DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (5350524bb654)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673
/* vim:set tw=80 expandtab softtabstop=2 ts=2 sw=2: */
/* 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/. */

/* This is a Cross-Platform ICO Decoder, which should work everywhere, including
 * Big-Endian machines like the PowerPC. */

#include "nsICODecoder.h"

#include <stdlib.h>

#include "mozilla/EndianUtils.h"
#include "mozilla/Move.h"

#include "RasterImage.h"

using namespace mozilla::gfx;

namespace mozilla {
namespace image {

// Constants.
static const uint32_t ICOHEADERSIZE = 6;
static const uint32_t BITMAPINFOSIZE = bmp::InfoHeaderLength::WIN_ICO;

// ----------------------------------------
// Actual Data Processing
// ----------------------------------------

// Obtains the number of colors from the bits per pixel
uint16_t
nsICODecoder::GetNumColors()
{
  uint16_t numColors = 0;
  if (mBPP <= 8) {
    switch (mBPP) {
    case 1:
      numColors = 2;
      break;
    case 4:
      numColors = 16;
      break;
    case 8:
      numColors = 256;
      break;
    default:
      numColors = (uint16_t)-1;
    }
  }
  return numColors;
}

nsICODecoder::nsICODecoder(RasterImage* aImage)
  : Decoder(aImage)
  , mLexer(Transition::To(ICOState::HEADER, ICOHEADERSIZE),
           Transition::TerminateSuccess())
  , mBiggestResourceColorDepth(0)
  , mBestResourceDelta(INT_MIN)
  , mBestResourceColorDepth(0)
  , mNumIcons(0)
  , mCurrIcon(0)
  , mBPP(0)
  , mMaskRowSize(0)
  , mCurrMaskLine(0)
  , mIsCursor(false)
  , mHasMaskAlpha(false)
{ }

nsresult
nsICODecoder::FinishInternal()
{
  // We shouldn't be called in error cases
  MOZ_ASSERT(!HasError(), "Shouldn't call FinishInternal after error!");

  return GetFinalStateFromContainedDecoder();
}

nsresult
nsICODecoder::FinishWithErrorInternal()
{
  return GetFinalStateFromContainedDecoder();
}

nsresult
nsICODecoder::GetFinalStateFromContainedDecoder()
{
  if (!mContainedDecoder) {
    return NS_OK;
  }

  MOZ_ASSERT(mContainedSourceBuffer,
             "Should have a SourceBuffer if we have a decoder");

  // Let the contained decoder finish up if necessary.
  if (!mContainedSourceBuffer->IsComplete()) {
    mContainedSourceBuffer->Complete(NS_OK);
    mContainedDecoder->Decode();
  }

  // Make our state the same as the state of the contained decoder.
  mDecodeDone = mContainedDecoder->GetDecodeDone();
  mProgress |= mContainedDecoder->TakeProgress();
  mInvalidRect.UnionRect(mInvalidRect, mContainedDecoder->TakeInvalidRect());
  mCurrentFrame = mContainedDecoder->GetCurrentFrameRef();

  // Propagate errors.
  nsresult rv = HasError() || mContainedDecoder->HasError()
              ? NS_ERROR_FAILURE
              : NS_OK;

  MOZ_ASSERT(NS_FAILED(rv) || !mCurrentFrame || mCurrentFrame->IsFinished());
  return rv;
}

bool
nsICODecoder::CheckAndFixBitmapSize(int8_t* aBIH)
{
  // Get the width from the BMP file information header. This is
  // (unintuitively) a signed integer; see the documentation at:
  //
  //   https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx
  //
  // However, we reject negative widths since they aren't meaningful.
  const int32_t width = LittleEndian::readInt32(aBIH + 4);
  if (width <= 0 || width > 256) {
    return false;
  }

  // Verify that the BMP width matches the width we got from the ICO directory
  // entry. If not, decoding fails, because if we were to allow it to continue
  // the intrinsic size of the image wouldn't match the size of the decoded
  // surface.
  if (width != int32_t(GetRealWidth())) {
    return false;
  }

  // Get the height from the BMP file information header. This is also signed,
  // but in this case negative values are meaningful; see below.
  int32_t height = LittleEndian::readInt32(aBIH + 8);
  if (height == 0) {
    return false;
  }

  // BMPs can be stored inverted by having a negative height.
  // XXX(seth): Should we really be writing the absolute value into the BIH
  // below? Seems like this could be problematic for inverted BMPs.
  height = abs(height);

  // The height field is double the actual height of the image to account for
  // the AND mask. This is true even if the AND mask is not present.
  height /= 2;
  if (height > 256) {
    return false;
  }

  // Verify that the BMP height matches the height we got from the ICO directory
  // entry. If not, again, decoding fails.
  if (height != int32_t(GetRealHeight())) {
    return false;
  }

  // Fix the BMP height in the BIH so that the BMP decoder, which does not know
  // about the AND mask that may follow the actual bitmap, can work properly.
  LittleEndian::writeInt32(aBIH + 8, GetRealHeight());

  return true;
}

LexerTransition<ICOState>
nsICODecoder::ReadHeader(const char* aData)
{
  // If the third byte is 1, this is an icon. If 2, a cursor.
  if ((aData[2] != 1) && (aData[2] != 2)) {
    return Transition::TerminateFailure();
  }
  mIsCursor = (aData[2] == 2);

  // The fifth and sixth bytes specify the number of resources in the file.
  mNumIcons = LittleEndian::readUint16(aData + 4);
  if (mNumIcons == 0) {
    return Transition::TerminateSuccess(); // Nothing to do.
  }

  // Downscale-during-decode can end up decoding different resources in the ICO
  // file depending on the target size. Since the resources are not necessarily
  // scaled versions of the same image, some may be transparent and some may not
  // be. We could be precise about transparency if we decoded the metadata of
  // every resource, but for now we don't and it's safest to assume that
  // transparency could be present.
  PostHasTransparency();

  return Transition::To(ICOState::DIR_ENTRY, ICODIRENTRYSIZE);
}

size_t
nsICODecoder::FirstResourceOffset() const
{
  MOZ_ASSERT(mNumIcons > 0,
             "Calling FirstResourceOffset before processing header");

  // The first resource starts right after the directory, which starts right
  // after the ICO header.
  return ICOHEADERSIZE + mNumIcons * ICODIRENTRYSIZE;
}

LexerTransition<ICOState>
nsICODecoder::ReadDirEntry(const char* aData)
{
  mCurrIcon++;

  // Read the directory entry.
  IconDirEntry e;
  e.mWidth       = aData[0];
  e.mHeight      = aData[1];
  e.mColorCount  = aData[2];
  e.mReserved    = aData[3];
  e.mPlanes      = LittleEndian::readUint16(aData + 4);
  e.mBitCount    = LittleEndian::readUint16(aData + 6);
  e.mBytesInRes  = LittleEndian::readUint32(aData + 8);
  e.mImageOffset = LittleEndian::readUint32(aData + 12);

  // If an explicit output size was specified, we'll try to select the resource
  // that matches it best below.
  const Maybe<IntSize> desiredSize = ExplicitOutputSize();

  // Determine if this is the biggest resource we've seen so far. We always use
  // the biggest resource for the intrinsic size, and if we don't have a
  // specific desired size, we select it as the best resource as well.
  IntSize entrySize(GetRealWidth(e), GetRealHeight(e));
  if (e.mBitCount >= mBiggestResourceColorDepth &&
      entrySize.width * entrySize.height >=
        mBiggestResourceSize.width * mBiggestResourceSize.height) {
    mBiggestResourceSize = entrySize;
    mBiggestResourceColorDepth = e.mBitCount;
    mBiggestResourceHotSpot = IntSize(e.mXHotspot, e.mYHotspot);

    if (!desiredSize) {
      mDirEntry = e;
    }
  }

  if (desiredSize) {
    // Calculate the delta between this resource's size and the desired size, so
    // we can see if it is better than our current-best option.  In the case of
    // several equally-good resources, we use the last one. "Better" in this
    // case is determined by |delta|, a measure of the difference in size
    // between the entry we've found and the desired size. We will choose the
    // smallest resource that is greater than or equal to the desired size (i.e.
    // we assume it's better to downscale a larger icon than to upscale a
    // smaller one).
    int32_t delta = std::min(entrySize.width - desiredSize->width,
                             entrySize.height - desiredSize->height);
    if (e.mBitCount >= mBestResourceColorDepth &&
        ((mBestResourceDelta < 0 && delta >= mBestResourceDelta) ||
         (delta >= 0 && delta <= mBestResourceDelta))) {
      mBestResourceDelta = delta;
      mBestResourceColorDepth = e.mBitCount;
      mDirEntry = e;
    }
  }

  if (mCurrIcon == mNumIcons) {
    // Ensure the resource we selected has an offset past the ICO headers.
    if (mDirEntry.mImageOffset < FirstResourceOffset()) {
      return Transition::TerminateFailure();
    }

    // If this is a cursor, set the hotspot. We use the hotspot from the biggest
    // resource since we also use that resource for the intrinsic size.
    if (mIsCursor) {
      mImageMetadata.SetHotspot(mBiggestResourceHotSpot.width,
                                mBiggestResourceHotSpot.height);
    }

    // We always report the biggest resource's size as the intrinsic size; this
    // is necessary for downscale-during-decode to work since we won't even
    // attempt to *upscale* while decoding.
    PostSize(mBiggestResourceSize.width, mBiggestResourceSize.height);
    if (IsMetadataDecode()) {
      return Transition::TerminateSuccess();
    }

    // If the resource we selected matches the output size perfectly, we don't
    // need to do any downscaling.
    if (GetRealSize() == OutputSize()) {
      MOZ_ASSERT_IF(desiredSize, GetRealSize() == *desiredSize);
      MOZ_ASSERT_IF(!desiredSize, GetRealSize() == Size());
      mDownscaler.reset();
    }

    size_t offsetToResource = mDirEntry.mImageOffset - FirstResourceOffset();
    return Transition::ToUnbuffered(ICOState::FOUND_RESOURCE,
                                    ICOState::SKIP_TO_RESOURCE,
                                    offsetToResource);
  }

  return Transition::To(ICOState::DIR_ENTRY, ICODIRENTRYSIZE);
}

LexerTransition<ICOState>
nsICODecoder::SniffResource(const char* aData)
{
  // We use the first PNGSIGNATURESIZE bytes to determine whether this resource
  // is a PNG or a BMP.
  bool isPNG = !memcmp(aData, nsPNGDecoder::pngSignatureBytes,
                       PNGSIGNATURESIZE);
  if (isPNG) {
    // Create a PNG decoder which will do the rest of the work for us.
    mContainedSourceBuffer = new SourceBuffer();
    mContainedSourceBuffer->ExpectLength(mDirEntry.mBytesInRes);
    mContainedDecoder =
      DecoderFactory::CreateDecoderForICOResource(DecoderType::PNG,
                                                  WrapNotNull(mContainedSourceBuffer),
                                                  WrapNotNull(this));

    if (!WriteToContainedDecoder(aData, PNGSIGNATURESIZE)) {
      return Transition::TerminateFailure();
    }

    if (mDirEntry.mBytesInRes <= PNGSIGNATURESIZE) {
      return Transition::TerminateFailure();
    }

    // Read in the rest of the PNG unbuffered.
    size_t toRead = mDirEntry.mBytesInRes - PNGSIGNATURESIZE;
    return Transition::ToUnbuffered(ICOState::FINISHED_RESOURCE,
                                    ICOState::READ_PNG,
                                    toRead);
  } else {
    // Make sure we have a sane size for the bitmap information header.
    int32_t bihSize = LittleEndian::readUint32(aData);
    if (bihSize != static_cast<int32_t>(BITMAPINFOSIZE)) {
      return Transition::TerminateFailure();
    }

    // Buffer the first part of the bitmap information header.
    memcpy(mBIHraw, aData, PNGSIGNATURESIZE);

    // Read in the rest of the bitmap information header.
    return Transition::To(ICOState::READ_BIH,
                          BITMAPINFOSIZE - PNGSIGNATURESIZE);
  }
}

LexerTransition<ICOState>
nsICODecoder::ReadPNG(const char* aData, uint32_t aLen)
{
  if (!WriteToContainedDecoder(aData, aLen)) {
    return Transition::TerminateFailure();
  }

  // Raymond Chen says that 32bpp only are valid PNG ICOs
  // http://blogs.msdn.com/b/oldnewthing/archive/2010/10/22/10079192.aspx
  if (!static_cast<nsPNGDecoder*>(mContainedDecoder.get())->IsValidICO()) {
    return Transition::TerminateFailure();
  }

  return Transition::ContinueUnbuffered(ICOState::READ_PNG);
}

LexerTransition<ICOState>
nsICODecoder::ReadBIH(const char* aData)
{
  // Buffer the rest of the bitmap information header.
  memcpy(mBIHraw + PNGSIGNATURESIZE, aData, BITMAPINFOSIZE - PNGSIGNATURESIZE);

  // Extract the BPP from the BIH header; it should be trusted over the one
  // we have from the ICO header which is usually set to 0.
  mBPP = LittleEndian::readUint16(mBIHraw + 14);

  // The ICO format when containing a BMP does not include the 14 byte
  // bitmap file header. So we create the BMP decoder via the constructor that
  // tells it to skip this, and pass in the required data (dataOffset) that
  // would have been present in the header.
  uint32_t dataOffset = bmp::FILE_HEADER_LENGTH + BITMAPINFOSIZE;
  if (mDirEntry.mBitCount <= 8) {
    // The color table is present only if BPP is <= 8.
    uint16_t numColors = GetNumColors();
    if (numColors == (uint16_t)-1) {
      return Transition::TerminateFailure();
    }
    dataOffset += 4 * numColors;
  }

  // Create a BMP decoder which will do most of the work for us; the exception
  // is the AND mask, which isn't present in standalone BMPs.
  mContainedSourceBuffer = new SourceBuffer();
  mContainedSourceBuffer->ExpectLength(mDirEntry.mBytesInRes);
  mContainedDecoder =
    DecoderFactory::CreateDecoderForICOResource(DecoderType::BMP,
                                                WrapNotNull(mContainedSourceBuffer),
                                                WrapNotNull(this),
                                                Some(dataOffset));
  RefPtr<nsBMPDecoder> bmpDecoder =
    static_cast<nsBMPDecoder*>(mContainedDecoder.get());

  // Verify that the BIH width and height values match the ICO directory entry,
  // and fix the BIH height value to compensate for the fact that the underlying
  // BMP decoder doesn't know about AND masks.
  if (!CheckAndFixBitmapSize(reinterpret_cast<int8_t*>(mBIHraw))) {
    return Transition::TerminateFailure();
  }

  // Write out the BMP's bitmap info header.
  if (!WriteToContainedDecoder(mBIHraw, sizeof(mBIHraw))) {
    return Transition::TerminateFailure();
  }

  // Check to make sure we have valid color settings.
  uint16_t numColors = GetNumColors();
  if (numColors == uint16_t(-1)) {
    return Transition::TerminateFailure();
  }

  // Do we have an AND mask on this BMP? If so, we need to read it after we read
  // the BMP data itself.
  uint32_t bmpDataLength = bmpDecoder->GetCompressedImageSize() + 4 * numColors;
  bool hasANDMask = (BITMAPINFOSIZE + bmpDataLength) < mDirEntry.mBytesInRes;
  ICOState afterBMPState = hasANDMask ? ICOState::PREPARE_FOR_MASK
                                      : ICOState::FINISHED_RESOURCE;

  // Read in the rest of the BMP unbuffered.
  return Transition::ToUnbuffered(afterBMPState,
                                  ICOState::READ_BMP,
                                  bmpDataLength);
}

LexerTransition<ICOState>
nsICODecoder::ReadBMP(const char* aData, uint32_t aLen)
{
  if (!WriteToContainedDecoder(aData, aLen)) {
    return Transition::TerminateFailure();
  }

  return Transition::ContinueUnbuffered(ICOState::READ_BMP);
}

LexerTransition<ICOState>
nsICODecoder::PrepareForMask()
{
  RefPtr<nsBMPDecoder> bmpDecoder =
    static_cast<nsBMPDecoder*>(mContainedDecoder.get());

  uint16_t numColors = GetNumColors();
  MOZ_ASSERT(numColors != uint16_t(-1));

  // Determine the length of the AND mask.
  uint32_t bmpLengthWithHeader =
    BITMAPINFOSIZE + bmpDecoder->GetCompressedImageSize() + 4 * numColors;
  MOZ_ASSERT(bmpLengthWithHeader < mDirEntry.mBytesInRes);
  uint32_t maskLength = mDirEntry.mBytesInRes - bmpLengthWithHeader;

  // If the BMP provides its own transparency, we ignore the AND mask. We can
  // also obviously ignore it if the image has zero width or zero height.
  if (bmpDecoder->HasTransparency() ||
      GetRealWidth() == 0 || GetRealHeight() == 0) {
    return Transition::ToUnbuffered(ICOState::FINISHED_RESOURCE,
                                    ICOState::SKIP_MASK,
                                    maskLength);
  }

  // Compute the row size for the mask.
  mMaskRowSize = ((GetRealWidth() + 31) / 32) * 4; // + 31 to round up

  // If the expected size of the AND mask is larger than its actual size, then
  // we must have a truncated (and therefore corrupt) AND mask.
  uint32_t expectedLength = mMaskRowSize * GetRealHeight();
  if (maskLength < expectedLength) {
    return Transition::TerminateFailure();
  }

  // If we're downscaling, the mask is the wrong size for the surface we've
  // produced, so we need to downscale the mask into a temporary buffer and then
  // combine the mask's alpha values with the color values from the image.
  if (mDownscaler) {
    MOZ_ASSERT(bmpDecoder->GetImageDataLength() ==
                 mDownscaler->TargetSize().width *
                 mDownscaler->TargetSize().height *
                 sizeof(uint32_t));
    mMaskBuffer = MakeUnique<uint8_t[]>(bmpDecoder->GetImageDataLength());
    nsresult rv = mDownscaler->BeginFrame(GetRealSize(), Nothing(),
                                          mMaskBuffer.get(),
                                          /* aHasAlpha = */ true,
                                          /* aFlipVertically = */ true);
    if (NS_FAILED(rv)) {
      return Transition::TerminateFailure();
    }
  }

  mCurrMaskLine = GetRealHeight();
  return Transition::To(ICOState::READ_MASK_ROW, mMaskRowSize);
}


LexerTransition<ICOState>
nsICODecoder::ReadMaskRow(const char* aData)
{
  mCurrMaskLine--;

  uint8_t sawTransparency = 0;

  // Get the mask row we're reading.
  const uint8_t* mask = reinterpret_cast<const uint8_t*>(aData);
  const uint8_t* maskRowEnd = mask + mMaskRowSize;

  // Get the corresponding row of the mask buffer (if we're downscaling) or the
  // decoded image data (if we're not).
  uint32_t* decoded = nullptr;
  if (mDownscaler) {
    // Initialize the row to all white and fully opaque.
    memset(mDownscaler->RowBuffer(), 0xFF, GetRealWidth() * sizeof(uint32_t));

    decoded = reinterpret_cast<uint32_t*>(mDownscaler->RowBuffer());
  } else {
    RefPtr<nsBMPDecoder> bmpDecoder =
      static_cast<nsBMPDecoder*>(mContainedDecoder.get());
    uint32_t* imageData = bmpDecoder->GetImageData();
    if (!imageData) {
      return Transition::TerminateFailure();
    }

    decoded = imageData + mCurrMaskLine * GetRealWidth();
  }

  MOZ_ASSERT(decoded);
  uint32_t* decodedRowEnd = decoded + GetRealWidth();

  // Iterate simultaneously through the AND mask and the image data.
  while (mask < maskRowEnd) {
    uint8_t idx = *mask++;
    sawTransparency |= idx;
    for (uint8_t bit = 0x80; bit && decoded < decodedRowEnd; bit >>= 1) {
      // Clear pixel completely for transparency.
      if (idx & bit) {
        *decoded = 0;
      }
      decoded++;
    }
  }

  if (mDownscaler) {
    mDownscaler->CommitRow();
  }

  // If any bits are set in sawTransparency, then we know at least one pixel was
  // transparent.
  if (sawTransparency) {
    mHasMaskAlpha = true;
  }

  if (mCurrMaskLine == 0) {
    return Transition::To(ICOState::FINISH_MASK, 0);
  }

  return Transition::To(ICOState::READ_MASK_ROW, mMaskRowSize);
}

LexerTransition<ICOState>
nsICODecoder::FinishMask()
{
  // If we're downscaling, we now have the appropriate alpha values in
  // mMaskBuffer. We just need to transfer them to the image.
  if (mDownscaler) {
    // Retrieve the image data.
    RefPtr<nsBMPDecoder> bmpDecoder =
      static_cast<nsBMPDecoder*>(mContainedDecoder.get());
    uint8_t* imageData = reinterpret_cast<uint8_t*>(bmpDecoder->GetImageData());
    if (!imageData) {
      return Transition::TerminateFailure();
    }

    // Iterate through the alpha values, copying from mask to image.
    MOZ_ASSERT(mMaskBuffer);
    MOZ_ASSERT(bmpDecoder->GetImageDataLength() > 0);
    for (size_t i = 3 ; i < bmpDecoder->GetImageDataLength() ; i += 4) {
      imageData[i] = mMaskBuffer[i];
    }
  }

  return Transition::To(ICOState::FINISHED_RESOURCE, 0);
}

LexerTransition<ICOState>
nsICODecoder::FinishResource()
{
  // Make sure the actual size of the resource matches the size in the directory
  // entry. If not, we consider the image corrupt.
  if (mContainedDecoder->HasSize() &&
      mContainedDecoder->Size() != GetRealSize()) {
    return Transition::TerminateFailure();
  }

  return Transition::TerminateSuccess();
}

LexerResult
nsICODecoder::DoDecode(SourceBufferIterator& aIterator, IResumable* aOnResume)
{
  MOZ_ASSERT(!HasError(), "Shouldn't call DoDecode after error!");

  return mLexer.Lex(aIterator, aOnResume,
                    [=](ICOState aState, const char* aData, size_t aLength) {
    switch (aState) {
      case ICOState::HEADER:
        return ReadHeader(aData);
      case ICOState::DIR_ENTRY:
        return ReadDirEntry(aData);
      case ICOState::SKIP_TO_RESOURCE:
        return Transition::ContinueUnbuffered(ICOState::SKIP_TO_RESOURCE);
      case ICOState::FOUND_RESOURCE:
        return Transition::To(ICOState::SNIFF_RESOURCE, PNGSIGNATURESIZE);
      case ICOState::SNIFF_RESOURCE:
        return SniffResource(aData);
      case ICOState::READ_PNG:
        return ReadPNG(aData, aLength);
      case ICOState::READ_BIH:
        return ReadBIH(aData);
      case ICOState::READ_BMP:
        return ReadBMP(aData, aLength);
      case ICOState::PREPARE_FOR_MASK:
        return PrepareForMask();
      case ICOState::READ_MASK_ROW:
        return ReadMaskRow(aData);
      case ICOState::FINISH_MASK:
        return FinishMask();
      case ICOState::SKIP_MASK:
        return Transition::ContinueUnbuffered(ICOState::SKIP_MASK);
      case ICOState::FINISHED_RESOURCE:
        return FinishResource();
      default:
        MOZ_CRASH("Unknown ICOState");
    }
  });
}

bool
nsICODecoder::WriteToContainedDecoder(const char* aBuffer, uint32_t aCount)
{
  MOZ_ASSERT(mContainedDecoder);
  MOZ_ASSERT(mContainedSourceBuffer);

  // Append the provided data to the SourceBuffer that the contained decoder is
  // reading from.
  mContainedSourceBuffer->Append(aBuffer, aCount);

  bool succeeded = true;

  // Write to the contained decoder. If we run out of data, the ICO decoder will
  // get resumed when there's more data available, as usual, so we don't need
  // the contained decoder to get resumed too. To avoid that, we provide an
  // IResumable which just does nothing.
  LexerResult result = mContainedDecoder->Decode();
  if (result == LexerResult(TerminalState::FAILURE)) {
    succeeded = false;
  }

  MOZ_ASSERT(result != LexerResult(Yield::OUTPUT_AVAILABLE),
             "Unexpected yield");

  // Make our state the same as the state of the contained decoder, and
  // propagate errors.
  mProgress |= mContainedDecoder->TakeProgress();
  mInvalidRect.UnionRect(mInvalidRect, mContainedDecoder->TakeInvalidRect());
  if (mContainedDecoder->HasError()) {
    succeeded = false;
  }

  return succeeded;
}

} // namespace image
} // namespace mozilla