specialized-io

Description

Fast I/O procedures specialized for different types. Instead of using the Scheme procedure read, specialized procedures can be used, so:

The table below is a simple comaprison done in one system. (This is not a real benchmark; it is just meant to give an approximate idea of what the speedup could be, and even then, the results on a different machine could be diferent!)

                scheme    specialized-io   speedup
-------------------------------------------------
write fixnum     6.516      4.396          1.4823
read  fixnum     27.98      6.304          4.4385

write flonum     9.596      6.076          1.5793
read  flonum    99.396      5.776          17.208

write complex  155.092     20.776          7.4650
read  complex   212.08     22.776          9.3116
-------------------------------------------------

The source for the benchmarks is in the subversion repository.

Author

Jeronimo Pellegrini

Requirements

Example

(use specialized-io)

(let ((v (read-flonum (current-input-port))))
  (write-flonum (fp* 2.5 v) (current-output-port)))

Note that you can use fp* with a value returned from read-flonum (it's guaranteed to be a flonum).

Documentation

[procedure] (read-fixnum PORT)
[procedure] (read-flonum PORT)
[procedure] (read-complex PORT)
[procedure] (read-one-char PORT)

These procedures read one object of a specific type from an input-port. There are no runtime checks in the Scheme way; the procedures will just call error if anything goes wront (EOF, lexical error etc).

[procedure] (write-fixnum VALUE PORT)
[procedure] (write-flonum VALUE PORT)
[procedure] (write-complex VALUE PORT)
[procedure] (write-one-char VALUE PORT)

These procedures write one object of a specific type to an output-port. There are no runtime checks in the Scheme way; the procedures will just call error if anything goes wront (EOF, lexical error etc).

[procedure] (write-one-string STRING PORT)

This procedure writes a string to the output port.

[procedure] (read-string-until CHAR PORT)
[procedure] (read-string-between LEFTCHAR RIGHTCHAR PORT)

These procedures read a string from the input port. read-string-until will read from the current position of the stream until CHAR is found (and CHAR will be included in the resulting string). read-string-between will first search for LEFTCHAR then read until RIGHTCHAR is found.

[parameter] specialized-io-error

This variable should be bound to a procedure that will be called when parsing fails. By default it's bound to error. To change it, call (specialized-io some-other-error-procedure).

[parameter] +specialized-io-string-buffer-size+

This is the size of the buffer in which strings are read. When the buffer becomes full, its size is doubled. This default value is 500. To change it, call (+specialized-io-string-buffer-size+ N), where N is the desired buffer size.

Limitations

The procedures in this egg are not safe. They may crash if called with arguments different form the expected. In particular, the ports that may be passed to these procedures are those bound to C file descriptors: files, standard input/ourput/error, etc. They do not work, for example, with string ports.

More examples

Create a file named "in", with the following content:

10
1.2 1.3 .14 4.2 .5 6.6 7.0 00 0.0 10.0

The code below will read the numbers in the file and put them in a vector.

(use specialized-io)
(use srfi-4)

(define port (open-input-file "in"))

(let ((n (read-fixnum port)))
  (let ((vec (make-f64vector n)))
    (do ((i 0 (fx+ 1 i)))
        ((fx= i n))
      (f64vector-set! vec i (read-flonum port)))
    vec))

==> #f64(1.2 1.3 0.14 4.2 0.5 6.6 7.0 0.0 0.0 10.0)

Changelog

License

 Copyright (c) 2010, 2011, 2012 Jeronimo C. Pellegrini
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