113 lines
2.6 KiB
C++
113 lines
2.6 KiB
C++
/*
|
|
* \brief A guard for arbitrary allocators to limit memory exhaustion
|
|
* \author Stefan Kalkowski
|
|
* \date 2010-08-20
|
|
*/
|
|
|
|
/*
|
|
* Copyright (C) 2010-2013 Genode Labs GmbH
|
|
*
|
|
* This file is part of the Genode OS framework, which is distributed
|
|
* under the terms of the GNU General Public License version 2.
|
|
*/
|
|
|
|
#ifndef _ALLOCATOR_GUARD_H_
|
|
#define _ALLOCATOR_GUARD_H_
|
|
|
|
#include <base/allocator.h>
|
|
#include <base/printf.h>
|
|
#include <base/stdint.h>
|
|
|
|
namespace Genode { class Allocator_guard; }
|
|
|
|
|
|
/**
|
|
* This class acts as guard for arbitrary allocators to limit
|
|
* memory exhaustion
|
|
*/
|
|
class Genode::Allocator_guard : public Allocator
|
|
{
|
|
private:
|
|
|
|
Allocator *_allocator; /* allocator to guard */
|
|
size_t _amount; /* total amount */
|
|
size_t _consumed; /* already consumed bytes */
|
|
|
|
public:
|
|
|
|
Allocator_guard(Allocator *allocator, size_t amount)
|
|
: _allocator(allocator), _amount(amount), _consumed(0) { }
|
|
|
|
/**
|
|
* Extend allocation limit
|
|
*/
|
|
void upgrade(size_t additional_amount) {
|
|
_amount += additional_amount; }
|
|
|
|
/**
|
|
* Consume bytes without actually allocating them
|
|
*/
|
|
bool withdraw(size_t size)
|
|
{
|
|
if ((_amount - _consumed) < size)
|
|
return false;
|
|
|
|
_consumed += size;
|
|
return true;
|
|
}
|
|
|
|
/*************************
|
|
** Allocator interface **
|
|
*************************/
|
|
|
|
/**
|
|
* Allocate block
|
|
*
|
|
* \param size block size to allocate
|
|
* \param out_addr resulting pointer to the new block,
|
|
* undefined in the error case
|
|
* \return true on success
|
|
*/
|
|
bool alloc(size_t size, void **out_addr) override
|
|
{
|
|
if ((_amount - _consumed) < (size + _allocator->overhead(size))) {
|
|
PWRN("Quota exceeded! amount=%zu, size=%zu, consumed=%zu",
|
|
_amount, (size + _allocator->overhead(size)), _consumed);
|
|
return false;
|
|
}
|
|
bool b = _allocator->alloc(size, out_addr);
|
|
if (b)
|
|
_consumed += size + _allocator->overhead(size);
|
|
return b;
|
|
}
|
|
|
|
/**
|
|
* Free block a previously allocated block
|
|
*/
|
|
void free(void *addr, size_t size) override
|
|
{
|
|
_allocator->free(addr, size);
|
|
_consumed -= size + _allocator->overhead(size);
|
|
}
|
|
|
|
/**
|
|
* Return amount of backing store consumed by the allocator
|
|
*/
|
|
size_t consumed() const override { return _consumed; }
|
|
|
|
/**
|
|
* Return allocation limit
|
|
*/
|
|
size_t quota() const { return _amount; }
|
|
|
|
/**
|
|
* Return meta-data overhead per block
|
|
*/
|
|
size_t overhead(size_t size) const override { return _allocator->overhead(size); }
|
|
|
|
bool need_size_for_free() const override {
|
|
return _allocator->need_size_for_free(); }
|
|
};
|
|
|
|
#endif /* _ALLOCATOR_GUARD_H_ */
|