Subject: Re: fast io
From: Erik Naggum <>
Date: 1997/01/20
Newsgroups: comp.lang.lisp
Message-ID: <>

* Bjorn Borud
| I am looking for ways to read and write blocks of data fast in Scheme or
| Common Lisp, but I can only find per-character IO-routines or, at best,
| per-line.  what I would like to do is to read entire files using read()
| or equivalent -- or perhaps something like mmap().

ANSI Common Lisp has `read-sequence' and `write-sequence'.  I have answered
the exact same question from somebody else from GUARDIAN.NO in no.lisp, and
I don't feel like translating.  however, here's the code I suggested:

  (let ((block (make-array '(8192) :element-type 'character)))
    (with-open-file (stream <file> :element-type 'character)
      ... (read-sequence block stream) ...))

in Franz, Inc's, Allegro Common Lisp 4.3 for Unix, this uses the `read'
system call directly from file descriptor to the block, at least as far as
I can determine, and it also returns the same value as the `read' system
call returned.

in Allegro, you can also give an array static allocation, so you are
guaranteed that it won't be moved during garbage collection

I have not seen anything that supports `mmap', and I can't offhand see how
I could do it work since `mmap' interacts with memory in weird ways and I
don't know how or if that would upset Allegro.  it might be a trivial
question of using the Foreign Function Interface extension to Common Lisp.
I don't have time to investigate that right now.

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