Interface to memory-mapped files for POSIX and Windows systems.
- memory-mapped-file? Xprocedure
Returns #t, if X is an object representing a memory mapped file, or #f otherwise.
- map-file-to-memory ADDRESS LEN PROTECTION FLAG FILENO #!optional OFFSETprocedure
Maps a section of a file to memory using the C function mmap(). ADDRESS should be a foreign pointer object or #f; LEN specifies the size of the section to be mapped; PROTECTION should be one or more of the flags prot/read, prot/write, prot/exec or prot/none bitwise-iored together; FLAG should be one or more of the flags map/fixed, map/shared, map/private, map/anonymous or map/file; FILENO should be the file-descriptor of the mapped file. The optional argument OFFSET gives the offset of the section of the file to be mapped and defaults to 0. This procedure returns an object representing the mapped file section. The procedure move-memory! can be used to access the mapped memory.
- memory-mapped-file-pointer MMAPprocedure
Returns a machine pointer to the start of the memory region to which the file is mapped.
- unmap-file-from-memory MMAP #!optional LENprocedure
Unmaps the section of a file mapped to memory using the C function munmap(). MMAP should be a mapped file as returned by the procedure map-file-to-memory. The optional argument LEN specifies the length of the section to be unmapped and defaults to the complete length given when the file was mapped.
;; example-mmap.scm ;; ;; basic example of memory mapped I/O ;; ;; This example does no error checking or cleanup, and serves ;; only to demonstrate how the mmap functions work together. ;; (use memory-mapped-files) (use posix lolevel) ; open a file using the posix module, so we have the file descriptor. (let* ((fd (file-open "example-mmap.scm" (+ open/rdonly open/nonblock))) ; fstat(2) the file descriptor fd to determine its size (size (file-size fd)) ; mmap(2) the file for reading. (mmap (map-file-to-memory #f size prot/read (+ map/file map/shared) fd)) ; return a pointer object to the beginning of the memory map. (buf (memory-mapped-file-pointer mmap)) ; allocate a string the same size as the file. (str (make-string size))) ; copy the mapped memory into a string (move-memory! buf str size) (display str) ; alternately, print the string byte-by-byte without copying. (let loop ((p buf) (i 0)) (unless (= i size) (display (integer->char (pointer-s8-ref p))) (loop (pointer+ p 1) (+ i 1)))))
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- Fix build on Haiku and other platforms without MAP_FILE
- Fixed Windows build.
- Extracted from posix core library unit and released as an egg.