Consolidate GPU buffer implementations

src/gpu/GrBuffer.h

Index: src/gpu/GrBuffer.h
diff --git a/src/gpu/GrBuffer.h b/src/gpu/GrBuffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..4fadba6aa72f7bc3d4252a38b63259053a80a472
--- /dev/null
+++ b/src/gpu/GrBuffer.h
@@ -0,0 +1,145 @@
+/*
+ * 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 GrBuffer_DEFINED
+#define GrBuffer_DEFINED
+
+#include "GrGpuResource.h"
+
+class GrGpu;
+
+class GrBuffer : public GrGpuResource {
+public:
+    /**
+     * Computes a scratch key for a buffer with a "dynamic" access pattern. (Buffers with "static"
+     * and "stream" access patterns are disqualified by nature from being cached and reused.)
+     */
+    static void ComputeScratchKeyForDynamicBuffer(GrBufferType type, size_t size,
+                                                  GrScratchKey* key) {
+        static const GrScratchKey::ResourceType kType = GrScratchKey::GenerateResourceType();
+        GrScratchKey::Builder builder(key, kType, 1 + (sizeof(size_t) + 3) / 4);
+        // TODO: There's not always reason to cache a buffer by type. In some (all?) APIs it's just
+        // a chunk of memory we can use/reuse for any type of data. We really only need to
+        // differentiate between the "read" types (e.g. kGpuToCpu_BufferType) and "draw" types.
+        builder[0] = type;
+        builder[1] = (uint32_t)size;
+        if (sizeof(size_t) > 4) {
+            builder[2] = (uint32_t)((uint64_t)size >> 32);
+        }
+    }
+
+    GrBufferType type() const { return fType; }
+
+    GrAccessPattern accessPattern() const { return fAccessPattern; }
+
+    /**
+     * Returns true if the buffer is a wrapper around a CPU array. If true it
+     * indicates that map will always succeed and will be free.
+     */
+    bool isCPUBacked() const { return fCPUBacked; }
+
+    /**
+     * Maps the buffer to be written by the CPU.
+     *
+     * The previous content of the buffer is invalidated. It is an error
+     * to draw from the buffer while it is mapped. It may fail if the backend
+     * doesn't support mapping the buffer. If the buffer is CPU backed then
+     * it will always succeed and is a free operation. Once a buffer is mapped,
+     * subsequent calls to map() are ignored.
+     *
+     * Note that buffer mapping does not go through GrContext and therefore is
+     * not serialized with other operations.
+     *
+     * @return a pointer to the data or nullptr if the map fails.
+     */
+     void* map() {
+         if (!fMapPtr) {
+             this->onMap();
+         }
+         return fMapPtr;
+     }
+
+    /**
+     * Unmaps the buffer.
+     *
+     * The pointer returned by the previous map call will no longer be valid.
+     */
+     void unmap() {
+         SkASSERT(fMapPtr);
+         this->onUnmap();
+         fMapPtr = nullptr;
+     }
+
+    /**
+     * Returns the same ptr that map() returned at time of map or nullptr if the
+     * is not mapped.
+     *
+     * @return ptr to mapped buffer data or nullptr if buffer is not mapped.
+     */
+     void* mapPtr() const { return fMapPtr; }
+
+    /**
+     Queries whether the buffer has been mapped.
+
+     @return true if the buffer is mapped, false otherwise.
+     */
+     bool isMapped() const { return SkToBool(fMapPtr); }
+
+    /**
+     * Updates the buffer data.
+     *
+     * The size of the buffer will be preserved. The src data will be
+     * placed at the beginning of the buffer and any remaining contents will
+     * be undefined. srcSizeInBytes must be <= to the buffer size.
+     *
+     * The buffer must not be mapped.
+     *
+     * Note that buffer updates do not go through GrContext and therefore are
+     * not serialized with other operations.
+     *
+     * @return returns true if the update succeeds, false otherwise.
+     */
+    bool updateData(const void* src, size_t srcSizeInBytes) {
+        SkASSERT(!this->isMapped());
+        SkASSERT(srcSizeInBytes <= fGpuMemorySize);
+        return this->onUpdateData(src, srcSizeInBytes);
+    }
+
+protected:
+    GrBuffer(GrGpu* gpu, GrBufferType type, size_t gpuMemorySize, GrAccessPattern accessPattern,
+             bool cpuBacked)
+        : INHERITED(gpu, kCached_LifeCycle),
+          fMapPtr(nullptr),
+          fType(type),
+          fGpuMemorySize(gpuMemorySize), // TODO: Zero for cpu backed buffers?
+          fAccessPattern(accessPattern),
+          fCPUBacked(cpuBacked) {
+        if (!fCPUBacked && SkIsPow2(fGpuMemorySize) && kDynamic_GrAccessPattern == fAccessPattern) {
+            GrScratchKey key;
+            ComputeScratchKeyForDynamicBuffer(fType, fGpuMemorySize, &key);
+            this->setScratchKey(key);
+        }
+    }
+
+    void* fMapPtr;
+
+private:
+    virtual size_t onGpuMemorySize() const { return fGpuMemorySize; }
+
+    virtual void onMap() = 0;
+    virtual void onUnmap() = 0;
+    virtual bool onUpdateData(const void* src, size_t srcSizeInBytes) = 0;
+
+    GrBufferType      fType;
+    size_t            fGpuMemorySize;
+    GrAccessPattern   fAccessPattern;
+    bool              fCPUBacked;
+
+    typedef GrGpuResource INHERITED;
+};
+
+#endif