[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: read-all ?
Re: read-all ?
Tue, 22 Jan 2013 11:01:35 +0100
Gnus/5.130005 (Ma Gnus v0.5) Emacs/24.2 (gnu/linux)
Andy Wingo <address@hidden> skribis:
> On Tue 22 Jan 2013 10:15, Andy Wingo <address@hidden> writes:
>> Patch attached. I didn't update the docs because it wasn't clear to me
>> that (ice-9 rdelim) is actually the right place to put it.
>> What do you think? Should we perhaps put it in a new (ice-9 ports)?
I would avoid adding a new module, unless there are other things to put
>> Are the names right?
‘read-all’ doesn’t convey the idea that it’s textual (unlike the R6RS
Perhaps ‘port-contents-as-string’, or ‘read-all-string’, or...?
> +(define* (read-all! buf #:optional
> + (port (current-input-port))
> + (start 0) (end (string-length buf)))
> + "Read all of the characters out of PORT and write them to BUF.
> +Returns the number of characters read.
> +This function only reads out characters from PORT if it will be able to
> +write them to BUF. That is to say, if BUF is smaller than the number of
> +available characters, then BUF will be filled, and characters will be
> +left in the port."
> + (check-arg buf (string? buf) "not a string")
> + (check-arg start (index? start) "bad index")
> + (check-arg end (index? end) "bad index")
> + (check-arg start (<= start end) "start beyond end")
> + (check-arg end (<= end (string-length buf)) "end beyond string length")
> + (let lp ((n start))
> + (if (< n end)
> + (let ((c (read-char port)))
> + (if (eof-object? c)
> + (- n start)
> + (begin
> + (string-set! buf n c)
> + (lp (1+ n)))))
> + (- n start))))
As you note, this is fairly inefficient, like ‘get-string-n!’.
Given that ‘string-set!’ is (unduly) costly, I wonder if consing all the
chars and then calling ‘list->string’ wouldn’t be more efficient in time
(it’d be less efficient in space.)