This header provides the meomry map functions mmap and munmap. More...
Functions | |
void * | mmap (void *addr, size_t len, int prot, int flags, int fd, off_t offset) |
Creates or opens a named or unnamed file mapping object for a specified file and maps a view of a file mapping into the address space of a calling process. More... | |
int | munmap (void *addr, size_t len) |
Unmaps a mapped view of a file from the calling process's address space. More... | |
int | madvise (void *addr, size_t length, int advice) |
give advice about use of memory More... | |
This header provides the meomry map functions mmap and munmap.
void* mmap | ( | void * | addr, |
size_t | len, | ||
int | prot, | ||
int | flags, | ||
int | fd, | ||
off_t | offset | ||
) |
Creates or opens a named or unnamed file mapping object for a specified file and maps a view of a file mapping into the address space of a calling process.
addr | Unused |
len | Number of bytes to be mapped. |
prot | Protections. |
flags | Type of the mapped object. |
fd | File descriptor that describes the object to map. |
offset | Number of bytes from which to start the mapping. |
Create or open an unnamed file mapping object for a specified file described by the file descriptor fd
. The number of bytes that are mapped is given by len
and start after offset
bytes. The parameter addr
is unused.
The only type of the mapped object that is supported is MAP_SHARED
. If another value if given, -1 is returned.
prot
specifies the protection of the mapped region. If PROT_EXEC is used, it set the execute access. If PROT_READ is used, it sets the read access. If PROT_WRITE is used, it sets the write access.
If the map view of file can not be created, -1 is returned. If the mappping can not be done, -1 is returned.
If no error occurred, the starting address of the mapped view is returned.
Conformity: None.
int munmap | ( | void * | addr, |
size_t | len | ||
) |
Unmaps a mapped view of a file from the calling process's address space.
addr | Pointer to the base address. |
len | Unused. |
Unmaps a mapped view of a file from the calling process's address space. addr
is the pointer to the base address. This value must be identical to the value returned by a previous call to mmap(). The parameter len
is unsed.
Conformity: None.
int madvise | ( | void * | addr, |
size_t | length, | ||
int | advice | ||
) |
give advice about use of memory
addr | Unused. |
length | Unused. |
advice | Unused. |
The madvise() system call advises the kernel about how to handle paging input/output in the address range beginning at address addr and with size length bytes. It allows an application to tell the kernel how it expects to use some mapped or shared memory areas, so that the kernel can choose appropriate read-ahead and caching techniques. This call does not influence the semantics of the application (except in the case of MADV_DONTNEED), but may influence its performance. The kernel is free to ignore the advice.
Conformity: None.