/* Copyright (c) 2006, Google Inc.
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*
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* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
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* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#if !defined(_BASE_LOW_LEVEL_ALLOC_H_)
#define _BASE_LOW_LEVEL_ALLOC_H_
// A simple thread-safe memory allocator that does not depend on
// mutexes or thread-specific data. It is intended to be used
// sparingly, and only when malloc() would introduce an unwanted
// dependency, such as inside the heap-checker.
#include <config.h>
#include <stddef.h> // for size_t
#include "base/basictypes.h"
class LowLevelAlloc {
public:
struct Arena; // an arena from which memory may be allocated
// Returns a pointer to a block of at least "request" bytes
// that have been newly allocated from the specific arena.
// for Alloc() call the DefaultArena() is used.
// Returns 0 if passed request==0.
// Does not return 0 under other circumstances; it crashes if memory
// is not available.
static void *Alloc(size_t request)
ATTRIBUTE_SECTION(malloc_hook);
static void *AllocWithArena(size_t request, Arena *arena)
ATTRIBUTE_SECTION(malloc_hook);
// Deallocates a region of memory that was previously allocated with
// Alloc(). Does nothing if passed 0. "s" must be either 0,
// or must have been returned from a call to Alloc() and not yet passed to
// Free() since that call to Alloc(). The space is returned to the arena
// from which it was allocated.
static void Free(void *s) ATTRIBUTE_SECTION(malloc_hook);
// ATTRIBUTE_SECTION(malloc_hook) for Alloc* and Free
// are to put all callers of MallocHook::Invoke* in this module
// into special section,
// so that MallocHook::GetCallerStackTrace can function accurately.
// Create a new arena.
// The root metadata for the new arena is allocated in the
// meta_data_arena; the DefaultArena() can be passed for meta_data_arena.
// These values may be ored into flags:
enum {
// Report calls to Alloc() and Free() via the MallocHook interface.
// Set in the DefaultArena.
kCallMallocHook = 0x0001,
// Make calls to Alloc(), Free() be async-signal-safe. Not set in
// DefaultArena().
kAsyncSignalSafe = 0x0002,
// When used with DefaultArena(), the NewArena() and DeleteArena() calls
// obey the flags given explicitly in the NewArena() call, even if those
// flags differ from the settings in DefaultArena(). So the call
// NewArena(kAsyncSignalSafe, DefaultArena()) is itself async-signal-safe,
// as well as generatating an arena that provides async-signal-safe
// Alloc/Free.
};
static Arena *NewArena(int32 flags, Arena *meta_data_arena);
// Destroys an arena allocated by NewArena and returns true,
// provided no allocated blocks remain in the arena.
// If allocated blocks remain in the arena, does nothing and
// returns false.
// It is illegal to attempt to destroy the DefaultArena().
static bool DeleteArena(Arena *arena);
// The default arena that always exists.
static Arena *DefaultArena();
private:
LowLevelAlloc(); // no instances
};
#endif