Implement texel buffers

include/gpu/GrBufferAccess.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrBufferAccess_DEFINED
+#define GrBufferAccess_DEFINED
+
+#include "GrBuffer.h"
+#include "GrGpuResourceRef.h"
+
+/**
+ * Used to represent a texel buffer that will be read in a GrProcessor. It holds a GrBuffer along
+ * with an associated offset and texel config.
+ */
+class GrBufferAccess : public SkNoncopyable {
+public:
+    /**
+     * Must be initialized before adding to a GrProcessor's buffer access list.
+     */
+    void reset(intptr_t offsetInBytes, GrPixelConfig texelConfig, GrBuffer* buffer,
+               GrShaderFlags visibility = kFragment_GrShaderFlag) {
+        fOffsetInBytes = offsetInBytes;
+        fTexelConfig = texelConfig;
+        fBuffer.set(SkRef(buffer), kRead_GrIOType);
+        fVisibility = visibility;
+    }
+
+    bool operator==(const GrBufferAccess& that) const {
+        return fOffsetInBytes == that.fOffsetInBytes &&
+               fTexelConfig == that.fTexelConfig &&
+               this->buffer() == that.buffer() &&
+               fVisibility == that.fVisibility;
+    }
+
+    bool operator!=(const GrBufferAccess& that) const { return !(*this == that); }
+
+    intptr_t offsetInBytes() const { return fOffsetInBytes; }
+    GrPixelConfig texelConfig() const { return fTexelConfig; }
+    GrBuffer* buffer() const { return fBuffer.get(); }
+    GrShaderFlags visibility() const { return fVisibility; }
+
+    /**
+     * For internal use by GrProcessor.
+     */
+    const GrGpuResourceRef* getProgramBuffer() const { return &fBuffer;}
+
+private:
+    intptr_t                      fOffsetInBytes;
+    GrPixelConfig                 fTexelConfig;
+    GrTGpuResourceRef<GrBuffer>   fBuffer;
+    GrShaderFlags                 fVisibility;
+
+    typedef SkNoncopyable INHERITED;
+};
+
+#endif