h"
  #include "media/base/decrypt_config.h"
  #include "media/base/media_export.h"
  #include "media/base/timestamp_constants.h"
  #include "media/base/unaligned_shared_memory.h"
  
  namespace media {
  
  // A specialized buffer for interfacing with audio / video decoders.
  //
  // Specifically ensures that data is aligned and padded as necessary by the
  // underlying decoding framework.  On desktop platforms this means memory is
  // allocated using FFmpeg with particular alignment and padding requirements.
  //
  // Also includes decoder specific functionality for decryption.
  //
  // NOTE: It is illegal to call any method when end_of_stream() is true.
  class MEDIA_EXPORT DecoderBuffer
      : public base::RefCountedThreadSafe<DecoderBuffer> {
   public:
    enum {
      kPaddingSize = 64,
  #if defined(ARCH_CPU_ARM_FAMILY)
      kAlignmentSize = 16
  #else
      kAlignmentSize = 32
  #endif
    };
  
    // Allocates buffer with |size| >= 0.  Buffer will be padded and aligned
    // as necessary, and |is_key_frame_| will default to false.
    explicit DecoderBuffer(size_t size);
  
    // Create a DecoderBuffer whose |data_| is copied from |data|.  Buffer will be
    // padded and aligned as necessary.  |data| must not be NULL and |size| >= 0.
    // The buffer's |is_key_frame_| will default to false.
    static scoped_refptr<DecoderBuffer> CopyFrom(const uint8_t* data,
                                                 size_t size);
  
    // Create a DecoderBuffer whose |data_| is copied from |data| and |side_data_|
    // is copied from |side_data|. Buffers will be padded and aligned as necessary
    // Data pointers must not be NULL and sizes must be >= 0. The buffer's
    // |is_key_frame_| will default to false.
    static scoped_refptr<DecoderBuffer> CopyFrom(const uint8_t* data,
                                                 size_t size,
                                                 const uint8_t* side_data,
                                                 size_t side_data_size);
  
    // Create a DecoderBuffer where data() of |size| bytes resides within the
    // memory referred to by |handle| at non-negative offset |offset|. The
    // buffer's |is_key_frame_| will default to false.
    //
    // The shared memory will be mapped read-only.
    //
    // If mapping fails, nullptr will be returned. In all cases |handle| is
    // consumed.
    static scoped_refptr<DecoderBuffer> FromSharedMemoryHandle(
        const base::SharedMemoryHandle& handle,
        off_t offset,
        size_t size);
  
    // Create a DecoderBuffer indicating we've reached end of stream.
    //
    // Calling any method other than end_of_stream() on the resulting buffer
    // is disallowed.
    static scoped_refptr<DecoderBuffer> CreateEOSBuffer();
  
    base::TimeDelta timestamp() const {
      DCHECK(!end_of_stream());
      return timestamp_;
    }
  
    // TODO(dalecurtis): This should be renamed at some point, but to avoid a yak
    // shave keep as a virtual with hacker_style() for now.
    virtual void set_timestamp(base::TimeDelta timestamp);
  
    base::TimeDelta duration() const {
      DCHECK(!end_of_stream());
      return duration_;
    }
  
    void set_duration(base::TimeDelta duration) {
      DCHECK(!end_of_stream());
      DCHECK(duration == kNoTimestamp ||
             (duration >= base::TimeDelta() && duration != kInfiniteDuration))
          << duration.InSecondsF();
      duration_ = duration;
    }
  
    const uint8_t* data() const {
      DCHECK(!end_of_stream());
      if (shm_)
        return static_cast<uint8_t*>(shm_->memory());
      return data_.get();
    }
  
    // TODO(sandersd): Remove writable_data(). https://crbug.com/834088
    uint8_t* writable_data() const {
      DCHECK(!end_of_stream());
      DCHECK(!shm_);
      return data_.get();
    }
  
    size_t data_size() const {
      DCHECK(!end_of_stream());
      return size_;
    }
  
    const uint8_t* side_data() const {
      DCHECK(!end_of_stream());
      return side_data_.get();
    }
  
    size_t side_data_size() const {
      DCHECK(!end_of_stream());
      return side_data_size_;
    }
  
    // A discard window indicates the amount of data which should be discard from
    // this buffer after decoding.  The first value is the amount of the front and
    // the second the amount off the back.  A value of kInfiniteDuration for the
    // first value indicates the entire buffer should be discarded; the second
    // value must be base::TimeDelta() in this case.
    typedef std::pair<base::TimeDelta, base::TimeDelta> DiscardPadding;
    const DiscardPadding& discard_padding() const {
      DCHECK(!end_of_stream());
      return discard_padding_;
    }
  
    void set_discard_padding(const DiscardPadding& discard_padding) {
      DCHECK(!end_of_stream());
      discard_padding_ = discard_padding;
    }
  
    const DecryptConfig* decrypt_config() const {
      DCHECK(!end_of_stream());
      return decrypt_config_.get();
    }
  
    void set_decrypt_config(std::unique_ptr<DecryptConfig> decrypt_config) {
      DCHECK(!end_of_stream());
      decrypt_config_ = std::move(decrypt_config);
    }
  
    // If there's no data in this buffer, it represents end of stream.
    bool end_of_stream() const { return !shm_ && !data_; }
  
    bool is_key_frame() const {
      DCHECK(!end_of_stream());
      return is_key_frame_;
    }
  
    void set_is_key_frame(bool is_key_frame) {
      DCHECK(!end_of_stream());
      is_key_frame_ = is_key_frame;
    }
  
    // Returns true if all fields in |buffer| matches this buffer
    // including |data_| and |side_data_|.
    bool MatchesForTesting(const DecoderBuffer& buffer) const;
  
    // Returns a human-readable string describing |*this|.
    std::string AsHumanReadableString() const;
  
    // Replaces any existing side data with data copied from |side_data|.
    void CopySideDataFrom(const uint8_t* side_data, size_t side_data_size);
  
   protected:
    friend class base::RefCountedThreadSafe<DecoderBuffer>;
  
    // Allocates a buffer of size |size| >= 0 and copies |data| into it.  Buffer
    // will be padded and aligned as necessary.  If |data| is NULL then |data_| is
    // set to NULL and |buffer_size_| to 0.  |is_key_frame_| will default to
    // false.
    DecoderBuffer(const uint8_t* data,
                  size_t size,
                  const uint8_t* side_data,
                  size_t side_data_size);
  
    DecoderBuffer(std::unique_ptr<UnalignedSharedMemory> shm, size_t size);
  
    virtual ~DecoderBuffer();
  
   private:
    base::TimeDelta timestamp_;
    base::TimeDelta duration_;
  
    size_t size_;
    std::unique_ptr<uint8_t, base::AlignedFreeDeleter> data_;
    size_t side_data_size_;
    std::unique_ptr<uint8_t, base::AlignedFreeDeleter> side_data_;
    std::unique_ptr<UnalignedSharedMemory> shm_;
    std::unique_ptr<DecryptConfig> decrypt_config_;
    DiscardPadding discard_padding_;
    bool is_key_frame_;
  
    // Constructor helper method for memory allocations.
    void Initialize();
  
    DISALLOW_COPY_AND_ASSIGN(DecoderBuffer);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_BASE_DECODER_BUFFER_H_
  