| // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- |
| /* Copyright (c) 2006, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * 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. |
| * * Neither the name of Google Inc. nor the names of its |
| * 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 |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * 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 |