Add a simpler key type for scratch resource keys.

include/gpu/GrResourceKey.h

Index: include/gpu/GrResourceKey.h
diff --git a/include/gpu/GrResourceKey.h b/include/gpu/GrResourceKey.h
index 6a9ff895212c53c81f349701f6139287a50c4fb5..f662ed5511e36aa29ce3a0ac1ad8bc6d0a723d61 100644
--- a/include/gpu/GrResourceKey.h
+++ b/include/gpu/GrResourceKey.h
@@ -10,48 +10,116 @@
 #define GrResourceKey_DEFINED
 
 #include "GrTypes.h"
+#include "SkTemplates.h"
 #include "GrBinHashKey.h"
 
-class GrResourceKey {
+/**
+ * A key used for scratch resources. The key consists of a resource type (subclass) identifier, a
+ * hash, a data length, and type-specific data. A Builder object is used to initialize the
+ * key contents. The contents must be initialized before the key can be used.
+ */
+class GrScratchKey {
 public:
-    static GrCacheID::Domain ScratchDomain();
+    /** Uniquely identifies the type of resource that is cached as scratch. */
+    typedef uint32_t ResourceType;
+    /** Generate a unique ResourceType. */
+    static ResourceType GenerateResourceType();
+
+    GrScratchKey() { this->reset(); }
+    GrScratchKey(const GrScratchKey& that) { *this = that; }
+
+    /** Reset to an invalid key. */
+    void reset() {
+        fKey.reset(kMetaDataCnt);
+        fKey[kHash_MetaDataIdx] = 0;
+        fKey[kTypeAndSize_MetaDataIdx] = kInvalidResourceType;
+    }
+
+    bool isValid() const { return kInvalidResourceType != this->resourceType(); }
+
+    ResourceType resourceType() const { return fKey[kTypeAndSize_MetaDataIdx] & 0xffff; }
+
+    uint32_t hash() const { return fKey[kHash_MetaDataIdx]; }
+
+    size_t size() const { return SkToInt(fKey[kTypeAndSize_MetaDataIdx] >> 16); }
+
+    const uint32_t* data() const { return &fKey[kMetaDataCnt]; }
+
+    GrScratchKey& operator=(const GrScratchKey& that) {
+        size_t size = that.size();
+        fKey.reset(SkToInt(size));
+        memcpy(fKey.get(), that.fKey.get(), size);
+        return *this;
+    }
+
+    bool operator==(const GrScratchKey& that) const {
+        return 0 == memcmp(fKey.get(), that.fKey.get(), this->size());
+    }
+    bool operator!=(const GrScratchKey& that) const { return !(*this == that); }
+
+    /** Used to initialize scratch key. */
+    class Builder {
+    public:
+        Builder(GrScratchKey* key, ResourceType type, int data32Count) : fKey(key) {
+            SkASSERT(data32Count >= 0);
+            SkASSERT(type != kInvalidResourceType);
+            key->fKey.reset(kMetaDataCnt + data32Count);
+            SkASSERT(type <= SK_MaxU16);
+            int size = (data32Count + kMetaDataCnt) * sizeof(uint32_t);
+            SkASSERT(size <= SK_MaxU16);
+            key->fKey[kTypeAndSize_MetaDataIdx] = type | (size << 16);
+        }
+
+        ~Builder() { this->finish(); }
+
+        void finish();
+
+        uint32_t& operator[](int dataIdx) {
+            SkASSERT(fKey);
+            SkDEBUGCODE(size_t dataCount = fKey->size() / sizeof(uint32_t) - kMetaDataCnt;)
+            SkASSERT(SkToU32(dataIdx) < dataCount);
+            return fKey->fKey[kMetaDataCnt + dataIdx];
+        }
+
+    private:
+        GrScratchKey* fKey;
+    };
 
-    /** Uniquely identifies the GrGpuResource subclass in the key to avoid collisions
-        across resource types. */
-    typedef uint8_t ResourceType;
+private:
+    enum MetaDataIdx {
+        kHash_MetaDataIdx,
+        // The resource type and size are packed into a single uint32_t.
+        kTypeAndSize_MetaDataIdx,
+
+        kLastMetaDataIdx = kTypeAndSize_MetaDataIdx
+    };
+    static const uint32_t kInvalidResourceType = 0;
+    static const uint32_t kMetaDataCnt = kLastMetaDataIdx + 1;
+
+    // Stencil and textures each require 2 uint32_t values.
+    SkAutoSTArray<kMetaDataCnt + 2, uint32_t> fKey;
+};
 
+class GrResourceKey {
+public:
     /** Flags set by the GrGpuResource subclass. */
     typedef uint8_t ResourceFlags;
 
-    /** Generate a unique ResourceType */
-    static ResourceType GenerateResourceType();
-
     /** Creates a key for resource */
-    GrResourceKey(const GrCacheID& id, ResourceType type, ResourceFlags flags) {
-        this->init(id.getDomain(), id.getKey(), type, flags);
+    GrResourceKey(const GrCacheID& id, ResourceFlags flags) {
+        this->init(id.getDomain(), id.getKey(), flags);
     };
 
     GrResourceKey(const GrResourceKey& src) { fKey = src.fKey; }
 
     GrResourceKey() { fKey.reset(); }
 
-    void reset(const GrCacheID& id, ResourceType type, ResourceFlags flags) {
-        this->init(id.getDomain(), id.getKey(), type, flags);
+    void reset(const GrCacheID& id, ResourceFlags flags) {
+        this->init(id.getDomain(), id.getKey(), flags);
     }
 
     uint32_t getHash() const { return fKey.getHash(); }
 
-    bool isScratch() const {
-        return ScratchDomain() ==
-            *reinterpret_cast<const GrCacheID::Domain*>(fKey.getData() +
-                                                        kCacheIDDomainOffset);
-    }
-
-    ResourceType getResourceType() const {
-        return *reinterpret_cast<const ResourceType*>(fKey.getData() +
-                                                      kResourceTypeOffset);
-    }
-
     ResourceFlags getResourceFlags() const {
         return *reinterpret_cast<const ResourceFlags*>(fKey.getData() +
                                                        kResourceFlagsOffset);
@@ -62,27 +130,17 @@ public:
     // A key indicating that the resource is not usable as a scratch resource.
     static GrResourceKey& NullScratchKey();
 
-    bool isNullScratch() const {
-        return this->isScratch() && NoneResourceType() == this->getResourceType();
-    }
-
 private:
     enum {
         kCacheIDKeyOffset = 0,
         kCacheIDDomainOffset = kCacheIDKeyOffset + sizeof(GrCacheID::Key),
-        kResourceTypeOffset = kCacheIDDomainOffset + sizeof(GrCacheID::Domain),
-        kResourceFlagsOffset = kResourceTypeOffset + sizeof(ResourceType),
+        kResourceFlagsOffset = kCacheIDDomainOffset + sizeof(GrCacheID::Domain),
         kPadOffset = kResourceFlagsOffset + sizeof(ResourceFlags),
         kKeySize = SkAlign4(kPadOffset),
         kPadSize = kKeySize - kPadOffset
     };
 
-    static ResourceType NoneResourceType();
-
-    void init(const GrCacheID::Domain domain,
-              const GrCacheID::Key& key,
-              ResourceType type,
-              ResourceFlags flags) {
+    void init(const GrCacheID::Domain domain, const GrCacheID::Key& key, ResourceFlags flags) {
         union {
             uint8_t  fKey8[kKeySize];
             uint32_t fKey32[kKeySize / 4];
@@ -91,7 +149,6 @@ private:
         uint8_t* k = keyData.fKey8;
         memcpy(k + kCacheIDKeyOffset, key.fData8, sizeof(GrCacheID::Key));
         memcpy(k + kCacheIDDomainOffset, &domain, sizeof(GrCacheID::Domain));
-        memcpy(k + kResourceTypeOffset, &type, sizeof(ResourceType));
         memcpy(k + kResourceFlagsOffset, &flags, sizeof(ResourceFlags));
         memset(k + kPadOffset, 0, kPadSize);
         fKey.setKeyData(keyData.fKey32);