blob: 607e6b2b00553bcffc02f82149a748929fc9ebf8 [file] [log] [blame]
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "platform/utils.h"
#include "vm/globals.h"
#include "vm/memory_region.h"
namespace dart {
class VirtualMemory {
enum Protection {
// The reserved memory is unmapped on destruction.
uword start() const { return region_.start(); }
uword end() const { return region_.end(); }
void* address() const { return region_.pointer(); }
intptr_t size() const { return region_.size(); }
static void InitOnce();
bool Contains(uword addr) const {
return region_.Contains(addr);
// Commits the virtual memory area, which is guaranteed to be zeroed. Returns
// true on success and false on failure (e.g., out-of-memory).
bool Commit(bool is_executable) {
return Commit(start(), size(), is_executable);
// Changes the protection of the virtual memory area.
static bool Protect(void* address, intptr_t size, Protection mode);
bool Protect(Protection mode) {
return Protect(address(), size(), mode);
// Reserves a virtual memory segment with size. If a segment of the requested
// size cannot be allocated NULL is returned.
static VirtualMemory* Reserve(intptr_t size) {
return ReserveInternal(size);
static intptr_t PageSize() {
ASSERT(page_size_ != 0);
return page_size_;
static bool InSamePage(uword address0, uword address1);
// Truncate this virtual memory segment. If try_unmap is false, the
// memory beyond the new end is still accessible, but will be returned
// upon destruction.
void Truncate(intptr_t new_size, bool try_unmap = true);
// Commit a reserved memory area, so that the memory can be accessed.
bool Commit(uword addr, intptr_t size, bool is_executable);
static VirtualMemory* ReserveInternal(intptr_t size);
// Free a sub segment. On operating systems that support it this
// can give back the virtual memory to the system. Returns true on success.
static bool FreeSubSegment(void* address, intptr_t size);
// This constructor is only used internally when reserving new virtual spaces.
// It does not reserve any virtual address space on its own.
explicit VirtualMemory(const MemoryRegion& region) :
region_(region.pointer(), region.size()),
reserved_size_(region.size()) { }
MemoryRegion region_;
// The size of the underlying reservation not yet given back to the OS.
// Its start coincides with region_, but its size might not, due to Truncate.
intptr_t reserved_size_;
static uword page_size_;
} // namespace dart