blob: f7ada1f548ff77fdd22f486e695709bd7261ba8a [file] [log] [blame]
/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "src/codec/SkWuffsCodec.h"
#include "include/core/SkBitmap.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/private/SkMalloc.h"
#include "src/codec/SkFrameHolder.h"
#include "src/codec/SkSampler.h"
#include "src/codec/SkScalingCodec.h"
#include "src/core/SkDraw.h"
#include "src/core/SkRasterClip.h"
#include "src/core/SkUtils.h"
#include <limits.h>
// Wuffs ships as a "single file C library" or "header file library" as per
// https://github.com/nothings/stb/blob/master/docs/stb_howto.txt
//
// As we have not #define'd WUFFS_IMPLEMENTATION, the #include here is
// including a header file, even though that file name ends in ".c".
#if defined(WUFFS_IMPLEMENTATION)
#error "SkWuffsCodec should not #define WUFFS_IMPLEMENTATION"
#endif
#include "wuffs-v0.2.c"
#if WUFFS_VERSION_BUILD_METADATA_COMMIT_COUNT < 1942
#error "Wuffs version is too old. Upgrade to the latest version."
#endif
#define SK_WUFFS_CODEC_BUFFER_SIZE 4096
static bool fill_buffer(wuffs_base__io_buffer* b, SkStream* s) {
b->compact();
size_t num_read = s->read(b->data.ptr + b->meta.wi, b->data.len - b->meta.wi);
b->meta.wi += num_read;
b->meta.closed = s->isAtEnd();
return num_read > 0;
}
static bool seek_buffer(wuffs_base__io_buffer* b, SkStream* s, uint64_t pos) {
// Try to re-position the io_buffer's meta.ri read-index first, which is
// cheaper than seeking in the backing SkStream.
if ((pos >= b->meta.pos) && (pos - b->meta.pos <= b->meta.wi)) {
b->meta.ri = pos - b->meta.pos;
return true;
}
// Seek in the backing SkStream.
if ((pos > SIZE_MAX) || (!s->seek(pos))) {
return false;
}
b->meta.wi = 0;
b->meta.ri = 0;
b->meta.pos = pos;
b->meta.closed = false;
return true;
}
static SkEncodedInfo::Alpha wuffs_blend_to_skia_alpha(wuffs_base__animation_blend w) {
return (w == WUFFS_BASE__ANIMATION_BLEND__OPAQUE) ? SkEncodedInfo::kOpaque_Alpha
: SkEncodedInfo::kUnpremul_Alpha;
}
static SkCodecAnimation::Blend wuffs_blend_to_skia_blend(wuffs_base__animation_blend w) {
return (w == WUFFS_BASE__ANIMATION_BLEND__SRC) ? SkCodecAnimation::Blend::kBG
: SkCodecAnimation::Blend::kPriorFrame;
}
static SkCodecAnimation::DisposalMethod wuffs_disposal_to_skia_disposal(
wuffs_base__animation_disposal w) {
switch (w) {
case WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_BACKGROUND:
return SkCodecAnimation::DisposalMethod::kRestoreBGColor;
case WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_PREVIOUS:
return SkCodecAnimation::DisposalMethod::kRestorePrevious;
default:
return SkCodecAnimation::DisposalMethod::kKeep;
}
}
// -------------------------------- Class definitions
class SkWuffsCodec;
class SkWuffsFrame final : public SkFrame {
public:
SkWuffsFrame(wuffs_base__frame_config* fc);
SkCodec::FrameInfo frameInfo(bool fullyReceived) const;
uint64_t ioPosition() const;
// SkFrame overrides.
SkEncodedInfo::Alpha onReportedAlpha() const override;
private:
uint64_t fIOPosition;
SkEncodedInfo::Alpha fReportedAlpha;
typedef SkFrame INHERITED;
};
// SkWuffsFrameHolder is a trivial indirector that forwards its calls onto a
// SkWuffsCodec. It is a separate class as SkWuffsCodec would otherwise
// inherit from both SkCodec and SkFrameHolder, and Skia style discourages
// multiple inheritance (e.g. with its "typedef Foo INHERITED" convention).
class SkWuffsFrameHolder final : public SkFrameHolder {
public:
SkWuffsFrameHolder() : INHERITED() {}
void init(SkWuffsCodec* codec, int width, int height);
// SkFrameHolder overrides.
const SkFrame* onGetFrame(int i) const override;
private:
const SkWuffsCodec* fCodec;
typedef SkFrameHolder INHERITED;
};
class SkWuffsCodec final : public SkScalingCodec {
public:
SkWuffsCodec(SkEncodedInfo&& encodedInfo,
std::unique_ptr<SkStream> stream,
std::unique_ptr<wuffs_gif__decoder, decltype(&sk_free)> dec,
std::unique_ptr<uint8_t, decltype(&sk_free)> pixbuf_ptr,
std::unique_ptr<uint8_t, decltype(&sk_free)> workbuf_ptr,
size_t workbuf_len,
wuffs_base__image_config imgcfg,
wuffs_base__pixel_buffer pixbuf,
wuffs_base__io_buffer iobuf);
const SkWuffsFrame* frame(int i) const;
private:
// SkCodec overrides.
SkEncodedImageFormat onGetEncodedFormat() const override;
Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&, int*) override;
const SkFrameHolder* getFrameHolder() const override;
Result onStartIncrementalDecode(const SkImageInfo& dstInfo,
void* dst,
size_t rowBytes,
const SkCodec::Options& options) override;
Result onIncrementalDecode(int* rowsDecoded) override;
int onGetFrameCount() override;
bool onGetFrameInfo(int, FrameInfo*) const override;
int onGetRepetitionCount() override;
void readFrames();
Result seekFrame(int frameIndex);
Result resetDecoder();
const char* decodeFrameConfig();
const char* decodeFrame();
void updateNumFullyReceivedFrames();
SkWuffsFrameHolder fFrameHolder;
std::unique_ptr<SkStream> fStream;
std::unique_ptr<wuffs_gif__decoder, decltype(&sk_free)> fDecoder;
std::unique_ptr<uint8_t, decltype(&sk_free)> fPixbufPtr;
std::unique_ptr<uint8_t, decltype(&sk_free)> fWorkbufPtr;
size_t fWorkbufLen;
const uint64_t fFirstFrameIOPosition;
wuffs_base__frame_config fFrameConfig;
wuffs_base__pixel_buffer fPixelBuffer;
wuffs_base__io_buffer fIOBuffer;
// Incremental decoding state.
uint8_t* fIncrDecDst;
size_t fIncrDecRowBytes;
bool fFirstCallToIncrementalDecode;
uint64_t fNumFullyReceivedFrames;
std::vector<SkWuffsFrame> fFrames;
bool fFramesComplete;
// If calling an fDecoder method returns an incomplete status, then
// fDecoder is suspended in a coroutine (i.e. waiting on I/O or halted on a
// non-recoverable error). To keep its internal proof-of-safety invariants
// consistent, there's only two things you can safely do with a suspended
// Wuffs object: resume the coroutine, or reset all state (memset to zero
// and start again).
//
// If fDecoderIsSuspended, and we aren't sure that we're going to resume
// the coroutine, then we will need to call this->resetDecoder before
// calling other fDecoder methods.
bool fDecoderIsSuspended;
uint8_t fBuffer[SK_WUFFS_CODEC_BUFFER_SIZE];
typedef SkScalingCodec INHERITED;
};
// -------------------------------- SkWuffsFrame implementation
SkWuffsFrame::SkWuffsFrame(wuffs_base__frame_config* fc)
: INHERITED(fc->index()),
fIOPosition(fc->io_position()),
fReportedAlpha(wuffs_blend_to_skia_alpha(fc->blend())) {
wuffs_base__rect_ie_u32 r = fc->bounds();
this->setXYWH(r.min_incl_x, r.min_incl_y, r.width(), r.height());
this->setDisposalMethod(wuffs_disposal_to_skia_disposal(fc->disposal()));
this->setDuration(fc->duration() / WUFFS_BASE__FLICKS_PER_MILLISECOND);
this->setBlend(wuffs_blend_to_skia_blend(fc->blend()));
}
SkCodec::FrameInfo SkWuffsFrame::frameInfo(bool fullyReceived) const {
SkCodec::FrameInfo ret;
ret.fRequiredFrame = getRequiredFrame();
ret.fDuration = getDuration();
ret.fFullyReceived = fullyReceived;
ret.fAlphaType = hasAlpha() ? kUnpremul_SkAlphaType : kOpaque_SkAlphaType;
ret.fDisposalMethod = getDisposalMethod();
return ret;
}
uint64_t SkWuffsFrame::ioPosition() const {
return fIOPosition;
}
SkEncodedInfo::Alpha SkWuffsFrame::onReportedAlpha() const {
return fReportedAlpha;
}
// -------------------------------- SkWuffsFrameHolder implementation
void SkWuffsFrameHolder::init(SkWuffsCodec* codec, int width, int height) {
fCodec = codec;
// Initialize SkFrameHolder's (the superclass) fields.
fScreenWidth = width;
fScreenHeight = height;
}
const SkFrame* SkWuffsFrameHolder::onGetFrame(int i) const {
return fCodec->frame(i);
};
// -------------------------------- SkWuffsCodec implementation
SkWuffsCodec::SkWuffsCodec(SkEncodedInfo&& encodedInfo,
std::unique_ptr<SkStream> stream,
std::unique_ptr<wuffs_gif__decoder, decltype(&sk_free)> dec,
std::unique_ptr<uint8_t, decltype(&sk_free)> pixbuf_ptr,
std::unique_ptr<uint8_t, decltype(&sk_free)> workbuf_ptr,
size_t workbuf_len,
wuffs_base__image_config imgcfg,
wuffs_base__pixel_buffer pixbuf,
wuffs_base__io_buffer iobuf)
: INHERITED(std::move(encodedInfo),
skcms_PixelFormat_RGBA_8888,
// Pass a nullptr SkStream to the SkCodec constructor. We
// manage the stream ourselves, as the default SkCodec behavior
// is too trigger-happy on rewinding the stream.
nullptr),
fFrameHolder(),
fStream(std::move(stream)),
fDecoder(std::move(dec)),
fPixbufPtr(std::move(pixbuf_ptr)),
fWorkbufPtr(std::move(workbuf_ptr)),
fWorkbufLen(workbuf_len),
fFirstFrameIOPosition(imgcfg.first_frame_io_position()),
fFrameConfig(wuffs_base__null_frame_config()),
fPixelBuffer(pixbuf),
fIOBuffer(wuffs_base__empty_io_buffer()),
fIncrDecDst(nullptr),
fIncrDecRowBytes(0),
fFirstCallToIncrementalDecode(false),
fNumFullyReceivedFrames(0),
fFramesComplete(false),
fDecoderIsSuspended(false) {
fFrameHolder.init(this, imgcfg.pixcfg.width(), imgcfg.pixcfg.height());
// Initialize fIOBuffer's fields, copying any outstanding data from iobuf to
// fIOBuffer, as iobuf's backing array may not be valid for the lifetime of
// this SkWuffsCodec object, but fIOBuffer's backing array (fBuffer) is.
SkASSERT(iobuf.data.len == SK_WUFFS_CODEC_BUFFER_SIZE);
memmove(fBuffer, iobuf.data.ptr, iobuf.meta.wi);
fIOBuffer.data = wuffs_base__make_slice_u8(fBuffer, SK_WUFFS_CODEC_BUFFER_SIZE);
fIOBuffer.meta = iobuf.meta;
}
const SkWuffsFrame* SkWuffsCodec::frame(int i) const {
if ((0 <= i) && (static_cast<size_t>(i) < fFrames.size())) {
return &fFrames[i];
}
return nullptr;
}
SkEncodedImageFormat SkWuffsCodec::onGetEncodedFormat() const {
return SkEncodedImageFormat::kGIF;
}
SkCodec::Result SkWuffsCodec::onGetPixels(const SkImageInfo& dstInfo,
void* dst,
size_t rowBytes,
const Options& options,
int* rowsDecoded) {
SkCodec::Result result = this->onStartIncrementalDecode(dstInfo, dst, rowBytes, options);
if (result != kSuccess) {
return result;
}
return this->onIncrementalDecode(rowsDecoded);
}
const SkFrameHolder* SkWuffsCodec::getFrameHolder() const {
return &fFrameHolder;
}
SkCodec::Result SkWuffsCodec::onStartIncrementalDecode(const SkImageInfo& dstInfo,
void* dst,
size_t rowBytes,
const SkCodec::Options& options) {
if (!dst) {
return SkCodec::kInvalidParameters;
}
if (options.fSubset) {
return SkCodec::kUnimplemented;
}
if (options.fFrameIndex > 0 && SkColorTypeIsAlwaysOpaque(dstInfo.colorType())) {
return SkCodec::kInvalidConversion;
}
SkCodec::Result result = this->seekFrame(options.fFrameIndex);
if (result != SkCodec::kSuccess) {
return result;
}
const char* status = this->decodeFrameConfig();
if (status == wuffs_base__suspension__short_read) {
return SkCodec::kIncompleteInput;
} else if (status != nullptr) {
SkCodecPrintf("decodeFrameConfig: %s", status);
return SkCodec::kErrorInInput;
}
uint32_t src_bits_per_pixel =
wuffs_base__pixel_format__bits_per_pixel(fPixelBuffer.pixcfg.pixel_format());
if ((src_bits_per_pixel == 0) || (src_bits_per_pixel % 8 != 0)) {
return SkCodec::kInternalError;
}
size_t src_bytes_per_pixel = src_bits_per_pixel / 8;
// Zero-initialize Wuffs' buffer covering the frame rect.
wuffs_base__rect_ie_u32 frame_rect = fFrameConfig.bounds();
wuffs_base__table_u8 pixels = fPixelBuffer.plane(0);
for (uint32_t y = frame_rect.min_incl_y; y < frame_rect.max_excl_y; y++) {
sk_bzero(pixels.ptr + (y * pixels.stride) + (frame_rect.min_incl_x * src_bytes_per_pixel),
frame_rect.width() * src_bytes_per_pixel);
}
fIncrDecDst = static_cast<uint8_t*>(dst);
fIncrDecRowBytes = rowBytes;
fFirstCallToIncrementalDecode = true;
return SkCodec::kSuccess;
}
static SkAlphaType to_alpha_type(bool opaque) {
return opaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType;
}
SkCodec::Result SkWuffsCodec::onIncrementalDecode(int* rowsDecoded) {
if (!fIncrDecDst) {
return SkCodec::kInternalError;
}
SkCodec::Result result = SkCodec::kSuccess;
const char* status = this->decodeFrame();
bool independent;
SkAlphaType alphaType;
const int index = options().fFrameIndex;
if (index == 0) {
independent = true;
alphaType = to_alpha_type(getEncodedInfo().opaque());
} else {
const SkWuffsFrame* f = this->frame(index);
independent = f->getRequiredFrame() == SkCodec::kNoFrame;
alphaType = to_alpha_type(f->reportedAlpha() == SkEncodedInfo::kOpaque_Alpha);
}
if (status != nullptr) {
if (status == wuffs_base__suspension__short_read) {
result = SkCodec::kIncompleteInput;
} else {
SkCodecPrintf("decodeFrame: %s", status);
result = SkCodec::kErrorInInput;
}
if (!independent) {
// For a dependent frame, we cannot blend the partial result, since
// that will overwrite the contribution from prior frames.
return result;
}
}
uint32_t src_bits_per_pixel =
wuffs_base__pixel_format__bits_per_pixel(fPixelBuffer.pixcfg.pixel_format());
if ((src_bits_per_pixel == 0) || (src_bits_per_pixel % 8 != 0)) {
return SkCodec::kInternalError;
}
size_t src_bytes_per_pixel = src_bits_per_pixel / 8;
wuffs_base__rect_ie_u32 frame_rect = fFrameConfig.bounds();
if (fFirstCallToIncrementalDecode) {
if (frame_rect.width() > (SIZE_MAX / src_bytes_per_pixel)) {
return SkCodec::kInternalError;
}
auto bounds = SkIRect::MakeLTRB(frame_rect.min_incl_x, frame_rect.min_incl_y,
frame_rect.max_excl_x, frame_rect.max_excl_y);
// If the frame rect does not fill the output, ensure that those pixels are not
// left uninitialized.
if (independent && (bounds != this->bounds() || result != kSuccess)) {
SkSampler::Fill(dstInfo(), fIncrDecDst, fIncrDecRowBytes,
options().fZeroInitialized);
}
fFirstCallToIncrementalDecode = false;
} else {
// Existing clients intend to only show frames beyond the first if they
// are complete (based on FrameInfo::fFullyReceived), since it might
// look jarring to draw a partial frame over an existing frame. If they
// changed their behavior and expected to continue decoding a partial
// frame after the first one, we'll need to update our blending code.
// Otherwise, if the frame were interlaced and not independent, the
// second pass may have an overlapping dirty_rect with the first,
// resulting in blending with the first pass.
SkASSERT(index == 0);
}
if (rowsDecoded) {
*rowsDecoded = dstInfo().height();
}
// If the frame's dirty rect is empty, no need to swizzle.
wuffs_base__rect_ie_u32 dirty_rect = fDecoder->frame_dirty_rect();
if (!dirty_rect.is_empty()) {
wuffs_base__table_u8 pixels = fPixelBuffer.plane(0);
// The Wuffs model is that the dst buffer is the image, not the frame.
// The expectation is that you allocate the buffer once, but re-use it
// for the N frames, regardless of each frame's top-left co-ordinate.
//
// To get from the start (in the X-direction) of the image to the start
// of the dirty_rect, we adjust s by (dirty_rect.min_incl_x * src_bytes_per_pixel).
uint8_t* s = pixels.ptr + (dirty_rect.min_incl_y * pixels.stride)
+ (dirty_rect.min_incl_x * src_bytes_per_pixel);
// Currently, this is only used for GIF, which will never have an ICC profile. When it is
// used for other formats that might have one, we will need to transform from profiles that
// do not have corresponding SkColorSpaces.
SkASSERT(!getEncodedInfo().profile());
auto srcInfo = getInfo().makeWH(dirty_rect.width(), dirty_rect.height())
.makeAlphaType(alphaType);
SkBitmap src;
src.installPixels(srcInfo, s, pixels.stride);
SkPaint paint;
if (independent) {
paint.setBlendMode(SkBlendMode::kSrc);
}
SkDraw draw;
draw.fDst.reset(dstInfo(), fIncrDecDst, fIncrDecRowBytes);
SkMatrix matrix = SkMatrix::MakeRectToRect(SkRect::Make(this->dimensions()),
SkRect::Make(this->dstInfo().dimensions()),
SkMatrix::kFill_ScaleToFit);
draw.fMatrix = &matrix;
SkRasterClip rc(SkIRect::MakeSize(this->dstInfo().dimensions()));
draw.fRC = &rc;
SkMatrix translate = SkMatrix::MakeTrans(dirty_rect.min_incl_x, dirty_rect.min_incl_y);
draw.drawBitmap(src, translate, nullptr, paint);
}
if (result == SkCodec::kSuccess) {
fIncrDecDst = nullptr;
fIncrDecRowBytes = 0;
}
return result;
}
int SkWuffsCodec::onGetFrameCount() {
// It is valid, in terms of the SkCodec API, to call SkCodec::getFrameCount
// while in an incremental decode (after onStartIncrementalDecode returns
// and before onIncrementalDecode returns kSuccess).
//
// We should not advance the SkWuffsCodec' stream while doing so, even
// though other SkCodec implementations can return increasing values from
// onGetFrameCount when given more data. If we tried to do so, the
// subsequent resume of the incremental decode would continue reading from
// a different position in the I/O stream, leading to an incorrect error.
//
// Other SkCodec implementations can move the stream forward during
// onGetFrameCount because they assume that the stream is rewindable /
// seekable. For example, an alternative GIF implementation may choose to
// store, for each frame walked past when merely counting the number of
// frames, the I/O position of each of the frame's GIF data blocks. (A GIF
// frame's compressed data can have multiple data blocks, each at most 255
// bytes in length). Obviously, this can require O(numberOfFrames) extra
// memory to store these I/O positions. The constant factor is small, but
// it's still O(N), not O(1).
//
// Wuffs and SkWuffsCodec tries to minimize relying on the rewindable /
// seekable assumption. By design, Wuffs per se aims for O(1) memory use
// (after any pixel buffers are allocated) instead of O(N), and its I/O
// type, wuffs_base__io_buffer, is not necessarily rewindable or seekable.
//
// The Wuffs API provides a limited, optional form of seeking, to the start
// of an animation frame's data, but does not provide arbitrary save and
// load of its internal state whilst in the middle of an animation frame.
bool incrementalDecodeIsInProgress = fIncrDecDst != nullptr;
if (!fFramesComplete && !incrementalDecodeIsInProgress) {
this->readFrames();
this->updateNumFullyReceivedFrames();
}
return fFrames.size();
}
bool SkWuffsCodec::onGetFrameInfo(int i, SkCodec::FrameInfo* frameInfo) const {
const SkWuffsFrame* f = this->frame(i);
if (!f) {
return false;
}
if (frameInfo) {
*frameInfo = f->frameInfo(static_cast<uint64_t>(i) < this->fNumFullyReceivedFrames);
}
return true;
}
int SkWuffsCodec::onGetRepetitionCount() {
// Convert from Wuffs's loop count to Skia's repeat count. Wuffs' uint32_t
// number is how many times to play the loop. Skia's int number is how many
// times to play the loop *after the first play*. Wuffs and Skia use 0 and
// kRepetitionCountInfinite respectively to mean loop forever.
uint32_t n = fDecoder->num_animation_loops();
if (n == 0) {
return SkCodec::kRepetitionCountInfinite;
}
n--;
return n < INT_MAX ? n : INT_MAX;
}
void SkWuffsCodec::readFrames() {
size_t n = fFrames.size();
int i = n ? n - 1 : 0;
if (this->seekFrame(i) != SkCodec::kSuccess) {
return;
}
// Iterate through the frames, converting from Wuffs'
// wuffs_base__frame_config type to Skia's SkWuffsFrame type.
for (; i < INT_MAX; i++) {
const char* status = this->decodeFrameConfig();
if (status == nullptr) {
// No-op.
} else if (status == wuffs_base__warning__end_of_data) {
break;
} else {
return;
}
if (static_cast<size_t>(i) < fFrames.size()) {
continue;
}
fFrames.emplace_back(&fFrameConfig);
SkWuffsFrame* f = &fFrames[fFrames.size() - 1];
fFrameHolder.setAlphaAndRequiredFrame(f);
}
fFramesComplete = true;
}
SkCodec::Result SkWuffsCodec::seekFrame(int frameIndex) {
if (fDecoderIsSuspended) {
SkCodec::Result res = this->resetDecoder();
if (res != SkCodec::kSuccess) {
return res;
}
}
uint64_t pos = 0;
if (frameIndex < 0) {
return SkCodec::kInternalError;
} else if (frameIndex == 0) {
pos = fFirstFrameIOPosition;
} else if (static_cast<size_t>(frameIndex) < fFrames.size()) {
pos = fFrames[frameIndex].ioPosition();
} else {
return SkCodec::kInternalError;
}
if (!seek_buffer(&fIOBuffer, fStream.get(), pos)) {
return SkCodec::kInternalError;
}
const char* status = fDecoder->restart_frame(frameIndex, fIOBuffer.reader_io_position());
if (status != nullptr) {
return SkCodec::kInternalError;
}
return SkCodec::kSuccess;
}
// An overview of the Wuffs decoding API:
//
// An animated image (such as GIF) has an image header and then N frames. The
// image header gives e.g. the overall image's width and height. Each frame
// consists of a frame header (e.g. frame rectangle bounds, display duration)
// and a payload (the pixels).
//
// In Wuffs terminology, there is one image config and then N pairs of
// (frame_config, frame). To decode everything (without knowing N in advance)
// sequentially:
// - call wuffs_gif__decoder::decode_image_config
// - while (true) {
// - call wuffs_gif__decoder::decode_frame_config
// - if that returned wuffs_base__warning__end_of_data, break
// - call wuffs_gif__decoder::decode_frame
// - }
//
// The first argument to each decode_foo method is the destination struct to
// store the decoded information.
//
// For random (instead of sequential) access to an image's frames, call
// wuffs_gif__decoder::restart_frame to prepare to decode the i'th frame.
// Essentially, it restores the state to be at the top of the while loop above.
// The wuffs_base__io_buffer's reader position will also need to be set at the
// right point in the source data stream. The position for the i'th frame is
// calculated by the i'th decode_frame_config call. You can only call
// restart_frame after decode_image_config is called, explicitly or implicitly
// (see below), as decoding a single frame might require for-all-frames
// information like the overall image dimensions and the global palette.
//
// All of those decode_xxx calls are optional. For example, if
// decode_image_config is not called, then the first decode_frame_config call
// will implicitly parse and verify the image header, before parsing the first
// frame's header. Similarly, you can call only decode_frame N times, without
// calling decode_image_config or decode_frame_config, if you already know
// metadata like N and each frame's rectangle bounds by some other means (e.g.
// this is a first party, statically known image).
//
// Specifically, starting with an unknown (but re-windable) GIF image, if you
// want to just find N (i.e. count the number of frames), you can loop calling
// only the decode_frame_config method and avoid calling the more expensive
// decode_frame method. In terms of the underlying GIF image format, this will
// skip over the LZW-encoded pixel data, avoiding the costly LZW decompression.
//
// Those decode_xxx methods are also suspendible. They will return early (with
// a status code that is_suspendible and therefore isn't is_complete) if there
// isn't enough source data to complete the operation: an incremental decode.
// Calling decode_xxx again with additional source data will resume the
// previous operation, instead of starting a new operation. Calling decode_yyy
// whilst decode_xxx is suspended will result in an error.
//
// Once an error is encountered, whether from invalid source data or from a
// programming error such as calling decode_yyy while suspended in decode_xxx,
// all subsequent calls will be no-ops that return an error. To reset the
// decoder into something that does productive work, memset the entire struct
// to zero, check the Wuffs version and then, in order to be able to call
// restart_frame, call decode_image_config. The io_buffer and its associated
// stream will also need to be rewound.
static SkCodec::Result reset_and_decode_image_config(wuffs_gif__decoder* decoder,
wuffs_base__image_config* imgcfg,
wuffs_base__io_buffer* b,
SkStream* s) {
// Calling decoder->initialize will memset it to zero.
const char* status = decoder->initialize(sizeof__wuffs_gif__decoder(), WUFFS_VERSION, 0);
if (status != nullptr) {
SkCodecPrintf("initialize: %s", status);
return SkCodec::kInternalError;
}
while (true) {
status = decoder->decode_image_config(imgcfg, b);
if (status == nullptr) {
break;
} else if (status != wuffs_base__suspension__short_read) {
SkCodecPrintf("decode_image_config: %s", status);
return SkCodec::kErrorInInput;
} else if (!fill_buffer(b, s)) {
return SkCodec::kIncompleteInput;
}
}
// A GIF image's natural color model is indexed color: 1 byte per pixel,
// indexing a 256-element palette.
//
// For Skia, we override that to decode to 4 bytes per pixel, BGRA or RGBA.
wuffs_base__pixel_format pixfmt = 0;
switch (kN32_SkColorType) {
case kBGRA_8888_SkColorType:
pixfmt = WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL;
break;
case kRGBA_8888_SkColorType:
pixfmt = WUFFS_BASE__PIXEL_FORMAT__RGBA_NONPREMUL;
break;
default:
return SkCodec::kInternalError;
}
if (imgcfg) {
imgcfg->pixcfg.set(pixfmt, WUFFS_BASE__PIXEL_SUBSAMPLING__NONE, imgcfg->pixcfg.width(),
imgcfg->pixcfg.height());
}
return SkCodec::kSuccess;
}
SkCodec::Result SkWuffsCodec::resetDecoder() {
if (!fStream->rewind()) {
return SkCodec::kInternalError;
}
fIOBuffer.meta = wuffs_base__empty_io_buffer_meta();
SkCodec::Result result =
reset_and_decode_image_config(fDecoder.get(), nullptr, &fIOBuffer, fStream.get());
if (result == SkCodec::kIncompleteInput) {
return SkCodec::kInternalError;
} else if (result != SkCodec::kSuccess) {
return result;
}
fDecoderIsSuspended = false;
return SkCodec::kSuccess;
}
const char* SkWuffsCodec::decodeFrameConfig() {
while (true) {
const char* status = fDecoder->decode_frame_config(&fFrameConfig, &fIOBuffer);
if ((status == wuffs_base__suspension__short_read) &&
fill_buffer(&fIOBuffer, fStream.get())) {
continue;
}
fDecoderIsSuspended = !wuffs_base__status__is_complete(status);
this->updateNumFullyReceivedFrames();
return status;
}
}
const char* SkWuffsCodec::decodeFrame() {
while (true) {
const char* status =
fDecoder->decode_frame(&fPixelBuffer, &fIOBuffer,
wuffs_base__make_slice_u8(fWorkbufPtr.get(), fWorkbufLen), NULL);
if ((status == wuffs_base__suspension__short_read) &&
fill_buffer(&fIOBuffer, fStream.get())) {
continue;
}
fDecoderIsSuspended = !wuffs_base__status__is_complete(status);
this->updateNumFullyReceivedFrames();
return status;
}
}
void SkWuffsCodec::updateNumFullyReceivedFrames() {
// num_decoded_frames's return value, n, can change over time, both up and
// down, as we seek back and forth in the underlying stream.
// fNumFullyReceivedFrames is the highest n we've seen.
uint64_t n = fDecoder->num_decoded_frames();
if (fNumFullyReceivedFrames < n) {
fNumFullyReceivedFrames = n;
}
}
// -------------------------------- SkWuffsCodec.h functions
bool SkWuffsCodec_IsFormat(const void* buf, size_t bytesRead) {
constexpr const char* gif_ptr = "GIF8";
constexpr size_t gif_len = 4;
return (bytesRead >= gif_len) && (memcmp(buf, gif_ptr, gif_len) == 0);
}
std::unique_ptr<SkCodec> SkWuffsCodec_MakeFromStream(std::unique_ptr<SkStream> stream,
SkCodec::Result* result) {
uint8_t buffer[SK_WUFFS_CODEC_BUFFER_SIZE];
wuffs_base__io_buffer iobuf =
wuffs_base__make_io_buffer(wuffs_base__make_slice_u8(buffer, SK_WUFFS_CODEC_BUFFER_SIZE),
wuffs_base__empty_io_buffer_meta());
wuffs_base__image_config imgcfg = wuffs_base__null_image_config();
// Wuffs is primarily a C library, not a C++ one. Furthermore, outside of
// the wuffs_base__etc types, the sizeof a file format specific type like
// GIF's wuffs_gif__decoder can vary between Wuffs versions. If p is of
// type wuffs_gif__decoder*, then the supported API treats p as a pointer
// to an opaque type: a private implementation detail. The API is always
// "set_foo(p, etc)" and not "p->foo = etc".
//
// See https://en.wikipedia.org/wiki/Opaque_pointer#C
//
// Thus, we don't use C++'s new operator (which requires knowing the sizeof
// the struct at compile time). Instead, we use sk_malloc_canfail, with
// sizeof__wuffs_gif__decoder returning the appropriate value for the
// (statically or dynamically) linked version of the Wuffs library.
//
// As a C (not C++) library, none of the Wuffs types have constructors or
// destructors.
//
// In RAII style, we can still use std::unique_ptr with these pointers, but
// we pair the pointer with sk_free instead of C++'s delete.
void* decoder_raw = sk_malloc_canfail(sizeof__wuffs_gif__decoder());
if (!decoder_raw) {
*result = SkCodec::kInternalError;
return nullptr;
}
std::unique_ptr<wuffs_gif__decoder, decltype(&sk_free)> decoder(
reinterpret_cast<wuffs_gif__decoder*>(decoder_raw), &sk_free);
SkCodec::Result reset_result =
reset_and_decode_image_config(decoder.get(), &imgcfg, &iobuf, stream.get());
if (reset_result != SkCodec::kSuccess) {
*result = reset_result;
return nullptr;
}
uint32_t width = imgcfg.pixcfg.width();
uint32_t height = imgcfg.pixcfg.height();
if ((width == 0) || (width > INT_MAX) || (height == 0) || (height > INT_MAX)) {
*result = SkCodec::kInvalidInput;
return nullptr;
}
uint64_t workbuf_len = decoder->workbuf_len().max_incl;
void* workbuf_ptr_raw = nullptr;
if (workbuf_len) {
workbuf_ptr_raw = workbuf_len <= SIZE_MAX ? sk_malloc_canfail(workbuf_len) : nullptr;
if (!workbuf_ptr_raw) {
*result = SkCodec::kInternalError;
return nullptr;
}
}
std::unique_ptr<uint8_t, decltype(&sk_free)> workbuf_ptr(
reinterpret_cast<uint8_t*>(workbuf_ptr_raw), &sk_free);
uint64_t pixbuf_len = imgcfg.pixcfg.pixbuf_len();
void* pixbuf_ptr_raw = pixbuf_len <= SIZE_MAX ? sk_malloc_canfail(pixbuf_len) : nullptr;
if (!pixbuf_ptr_raw) {
*result = SkCodec::kInternalError;
return nullptr;
}
std::unique_ptr<uint8_t, decltype(&sk_free)> pixbuf_ptr(
reinterpret_cast<uint8_t*>(pixbuf_ptr_raw), &sk_free);
wuffs_base__pixel_buffer pixbuf = wuffs_base__null_pixel_buffer();
const char* status = pixbuf.set_from_slice(
&imgcfg.pixcfg, wuffs_base__make_slice_u8(pixbuf_ptr.get(), SkToSizeT(pixbuf_len)));
if (status != nullptr) {
SkCodecPrintf("set_from_slice: %s", status);
*result = SkCodec::kInternalError;
return nullptr;
}
SkEncodedInfo::Color color =
(imgcfg.pixcfg.pixel_format() == WUFFS_BASE__PIXEL_FORMAT__BGRA_NONPREMUL)
? SkEncodedInfo::kBGRA_Color
: SkEncodedInfo::kRGBA_Color;
// In Skia's API, the alpha we calculate here and return is only for the
// first frame.
SkEncodedInfo::Alpha alpha = imgcfg.first_frame_is_opaque() ? SkEncodedInfo::kOpaque_Alpha
: SkEncodedInfo::kBinary_Alpha;
SkEncodedInfo encodedInfo = SkEncodedInfo::Make(width, height, color, alpha, 8);
*result = SkCodec::kSuccess;
return std::unique_ptr<SkCodec>(new SkWuffsCodec(
std::move(encodedInfo), std::move(stream), std::move(decoder), std::move(pixbuf_ptr),
std::move(workbuf_ptr), workbuf_len, imgcfg, pixbuf, iobuf));
}