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gecko-dev/image/SurfacePipe.h

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/* -*- 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/. */
/**
* A SurfacePipe is a pipeline that consists of a series of SurfaceFilters
* terminating in a SurfaceSink. Each SurfaceFilter transforms the image data in
* some way before the SurfaceSink ultimately writes it to the surface. This
* design allows for each transformation to be tested independently, for the
* transformations to be combined as needed to meet the needs of different
* situations, and for all image decoders to share the same code for these
* transformations.
*
* Writing to the SurfacePipe is done using lambdas that act as generator
* functions. Because the SurfacePipe machinery controls where the writes take
* place, a bug in an image decoder cannot cause a buffer overflow of the
* underlying surface. In particular, when using WritePixels() a buffer overflow
* is impossible as long as the SurfacePipe code is correct.
*/
#ifndef mozilla_image_SurfacePipe_h
#define mozilla_image_SurfacePipe_h
#include <stdint.h>
#include "mozilla/Maybe.h"
#include "mozilla/Move.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/unused.h"
#include "mozilla/Variant.h"
#include "mozilla/gfx/2D.h"
namespace mozilla {
namespace image {
class Decoder;
/**
* An invalid rect for a surface. Results are given both in the space of the
* input image (i.e., before any SurfaceFilters are applied) and in the space
* of the output surface (after all SurfaceFilters).
*/
struct SurfaceInvalidRect
{
gfx::IntRect mInputSpaceRect; /// The invalid rect in pre-SurfacePipe space.
gfx::IntRect mOutputSpaceRect; /// The invalid rect in post-SurfacePipe space.
};
/**
* An enum used to allow the lambdas passed to WritePixels() and WriteRows() to
* communicate their state to the caller.
*/
enum class WriteState : uint8_t
{
NEED_MORE_DATA, /// The lambda ran out of data.
FINISHED, /// The lambda is done writing to the surface; future writes
/// will fail.
ERROR /// The lambda encountered an error. The caller may recover
/// if possible and continue to write. (This never indicates
/// an error in the SurfacePipe machinery itself; it's only
/// generated by the lambdas.)
};
/**
* A template alias used to make the return value of WritePixels() lambdas
* (which may return either a pixel value or a WriteState) easier to specify.
* WriteRows() doesn't need such a template alias since WriteRows() lambdas
* don't return a pixel value.
*/
template <typename PixelType>
using NextPixel = Variant<PixelType, WriteState>;
/**
* SurfaceFilter is the abstract superclass of SurfacePipe pipeline stages.
* It implements the the code that actually writes to the surface -
* WritePixels() and WriteRows() - which are non-virtual for efficiency.
*
* SurfaceFilter's API is nonpublic; only SurfacePipe and other SurfaceFilters
* should use it. Non-SurfacePipe code should use the methods on SurfacePipe.
*
* To implement a SurfaceFilter, it's necessary to subclass SurfaceFilter and
* implement, at a minimum, the pure virtual methods. It's also necessary to
* define a Config struct with a Filter typedef member that identifies the
* matching SurfaceFilter class, and a Configure() template method. See an
* existing SurfaceFilter subclass, such as RemoveFrameRectFilter, for an
* example of how the Configure() method must be implemented. It takes a list of
* Config structs, passes the tail of the list to the next filter in the chain's
* Configure() method, and then uses the head of the list to configure itself. A
* SurfaceFilter's Configure() method must also call
* SurfaceFilter::ConfigureFilter() to provide WritePixels() and WriteRows()
* with the information they need to do their jobs.
*/
class SurfaceFilter
{
public:
SurfaceFilter()
: mRowPointer(nullptr)
, mCol(0)
, mPixelSize(0)
{ }
virtual ~SurfaceFilter() { }
/**
* Reset this surface to the first row. It's legal for this filter to throw
* away any previously written data at this point, as all rows must be written
* to on every pass.
*
* @return a pointer to the buffer for the first row.
*/
uint8_t* ResetToFirstRow()
{
mCol = 0;
mRowPointer = DoResetToFirstRow();
return mRowPointer;
}
/// @return a pointer to the buffer for the current row.
uint8_t* CurrentRowPointer() const { return mRowPointer; }
/// @return true if we've finished writing to the surface.
bool IsSurfaceFinished() const { return mRowPointer == nullptr; }
/// @return the input size this filter expects.
gfx::IntSize InputSize() const { return mInputSize; }
/**
* Write pixels to the surface one at a time by repeatedly calling a lambda
* that yields pixels. WritePixels() should be preferred over WriteRows()
* whenever using it will not introduce additional copies or other performance
* penalties, because it is completely memory safe.
*
* Writing continues until every pixel in the surface has been written to
* (i.e., IsSurfaceFinished() returns true) or the lambda returns a WriteState
* which WritePixels() will return to the caller.
*
* The template parameter PixelType must be uint8_t (for paletted surfaces) or
* uint32_t (for BGRA/BGRX surfaces) and must be in agreement with the pixel
* size passed to ConfigureFilter().
*
* XXX(seth): We'll remove all support for paletted surfaces in bug 1247520,
* which means we can remove the PixelType template parameter from this
* method.
*
* @param aFunc A lambda that functions as a generator, yielding the next
* pixel in the surface each time it's called. The lambda must
* return a NextPixel<PixelType> value.
*
* @return A WriteState value indicating the lambda generator's state.
* WritePixels() itself will return WriteState::FINISHED if writing
* has finished, regardless of the lambda's internal state.
*/
template <typename PixelType, typename Func>
WriteState WritePixels(Func aFunc)
{
MOZ_ASSERT(mPixelSize == 1 || mPixelSize == 4);
MOZ_ASSERT_IF(mPixelSize == 1, sizeof(PixelType) == sizeof(uint8_t));
MOZ_ASSERT_IF(mPixelSize == 4, sizeof(PixelType) == sizeof(uint32_t));
while (!IsSurfaceFinished()) {
PixelType* rowPtr = reinterpret_cast<PixelType*>(mRowPointer);
for (; mCol < mInputSize.width; ++mCol) {
NextPixel<PixelType> result = aFunc();
if (result.template is<PixelType>()) {
rowPtr[mCol] = result.template as<PixelType>();
continue;
}
switch (result.template as<WriteState>()) {
case WriteState::NEED_MORE_DATA:
return WriteState::NEED_MORE_DATA;
case WriteState::FINISHED:
// Make sure that IsSurfaceFinished() returns true so the caller
// can't write anything else to the pipeline.
mRowPointer = nullptr;
mCol = 0;
return WriteState::FINISHED;
case WriteState::ERROR:
// Note that we don't need to record this anywhere, because this
// indicates an error in aFunc, and there's nothing wrong with our
// machinery. The caller can recover as needed and continue writing to
// the row.
return WriteState::ERROR;
}
}
// We've finished the row.
mRowPointer = AdvanceRow();
mCol = 0;
}
// We've finished the entire surface.
return WriteState::FINISHED;
}
/**
* Write rows to the surface one at a time by repeatedly calling a lambda
* that yields rows. Because WriteRows() is not completely memory safe,
* WritePixels() should be preferred whenever it can be used without
* introducing additional copies or other performance penalties.
*
* Writing continues until every row in the surface has been written to (i.e.,
* IsSurfaceFinished() returns true) or the lambda returns a WriteState which
* WriteRows() will return to the caller.
*
* The template parameter PixelType must be uint8_t (for paletted surfaces) or
* uint32_t (for BGRA/BGRX surfaces) and must be in agreement with the pixel
* size passed to ConfigureFilter().
*
* XXX(seth): We'll remove all support for paletted surfaces in bug 1247520,
* which means we can remove the PixelType template parameter from this
* method.
*
* @param aFunc A lambda that functions as a generator, yielding the next
* row in the surface each time it's called. The lambda must
* return a Maybe<WriteState> value; if Some(), the return value
* indicates a WriteState to return to the caller, while
* Nothing() indicates that the lambda can generate more rows.
*
* @return A WriteState value indicating the lambda generator's state.
* WriteRows() itself will return WriteState::FINISHED if writing
* has finished, regardless of the lambda's internal state.
*/
template <typename PixelType, typename Func>
WriteState WriteRows(Func aFunc)
{
MOZ_ASSERT(mPixelSize == 1 || mPixelSize == 4);
MOZ_ASSERT_IF(mPixelSize == 1, sizeof(PixelType) == sizeof(uint8_t));
MOZ_ASSERT_IF(mPixelSize == 4, sizeof(PixelType) == sizeof(uint32_t));
if (IsSurfaceFinished()) {
return WriteState::FINISHED; // Already done.
}
while (true) {
PixelType* rowPtr = reinterpret_cast<PixelType*>(mRowPointer);
Maybe<WriteState> result = aFunc(rowPtr, mInputSize.width);
if (result != Some(WriteState::ERROR)) {
mCol = 0;
mRowPointer = AdvanceRow(); // We've finished the row.
}
if (IsSurfaceFinished()) {
break;
}
if (result == Some(WriteState::FINISHED)) {
// Make sure that IsSurfaceFinished() returns true so the caller can't
// write anything else to the pipeline.
mRowPointer = nullptr;
mCol = 0;
}
if (result) {
return *result;
}
}
// We've finished the entire surface.
return WriteState::FINISHED;
}
//////////////////////////////////////////////////////////////////////////////
// Methods Subclasses Should Override
//////////////////////////////////////////////////////////////////////////////
/// @return true if this SurfaceFilter can be used with paletted surfaces.
virtual bool IsValidPalettedPipe() const { return false; }
/**
* Called by WritePixels() and WriteRows() to advance this filter to the next
* row.
*
* @return a pointer to the buffer for the next row, or nullptr to indicate
* that we've finished the entire surface.
*/
virtual uint8_t* AdvanceRow() = 0;
/**
* @return a SurfaceInvalidRect representing the region of the surface that
* has been written to since the last time TakeInvalidRect() was
* called, or Nothing() if the region is empty (i.e. nothing has been
* written).
*/
virtual Maybe<SurfaceInvalidRect> TakeInvalidRect() = 0;
protected:
/**
* Called by ResetToFirstRow() to actually perform the reset. It's legal to
* throw away any previously written data at this point, as all rows must be
* written to on every pass.
*/
virtual uint8_t* DoResetToFirstRow() = 0;
//////////////////////////////////////////////////////////////////////////////
// Methods For Internal Use By Subclasses
//////////////////////////////////////////////////////////////////////////////
/**
* Called by subclasses' Configure() methods to initialize the configuration
* of this filter. After the filter is configured, calls ResetToFirstRow().
*
* @param aInputSize The input size of this filter, in pixels. The previous
* filter in the chain will expect to write into rows
* |aInputSize.width| pixels wide.
* @param aPixelSize How large, in bytes, each pixel in the surface is. This
* should be either 1 for paletted images or 4 for BGRA/BGRX
* images.
*/
void ConfigureFilter(gfx::IntSize aInputSize, uint8_t aPixelSize)
{
mInputSize = aInputSize;
mPixelSize = aPixelSize;
ResetToFirstRow();
}
private:
gfx::IntSize mInputSize; /// The size of the input this filter expects.
uint8_t* mRowPointer; /// Pointer to the current row or null if finished.
int32_t mCol; /// The current column we're writing to. (0-indexed)
uint8_t mPixelSize; /// How large each pixel in the surface is, in bytes.
};
class NullSurfaceSink;
/// A trivial configuration struct for NullSurfaceSink.
struct NullSurfaceConfig
{
using Filter = NullSurfaceSink;
};
/**
* NullSurfaceSink is a trivial SurfaceFilter implementation that behaves as if
* it were a zero-size SurfaceSink. It's used as the default filter chain for an
* uninitialized SurfacePipe.
*
* To avoid unnecessary allocations when creating SurfacePipe objects,
* NullSurfaceSink is a singleton. (This implies that the implementation must be
* stateless.)
*/
class NullSurfaceSink final : public SurfaceFilter
{
public:
/// Returns the singleton instance of NullSurfaceSink.
static NullSurfaceSink* Singleton();
virtual ~NullSurfaceSink() { }
nsresult Configure(const NullSurfaceConfig& aConfig);
Maybe<SurfaceInvalidRect> TakeInvalidRect() override { return Nothing(); }
uint8_t* AdvanceRow() override { return nullptr; }
protected:
uint8_t* DoResetToFirstRow() override { return nullptr; }
private:
static UniquePtr<NullSurfaceSink> sSingleton; /// The singleton instance.
};
/**
* SurfacePipe is the public API that decoders should use to interact with a
* SurfaceFilter pipeline.
*/
class SurfacePipe
{
public:
/// Initialize global state used by all SurfacePipes.
static void Initialize() { NullSurfaceSink::Singleton(); }
SurfacePipe()
: mHead(NullSurfaceSink::Singleton())
{ }
SurfacePipe(SurfacePipe&& aOther)
: mHead(Move(aOther.mHead))
{ }
~SurfacePipe()
{
// Ensure that we don't free the NullSurfaceSink singleton.
if (mHead.get() == NullSurfaceSink::Singleton()) {
Unused << mHead.release();
}
}
SurfacePipe& operator=(SurfacePipe&& aOther)
{
MOZ_ASSERT(this != &aOther);
// Ensure that we don't free the NullSurfaceSink singleton.
if (mHead.get() == NullSurfaceSink::Singleton()) {
Unused << mHead.release();
}
mHead = Move(aOther.mHead);
return *this;
}
/// Begins a new pass, seeking to the first row of the surface.
void ResetToFirstRow() { mHead->ResetToFirstRow(); }
/**
* Write pixels to the surface one at a time by repeatedly calling a lambda
* that yields pixels. WritePixels() should be preferred over WriteRows()
* whenever using it will not introduce additional copies or other performance
* penalties, because it is completely memory safe.
*
* @see SurfaceFilter::WritePixels() for the canonical documentation.
*/
template <typename PixelType, typename Func>
WriteState WritePixels(Func aFunc)
{
return mHead->WritePixels<PixelType>(Forward<Func>(aFunc));
}
/**
* Write rows to the surface one at a time by repeatedly calling a lambda
* that yields rows. Because WriteRows() is not completely memory safe,
* WritePixels() should be preferred whenever it can be used without
* introducing additional copies or other performance penalties.
*
* @see SurfaceFilter::WriteRows() for the canonical documentation.
*/
template <typename PixelType, typename Func>
WriteState WriteRows(Func aFunc)
{
return mHead->WriteRows<PixelType>(Forward<Func>(aFunc));
}
/// @return true if we've finished writing to the surface.
bool IsSurfaceFinished() const { return mHead->IsSurfaceFinished(); }
/// @see SurfaceFilter::TakeInvalidRect() for the canonical documentation.
Maybe<SurfaceInvalidRect> TakeInvalidRect() const
{
return mHead->TakeInvalidRect();
}
private:
friend class SurfacePipeFactory;
friend class TestSurfacePipeFactory;
explicit SurfacePipe(UniquePtr<SurfaceFilter>&& aHead)
: mHead(Move(aHead))
{ }
SurfacePipe(const SurfacePipe&) = delete;
SurfacePipe& operator=(const SurfacePipe&) = delete;
UniquePtr<SurfaceFilter> mHead; /// The first filter in the chain.
};
/**
* AbstractSurfaceSink contains shared implementation for both SurfaceSink and
* PalettedSurfaceSink.
*/
class AbstractSurfaceSink : public SurfaceFilter
{
public:
AbstractSurfaceSink()
: mImageData(nullptr)
, mImageDataLength(0)
, mRow(0)
, mFlipVertically(false)
{ }
Maybe<SurfaceInvalidRect> TakeInvalidRect() override final;
uint8_t* AdvanceRow() override final;
protected:
uint8_t* DoResetToFirstRow() override final;
virtual uint8_t* GetRowPointer() const = 0;
gfx::IntRect mInvalidRect; /// The region of the surface that has been written
/// to since the last call to TakeInvalidRect().
uint8_t* mImageData; /// A pointer to the beginning of the surface data.
uint32_t mImageDataLength; /// The length of the surface data.
uint32_t mRow; /// The row to which we're writing. (0-indexed)
bool mFlipVertically; /// If true, write the rows from top to bottom.
};
class SurfaceSink;
/// A configuration struct for SurfaceSink.
struct SurfaceConfig
{
using Filter = SurfaceSink;
Decoder* mDecoder; /// Which Decoder to use to allocate the surface.
uint32_t mFrameNum; /// Which frame of animation this surface is for.
gfx::IntSize mOutputSize; /// The size of the surface.
gfx::SurfaceFormat mFormat; /// The surface format (BGRA or BGRX).
bool mFlipVertically; /// If true, write the rows from bottom to top.
};
/**
* A sink for normal (i.e., non-paletted) surfaces. It handles the allocation of
* the surface and protects against buffer overflow. This sink should be used
* for all non-animated images and for the first frame of animated images.
*
* Sinks must always be at the end of the SurfaceFilter chain.
*/
class SurfaceSink final : public AbstractSurfaceSink
{
public:
nsresult Configure(const SurfaceConfig& aConfig);
protected:
uint8_t* GetRowPointer() const override;
};
class PalettedSurfaceSink;
struct PalettedSurfaceConfig
{
using Filter = PalettedSurfaceSink;
Decoder* mDecoder; /// Which Decoder to use to allocate the surface.
uint32_t mFrameNum; /// Which frame of animation this surface is for.
gfx::IntSize mOutputSize; /// The logical size of the surface.
gfx::IntRect mFrameRect; /// The surface subrect which contains data.
gfx::SurfaceFormat mFormat; /// The surface format (BGRA or BGRX).
uint8_t mPaletteDepth; /// The palette depth of this surface.
bool mFlipVertically; /// If true, write the rows from bottom to top.
};
/**
* A sink for paletted surfaces. It handles the allocation of the surface and
* protects against buffer overflow. This sink can be used for frames of
* animated images except the first.
*
* Sinks must always be at the end of the SurfaceFilter chain.
*
* XXX(seth): We'll remove all support for paletted surfaces in bug 1247520,
* which means we can remove PalettedSurfaceSink entirely.
*/
class PalettedSurfaceSink final : public AbstractSurfaceSink
{
public:
bool IsValidPalettedPipe() const override { return true; }
nsresult Configure(const PalettedSurfaceConfig& aConfig);
protected:
uint8_t* GetRowPointer() const override;
private:
/**
* The surface subrect which contains data. Note that the surface size we
* actually allocate is the size of the frame rect, not the logical size of
* the surface.
*/
gfx::IntRect mFrameRect;
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_SurfacePipe_h
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