text: // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
  // Copyright (c) 2005, 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.
  
  // ---
  // Author: Sanjay Ghemawat
  //
  // Routine that uses sbrk/mmap to allocate memory from the system.
  // Useful for implementing malloc.
  
  #ifndef TCMALLOC_SYSTEM_ALLOC_H_
  #define TCMALLOC_SYSTEM_ALLOC_H_
  
  #include <config.h>
  #include <stddef.h>                     // for size_t
  
  class SysAllocator;
  
  // REQUIRES: "alignment" is a power of two or "0" to indicate default alignment
  //
  // Allocate and return "N" bytes of zeroed memory.
  //
  // If actual_bytes is NULL then the returned memory is exactly the
  // requested size.  If actual bytes is non-NULL then the allocator
  // may optionally return more bytes than asked for (i.e. return an
  // entire "huge" page if a huge page allocator is in use).
  //
  // The returned pointer is a multiple of "alignment" if non-zero. The
  // returned pointer will always be aligned suitably for holding a
  // void*, double, or size_t. In addition, if this platform defines
  // CACHELINE_ALIGNED, the return pointer will always be cacheline
  // aligned.
  //
  // Returns NULL when out of memory.
  extern PERFTOOLS_DLL_DECL
  void* TCMalloc_SystemAlloc(size_t bytes, size_t *actual_bytes,
  			   size_t alignment = 0);
  
  // This call is a hint to the operating system that the pages
  // contained in the specified range of memory will not be used for a
  // while, and can be released for use by other processes or the OS.
  // Pages which are released in this way may be destroyed (zeroed) by
  // the OS.  The benefit of this function is that it frees memory for
  // use by the system, the cost is that the pages are faulted back into
  // the address space next time they are touched, which can impact
  // performance.  (Only pages fully covered by the memory region will
  // be released, partial pages will not.)
  //
  // Returns false if release failed or not supported.
  extern PERFTOOLS_DLL_DECL
  bool TCMalloc_SystemRelease(void* start, size_t length);
  
  // Called to ressurect memory which has been previously released
  // to the system via TCMalloc_SystemRelease.  An attempt to
  // commit a page that is already committed does not cause this
  // function to fail.
  extern PERFTOOLS_DLL_DECL
  void TCMalloc_SystemCommit(void* start, size_t length);
  
  // The current system allocator.
  extern PERFTOOLS_DLL_DECL SysAllocator* tcmalloc_sys_alloc;
  
  // Number of bytes taken from system.
  extern PERFTOOLS_DLL_DECL size_t TCMalloc_SystemTaken;
  
  #endif /* TCMALLOC_SYSTEM_ALLOC_H_ */
  