Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 499 insertions, 0 deletions

diff --git a/image/SourceBuffer.h b/image/SourceBuffer.h
new file mode 100644
index 0000000000..79188fb882
--- /dev/null
+++ b/image/SourceBuffer.h
@@ -0,0 +1,499 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 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/. */
+
+/**
+ * SourceBuffer is a single producer, multiple consumer data structure used for
+ * storing image source (compressed) data.
+ */
+
+#ifndef mozilla_image_sourcebuffer_h
+#define mozilla_image_sourcebuffer_h
+
+#include <algorithm>
+#include <utility>
+
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/RefCounted.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "nsTArray.h"
+
+class nsIInputStream;
+
+namespace mozilla {
+namespace image {
+
+class SourceBuffer;
+
+/**
+ * IResumable is an interface for classes that can schedule themselves to resume
+ * their work later. An implementation of IResumable generally should post a
+ * runnable to some event target which continues the work of the task.
+ */
+struct IResumable {
+  MOZ_DECLARE_REFCOUNTED_TYPENAME(IResumable)
+
+  // Subclasses may or may not be XPCOM classes, so we just require that they
+  // implement AddRef and Release.
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  virtual void Resume() = 0;
+
+ protected:
+  virtual ~IResumable() {}
+};
+
+/**
+ * SourceBufferIterator is a class that allows consumers of image source data to
+ * read the contents of a SourceBuffer sequentially.
+ *
+ * Consumers can advance through the SourceBuffer by calling
+ * AdvanceOrScheduleResume() repeatedly. After every advance, they should call
+ * check the return value, which will tell them the iterator's new state.
+ *
+ * If WAITING is returned, AdvanceOrScheduleResume() has arranged
+ * to call the consumer's Resume() method later, so the consumer should save its
+ * state if needed and stop running.
+ *
+ * If the iterator's new state is READY, then the consumer can call Data() and
+ * Length() to read new data from the SourceBuffer.
+ *
+ * Finally, in the COMPLETE state the consumer can call CompletionStatus() to
+ * get the status passed to SourceBuffer::Complete().
+ */
+class SourceBufferIterator final {
+ public:
+  enum State {
+    START,    // The iterator is at the beginning of the buffer.
+    READY,    // The iterator is pointing to new data.
+    WAITING,  // The iterator is blocked and the caller must yield.
+    COMPLETE  // The iterator is pointing to the end of the buffer.
+  };
+
+  explicit SourceBufferIterator(SourceBuffer* aOwner, size_t aReadLimit)
+      : mOwner(aOwner),
+        mState(START),
+        mChunkCount(0),
+        mByteCount(0),
+        mRemainderToRead(aReadLimit) {
+    MOZ_ASSERT(aOwner);
+    mData.mIterating.mChunk = 0;
+    mData.mIterating.mData = nullptr;
+    mData.mIterating.mOffset = 0;
+    mData.mIterating.mAvailableLength = 0;
+    mData.mIterating.mNextReadLength = 0;
+  }
+
+  SourceBufferIterator(SourceBufferIterator&& aOther)
+      : mOwner(std::move(aOther.mOwner)),
+        mState(aOther.mState),
+        mData(aOther.mData),
+        mChunkCount(aOther.mChunkCount),
+        mByteCount(aOther.mByteCount),
+        mRemainderToRead(aOther.mRemainderToRead) {}
+
+  ~SourceBufferIterator();
+
+  SourceBufferIterator& operator=(SourceBufferIterator&& aOther);
+
+  /**
+   * Returns true if there are no more than @aBytes remaining in the
+   * SourceBuffer. If the SourceBuffer is not yet complete, returns false.
+   */
+  bool RemainingBytesIsNoMoreThan(size_t aBytes) const;
+
+  /**
+   * Advances the iterator through the SourceBuffer if possible. Advances no
+   * more than @aRequestedBytes bytes. (Use SIZE_MAX to advance as much as
+   * possible.)
+   *
+   * This is a wrapper around AdvanceOrScheduleResume() that makes it clearer at
+   * the callsite when the no resuming is intended.
+   *
+   * @return State::READY if the iterator was successfully advanced.
+   *         State::WAITING if the iterator could not be advanced because it's
+   *           at the end of the underlying SourceBuffer, but the SourceBuffer
+   *           may still receive additional data.
+   *         State::COMPLETE if the iterator could not be advanced because it's
+   *           at the end of the underlying SourceBuffer and the SourceBuffer is
+   *           marked complete (i.e., it will never receive any additional
+   *           data).
+   */
+  State Advance(size_t aRequestedBytes) {
+    return AdvanceOrScheduleResume(aRequestedBytes, nullptr);
+  }
+
+  /**
+   * Advances the iterator through the SourceBuffer if possible. Advances no
+   * more than @aRequestedBytes bytes. (Use SIZE_MAX to advance as much as
+   * possible.) If advancing is not possible and @aConsumer is not null,
+   * arranges to call the @aConsumer's Resume() method when more data is
+   * available.
+   *
+   * @return State::READY if the iterator was successfully advanced.
+   *         State::WAITING if the iterator could not be advanced because it's
+   *           at the end of the underlying SourceBuffer, but the SourceBuffer
+   *           may still receive additional data. @aConsumer's Resume() method
+   *           will be called when additional data is available.
+   *         State::COMPLETE if the iterator could not be advanced because it's
+   *           at the end of the underlying SourceBuffer and the SourceBuffer is
+   *           marked complete (i.e., it will never receive any additional
+   *           data).
+   */
+  State AdvanceOrScheduleResume(size_t aRequestedBytes, IResumable* aConsumer);
+
+  /// If at the end, returns the status passed to SourceBuffer::Complete().
+  nsresult CompletionStatus() const {
+    MOZ_ASSERT(mState == COMPLETE,
+               "Calling CompletionStatus() in the wrong state");
+    return mState == COMPLETE ? mData.mAtEnd.mStatus : NS_OK;
+  }
+
+  /// If we're ready to read, returns a pointer to the new data.
+  const char* Data() const {
+    MOZ_ASSERT(mState == READY, "Calling Data() in the wrong state");
+    return mState == READY ? mData.mIterating.mData + mData.mIterating.mOffset
+                           : nullptr;
+  }
+
+  /// If we're ready to read, returns the length of the new data.
+  size_t Length() const {
+    MOZ_ASSERT(mState == READY, "Calling Length() in the wrong state");
+    return mState == READY ? mData.mIterating.mNextReadLength : 0;
+  }
+
+  /// If we're ready to read, returns whether or not everything available thus
+  /// far has been in the same contiguous buffer.
+  bool IsContiguous() const {
+    MOZ_ASSERT(mState == READY, "Calling IsContiguous() in the wrong state");
+    return mState == READY ? mData.mIterating.mChunk == 0 : false;
+  }
+
+  /// @return a count of the chunks we've advanced through.
+  uint32_t ChunkCount() const { return mChunkCount; }
+
+  /// @return a count of the bytes in all chunks we've advanced through.
+  size_t ByteCount() const { return mByteCount; }
+
+  /// @return the source buffer which owns the iterator.
+  SourceBuffer* Owner() const {
+    MOZ_ASSERT(mOwner);
+    return mOwner;
+  }
+
+  /// @return the current offset from the beginning of the buffer.
+  size_t Position() const {
+    return mByteCount - mData.mIterating.mAvailableLength;
+  }
+
+ private:
+  friend class SourceBuffer;
+
+  SourceBufferIterator(const SourceBufferIterator&) = delete;
+  SourceBufferIterator& operator=(const SourceBufferIterator&) = delete;
+
+  bool HasMore() const { return mState != COMPLETE; }
+
+  State AdvanceFromLocalBuffer(size_t aRequestedBytes) {
+    MOZ_ASSERT(mState == READY, "Advancing in the wrong state");
+    MOZ_ASSERT(mData.mIterating.mAvailableLength > 0,
+               "The local buffer shouldn't be empty");
+    MOZ_ASSERT(mData.mIterating.mNextReadLength == 0,
+               "Advancing without consuming previous data");
+
+    mData.mIterating.mNextReadLength =
+        std::min(mData.mIterating.mAvailableLength, aRequestedBytes);
+
+    return READY;
+  }
+
+  State SetReady(uint32_t aChunk, const char* aData, size_t aOffset,
+                 size_t aAvailableLength, size_t aRequestedBytes) {
+    MOZ_ASSERT(mState != COMPLETE);
+    mState = READY;
+
+    // Prevent the iterator from reporting more data than it is allowed to read.
+    if (aAvailableLength > mRemainderToRead) {
+      aAvailableLength = mRemainderToRead;
+    }
+
+    // Update state.
+    mData.mIterating.mChunk = aChunk;
+    mData.mIterating.mData = aData;
+    mData.mIterating.mOffset = aOffset;
+    mData.mIterating.mAvailableLength = aAvailableLength;
+
+    // Update metrics.
+    mChunkCount++;
+    mByteCount += aAvailableLength;
+
+    // Attempt to advance by the requested number of bytes.
+    return AdvanceFromLocalBuffer(aRequestedBytes);
+  }
+
+  State SetWaiting(bool aHasConsumer) {
+    MOZ_ASSERT(mState != COMPLETE);
+    // Without a consumer, we won't know when to wake up precisely. Caller
+    // convention should mean that we don't try to advance unless we have
+    // written new data, but that doesn't mean we got enough.
+    MOZ_ASSERT(mState != WAITING || !aHasConsumer,
+               "Did we get a spurious wakeup somehow?");
+    return mState = WAITING;
+  }
+
+  State SetComplete(nsresult aStatus) {
+    mData.mAtEnd.mStatus = aStatus;
+    return mState = COMPLETE;
+  }
+
+  RefPtr<SourceBuffer> mOwner;
+
+  State mState;
+
+  /**
+   * This union contains our iteration state if we're still iterating (for
+   * states START, READY, and WAITING) and the status the SourceBuffer was
+   * completed with if we're in state COMPLETE.
+   */
+  union {
+    struct {
+      uint32_t mChunk;    // Index of the chunk in SourceBuffer.
+      const char* mData;  // Pointer to the start of the chunk.
+      size_t mOffset;     // Current read position of the iterator relative to
+                          // mData.
+      size_t mAvailableLength;  // How many bytes remain unread in the chunk,
+                                // relative to mOffset.
+      size_t
+          mNextReadLength;  // How many bytes the last iterator advance
+                            // requested to be read, so that we know much
+                            // to increase mOffset and reduce mAvailableLength
+                            // by when the next advance is requested.
+    } mIterating;  // Cached info of the chunk currently iterating over.
+    struct {
+      nsresult mStatus;  // Status code indicating if we read all the data.
+    } mAtEnd;            // State info after iterator is complete.
+  } mData;
+
+  uint32_t mChunkCount;  // Count of chunks observed, including current chunk.
+  size_t mByteCount;     // Count of readable bytes observed, including unread
+                         // bytes from the current chunk.
+  size_t mRemainderToRead;  // Count of bytes left to read if there is a maximum
+                            // imposed by the caller. SIZE_MAX if unlimited.
+};
+
+/**
+ * SourceBuffer is a parallel data structure used for storing image source
+ * (compressed) data.
+ *
+ * SourceBuffer is a single producer, multiple consumer data structure. The
+ * single producer calls Append() to append data to the buffer. In parallel,
+ * multiple consumers can call Iterator(), which returns a SourceBufferIterator
+ * that they can use to iterate through the buffer. The SourceBufferIterator
+ * returns a series of pointers which remain stable for lifetime of the
+ * SourceBuffer, and the data they point to is immutable, ensuring that the
+ * producer never interferes with the consumers.
+ *
+ * In order to avoid blocking, SourceBuffer works with SourceBufferIterator to
+ * keep a list of consumers which are waiting for new data, and to resume them
+ * when the producer appends more. All consumers must implement the IResumable
+ * interface to make this possible.
+ */
+class SourceBuffer final {
+ public:
+  MOZ_DECLARE_REFCOUNTED_TYPENAME(image::SourceBuffer)
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(image::SourceBuffer)
+
+  SourceBuffer();
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Producer methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  /**
+   * If the producer knows how long the source data will be, it should call
+   * ExpectLength, which enables SourceBuffer to preallocate its buffer.
+   */
+  nsresult ExpectLength(size_t aExpectedLength);
+
+  /// Append the provided data to the buffer.
+  nsresult Append(const char* aData, size_t aLength);
+
+  /// Append the data available on the provided nsIInputStream to the buffer.
+  nsresult AppendFromInputStream(nsIInputStream* aInputStream, uint32_t aCount);
+
+  /**
+   * Mark the buffer complete, with a status that will be available to
+   * consumers. Further calls to Append() are forbidden after Complete().
+   */
+  void Complete(nsresult aStatus);
+
+  /// Returns true if the buffer is complete.
+  bool IsComplete();
+
+  /// Memory reporting.
+  size_t SizeOfIncludingThisWithComputedFallback(MallocSizeOf) const;
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Consumer methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  /**
+   * Returns an iterator to this SourceBuffer, which cannot read more than the
+   * given length.
+   */
+  SourceBufferIterator Iterator(size_t aReadLength = SIZE_MAX);
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Consumer methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  /**
+   * The minimum chunk capacity we'll allocate, if we don't know the correct
+   * capacity (which would happen because ExpectLength() wasn't called or gave
+   * us the wrong value). This is only exposed for use by tests; if normal code
+   * is using this, it's doing something wrong.
+   */
+  static const size_t MIN_CHUNK_CAPACITY = 4096;
+
+  /**
+   * The maximum chunk capacity we'll allocate. This was historically the
+   * maximum we would preallocate based on the network size. We may adjust it
+   * in the future based on the IMAGE_DECODE_CHUNKS telemetry to ensure most
+   * images remain in a single chunk.
+   */
+  static const size_t MAX_CHUNK_CAPACITY = 20 * 1024 * 1024;
+
+ private:
+  friend class SourceBufferIterator;
+
+  ~SourceBuffer();
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Chunk type and chunk-related methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  class Chunk final {
+   public:
+    explicit Chunk(size_t aCapacity) : mCapacity(aCapacity), mLength(0) {
+      MOZ_ASSERT(aCapacity > 0, "Creating zero-capacity chunk");
+      mData = static_cast<char*>(malloc(mCapacity));
+    }
+
+    ~Chunk() { free(mData); }
+
+    Chunk(Chunk&& aOther)
+        : mCapacity(aOther.mCapacity),
+          mLength(aOther.mLength),
+          mData(aOther.mData) {
+      aOther.mCapacity = aOther.mLength = 0;
+      aOther.mData = nullptr;
+    }
+
+    Chunk& operator=(Chunk&& aOther) {
+      free(mData);
+      mCapacity = aOther.mCapacity;
+      mLength = aOther.mLength;
+      mData = aOther.mData;
+      aOther.mCapacity = aOther.mLength = 0;
+      aOther.mData = nullptr;
+      return *this;
+    }
+
+    bool AllocationFailed() const { return !mData; }
+    size_t Capacity() const { return mCapacity; }
+    size_t Length() const { return mLength; }
+
+    char* Data() const {
+      MOZ_ASSERT(mData, "Allocation failed but nobody checked for it");
+      return mData;
+    }
+
+    void AddLength(size_t aAdditionalLength) {
+      MOZ_ASSERT(mLength + aAdditionalLength <= mCapacity);
+      mLength += aAdditionalLength;
+    }
+
+    bool SetCapacity(size_t aCapacity) {
+      MOZ_ASSERT(mData, "Allocation failed but nobody checked for it");
+      char* data = static_cast<char*>(realloc(mData, aCapacity));
+      if (!data) {
+        return false;
+      }
+
+      mData = data;
+      mCapacity = aCapacity;
+      return true;
+    }
+
+   private:
+    Chunk(const Chunk&) = delete;
+    Chunk& operator=(const Chunk&) = delete;
+
+    size_t mCapacity;
+    size_t mLength;
+    char* mData;
+  };
+
+  nsresult AppendChunk(Maybe<Chunk>&& aChunk) MOZ_REQUIRES(mMutex);
+  Maybe<Chunk> CreateChunk(size_t aCapacity, size_t aExistingCapacity = 0,
+                           bool aRoundUp = true);
+  nsresult Compact() MOZ_REQUIRES(mMutex);
+  static size_t RoundedUpCapacity(size_t aCapacity);
+  size_t FibonacciCapacityWithMinimum(size_t aMinCapacity) MOZ_REQUIRES(mMutex);
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Iterator / consumer methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  void AddWaitingConsumer(IResumable* aConsumer) MOZ_REQUIRES(mMutex);
+  void ResumeWaitingConsumers() MOZ_REQUIRES(mMutex);
+
+  typedef SourceBufferIterator::State State;
+
+  State AdvanceIteratorOrScheduleResume(SourceBufferIterator& aIterator,
+                                        size_t aRequestedBytes,
+                                        IResumable* aConsumer);
+  bool RemainingBytesIsNoMoreThan(const SourceBufferIterator& aIterator,
+                                  size_t aBytes) const;
+
+  void OnIteratorRelease();
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Helper methods.
+  //////////////////////////////////////////////////////////////////////////////
+
+  nsresult HandleError(nsresult aError) MOZ_REQUIRES(mMutex);
+  bool IsEmpty() MOZ_REQUIRES(mMutex);
+  bool IsLastChunk(uint32_t aChunk) MOZ_REQUIRES(mMutex);
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Member variables.
+  //////////////////////////////////////////////////////////////////////////////
+
+  /// All private members are protected by mMutex.
+  mutable Mutex mMutex;
+
+  /// The data in this SourceBuffer, stored as a series of Chunks.
+  AutoTArray<Chunk, 1> mChunks MOZ_GUARDED_BY(mMutex);
+
+  /// Consumers which are waiting to be notified when new data is available.
+  nsTArray<RefPtr<IResumable>> mWaitingConsumers MOZ_GUARDED_BY(mMutex);
+
+  /// If present, marks this SourceBuffer complete with the given final status.
+  Maybe<nsresult> mStatus MOZ_GUARDED_BY(mMutex);
+
+  /// Count of active consumers.
+  uint32_t mConsumerCount MOZ_GUARDED_BY(mMutex);
+
+  /// True if compacting has been performed.
+  bool mCompacted MOZ_GUARDED_BY(mMutex);
+};
+
+}  // namespace image
+}  // namespace mozilla
+
+#endif  // mozilla_image_sourcebuffer_h