JavaScriptCore-621.1.tar.gz

[apple/javascriptcore.git] / wtf / TCSystemAlloc.h

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// 
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// ---
// 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__

// 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.
//
// Returns NULL when out of memory.
extern 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.)
extern void TCMalloc_SystemRelease(void* start, size_t length);

extern void TCMalloc_SystemCommit(void* start, size_t length);

#if !HAVE(MADV_FREE_REUSE) && !HAVE(MADV_DONTNEED) && !HAVE(MMAP) && !HAVE(VIRTUALALLOC)
inline void TCMalloc_SystemRelease(void*, size_t) { }
#endif

#if !HAVE(VIRTUALALLOC) && !HAVE(MADV_FREE_REUSE)
inline void TCMalloc_SystemCommit(void*, size_t) { }
#endif

#endif /* TCMALLOC_SYSTEM_ALLOC_H__ */