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// 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.
#ifndef VM_VIRTUAL_MEMORY_H_
#define VM_VIRTUAL_MEMORY_H_
#include "platform/utils.h"
#include "vm/globals.h"
#include "vm/memory_region.h"
namespace dart {
class VirtualMemory {
public:
enum Protection {
kNoAccess,
kReadOnly,
kReadWrite,
kReadExecute,
kReadWriteExecute
};
// The reserved memory is unmapped on destruction.
~VirtualMemory();
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.
bool Commit(bool is_executable) {
return Commit(start(), size(), is_executable);
}
// Changes the protection of the virtual memory area.
bool Protect(Protection 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);
// Reserves a virtual memory segment with the start address being aligned to
// the requested power of two.
static VirtualMemory* ReserveAligned(intptr_t size, intptr_t alignment);
static intptr_t PageSize() {
ASSERT(page_size_ != 0);
ASSERT(Utils::IsPowerOfTwo(page_size_));
return page_size_;
}
private:
// Truncate this virtual memory segment.
void Truncate(uword new_start, intptr_t size);
// Free a sub segment. On operating systems that support it this
// can give back the virtual memory to the system.
void 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.
VirtualMemory(const MemoryRegion& region, void* reserved_pointer) :
region_(region.pointer(), region.size()),
reserved_pointer_(reserved_pointer) { }
// Commit a reserved memory area, so that the memory can be accessed.
bool Commit(uword addr, intptr_t size, bool is_executable);
MemoryRegion region_;
// The original pointer returned by the OS for this virtual memory
// allocation or NULL. reserved_pointer_ is non-NULL only for
// platforms where virtual memory subregions cannot be given back to
// the OS. When non-null it might not coincide with
// region_.pointer() if the virtual memory region has been
// truncated.
void* reserved_pointer_;
static uword page_size_;
DISALLOW_IMPLICIT_CONSTRUCTORS(VirtualMemory);
};
} // namespace dart
#endif // VM_VIRTUAL_MEMORY_H_