Hi, I've been playing with nio lately and it's been quite fun to delve
in lower level stuff again, didn't do that in a long time. I've
translated a small example, just to read a file, and the result is
performing really well. Here's the code:
(defn read-file [#^String f #^String cs #^Integer buffer-size]
(with-open [cin (. (new FileInputStream f) getChannel)]
(let [buffer (. ByteBuffer (allocate buffer-size))
char-buffer (. ByteBuffer (allocate buffer-size))
charset (. Charset (forName cs))
decoder (. charset (newDecoder))
sb (new StringBuilder)
read #(. cin (read buffer))]
(loop [r (read)]
(if (= r -1)
(str sb)
(do
(. buffer flip)
(. sb (append (. decoder (decode buffer))))
(. buffer clear)
(recur (read))))))))
And a couple of micro-benchmarks in Windows XP SP3:
nio=> (time (dotimes [n 1000] (read-file ".emacs" "ISO-8859-1" 8192)))
"Elapsed time: 284.693456 msecs"
nio=> (time (dotimes [n 1000] (read-file ".emacs" "ISO-8859-1" 8192)))
"Elapsed time: 280.79918 msecs"
nio=> (time (dotimes [n 1000] (read-file ".emacs" "ISO-8859-1" 8192)))
"Elapsed time: 284.62619 msecs"
nio=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 530.622305 msecs"
nio=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 531.319221 msecs"
nio=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 527.439793 msecs"
And in Debian Linux 5.0:
user=> (time (dotimes [n 1000] (nio/read-file ".emacs" "ISO-8859-1"
8192)))
"Elapsed time: 243.364117 msecs"
user=> (time (dotimes [n 1000] (nio/read-file ".emacs" "ISO-8859-1"
8192)))
"Elapsed time: 247.718237 msecs"
user=> (time (dotimes [n 1000] (nio/read-file ".emacs" "ISO-8859-1"
8192)))
"Elapsed time: 246.027863 msecs"
user=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 320.073016 msecs"
user=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 309.658266 msecs"
user=> (time (dotimes [n 1000] (slurp ".emacs")))
"Elapsed time: 318.926749 msecs"
Things to note:
* Playing with buffer size obviously changes the results, still the
nio version always outperformed slurp in my tests. The smallest buffer
size I tried was 1024 bytes.
* The Debian machine is a virtual one running under Windows.
* Windows java is Sun's JDK version 1.6.0_06.
* Linux java is OpenJDK version 1.6.0_0.
- budu
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