base: Discardable memory types.

base/memory/discardable_memory_mac.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/memory/discardable_memory.h"
-
 #include <mach/mach.h>
 #include <sys/mman.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/memory/discardable_memory.h"
+#include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
 namespace {
 
 // The VM subsystem allows tagging of memory and 240-255 is reserved for
 // application use (see mach/vm_statistics.h). Pick 252 (after chromium's atomic
 // weight of ~52).
 const int kDiscardableMemoryTag = VM_MAKE_TAG(252);
 
 class DiscardableMemoryMac : public DiscardableMemory {
  public:
-  DiscardableMemoryMac(void* memory, size_t size)
-      : memory_(memory),
+  explicit DiscardableMemoryMac(size_t size)
+      : buffer_(0),
         size_(size) {
-    DCHECK(memory_);
+  }
+
+  bool Initialize() {

[Philippe, 2013/12/17 14:28:21]

Are you making this change for consistency with the other implementations? FWIW,
I preferred the previous version (which could have been improved with a static
factory method) but consistency is important too. 

[reveman, 2013/12/18 08:12:38]

This is for consistency. I might also move this implementation to a separate
file and add specific unit tests in the future as part of getting rid of
PurgeForTesting(). 

+    kern_return_t ret = vm_allocate(mach_task_self(),
+                                    &buffer_,
+                                    size_,
+                                    VM_FLAGS_PURGABLE |
+                                    VM_FLAGS_ANYWHERE |
+                                    kDiscardableMemoryTag);
+    if (ret != KERN_SUCCESS) {
+      DLOG(ERROR) << "vm_allocate() failed";
+      return false;
+    }
+
+    return true;
   }
 
   virtual ~DiscardableMemoryMac() {
-    vm_deallocate(mach_task_self(),
-                  reinterpret_cast<vm_address_t>(memory_),
-                  size_);
+    if (buffer_)
+      vm_deallocate(mach_task_self(), buffer_, size_);
   }
 
   virtual LockDiscardableMemoryStatus Lock() OVERRIDE {
-    DCHECK_EQ(0, mprotect(memory_, size_, PROT_READ | PROT_WRITE));
+    DCHECK_EQ(0, mprotect(buffer_, size_, PROT_READ | PROT_WRITE));
     int state = VM_PURGABLE_NONVOLATILE;
-    kern_return_t ret = vm_purgable_control(
-        mach_task_self(),
-        reinterpret_cast<vm_address_t>(memory_),
-        VM_PURGABLE_SET_STATE,
-        &state);
+    kern_return_t ret = vm_purgable_control(mach_task_self(),
+                                            buffer_,
+                                            VM_PURGABLE_SET_STATE,
+                                            &state);
     if (ret != KERN_SUCCESS)
       return DISCARDABLE_MEMORY_FAILED;
 
     return state & VM_PURGABLE_EMPTY ? DISCARDABLE_MEMORY_PURGED
                                      : DISCARDABLE_MEMORY_SUCCESS;
   }
 
   virtual void Unlock() OVERRIDE {
     int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
-    kern_return_t ret = vm_purgable_control(
-        mach_task_self(),
-        reinterpret_cast<vm_address_t>(memory_),
-        VM_PURGABLE_SET_STATE,
-        &state);
-    DCHECK_EQ(0, mprotect(memory_, size_, PROT_NONE));
+    kern_return_t ret = vm_purgable_control(mach_task_self(),
+                                            buffer_,
+                                            VM_PURGABLE_SET_STATE,
+                                            &state);
+    DCHECK_EQ(0, mprotect(buffer_, size_, PROT_NONE));
     if (ret != KERN_SUCCESS)
       DLOG(ERROR) << "Failed to unlock memory.";
   }
 
   virtual void* Memory() const OVERRIDE {
-    return memory_;
+    return buffer_;
   }
 
  private:
-  void* const memory_;
+  vm_address_t buffer_;
   const size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryMac);
 };
 
+struct SupportedTypeVector {
+  SupportedTypeVector() {
+    v.push_back(DISCARDABLE_MEMORY_MAC);
+    v.push_back(DISCARDABLE_MEMORY_EMULATED);
+  }
+  std::vector<DiscardableMemoryType> v;
+};
+LazyInstance<SupportedTypeVector>::Leaky g_supported_types =
+    LAZY_INSTANCE_INITIALIZER;
+
 }  // namespace
 
 // static
-bool DiscardableMemory::SupportedNatively() {
-  return true;
+const std::vector<DiscardableMemoryType>&
+    DiscardableMemory::GetSupportedTypes() {
+  return g_supported_types.Get().v;
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
     size_t size) {
-  vm_address_t buffer = 0;
-  kern_return_t ret = vm_allocate(mach_task_self(),
-                                  &buffer,
-                                  size,
-                                  VM_FLAGS_PURGABLE |
-                                  VM_FLAGS_ANYWHERE |
-                                  kDiscardableMemoryTag);
-  if (ret != KERN_SUCCESS) {
-    DLOG(ERROR) << "vm_allocate() failed";
-    return scoped_ptr<DiscardableMemory>();
+  switch (GetType()) {
+    case DISCARDABLE_MEMORY_NONE:
+    case DISCARDABLE_MEMORY_ANDROID:
+      return scoped_ptr<DiscardableMemory>();
+    case DISCARDABLE_MEMORY_MAC: {
+      scoped_ptr<DiscardableMemoryMac> memory(new DiscardableMemoryMac(size));
+      if (!memory->Initialize())
+        return scoped_ptr<DiscardableMemory>();
+
+      return memory.PassAs<DiscardableMemory>();
+    }
+    case DISCARDABLE_MEMORY_EMULATED: {
+      scoped_ptr<internal::DiscardableMemoryEmulated> memory(
+          new internal::DiscardableMemoryEmulated(size));
+      if (!memory->Initialize())
+        return scoped_ptr<DiscardableMemory>();
+
+      return memory.PassAs<DiscardableMemory>();
+    }
   }
-  return scoped_ptr<DiscardableMemory>(
-      new DiscardableMemoryMac(reinterpret_cast<void*>(buffer), size));
+
+  NOTREACHED();
+  return scoped_ptr<DiscardableMemory>();
 }
 
 // static
 bool DiscardableMemory::PurgeForTestingSupported() {
   return true;
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   int state = 0;
   vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
+  internal::DiscardableMemoryEmulated::PurgeForTesting();
 }
 
 }  // namespace base