1 files changed, 88 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/codec/SkStreamBuffer.cpp b/gfx/skia/skia/src/codec/SkStreamBuffer.cpp
new file mode 100644
index 0000000000..cdac862fdd
--- /dev/null
+++ b/gfx/skia/skia/src/codec/SkStreamBuffer.cpp
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2016 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/SkStreamBuffer.h"
+
+SkStreamBuffer::SkStreamBuffer(std::unique_ptr<SkStream> stream)
+    : fStream(std::move(stream))
+    , fPosition(0)
+    , fBytesBuffered(0)
+    , fHasLengthAndPosition(fStream->hasLength() && fStream->hasPosition())
+    , fTrulyBuffered(0)
+{}
+
+SkStreamBuffer::~SkStreamBuffer() {
+    fMarkedData.foreach([](size_t, SkData** data) { (*data)->unref(); });
+}
+
+const char* SkStreamBuffer::get() const {
+    SkASSERT(fBytesBuffered >= 1);
+    if (fHasLengthAndPosition && fTrulyBuffered < fBytesBuffered) {
+        const size_t bytesToBuffer = fBytesBuffered - fTrulyBuffered;
+        char* dst = SkTAddOffset<char>(const_cast<char*>(fBuffer), fTrulyBuffered);
+        SkDEBUGCODE(const size_t bytesRead =)
+        // This stream is rewindable, so it should be safe to call the non-const
+        // read()
+        const_cast<SkStream*>(fStream.get())->read(dst, bytesToBuffer);
+        SkASSERT(bytesRead == bytesToBuffer);
+        fTrulyBuffered = fBytesBuffered;
+    }
+    return fBuffer;
+}
+
+bool SkStreamBuffer::buffer(size_t totalBytesToBuffer) {
+    // FIXME (scroggo): What should we do if the client tries to read too much?
+    // Should not be a problem in GIF.
+    SkASSERT(totalBytesToBuffer <= kMaxSize);
+
+    if (totalBytesToBuffer <= fBytesBuffered) {
+        return true;
+    }
+
+    if (fHasLengthAndPosition) {
+        const size_t remaining = fStream->getLength() - fStream->getPosition() + fTrulyBuffered;
+        fBytesBuffered = SkTMin(remaining, totalBytesToBuffer);
+    } else {
+        const size_t extraBytes = totalBytesToBuffer - fBytesBuffered;
+        const size_t bytesBuffered = fStream->read(fBuffer + fBytesBuffered, extraBytes);
+        fBytesBuffered += bytesBuffered;
+    }
+    return fBytesBuffered == totalBytesToBuffer;
+}
+
+size_t SkStreamBuffer::markPosition() {
+    SkASSERT(fBytesBuffered >= 1);
+    if (!fHasLengthAndPosition) {
+        sk_sp<SkData> data(SkData::MakeWithCopy(fBuffer, fBytesBuffered));
+        SkASSERT(nullptr == fMarkedData.find(fPosition));
+        fMarkedData.set(fPosition, data.release());
+    }
+    return fPosition;
+}
+
+sk_sp<SkData> SkStreamBuffer::getDataAtPosition(size_t position, size_t length) {
+    if (!fHasLengthAndPosition) {
+        SkData** data = fMarkedData.find(position);
+        SkASSERT(data);
+        SkASSERT((*data)->size() == length);
+        return sk_ref_sp<SkData>(*data);
+    }
+
+    SkASSERT(length <= fStream->getLength() &&
+             position <= fStream->getLength() - length);
+
+    const size_t oldPosition = fStream->getPosition();
+    if (!fStream->seek(position)) {
+        return nullptr;
+    }
+
+    sk_sp<SkData> data(SkData::MakeUninitialized(length));
+    void* dst = data->writable_data();
+    const bool success = fStream->read(dst, length) == length;
+    fStream->seek(oldPosition);
+    return success ? data : nullptr;
+}