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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "VolatileBuffer.h"
#include "mozilla/Assertions.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/mozalloc.h"
#include <mach/mach.h>
#include <sys/mman.h>
#include <unistd.h>
#define MIN_VOLATILE_ALLOC_SIZE 8192
namespace mozilla {
VolatileBuffer::VolatileBuffer()
: mMutex("VolatileBuffer"),
mBuf(nullptr),
mSize(0),
mLockCount(0),
mHeap(false) {}
bool VolatileBuffer::Init(size_t aSize, size_t aAlignment) {
MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
MOZ_ASSERT(!(aAlignment % sizeof(void*)),
"Alignment must be multiple of pointer size");
mSize = aSize;
kern_return_t ret = 0;
if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
goto heap_alloc;
}
ret = vm_allocate(mach_task_self(), (vm_address_t*)&mBuf, mSize,
VM_FLAGS_PURGABLE | VM_FLAGS_ANYWHERE);
if (ret == KERN_SUCCESS) {
return true;
}
heap_alloc:
(void)posix_memalign(&mBuf, aAlignment, aSize);
mHeap = true;
return !!mBuf;
}
VolatileBuffer::~VolatileBuffer() {
MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
if (OnHeap()) {
free(mBuf);
} else {
vm_deallocate(mach_task_self(), (vm_address_t)mBuf, mSize);
}
}
bool VolatileBuffer::Lock(void** aBuf) {
MutexAutoLock lock(mMutex);
MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
*aBuf = mBuf;
if (++mLockCount > 1 || OnHeap()) {
return true;
}
int state = VM_PURGABLE_NONVOLATILE;
kern_return_t ret = vm_purgable_control(mach_task_self(), (vm_address_t)mBuf,
VM_PURGABLE_SET_STATE, &state);
return ret == KERN_SUCCESS && !(state & VM_PURGABLE_EMPTY);
}
void VolatileBuffer::Unlock() {
MutexAutoLock lock(mMutex);
MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
if (--mLockCount || OnHeap()) {
return;
}
int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
DebugOnly<kern_return_t> ret = vm_purgable_control(
mach_task_self(), (vm_address_t)mBuf, VM_PURGABLE_SET_STATE, &state);
MOZ_ASSERT(ret == KERN_SUCCESS, "Failed to set buffer as purgable");
}
bool VolatileBuffer::OnHeap() const { return mHeap; }
size_t VolatileBuffer::HeapSizeOfExcludingThis(
MallocSizeOf aMallocSizeOf) const {
return OnHeap() ? aMallocSizeOf(mBuf) : 0;
}
size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
if (OnHeap()) {
return 0;
}
unsigned long pagemask = getpagesize() - 1;
return (mSize + pagemask) & ~pagemask;
}
} // namespace mozilla
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