wtf/TCSystemAlloc.h

   1 // Copyright (c) 2005, 2007, Google Inc.
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  29
  30 // ---
  31 // Author: Sanjay Ghemawat
  32 //
  33 // Routine that uses sbrk/mmap to allocate memory from the system.
  34 // Useful for implementing malloc.
  35
  36 #ifndef TCMALLOC_SYSTEM_ALLOC_H__
  37 #define TCMALLOC_SYSTEM_ALLOC_H__
  38
  39 // REQUIRES: "alignment" is a power of two or "0" to indicate default alignment
  40 //
  41 // Allocate and return "N" bytes of zeroed memory.
  42 //
  43 // If actual_bytes is NULL then the returned memory is exactly the
  44 // requested size.  If actual bytes is non-NULL then the allocator
  45 // may optionally return more bytes than asked for (i.e. return an
  46 // entire "huge" page if a huge page allocator is in use).
  47 //
  48 // The returned pointer is a multiple of "alignment" if non-zero.
  49 //
  50 // Returns NULL when out of memory.
  51 extern void* TCMalloc_SystemAlloc(size_t bytes, size_t *actual_bytes,
  52                                   size_t alignment = 0);
  53
  54 // This call is a hint to the operating system that the pages
  55 // contained in the specified range of memory will not be used for a
  56 // while, and can be released for use by other processes or the OS.
  57 // Pages which are released in this way may be destroyed (zeroed) by
  58 // the OS.  The benefit of this function is that it frees memory for
  59 // use by the system, the cost is that the pages are faulted back into
  60 // the address space next time they are touched, which can impact
  61 // performance.  (Only pages fully covered by the memory region will
  62 // be released, partial pages will not.)
  63 extern void TCMalloc_SystemRelease(void* start, size_t length);
  64
  65 #if HAVE(VIRTUALALLOC)
  66 extern void TCMalloc_SystemCommit(void* start, size_t length);
  67 #else
  68 inline void TCMalloc_SystemCommit(void*, size_t) { }
  69 #endif
  70
  71 #endif /* TCMALLOC_SYSTEM_ALLOC_H__ */