move ashmem switching logic to SkDiscardableMemory::Create

src/ports/SkDiscardableMemory_ashmem.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include <unistd.h>
 #include <sys/mman.h>
 #include "SkDiscardableMemory.h"
+#include "SkDiscardableMemoryPool.h"
 #include "SkTypes.h"
 #include "android/ashmem.h"
 
 ////////////////////////////////////////////////////////////////////////////////
 namespace {
 /**
  *  DiscardableMemory implementation that uses the Android kernel's
  *  ashmem (Android shared memory).
  */
 class SkAshmemDiscardableMemory : public SkDiscardableMemory {
 public:
     SkAshmemDiscardableMemory(int fd, void* address, size_t size);
     virtual ~SkAshmemDiscardableMemory();
     virtual bool lock() SK_OVERRIDE;
     virtual void* data() SK_OVERRIDE;
     virtual void unlock() SK_OVERRIDE;
+    static SkAshmemDiscardableMemory* Create(size_t bytes);
+
 private:
     bool         fLocked;
     int          fFd;
     void*        fMemory;
     const size_t fSize;
 };
 
 SkAshmemDiscardableMemory::SkAshmemDiscardableMemory(int fd,
                                                      void* address,
                                                      size_t size)
@@ skipping 42 matching lines @@
     return fLocked ? fMemory : NULL;
 }
 
 void SkAshmemDiscardableMemory::unlock() {
     SkASSERT(fLocked);
     if (fLocked && (fFd != -1)) {
         ashmem_unpin_region(fFd, 0, 0);
     }
     fLocked = false;
 }
-}  // namespace
-////////////////////////////////////////////////////////////////////////////////
 
-SkDiscardableMemory* SkDiscardableMemory::Create(size_t bytes) {
+SkAshmemDiscardableMemory* SkAshmemDiscardableMemory::Create(size_t bytes) {
     // ashmem likes lengths on page boundaries.
     const size_t mask = getpagesize() - 1;
     size_t size = (bytes + mask) & ~mask;
 
     static const char name[] = "Skia_Ashmem_Discardable_Memory";
     int fd = ashmem_create_region(name, size);
     if (fd < 0) {
         return NULL;
     }
     if (0 != ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE)) {
         close(fd);
         return NULL;
     }
     void* addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
     if ((MAP_FAILED == addr) || (NULL == addr)) {
         close(fd);
         return NULL;
     }
 
     return SkNEW_ARGS(SkAshmemDiscardableMemory, (fd, addr, size));
 }
+}  // namespace
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef SK_ASHMEM_MINIMUM_MEMORY_SIZE
+// number taken from android/graphics/BitmapFactory.cpp
+#define SK_ASHMEM_MINIMUM_MEMORY_SIZE (32 * 1024)
+#endif  // SK_ASHMEM_MINIMUM_MEMORY_SIZE
+SkDiscardableMemory* SkDiscardableMemory::Create(size_t bytes) {
+    if (bytes < SK_ASHMEM_MINIMUM_MEMORY_SIZE) {
+        return SkGetGlobalDiscardableMemoryPool()->create(bytes);
+    } else {
+        return SkAshmemDiscardableMemory::Create(bytes);
+    }
+}
+