30 lines
1,014 B
Markdown
30 lines
1,014 B
Markdown
# Cachet, a simple cache system for `mmap`
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Cachet is a small library that provides a simple cache system for page-by-page
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read access on a block device. The cache system requires a map function, which
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can correspond to [Unix.map_file].
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Here's a simple example using `Unix.map_file`:
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```ocaml
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let shared = true
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let empty = Bigarray.Array1.create Bigarray.char Bigarray.c_layout 0
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let map fd ~pos len =
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let stat = Unix.fstat fd in
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let len = Int.min len (stat.Unix.st_size - pos) in
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if pos < stat.Unix.st_size
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then let barr = Unix.map_file fd ~pos:(Int64.of_int pos)
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Bigarray.char Bigarray.c_layout shared [| len |] in
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Bigarray.array1_of_genarray barr
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else empty
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external getpagesize : unit -> int = "unix_getpagesize" [@noalloc]
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let () =
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let fd = Unix.openfile "disk.img" Unix.[ O_RDONLY ] 0o644 in
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let finally () = Unix.close fd in
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Fun.protect ~finally @@ fun () ->
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let cache = Cachet.make ~pagesize:(getpagesize ()) ~map fd in
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let seq = Cachet.get_seq cache 0 in
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...
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```
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