Re: read-all ?

[Andy Wingo]

On Tue 22 Jan 2013 10:15, Andy Wingo <address@hidden> writes:

> Hi,
>
> On Sat 12 Jan 2013 22:22, address@hidden (Ludovic Courtès) writes:
>
>> Andy Wingo <address@hidden> skribis:
>>
>>> I find myself writing (read-delimited "" p) to slurp in a file as a
>>> string, but it's not a very straightforward way to say that.
>>>
>>> What about `read-all'?  We could add it to `(ice-9 rdelim)', I guess.
>>> R6RS calls this `read-string-all'.
>>
>> Sounds like a good idea.
>
> 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)?
> Are the names right?
>
> I started by writing it in C but I noticed the C was doing a very stupid
> get-and-set algorithm, so I figured it got no advantage and we should
> just write it in Scheme from the get-go.
>
> Andy

>From 056c69dee301f346d172293b71dfdc66ddfa0282 Mon Sep 17 00:00:00 2001
From: Andy Wingo <address@hidden>
Date: Tue, 22 Jan 2013 10:12:59 +0100
Subject: [PATCH] add read-all and read-all! to (ice-9 rdelim)

* module/ice-9/rdelim.scm (read-all!, read-all): New functions.
* test-suite/tests/rdelim.test: Add tests.
---
 module/ice-9/rdelim.scm      |   52 +++++++++++++++++++++++++++++++++++++-
 test-suite/tests/rdelim.test |   57 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 106 insertions(+), 3 deletions(-)

diff --git a/module/ice-9/rdelim.scm b/module/ice-9/rdelim.scm
index c6ab2ba..9938942 100644
--- a/module/ice-9/rdelim.scm
+++ b/module/ice-9/rdelim.scm
@@ -1,6 +1,6 @@
 ;;; installed-scm-file
 
-;;;; Copyright (C) 1997, 1999, 2000, 2001, 2006, 2010 Free Software 
Foundation, Inc.
+;;;; Copyright (C) 1997, 1999, 2000, 2001, 2006, 2010, 2013 Free Software 
Foundation, Inc.
 ;;;; 
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -26,6 +26,8 @@
             read-line!
             read-delimited
             read-delimited!
+            read-all
+            read-all!
             %read-delimited!
             %read-line
             write-line))
@@ -114,6 +116,54 @@
             (else (error "unexpected handle-delim value: "
                          handle-delim)))))))))
 
+(define-syntax-rule (check-arg arg exp message)
+  (unless exp
+    (error message arg)))
+
+(define (index? n)
+  (and (integer? n) (exact? n) (>= n 0)))
+
+(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))))
+
+(define* (read-all #:optional (port (current-input-port)))
+  "Read all of the characters out of PORT and return them as a string."
+  (let loop ((substrings '())
+             (total-chars 0)
+             (buf-size 100))           ; doubled each time through.
+    (let* ((buf (make-string buf-size))
+           (nchars (read-all! buf port))
+           (new-total (+ total-chars nchars)))
+      (cond
+       ((= nchars buf-size)
+        ;; buffer filled.
+        (loop (cons buf substrings) new-total (* buf-size 2)))
+       (else
+        (string-concatenate-reverse
+         (cons (substring buf 0 nchars) substrings)))))))
+
 ;;; read-line [PORT [HANDLE-DELIM]] reads a newline-terminated string
 ;;; from PORT.  The return value depends on the value of HANDLE-DELIM,
 ;;; which may be one of the symbols `trim', `concat', `peek' and
diff --git a/test-suite/tests/rdelim.test b/test-suite/tests/rdelim.test
index e61fc92..a102df6 100644
--- a/test-suite/tests/rdelim.test
+++ b/test-suite/tests/rdelim.test
@@ -1,7 +1,7 @@
 ;;;; rdelim.test --- Delimited I/O.      -*- mode: scheme; coding: utf-8; -*-
 ;;;; Ludovic Courtès <address@hidden>
 ;;;;
-;;;;   Copyright (C) 2011 Free Software Foundation, Inc.
+;;;;   Copyright (C) 2011, 2013 Free Software Foundation, Inc.
 ;;;;
 ;;;; This library is free software; you can redistribute it and/or
 ;;;; modify it under the terms of the GNU Lesser General Public
@@ -189,7 +189,60 @@
 
     (pass-if "eof, split"
       (eof-object? (read-delimited! ":" (make-string 7)
-                                    (open-input-string ""))))))
+                                    (open-input-string "")))))
+
+  (with-test-prefix "read-all"
+
+    (pass-if "short string"
+      (let* ((s "hello, world!")
+             (p (open-input-string s)))
+        (and (string=? (read-all p) s)
+             (string=? (read-all p) ""))))
+
+    (pass-if "100 chars"
+      (let* ((s (make-string 100 #\space))
+             (p (open-input-string s)))
+        (and (string=? (read-all p) s)
+             (string=? (read-all p) ""))))
+
+    (pass-if "longer than 100 chars"
+      (let* ((s (string-concatenate (make-list 20 "hello, world!")))
+             (p (open-input-string s)))
+        (and (string=? (read-all p) s)
+             (string=? (read-all p) "")))))
+
+  (with-test-prefix "read-all!"
+
+    (pass-if "buf smaller"
+      (let* ((s "hello, world!")
+             (len (1- (string-length s)))
+             (buf (make-string len #\.))
+             (p (open-input-string s)))
+        (and (= (read-all! buf p) len)
+             (string=? buf (substring s 0 len))
+             (= (read-all! buf p) 1)
+             (string=? (substring buf 0 1) (substring s len)))))
+
+    (pass-if "buf right size"
+      (let* ((s "hello, world!")
+             (len (string-length s))
+             (buf (make-string len #\.))
+             (p (open-input-string s)))
+        (and (= (read-all! buf p) len)
+             (string=? buf (substring s 0 len))
+             (= (read-all! buf p) 0)
+             (string=? buf (substring s 0 len)))))
+
+    (pass-if "buf bigger"
+      (let* ((s "hello, world!")
+             (len (string-length s))
+             (buf (make-string (1+ len) #\.))
+             (p (open-input-string s)))
+        (and (= (read-all! buf p) len)
+             (string=? (substring buf 0 len) s)
+             (= (read-all! buf p) 0)
+             (string=? (substring buf 0 len) s)
+             (string=? (substring buf len) "."))))))
 
 ;;; Local Variables:
 ;;; eval: (put 'with-test-prefix 'scheme-indent-function 1)
-- 
1.7.10.4

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