/* 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/. */

#include "nsPNGEncoder.h"

#include <bit>
#include <cstring>

#include "ImageLogging.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/UniquePtrExtensions.h"
#include "nsCRT.h"
#include "nsStreamUtils.h"
#include "nsString.h"
#include "prprf.h"

using namespace mozilla;

#include "mozilla/gfx/Swizzle.h"

static LazyLogModule sPNGEncoderLog("PNGEncoder");

NS_IMPL_ISUPPORTS(nsPNGEncoder, imgIEncoder, nsIInputStream,
                  nsIAsyncInputStream)

static bool IsHDRFormat(uint32_t aFormat) {
  return aFormat == imgIEncoder::INPUT_FORMAT_R10G10B10A2 ||
         aFormat == imgIEncoder::INPUT_FORMAT_RGBA_U10 ||
         aFormat == imgIEncoder::INPUT_FORMAT_RGBA_U12 ||
         aFormat == imgIEncoder::INPUT_FORMAT_RGBA_U16 ||
         aFormat == imgIEncoder::INPUT_FORMAT_RGBA_F16;
}

static bool HasAlpha(uint32_t aFormat) {
  return aFormat != imgIEncoder::INPUT_FORMAT_RGB;
}

static bool IsValidFormat(uint32_t aFormat) {
  return aFormat == imgIEncoder::INPUT_FORMAT_RGB ||
         aFormat == imgIEncoder::INPUT_FORMAT_RGBA ||
         aFormat == imgIEncoder::INPUT_FORMAT_HOSTARGB || IsHDRFormat(aFormat);
}

static uint32_t BytesPerPixel(uint32_t aFormat) {
  if (aFormat == imgIEncoder::INPUT_FORMAT_RGB) {
    return 3;
  }
  if (aFormat == imgIEncoder::INPUT_FORMAT_R10G10B10A2 ||
      aFormat == imgIEncoder::INPUT_FORMAT_RGBA ||
      aFormat == imgIEncoder::INPUT_FORMAT_HOSTARGB) {
    return 4;
  }
  return 8;
}

#define DEFAULT_ZLIB_LEVEL 3
#define DEFAULT_FILTERS PNG_FILTER_SUB

nsPNGEncoder::nsPNGEncoder()
    : mPNG(nullptr),
      mPNGinfo(nullptr),
      mAddCustomMetadata(false),
      mIsAnimation(false),
      mFinished(false),
      mImageBuffer(nullptr),
      mImageBufferSize(0),
      mImageBufferUsed(0),
      mImageBufferHash(0),
      mImageBufferReadPoint(0),
      mCallback(nullptr),
      mCallbackTarget(nullptr),
      mNotifyThreshold(0),
      mReentrantMonitor("nsPNGEncoder.mReentrantMonitor") {}

nsPNGEncoder::~nsPNGEncoder() {
  if (mImageBuffer) {
    free(mImageBuffer);
    mImageBuffer = nullptr;
  }
  // don't leak if EndImageEncode wasn't called
  if (mPNG) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
  }
}

// nsPNGEncoder::InitFromData
//
//    One output option is supported: "transparency=none" means that the
//    output PNG will not have an alpha channel, even if the input does.
//
//    Based partially on gfx/cairo/cairo/src/cairo-png.c
//    See also media/libpng/libpng-manual.txt

NS_IMETHODIMP
nsPNGEncoder::InitFromData(const uint8_t* aData,
                           uint32_t aLength,  // (unused, req'd by JS)
                           uint32_t aWidth, uint32_t aHeight, uint32_t aStride,
                           uint32_t aInputFormat,
                           const nsAString& aOutputOptions,
                           const nsACString& aRandomizationKey) {
  NS_ENSURE_ARG(aData);
  nsresult rv;

  MOZ_ASSERT_IF(aRandomizationKey.IsEmpty(), aRandomizationKey.IsVoid());
  if (!aRandomizationKey.IsEmpty()) {
    mAddCustomMetadata = true;
  }

  rv = StartImageEncode(aWidth, aHeight, aInputFormat, aOutputOptions);
  if (!NS_SUCCEEDED(rv)) {
    return rv;
  }

  rv = AddImageFrame(aData, aLength, aWidth, aHeight, aStride, aInputFormat,
                     aOutputOptions);
  if (!NS_SUCCEEDED(rv)) {
    return rv;
  }

  rv = MaybeAddCustomMetadata(aRandomizationKey);
  if (!NS_SUCCEEDED(rv)) {
    return rv;
  }

  rv = EndImageEncode();

  return rv;
}

NS_IMETHODIMP
nsPNGEncoder::SetColorSpaceInfo(
    imgIEncoder::CICPColourPrimaries aColourPrimaries,
    imgIEncoder::CICPTransferCharacteristics aTransferCharacteristics,
    imgIEncoder::CICPMatrixCoefficients aMatrixCoefficients, bool aFullRange) {
  mHasCICP = true;
  mColourPrimaries =
      static_cast<mozilla::gfx::CICP::ColourPrimaries>(aColourPrimaries);
  mTransferCharacteristics =
      static_cast<mozilla::gfx::CICP::TransferCharacteristics>(
          aTransferCharacteristics);
  mMatrixCoefficients =
      static_cast<mozilla::gfx::CICP::MatrixCoefficients>(aMatrixCoefficients);
  mFullRange = aFullRange;
  return NS_OK;
}

// nsPNGEncoder::StartImageEncode
//
//
// See ::InitFromData for other info.
NS_IMETHODIMP
nsPNGEncoder::StartImageEncode(uint32_t aWidth, uint32_t aHeight,
                               uint32_t aInputFormat,
                               const nsAString& aOutputOptions) {
  bool useTransparency = true, skipFirstFrame = false;
  uint32_t numFrames = 1;
  uint32_t numPlays = 0;  // For animations, 0 == forever
  int zlibLevel = DEFAULT_ZLIB_LEVEL;
  int filters = DEFAULT_FILTERS;

  // can't initialize more than once
  if (mImageBuffer != nullptr) {
    return NS_ERROR_ALREADY_INITIALIZED;
  }

  // validate input format
  if (!IsValidFormat(aInputFormat)) {
    return NS_ERROR_INVALID_ARG;
  }

  // PNG only supports 8-bit and 16-bit per channel. All wider-than-8-bit
  // input formats are encoded as 16-bit PNG. For 10-bit and 12-bit input,
  // values are scaled up to 16-bit and an sBIT chunk records the original
  // significant bit depth.
  if (IsHDRFormat(aInputFormat)) {
    mBitDepth = 16;
  }
  if (aInputFormat == INPUT_FORMAT_R10G10B10A2 ||
      aInputFormat == INPUT_FORMAT_RGBA_U10) {
    mInputBitDepth = 10;
  } else if (aInputFormat == INPUT_FORMAT_RGBA_U12) {
    mInputBitDepth = 12;
  }

  // parse and check any provided output options
  nsresult rv = ParseOptions(aOutputOptions, &useTransparency, &skipFirstFrame,
                             &numFrames, &numPlays, &zlibLevel, &filters,
                             nullptr, nullptr, nullptr, nullptr, nullptr);
  if (rv != NS_OK) {
    return rv;
  }

#ifdef PNG_APNG_SUPPORTED
  if (numFrames > 1) {
    mIsAnimation = true;
  }

#endif

  // initialize
  mPNG = png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, ErrorCallback,
                                 WarningCallback);
  if (!mPNG) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  mPNGinfo = png_create_info_struct(mPNG);
  if (!mPNGinfo) {
    png_destroy_write_struct(&mPNG, nullptr);
    return NS_ERROR_FAILURE;
  }

  // libpng's error handler jumps back here upon an error.
  // Note: It's important that all png_* callers do this, or errors
  // will result in a corrupt time-warped stack.
  if (setjmp(png_jmpbuf(mPNG))) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
    return NS_ERROR_FAILURE;
  }

#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
  png_set_compression_level(mPNG, zlibLevel);
#endif
#ifdef PNG_WRITE_FILTER_SUPPORTED
  png_set_filter(mPNG, PNG_FILTER_TYPE_BASE, filters);
#endif

  // Set up to read the data into our image buffer, start out with an 8K
  // estimated size. Note: we don't have to worry about freeing this data
  // in this function. It will be freed on object destruction.
  mImageBufferSize = 8192;
  mImageBuffer = (uint8_t*)malloc(mImageBufferSize);
  if (!mImageBuffer) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
    return NS_ERROR_OUT_OF_MEMORY;
  }
  mImageBufferUsed = 0;

  // set our callback for libpng to give us the data
  png_set_write_fn(mPNG, this, WriteCallback, nullptr);

  // include alpha?
  int colorType;
  if (HasAlpha(aInputFormat) && useTransparency) {
    colorType = PNG_COLOR_TYPE_RGB_ALPHA;
  } else {
    colorType = PNG_COLOR_TYPE_RGB;
  }

  png_set_IHDR(mPNG, mPNGinfo, aWidth, aHeight, static_cast<int>(mBitDepth),
               colorType, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
               PNG_FILTER_TYPE_DEFAULT);

  if (mInputBitDepth > 0) {
    png_color_8 sBIT;
    memset(&sBIT, 0, sizeof(sBIT));
    sBIT.red = mInputBitDepth;
    sBIT.green = mInputBitDepth;
    sBIT.blue = mInputBitDepth;
    if (colorType == PNG_COLOR_TYPE_RGB_ALPHA) {
      // R10G10B10A2 has only 2-bit alpha; other formats have uniform depth.
      sBIT.alpha =
          (aInputFormat == INPUT_FORMAT_R10G10B10A2) ? 2 : mInputBitDepth;
    }
    png_set_sBIT(mPNG, mPNGinfo, &sBIT);
  }

#ifdef PNG_cICP_SUPPORTED
  if (mHasCICP) {
    png_set_cICP(mPNG, mPNGinfo, static_cast<png_byte>(mColourPrimaries),
                 static_cast<png_byte>(mTransferCharacteristics),
                 static_cast<png_byte>(mMatrixCoefficients),
                 mFullRange ? 1 : 0);
  }
#endif

#ifdef PNG_APNG_SUPPORTED
  if (mIsAnimation) {
    png_set_first_frame_is_hidden(mPNG, mPNGinfo, skipFirstFrame);
    png_set_acTL(mPNG, mPNGinfo, numFrames, numPlays);
  }
#endif

  // XXX: support PLTE, gAMA, tRNS, bKGD?

  png_write_info(mPNG, mPNGinfo);

  // PNG uses big-endian for 16-bit samples. On little-endian hosts, tell
  // libpng to byte-swap from host endianness. This must be after
  // png_write_info because png_set_swap checks png_ptr->bit_depth, which
  // is set inside png_write_IHDR (called by png_write_info).
  if (mBitDepth == 16 && std::endian::native == std::endian::little) {
    png_set_swap(mPNG);
  }

  return NS_OK;
}

// Returns the number of bytes in the image buffer used.
NS_IMETHODIMP
nsPNGEncoder::GetImageBufferUsed(uint32_t* aOutputSize) {
  NS_ENSURE_ARG_POINTER(aOutputSize);
  *aOutputSize = mImageBufferUsed;
  return NS_OK;
}

// Returns a pointer to the start of the image buffer
NS_IMETHODIMP
nsPNGEncoder::GetImageBuffer(char** aOutputBuffer) {
  NS_ENSURE_ARG_POINTER(aOutputBuffer);
  *aOutputBuffer = reinterpret_cast<char*>(mImageBuffer);
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::AddImageFrame(const uint8_t* aData,
                            uint32_t aLength,  // (unused, req'd by JS)
                            uint32_t aWidth, uint32_t aHeight, uint32_t aStride,
                            uint32_t aInputFormat,
                            const nsAString& aFrameOptions) {
  bool useTransparency = true;
  int filters = DEFAULT_FILTERS;
  uint32_t delay_ms = 500;
#ifdef PNG_APNG_SUPPORTED
  uint32_t dispose_op = PNG_DISPOSE_OP_NONE;
  uint32_t blend_op = PNG_BLEND_OP_SOURCE;
#else
  uint32_t dispose_op;
  uint32_t blend_op;
#endif
  uint32_t x_offset = 0, y_offset = 0;

  // must be initialized
  if (mImageBuffer == nullptr) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  // EndImageEncode was done, or some error occurred earlier
  if (!mPNG) {
    return NS_BASE_STREAM_CLOSED;
  }

  // validate input format
  if (!IsValidFormat(aInputFormat)) {
    return NS_ERROR_INVALID_ARG;
  }

  // libpng's error handler jumps back here upon an error.
  if (setjmp(png_jmpbuf(mPNG))) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
    return NS_ERROR_FAILURE;
  }

  // parse and check any provided output options
  nsresult rv = ParseOptions(aFrameOptions, &useTransparency, nullptr, nullptr,
                             nullptr, nullptr, &filters, &dispose_op, &blend_op,
                             &delay_ms, &x_offset, &y_offset);
  if (rv != NS_OK) {
    return rv;
  }

#ifdef PNG_APNG_SUPPORTED
  if (mIsAnimation) {
    // XXX the row pointers arg (#3) is unused, can it be removed?
    png_write_frame_head(mPNG, mPNGinfo, nullptr, aWidth, aHeight, x_offset,
                         y_offset, delay_ms, 1000, dispose_op, blend_op);
  }
#endif

  // Stride is the padded width of each row, so it better be longer
  // (I'm afraid people will not understand what stride means, so
  // check it well)
  uint32_t bytesPerPixel = BytesPerPixel(aInputFormat);
  CheckedInt<uint32_t> minStride = CheckedInt<uint32_t>(aWidth) * bytesPerPixel;
  if (!minStride.isValid() || aStride < minStride.value()) {
    NS_WARNING("Invalid stride for InitFromData/AddImageFrame");
    return NS_ERROR_INVALID_ARG;
  }
  CheckedInt<uint32_t> maxOffset = CheckedInt<uint32_t>(aHeight) * aStride;
  if (!maxOffset.isValid()) {
    return NS_ERROR_INVALID_ARG;
  }

#ifdef PNG_WRITE_FILTER_SUPPORTED
  png_set_filter(mPNG, PNG_FILTER_TYPE_BASE, filters);
#endif

  // write each row: if we add more input formats, we may want to
  // generalize the conversions
  if (aInputFormat == INPUT_FORMAT_HOSTARGB) {
    // PNG requires RGBA with post-multiplied alpha, so we need to
    // convert
    UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(aWidth * 4);
    if (NS_WARN_IF(!row)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    for (uint32_t y = 0; y < aHeight; y++) {
      ConvertHostARGBRow(&aData[y * aStride], row.get(), aWidth,
                         useTransparency);
      png_write_row(mPNG, row.get());
    }
  } else if (aInputFormat == INPUT_FORMAT_RGBA && !useTransparency) {
    // RBGA, but we need to strip the alpha
    UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(aWidth * 4);
    if (NS_WARN_IF(!row)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    for (uint32_t y = 0; y < aHeight; y++) {
      StripAlpha(&aData[y * aStride], row.get(), aWidth);
      png_write_row(mPNG, row.get());
    }
  } else if (aInputFormat == INPUT_FORMAT_RGB ||
             aInputFormat == INPUT_FORMAT_RGBA) {
    // simple RBG(A), no conversion needed
    for (uint32_t y = 0; y < aHeight; y++) {
      png_write_row(mPNG, (uint8_t*)&aData[y * aStride]);
    }

  } else if (aInputFormat == INPUT_FORMAT_R10G10B10A2) {
    // Unpack R10G10B10A2: 0bAARRRRRRRRRRGGGGGGGGGGBBBBBBBBBB
    // Scale 10-bit color [0,1023] to 16-bit [0,65535] and 2-bit alpha [0,3]
    // to 16-bit [0,65535].
    uint32_t channels = useTransparency ? 4 : 3;
    uint32_t rowBytes = aWidth * channels * 2;
    UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(rowBytes);
    if (NS_WARN_IF(!row)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    for (uint32_t y = 0; y < aHeight; y++) {
      const uint32_t* src =
          reinterpret_cast<const uint32_t*>(&aData[y * aStride]);
      uint16_t* dst = reinterpret_cast<uint16_t*>(row.get());
      for (uint32_t x = 0; x < aWidth; x++) {
        uint32_t pixel = src[x];
        uint32_t b = pixel & 0x3FF;
        uint32_t g = (pixel >> 10) & 0x3FF;
        uint32_t r = (pixel >> 20) & 0x3FF;
        dst[x * channels + 0] = static_cast<uint16_t>((r * 65535 + 511) / 1023);
        dst[x * channels + 1] = static_cast<uint16_t>((g * 65535 + 511) / 1023);
        dst[x * channels + 2] = static_cast<uint16_t>((b * 65535 + 511) / 1023);
        if (useTransparency) {
          uint32_t a = (pixel >> 30) & 0x3;
          dst[x * channels + 3] = static_cast<uint16_t>((a * 65535 + 1) / 3);
        }
      }
      png_write_row(mPNG, row.get());
    }

  } else if (aInputFormat == INPUT_FORMAT_RGBA_U10 ||
             aInputFormat == INPUT_FORMAT_RGBA_U12) {
    // Scale 10-bit or 12-bit values up to 16-bit for PNG.
    uint32_t maxVal = (aInputFormat == INPUT_FORMAT_RGBA_U10) ? 1023 : 4095;
    uint32_t channels = useTransparency ? 4 : 3;
    uint32_t rowBytes = aWidth * channels * 2;
    UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(rowBytes);
    if (NS_WARN_IF(!row)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    for (uint32_t y = 0; y < aHeight; y++) {
      const uint16_t* src =
          reinterpret_cast<const uint16_t*>(&aData[y * aStride]);
      uint16_t* dst = reinterpret_cast<uint16_t*>(row.get());
      for (uint32_t x = 0; x < aWidth; x++) {
        for (uint32_t c = 0; c < channels; c++) {
          uint32_t val = src[x * 4 + c];
          dst[x * channels + c] =
              static_cast<uint16_t>((val * 65535 + maxVal / 2) / maxVal);
        }
      }
      png_write_row(mPNG, row.get());
    }

  } else if (aInputFormat == INPUT_FORMAT_RGBA_U16) {
    // libpng handles the byte swap via png_set_swap.
    if (useTransparency) {
      for (uint32_t y = 0; y < aHeight; y++) {
        png_write_row(mPNG, (uint8_t*)&aData[y * aStride]);
      }
    } else {
      // Strip alpha: copy only RGB channels.
      uint32_t rowBytes = aWidth * 3 * 2;
      UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(rowBytes);
      if (NS_WARN_IF(!row)) {
        return NS_ERROR_OUT_OF_MEMORY;
      }
      for (uint32_t y = 0; y < aHeight; y++) {
        const uint16_t* src =
            reinterpret_cast<const uint16_t*>(&aData[y * aStride]);
        uint16_t* dst = reinterpret_cast<uint16_t*>(row.get());
        for (uint32_t x = 0; x < aWidth; x++) {
          dst[x * 3 + 0] = src[x * 4 + 0];
          dst[x * 3 + 1] = src[x * 4 + 1];
          dst[x * 3 + 2] = src[x * 4 + 2];
        }
        png_write_row(mPNG, row.get());
      }
    }

  } else if (aInputFormat == INPUT_FORMAT_RGBA_F16) {
    // Convert float16 to uint16; libpng handles the byte swap.
    uint32_t channels = useTransparency ? 4 : 3;
    uint32_t rowBytes = aWidth * channels * 2;
    UniquePtr<uint8_t[]> row = MakeUniqueFallible<uint8_t[]>(rowBytes);
    if (NS_WARN_IF(!row)) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
    for (uint32_t y = 0; y < aHeight; y++) {
      const uint16_t* src =
          reinterpret_cast<const uint16_t*>(&aData[y * aStride]);
      uint16_t* dst = reinterpret_cast<uint16_t*>(row.get());
      mozilla::gfx::ConvertFloat16RowToUint16(src, dst, aWidth, channels);
      png_write_row(mPNG, row.get());
    }

  } else {
    MOZ_ASSERT_UNREACHABLE("Bad format type");
    return NS_ERROR_INVALID_ARG;
  }

#ifdef PNG_APNG_SUPPORTED
  if (mIsAnimation) {
    png_write_frame_tail(mPNG, mPNGinfo);
  }
#endif

  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::EndImageEncode() {
  // must be initialized
  if (mImageBuffer == nullptr) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  // EndImageEncode has already been called, or some error
  // occurred earlier
  if (!mPNG) {
    return NS_BASE_STREAM_CLOSED;
  }

  // libpng's error handler jumps back here upon an error.
  if (setjmp(png_jmpbuf(mPNG))) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
    return NS_ERROR_FAILURE;
  }

  png_write_end(mPNG, mPNGinfo);
  png_destroy_write_struct(&mPNG, &mPNGinfo);

  mFinished = true;
  NotifyListener();

  // if output callback can't get enough memory, it will free our buffer
  if (!mImageBuffer) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  return NS_OK;
}

nsresult nsPNGEncoder::MaybeAddCustomMetadata(
    const nsACString& aRandomizationKey) {
  MOZ_ASSERT_IF(mAddCustomMetadata, !aRandomizationKey.IsEmpty());

  if (!mAddCustomMetadata) {
    return NS_OK;
  }

  nsCString hex;
  nsresult rv = nsRFPService::GenerateRandomizationKeyFromHash(
      aRandomizationKey, mImageBufferHash, hex);
  NS_ENSURE_SUCCESS(rv, rv);

  if (setjmp(png_jmpbuf(mPNG))) {
    png_destroy_write_struct(&mPNG, &mPNGinfo);
    return NS_ERROR_FAILURE;
  }

  png_size_t chunkLength = 16;
  png_unknown_chunk chunk;
  chunk.name[0] = 'd';
  chunk.name[1] = 'e';
  chunk.name[2] = 'B';
  chunk.name[3] = 'G';
  chunk.name[4] = '\0';

  chunk.data = reinterpret_cast<png_byte*>(hex.BeginWriting());
  chunk.size = chunkLength;
  chunk.location = PNG_AFTER_IDAT;

  png_set_unknown_chunks(mPNG, mPNGinfo, &chunk, 1);
  png_set_unknown_chunk_location(mPNG, mPNGinfo, 0, PNG_AFTER_IDAT);

  return NS_OK;
}

nsresult nsPNGEncoder::ParseOptions(const nsAString& aOptions,
                                    bool* useTransparency, bool* skipFirstFrame,
                                    uint32_t* numFrames, uint32_t* numPlays,
                                    int* zlibLevel, int* filters,
                                    uint32_t* frameDispose,
                                    uint32_t* frameBlend, uint32_t* frameDelay,
                                    uint32_t* offsetX, uint32_t* offsetY) {
#ifdef PNG_APNG_SUPPORTED
  // Make a copy of aOptions, because strtok() will modify it.
  nsAutoCString optionsCopy;
  optionsCopy.Assign(NS_ConvertUTF16toUTF8(aOptions));
  char* options = optionsCopy.BeginWriting();

  while (char* token = nsCRT::strtok(options, ";", &options)) {
    // If there's an '=' character, split the token around it.
    char* equals = token;
    char* value = nullptr;
    while (*equals != '=' && *equals) {
      ++equals;
    }
    if (*equals == '=') {
      value = equals + 1;
    }

    if (value) {
      *equals = '\0';  // temporary null
    }

    // transparency=[yes|no|none]
    if (nsCRT::strcmp(token, "transparency") == 0 && useTransparency) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (nsCRT::strcmp(value, "none") == 0 ||
          nsCRT::strcmp(value, "no") == 0) {
        *useTransparency = false;
      } else if (nsCRT::strcmp(value, "yes") == 0) {
        *useTransparency = true;
      } else {
        return NS_ERROR_INVALID_ARG;
      }

      // skipfirstframe=[yes|no]
    } else if (nsCRT::strcmp(token, "skipfirstframe") == 0 && skipFirstFrame) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (nsCRT::strcmp(value, "no") == 0) {
        *skipFirstFrame = false;
      } else if (nsCRT::strcmp(value, "yes") == 0) {
        *skipFirstFrame = true;
      } else {
        return NS_ERROR_INVALID_ARG;
      }

      // frames=#
    } else if (nsCRT::strcmp(token, "frames") == 0 && numFrames) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (PR_sscanf(value, "%u", numFrames) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // frames=0 is nonsense.
      if (*numFrames == 0) {
        return NS_ERROR_INVALID_ARG;
      }

      // plays=#
    } else if (nsCRT::strcmp(token, "plays") == 0 && numPlays) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      // plays=0 to loop forever, otherwise play sequence specified
      // number of times
      if (PR_sscanf(value, "%u", numPlays) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // png-zlib-level=#
    } else if (nsCRT::strcmp(token, "png-zlib-level") == 0) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      int localZlibLevel = DEFAULT_ZLIB_LEVEL;
      if (PR_sscanf(value, "%d", &localZlibLevel) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // zlib-level 0-9 are the only valid values
      if (localZlibLevel < 0 || localZlibLevel > 9) {
        return NS_ERROR_INVALID_ARG;
      }

      if (zlibLevel) {
        *zlibLevel = localZlibLevel;
      }

      // png-filter=[no_filters|none|sub|up|avg|paeth|fast|all]
    } else if (nsCRT::strcmp(token, "png-filter") == 0) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (nsCRT::strcmp(value, "no_filters") == 0) {
        if (filters) {
          *filters = PNG_NO_FILTERS;
        }
      } else if (nsCRT::strcmp(value, "none") == 0) {
        if (filters) {
          *filters = PNG_FILTER_NONE;
        }
      } else if (nsCRT::strcmp(value, "sub") == 0) {
        if (filters) {
          *filters = PNG_FILTER_SUB;
        }
      } else if (nsCRT::strcmp(value, "up") == 0) {
        if (filters) {
          *filters = PNG_FILTER_UP;
        }
      } else if (nsCRT::strcmp(value, "avg") == 0) {
        if (filters) {
          *filters = PNG_FILTER_AVG;
        }
      } else if (nsCRT::strcmp(value, "paeth") == 0) {
        if (filters) {
          *filters = PNG_FILTER_PAETH;
        }
      } else if (nsCRT::strcmp(value, "fast") == 0) {
        if (filters) {
          *filters = PNG_FAST_FILTERS;
        }
      } else if (nsCRT::strcmp(value, "all") == 0) {
        if (filters) {
          *filters = PNG_ALL_FILTERS;
        }
      } else {
        return NS_ERROR_INVALID_ARG;
      }

      // dispose=[none|background|previous]
    } else if (nsCRT::strcmp(token, "dispose") == 0 && frameDispose) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (nsCRT::strcmp(value, "none") == 0) {
        *frameDispose = PNG_DISPOSE_OP_NONE;
      } else if (nsCRT::strcmp(value, "background") == 0) {
        *frameDispose = PNG_DISPOSE_OP_BACKGROUND;
      } else if (nsCRT::strcmp(value, "previous") == 0) {
        *frameDispose = PNG_DISPOSE_OP_PREVIOUS;
      } else {
        return NS_ERROR_INVALID_ARG;
      }

      // blend=[source|over]
    } else if (nsCRT::strcmp(token, "blend") == 0 && frameBlend) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (nsCRT::strcmp(value, "source") == 0) {
        *frameBlend = PNG_BLEND_OP_SOURCE;
      } else if (nsCRT::strcmp(value, "over") == 0) {
        *frameBlend = PNG_BLEND_OP_OVER;
      } else {
        return NS_ERROR_INVALID_ARG;
      }

      // delay=# (in ms)
    } else if (nsCRT::strcmp(token, "delay") == 0 && frameDelay) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (PR_sscanf(value, "%u", frameDelay) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // xoffset=#
    } else if (nsCRT::strcmp(token, "xoffset") == 0 && offsetX) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (PR_sscanf(value, "%u", offsetX) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // yoffset=#
    } else if (nsCRT::strcmp(token, "yoffset") == 0 && offsetY) {
      if (!value) {
        return NS_ERROR_INVALID_ARG;
      }

      if (PR_sscanf(value, "%u", offsetY) != 1) {
        return NS_ERROR_INVALID_ARG;
      }

      // unknown token name
    } else
      return NS_ERROR_INVALID_ARG;

    if (value) {
      *equals = '=';  // restore '=' so strtok doesn't get lost
    }
  }

#endif
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::Close() {
  if (mImageBuffer != nullptr) {
    free(mImageBuffer);
    mImageBuffer = nullptr;
    mImageBufferSize = 0;
    mImageBufferUsed = 0;
    mImageBufferReadPoint = 0;
  }
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::Available(uint64_t* _retval) {
  if (!mImageBuffer) {
    return NS_BASE_STREAM_CLOSED;
  }

  *_retval = mImageBufferUsed - mImageBufferReadPoint;
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::StreamStatus() {
  return mImageBuffer ? NS_OK : NS_BASE_STREAM_CLOSED;
}

NS_IMETHODIMP
nsPNGEncoder::Read(char* aBuf, uint32_t aCount, uint32_t* _retval) {
  return ReadSegments(NS_CopySegmentToBuffer, aBuf, aCount, _retval);
}

NS_IMETHODIMP
nsPNGEncoder::ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
                           uint32_t aCount, uint32_t* _retval) {
  // Avoid another thread reallocing the buffer underneath us
  ReentrantMonitorAutoEnter autoEnter(mReentrantMonitor);

  uint32_t maxCount = mImageBufferUsed - mImageBufferReadPoint;
  if (maxCount == 0) {
    *_retval = 0;
    return mFinished ? NS_OK : NS_BASE_STREAM_WOULD_BLOCK;
  }

  if (aCount > maxCount) {
    aCount = maxCount;
  }

  nsresult rv = aWriter(
      this, aClosure,
      reinterpret_cast<const char*>(mImageBuffer + mImageBufferReadPoint), 0,
      aCount, _retval);
  if (NS_SUCCEEDED(rv)) {
    NS_ASSERTION(*_retval <= aCount, "bad write count");
    mImageBufferReadPoint += *_retval;
  }

  // errors returned from the writer end here!
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::IsNonBlocking(bool* _retval) {
  *_retval = true;
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::AsyncWait(nsIInputStreamCallback* aCallback, uint32_t aFlags,
                        uint32_t aRequestedCount, nsIEventTarget* aTarget) {
  if (aFlags != 0) {
    return NS_ERROR_NOT_IMPLEMENTED;
  }

  if (mCallback || mCallbackTarget) {
    return NS_ERROR_UNEXPECTED;
  }

  mCallbackTarget = aTarget;
  // 0 means "any number of bytes except 0"
  mNotifyThreshold = aRequestedCount;
  if (!aRequestedCount) {
    mNotifyThreshold = 1024;  // We don't want to notify incessantly
  }

  // We set the callback absolutely last, because NotifyListener uses it to
  // determine if someone needs to be notified.  If we don't set it last,
  // NotifyListener might try to fire off a notification to a null target
  // which will generally cause non-threadsafe objects to be used off the main
  // thread
  mCallback = aCallback;

  // What we are being asked for may be present already
  NotifyListener();
  return NS_OK;
}

NS_IMETHODIMP
nsPNGEncoder::CloseWithStatus(nsresult aStatus) { return Close(); }

// nsPNGEncoder::ConvertHostARGBRow
//
//    Our colors are stored with premultiplied alphas, but PNGs use
//    post-multiplied alpha. This swaps to PNG-style alpha.
//
//    Copied from gfx/cairo/cairo/src/cairo-png.c

void nsPNGEncoder::ConvertHostARGBRow(const uint8_t* aSrc, uint8_t* aDest,
                                      uint32_t aPixelWidth,
                                      bool aUseTransparency) {
  uint32_t pixelStride = aUseTransparency ? 4 : 3;
  for (uint32_t x = 0; x < aPixelWidth; x++) {
    const uint32_t& pixelIn = ((const uint32_t*)(aSrc))[x];
    uint8_t* pixelOut = &aDest[x * pixelStride];

    uint8_t alpha = (pixelIn & 0xff000000) >> 24;
    pixelOut[pixelStride - 1] = alpha;  // overwritten below if pixelStride == 3
    if (alpha == 255) {
      pixelOut[0] = (pixelIn & 0xff0000) >> 16;
      pixelOut[1] = (pixelIn & 0x00ff00) >> 8;
      pixelOut[2] = (pixelIn & 0x0000ff);
    } else if (alpha == 0) {
      pixelOut[0] = pixelOut[1] = pixelOut[2] = 0;
    } else {
      pixelOut[0] = (((pixelIn & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
      pixelOut[1] = (((pixelIn & 0x00ff00) >> 8) * 255 + alpha / 2) / alpha;
      pixelOut[2] = (((pixelIn & 0x0000ff)) * 255 + alpha / 2) / alpha;
    }
  }
}

// nsPNGEncoder::StripAlpha
//
//    Input is RGBA, output is RGB

void nsPNGEncoder::StripAlpha(const uint8_t* aSrc, uint8_t* aDest,
                              uint32_t aPixelWidth) {
  for (uint32_t x = 0; x < aPixelWidth; x++) {
    const uint8_t* pixelIn = &aSrc[x * 4];
    uint8_t* pixelOut = &aDest[x * 3];
    pixelOut[0] = pixelIn[0];
    pixelOut[1] = pixelIn[1];
    pixelOut[2] = pixelIn[2];
  }
}

// nsPNGEncoder::WarningCallback

void nsPNGEncoder::WarningCallback(png_structp png_ptr,
                                   png_const_charp warning_msg) {
  MOZ_LOG(sPNGEncoderLog, LogLevel::Warning,
          ("libpng warning: %s\n", warning_msg));
}

// nsPNGEncoder::ErrorCallback

void nsPNGEncoder::ErrorCallback(png_structp png_ptr,
                                 png_const_charp error_msg) {
  MOZ_LOG(sPNGEncoderLog, LogLevel::Error, ("libpng error: %s\n", error_msg));
  png_longjmp(png_ptr, 1);
}

// nsPNGEncoder::WriteCallback

void  // static
nsPNGEncoder::WriteCallback(png_structp png, png_bytep data, png_size_t size) {
  nsPNGEncoder* that = static_cast<nsPNGEncoder*>(png_get_io_ptr(png));
  if (!that->mImageBuffer) {
    return;
  }

  CheckedUint32 sizeNeeded = CheckedUint32(that->mImageBufferUsed) + size;
  if (!sizeNeeded.isValid()) {
    // Take the lock to ensure that nobody is trying to read from the buffer
    // we are destroying
    ReentrantMonitorAutoEnter autoEnter(that->mReentrantMonitor);

    that->NullOutImageBuffer();
    return;
  }

  if (sizeNeeded.value() > that->mImageBufferSize) {
    // When we're reallocing the buffer we need to take the lock to ensure
    // that nobody is trying to read from the buffer we are destroying
    ReentrantMonitorAutoEnter autoEnter(that->mReentrantMonitor);

    while (sizeNeeded.value() > that->mImageBufferSize) {
      // expand buffer, just double each time
      CheckedUint32 bufferSize = CheckedUint32(that->mImageBufferSize) * 2;
      if (!bufferSize.isValid()) {
        that->NullOutImageBuffer();
        return;
      }
      that->mImageBufferSize *= 2;
      uint8_t* newBuf =
          (uint8_t*)realloc(that->mImageBuffer, that->mImageBufferSize);
      if (!newBuf) {
        // can't resize, just zero (this will keep us from writing more)
        that->NullOutImageBuffer();
        return;
      }
      that->mImageBuffer = newBuf;
    }
  }

  if (that->mAddCustomMetadata) {
    that->mImageBufferHash = HashBytes(data, size, that->mImageBufferHash);
  }

  memcpy(&that->mImageBuffer[that->mImageBufferUsed], data, size);
  that->mImageBufferUsed += size;
  that->NotifyListener();
}

void nsPNGEncoder::NullOutImageBuffer() {
  mReentrantMonitor.AssertCurrentThreadIn();

  free(mImageBuffer);
  mImageBuffer = nullptr;
  mImageBufferSize = 0;
  mImageBufferUsed = 0;
}

void nsPNGEncoder::NotifyListener() {
  // We might call this function on multiple threads (any threads that call
  // AsyncWait and any that do encoding) so we lock to avoid notifying the
  // listener twice about the same data (which generally leads to a truncated
  // image).
  ReentrantMonitorAutoEnter autoEnter(mReentrantMonitor);

  if (mCallback &&
      (mImageBufferUsed - mImageBufferReadPoint >= mNotifyThreshold ||
       mFinished)) {
    nsCOMPtr<nsIInputStreamCallback> callback;
    if (mCallbackTarget) {
      callback = NS_NewInputStreamReadyEvent("nsPNGEncoder::NotifyListener",
                                             mCallback, mCallbackTarget);
    } else {
      callback = mCallback;
    }

    NS_ASSERTION(callback, "Shouldn't fail to make the callback");
    // Null the callback first because OnInputStreamReady could reenter
    // AsyncWait
    mCallback = nullptr;
    mCallbackTarget = nullptr;
    mNotifyThreshold = 0;

    callback->OnInputStreamReady(this);
  }
}
