/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_image_decoders_nsBMPDecoder_h

#define mozilla_image_decoders_nsBMPDecoder_h

#include "BMPHeaders.h"

#include "Decoder.h"

#include "gfxColor.h"

#include "StreamingLexer.h"

#include "mozilla/UniquePtr.h"

namespace mozilla {

namespace image {

namespace bmp {

/// This struct contains the fields from the file header and info header that

/// we use during decoding. (Excluding bitfields fields, which are kept in

/// BitFields.)

struct Header {

  uint32_t mDataOffset;     // Offset to raster data.

  uint32_t mBIHSize;        // Header size.

  int32_t  mWidth;          // Image width.

  int32_t  mHeight;         // Image height.

  uint16_t mBpp;            // Bits per pixel.

  uint32_t mCompression;    // See struct Compression for valid values.

  uint32_t mImageSize;      // (compressed) image size. Can be 0 if

                            // mCompression==0.

  uint32_t mNumColors;      // Used colors.

  Header()

   : mDataOffset(0)

   , mBIHSize(0)

   , mWidth(0)

   , mHeight(0)

   , mBpp(0)

   , mCompression(0)

   , mImageSize(0)

   , mNumColors(0)

  {}

};

/// An entry in the color table.

struct ColorTableEntry {

  uint8_t mRed;

  uint8_t mGreen;

  uint8_t mBlue;

};

/// All the color-related bitfields for 16bpp and 32bpp images. We use this

/// even for older format BMPs that don't have explicit bitfields.

class BitFields {

  class Value {

    friend class BitFields;

    uint32_t mMask;       // The mask for the value.

    uint8_t mRightShift;  // The amount to right-shift after masking.

    uint8_t mBitWidth;    // The width (in bits) of the value.

    /// Sets the mask (and thus the right-shift and bit-width as well).

    void Set(uint32_t aMask);

  public:

    Value()

    {

      mMask = 0;

      mRightShift = 0;

      mBitWidth = 0;

    }

    /// Returns true if this channel is used. Only used for alpha.

    bool IsPresent() const { return mMask != 0x0; }

    /// Extracts the single color value from the multi-color value.

    uint8_t Get(uint32_t aVal) const;

    /// Like Get(), but specially for alpha.

    uint8_t GetAlpha(uint32_t aVal, bool& aHasAlphaOut) const;

    /// Specialized versions of Get() for when the bit-width is 5 or 8.

    /// (They will assert if called and the bit-width is not 5 or 8.)

    uint8_t Get5(uint32_t aVal) const;

    uint8_t Get8(uint32_t aVal) const;

  };

public:

  /// The individual color channels.

  Value mRed;

  Value mGreen;

  Value mBlue;

  Value mAlpha;

  /// Set bitfields to the standard 5-5-5 16bpp values.

  void SetR5G5B5();

  /// Set bitfields to the standard 8-8-8 32bpp values.

  void SetR8G8B8();

  /// Test if bitfields have the standard 5-5-5 16bpp values.

  bool IsR5G5B5() const;

  /// Test if bitfields have the standard 8-8-8 32bpp values.

  bool IsR8G8B8() const;

  /// Read the bitfields from a header. The reading of the alpha mask is

  /// optional.

  void ReadFromHeader(const char* aData, bool aReadAlpha);

  /// Length of the bitfields structure in the BMP file.

  static const size_t LENGTH = 12;

};

} // namespace bmp

class RasterImage;

/// Decoder for BMP-Files, as used by Windows and OS/2.

class nsBMPDecoder : public Decoder

{

public:

  ~nsBMPDecoder();

  DecoderType GetType() const override { return DecoderType::BMP; }

  /// @return true if this BMP is a valid ICO resource.

  bool IsValidICOResource() const override { return true; }

  /// Obtains the internal output image buffer.

  uint32_t* GetImageData() { return reinterpret_cast<uint32_t*>(mImageData); }

  /// Obtains the length of the internal output image buffer.

  size_t GetImageDataLength() const { return mImageDataLength; }

  /// Obtains the size of the compressed image resource.

  int32_t GetCompressedImageSize() const;

  /// Mark this BMP as being within an ICO file. Only used for testing purposes

  /// because the ICO-specific constructor does this marking automatically.

  void SetIsWithinICO() { mIsWithinICO = true; }

  /// Did the BMP file have alpha data of any kind? (Only use this after the

  /// bitmap has been fully decoded.)

  bool HasTransparency() const { return mDoesHaveTransparency; }

  LexerResult DoDecode(SourceBufferIterator& aIterator,

                       IResumable* aOnResume) override;

  nsresult BeforeFinishInternal() override;

  nsresult FinishInternal() override;

private:

  friend class DecoderFactory;

  enum class State {

    FILE_HEADER,

    INFO_HEADER_SIZE,

    INFO_HEADER_REST,

    BITFIELDS,

    COLOR_TABLE,

    GAP,

    AFTER_GAP,

    PIXEL_ROW,

    RLE_SEGMENT,

    RLE_DELTA,

    RLE_ABSOLUTE

  };

  // This is the constructor used for normal BMP images.

  explicit nsBMPDecoder(RasterImage* aImage);

  // This is the constructor used for BMP resources in ICO images.

  nsBMPDecoder(RasterImage* aImage, uint32_t aDataOffset);

  // Helper constructor called by the other two.

  nsBMPDecoder(RasterImage* aImage, State aState, size_t aLength);

  int32_t AbsoluteHeight() const { return abs(mH.mHeight); }

  uint32_t* RowBuffer();

  void FinishRow();

  LexerTransition<State> ReadFileHeader(const char* aData, size_t aLength);

  LexerTransition<State> ReadInfoHeaderSize(const char* aData, size_t aLength);

  LexerTransition<State> ReadInfoHeaderRest(const char* aData, size_t aLength);

  LexerTransition<State> ReadBitfields(const char* aData, size_t aLength);

  LexerTransition<State> ReadColorTable(const char* aData, size_t aLength);

  LexerTransition<State> SkipGap();

  LexerTransition<State> AfterGap();

  LexerTransition<State> ReadPixelRow(const char* aData);

  LexerTransition<State> ReadRLESegment(const char* aData);

  LexerTransition<State> ReadRLEDelta(const char* aData);

  LexerTransition<State> ReadRLEAbsolute(const char* aData, size_t aLength);

  StreamingLexer<State> mLexer;

  bmp::Header mH;

  // If the BMP is within an ICO file our treatment of it differs slightly.

  bool mIsWithinICO;

  bmp::BitFields mBitFields;

  // Might the image have transparency? Determined from the headers during

  // metadata decode. (Does not guarantee the image actually has transparency.)

  bool mMayHaveTransparency;

  // Does the image have transparency? Determined during full decoding, so only

  // use this after that has been completed.

  bool mDoesHaveTransparency;

  uint32_t mNumColors;      // The number of used colors, i.e. the number of

                            // entries in mColors, if it's present.

  UniquePtr<bmp::ColorTableEntry[]> mColors; // The color table, if it's present.

  uint32_t mBytesPerColor;  // 3 or 4, depending on the format

  // The number of bytes prior to the optional gap that have been read. This

  // is used to find the start of the pixel data.

  uint32_t mPreGapLength;

  uint32_t mPixelRowSize;   // The number of bytes per pixel row.

  int32_t mCurrentRow;      // Index of the row of the image that's currently

                            // being decoded: [height,1].

  int32_t mCurrentPos;      // Index into the current line. Used when

                            // doing RLE decoding and when filling in pixels

                            // for truncated files.

  // Only used in RLE_ABSOLUTE state: the number of pixels to read.

  uint32_t mAbsoluteModeNumPixels;

};

} // namespace image

} // namespace mozilla

#endif // mozilla_image_decoders_nsBMPDecoder_h