Move gif image decoder to SkCodec

third_party/WebKit/Source/platform/image-decoders/SegmentStream.cpp

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "platform/image-decoders/SegmentStream.h"
+
+namespace blink {
+
+SegmentStream::SegmentStream()
+    : m_reader(),
+      m_position(0),
+      m_hasReadAllContents(true),
+      m_isCleared(true) {}
+
+void SegmentStream::setReader(SegmentReader* reader, bool allContentsReceived) {
+  m_reader = reader;
+  if (reader) {
+    m_hasReadAllContents = reader->size() == m_position;
+    m_isCleared = m_position > m_reader->size();
+  } else {
+    m_hasReadAllContents = true;
+    m_isCleared = true;
+  }
+}
+
+size_t SegmentStream::read(void* buffer, size_t size) {
+  if (m_isCleared)
+    return 0;
+
+  size = std::min(size, m_reader->size() - m_position);
+
+  size_t bytesAdvanced = 0;
+  if (!buffer) {  // skipping, not reading
+    bytesAdvanced = size;
+  } else {
+    bytesAdvanced = peek(buffer, size);
+  }
+
+  m_position += bytesAdvanced;
+  m_hasReadAllContents = m_position == m_reader->size();
+
+  return bytesAdvanced;
+}
+
+size_t SegmentStream::peek(void* buffer, size_t size) const {
+  if (m_isCleared)
+    return 0;
+
+  size = std::min(size, m_reader->size() - m_position);
+
+  size_t peekPosition = m_position;
+  size_t totalBytesPeeked = 0;
+  char* bufferAsCharPtr = reinterpret_cast<char*>(buffer);
+  while (size) {
+    const char* segment = nullptr;
+    size_t bytesPeeked = m_reader->getSomeData(segment, peekPosition);
+    if (!bytesPeeked)
+      break;
+    if (bytesPeeked > size)
+      bytesPeeked = size;
+
+    memcpy(bufferAsCharPtr, segment, bytesPeeked);
+    bufferAsCharPtr += bytesPeeked;
+    size -= bytesPeeked;
+    totalBytesPeeked += bytesPeeked;
+    peekPosition += bytesPeeked;
+  }
+
+  return totalBytesPeeked;
+}
+
+bool SegmentStream::move(long offset) {
+  long absolutePosition = m_position + offset;
+
+  // clamp inside the bounds of the buffer size
+  absolutePosition = std::max(absolutePosition, 0l);
+  absolutePosition =
+      std::min(static_cast<size_t>(absolutePosition), m_reader->size());
+
+  m_position = absolutePosition;
+  m_hasReadAllContents = m_position == m_reader->size();
+
+  return true;
+}
+
+}  // namespace blink