Create a platform-dependent object for accessing purgeable memory.

src/ports/SkPurgeableMemoryBlock_mac.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 "SkPurgeableMemoryBlock.h"
+
+#include <mach/mach.h>
+
+bool SkPurgeableMemoryBlock::IsSupported() {
+    return true;
+}
+
+#ifdef SK_DEBUG
+bool SkPurgeableMemoryBlock::PlatformSupportsPurgingAllUnpinnedBlocks() {
+    return true;
+}
+
+bool SkPurgeableMemoryBlock::PurgeAllUnpinnedBlocks() {
+    // Unused.
+    int state = 0;
+    kern_return_t ret = vm_purgable_control(mach_task_self(), 0, VM_PURGABLE_PURGE_ALL, &state);
+    return ret == KERN_SUCCESS;
+}
+
+bool SkPurgeableMemoryBlock::purge() {
+    return false;
+}
+#endif
+
+static size_t round_to_page_size(size_t size) {
+    const size_t mask = 4096 - 1;
+    return (size + mask) & ~mask;
+}
+
+SkPurgeableMemoryBlock::SkPurgeableMemoryBlock(size_t size)
+    : fAddr(NULL)
+    , fSize(round_to_page_size(size))
+    , fPinned(false) {
+}
+
+SkPurgeableMemoryBlock::~SkPurgeableMemoryBlock() {
+    SkDEBUGCODE(kern_return_t ret =) vm_deallocate(mach_task_self(),
+                                                   reinterpret_cast<vm_address_t>(fAddr),
+                                                   static_cast<vm_size_t>(fSize));
+#ifdef SK_DEBUG
+    if (ret != KERN_SUCCESS) {
+        SkDebugf("SkPurgeableMemoryBlock destructor failed to deallocate.\n");
+    }
+#endif
+}
+
+void* SkPurgeableMemoryBlock::pin(SkPurgeableMemoryBlock::PinResult* pinResult) {
+    SkASSERT(!fPinned);
+    SkASSERT(pinResult != NULL);
+    if (NULL == fAddr) {
+        vm_address_t addr = 0;
+        kern_return_t ret = vm_allocate(mach_task_self(), &addr, static_cast<vm_size_t>(fSize),
+                                        VM_FLAGS_PURGABLE | VM_FLAGS_ANYWHERE);
+        if (KERN_SUCCESS == ret) {
+            fAddr = reinterpret_cast<void*>(addr);
+            *pinResult = kUninitialized_PinResult;
+            fPinned = true;
+        } else {
+            fAddr = NULL;
+        }
+    } else {
+        int state = VM_PURGABLE_NONVOLATILE;
+        kern_return_t ret = vm_purgable_control(mach_task_self(),
+                                                reinterpret_cast<vm_address_t>(fAddr),
+                                                VM_PURGABLE_SET_STATE, &state);
+        if (ret != KERN_SUCCESS) {
+            fAddr = NULL;
+            fPinned = false;
+            return NULL;
+        }
+
+        fPinned = true;
+
+        if (state & VM_PURGABLE_EMPTY) {
+            *pinResult = kUninitialized_PinResult;
+        } else {
+            *pinResult = kRetained_PinResult;
+        }
+    }
+    return fAddr;
+}
+
+void SkPurgeableMemoryBlock::unpin() {
+    SkASSERT(fPinned);
+    int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
+    SkDEBUGCODE(kern_return_t ret =) vm_purgable_control(mach_task_self(),
+                                                         reinterpret_cast<vm_address_t>(fAddr),
+                                                         VM_PURGABLE_SET_STATE, &state);
+    fPinned = false;
+
+#ifdef SK_DEBUG
+    if (ret != KERN_SUCCESS) {
+        SkDebugf("SkPurgeableMemoryBlock::unpin() failed.\n");
+    }
+#endif
+}
+