/
mmap.clj
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/
mmap.clj
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; Copyright (c) Chris Houser, April 2008. All rights reserved.
; The use and distribution terms for this software are covered by the
; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
; which can be found in the file epl-v10.html at the root of this distribution.
; By using this software in any fashion, you are agreeing to be bound by
; the terms of this license.
; You must not remove this notice, or any other, from this software.
; Functions for memory-mapping files, plus some functions that use a
; mmaped file for "normal" activies -- slurp, load-file, etc.
(ns
#^{:author "Chris Houser",
:doc "Functions for memory-mapping files, plus some functions that use a
mmaped file for \"normal\" activies -- slurp, load-file, etc."}
clojure.contrib.mmap
(:refer-clojure :exclude (slurp load-file))
(:import (java.nio ByteBuffer CharBuffer)
(java.io PushbackReader InputStream InputStreamReader
FileInputStream)))
;(set! *warn-on-reflection* true)
(def READ_ONLY #^{:private true}
(java.nio.channels.FileChannel$MapMode/READ_ONLY))
(defn mmap
"Memory-map the file named f. Returns a ByteBuffer."
[f]
(let [channel (.getChannel (FileInputStream. f))]
(.map channel READ_ONLY 0 (.size channel))))
(defn slurp
"Reads the file named by f and returns it as a string."
[#^String f]
(.. java.nio.charset.Charset (forName "UTF-8")
(newDecoder) (decode (mmap f))))
(defn buffer-stream
"Returns an InputStream for a ByteBuffer, such as returned by mmap."
[#^ByteBuffer buf]
(proxy [InputStream] []
(available [] (.remaining buf))
(read
([] (if (.hasRemaining buf) (.get buf) -1))
([dst offset len] (let [actlen (min (.remaining buf) len)]
(.get buf dst offset actlen)
(if (< actlen 1) -1 actlen))))))
(defn load-file [f]
"Like clojure.lang/load-file, but uses mmap internally."
(with-open [rdr (-> f mmap buffer-stream InputStreamReader. PushbackReader.)]
(load-reader rdr)))
(comment
(alias 'mmap 'clojure.contrib.mmap)
(alias 'core 'clojure.core)
;---
; zip_filter.clj is 95KB
(def tf "/home/chouser/build/clojure/src/clj/clojure/core.clj")
(println "\nload-file" tf)
(time (dotimes [_ 5] (core/load-file tf))) ; 5420.177813 msecs
(time (dotimes [_ 5] (mmap/load-file tf))) ; 7946.854434 msecs -- not so good
;---
; kern.log.0 is 961KB
(def tf "/var/log/kern.log.0")
(println "\nslurp" tf)
(time (dotimes [_ 10] (.length (core/slurp tf)))) ; 435.767226 msecs
(time (dotimes [_ 10] (.length (mmap/slurp tf)))) ; 93.176858 msecs
;---
; kern.log.0 is 961KB
(def tf "/var/log/kern.log.0")
(println "\nregex slurp large" tf)
(time (dotimes [_ 10] (count (re-seq #"EXT3.*" (core/slurp tf))))) ; 416
(time (dotimes [_ 10] (count (re-seq #"EXT3.*" (mmap/slurp tf))))) ; 101
;---
; mmap.clj is about 3.1KB
(def tf "/home/chouser/proj/clojure-contrib/src/clojure/contrib/mmap.clj")
(println "\nregex slurp small" tf)
(time (dotimes [_ 1000] (count (re-seq #"defn \S*" (core/slurp tf))))) ; 308
(time (dotimes [_ 1000] (count (re-seq #"defn \S*" (mmap/slurp tf))))) ; 198
)