Handle CRLF and Unicode line endings in read-line

* libguile/rdelim.c (scm_read_line): handle CRLF, LS and PS
* module/ice-9/suspendable-ports.scm (read-line): handle CRLF, LS, and PS
* module/web/http.scm (read-header-line): take advantage of CRLF in read-line
   (read-header): don't need to test for \return
* test-suite/tests/rdelim.test: new tests for read-line CRLF, LS and PS
* doc/ref/api-io.texi: update doc for read-line

doc/ref/api-io.texi

@@ -755,8 +755,10 @@ a specified set of characters.
 
 @deffn {Scheme Procedure} read-line [port] [handle-delim]
 Return a line of text from @var{port} if specified, otherwise from the
-value returned by @code{(current-input-port)}.  Under Unix, a line of text
+value returned by @code{(current-input-port)}.  Under Unix, a line of
-is terminated by the first end-of-line character or by end-of-file.
+text is terminated by the first end-of-line character or by end-of-file.
+The end-of-line characters handled are newline, carriage return plus
+newline, or the Unicode line or paragraph separators.
 
 If @var{handle-delim} is specified, it should be one of the following
 symbols:
@@ -771,7 +773,9 @@ Append the terminating delimiter (if any) to the returned string.
 Push the terminating delimiter (if any) back on to the port.
 @item split
 Return a pair containing the string read from the port and the
-terminating delimiter or end-of-file object.
+terminating delimiter or end-of-file object.  The delimiter will either
+be a single character for newline or the Unicode line or paragraph
+separators, or it will be the string @code{"\r\n"}.
 @end table
 @end deffn
 

libguile/rdelim.c

@@ -112,10 +112,11 @@ SCM_DEFINE (scm_read_delimited_x, "%read-delimited!", 3, 3, 0,
 
 SCM_DEFINE (scm_read_line, "%read-line", 0, 1, 0, 
             (SCM port),
-	    "Read a newline-terminated line from @var{port}, allocating storage as\n"
+	    "Read a line from @var{port}, allocating storage as necessary.\n"
-	    "necessary.  The newline terminator (if any) is removed from the string,\n"
+	    "The terminator (if any) is removed from the string,\n"
 	    "and a pair consisting of the line and its delimiter is returned.  The\n"
-	    "delimiter may be either a newline or the @var{eof-object}; if\n"
+	    "delimiter may be either a newline, return + newline, the Unicode\n"
+            "line or paragraph separators, or the @var{eof-object}; if\n"
 	    "@code{%read-line} is called at the end of file, it returns the pair\n"
 	    "@code{(#<eof> . #<eof>)}.")
 #define FUNC_NAME s_scm_read_line
@@ -127,6 +128,7 @@ SCM_DEFINE (scm_read_line, "%read-line", 0, 1, 0,
   SCM line, strings, result;
   scm_t_wchar buf[LINE_BUFFER_SIZE], delim;
   size_t index;
+  int cr = 0;
 
   if (SCM_UNBNDP (port))
     port = scm_current_input_port ();
@@ -152,12 +154,24 @@ SCM_DEFINE (scm_read_line, "%read-line", 0, 1, 0,
 	  buf[index] = scm_getc (port);
 	  switch (buf[index])
 	    {
-	    case EOF:
 	    case '\n':
 	      delim = buf[index];
               break;
 
+            case EOF:
+            case 0x2028:        /* U+2028 LINE SEPARATOR */
+            case 0x2029:        /* U+2029 PARAGRAPH SEPARATOR */
+              cr = 0;
+              delim = buf[index];
+              break;
+
+            case '\r':
+              cr = 1;
+              index ++;
+              break;
+
 	    default:
+              cr = 0;
 	      index++;
 	    }
 	}
@@ -165,20 +179,33 @@ SCM_DEFINE (scm_read_line, "%read-line", 0, 1, 0,
   while (delim == 0);
 
   if (SCM_LIKELY (scm_is_false (strings)))
+    {
       /* The fast path.  */
+      if (cr)
+        line = scm_from_utf32_stringn (buf, index - 1);
+      else
         line = scm_from_utf32_stringn (buf, index);
+    }
   else
     {
       /* Aggregate the intermediary results.  */
+      if (cr)
+        strings = scm_cons (scm_from_utf32_stringn (buf, index - 1), strings);
+      else
         strings = scm_cons (scm_from_utf32_stringn (buf, index), strings);
       line = scm_string_concatenate (scm_reverse (strings));
     }
 
   if (delim == EOF && scm_i_string_length (line) == 0)
     result = scm_cons (SCM_EOF_VAL, SCM_EOF_VAL);
+  else
+    {
+      if (cr)
+        result = scm_cons (line, scm_from_latin1_string("\r\n"));
       else
         result = scm_cons (line,
                            delim == EOF ? SCM_EOF_VAL : SCM_MAKE_CHAR (delim));
+    }
 
   return result;
 #undef LINE_BUFFER_SIZE

module/ice-9/suspendable-ports.scm

@@ -1,5 +1,5 @@
 ;;; Ports, implemented in Scheme
-;;; Copyright (C) 2016, 2019 Free Software Foundation, Inc.
+;;; Copyright (C) 2016, 2018, 2021 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 License as
@@ -689,10 +689,81 @@
 
 (define* (read-line #:optional (port (current-input-port))
                     (handle-delim 'trim))
-  (read-delimited "\n" port handle-delim))
+  (let* ((line/delim	(%read-line port))
+	 (line		(car line/delim))
+	 (delim		(cdr line/delim)))
+    (case handle-delim
+      ((trim) line)
+      ((split) line/delim)
+      ((concat) (if (and (string? line) (char? delim))
+		    (string-append line (string delim))
+		    line))
+      ((peek) (if (char? delim)
+		  (unread-char delim port))
+	      line)
+      (else
+       (error "unexpected handle-delim value: " handle-delim)))))
 
 (define* (%read-line port)
-  (read-line port 'split))
+  (let ((LINE_BUFFER_SIZE 256))
+    (let ((strings #f)
+          (result #f)
+          (buf (make-string LINE_BUFFER_SIZE #\nul))
+          (delim #f)
+          (index 0)
+          (cr #f)
+          (go #t))
+      (cond
+       ((not (input-port? port))
+        (error "Not an input port." port))
+       (else
+        (while go
+               (cond
+                ((>= index LINE_BUFFER_SIZE)
+                 (set! strings (cons (substring buf 0 index)
+                                     (or strings '())))
+                 (set! index 0))
+                (else
+                 (let ((c (read-char port)))
+                   (cond
+                    ((or (eof-object? c)
+                         (char=? c #\x2028)  ; U+2028 LINE SEPARATOR
+                         (char=? c #\x2029)) ; U+2029 PARAGRAPH SEPARATOR
+                     (set! cr #f)
+                     (set! delim c))
+                    ((char=? c #\newline)
+                     (set! delim c))
+                    ((char=? c #\return)
+                     (set! cr #t)
+                     (string-set! buf index c)
+                     (set! index (1+ index)))
+                    (else
+                     (set! cr #f)
+                     (string-set! buf index c)
+                     (set! index (1+ index)))))))
+
+               (if (or (eof-object? delim)
+                       (char? delim))
+                   (set! go #f)))
+      (let ((line (if (not strings)
+                      ;; A short string.
+                      (if cr
+                          (substring buf 0 (1- index))
+                          (substring buf 0 index))
+                      ;; Else, aggregate the intermediary results.
+                      (begin
+                        (if cr
+                            (set! strings (cons (substring buf 0 (1- index)) strings))
+                            (set! strings (cons (substring buf 0 index) strings)))
+                        (apply string-append (reverse strings))))))
+
+        (if (and (eof-object? delim)
+                 (zero? (string-length line)))
+            (cons the-eof-object the-eof-object)
+            ;; Else
+            (if cr
+                (cons line "\r\n")
+                (cons line delim)))))))))
 
 (define* (put-string port str #:optional (start 0)
                      (count (- (string-length str) start)))

module/web/http.scm

@@ -157,13 +157,12 @@ The default writer will call ‘put-string’."
 Raise a 'bad-header' exception if the line does not end in CRLF or LF,
 or if EOF is reached."
   (match (%read-line port)
+    (((? string? line) . "\r\n")
+     line)
     (((? string? line) . #\newline)
-     ;; '%read-line' does not consider #\return a delimiter; so if it's
+     ;; We are more tolerant than the RFC in that we tolerate LF-only
-     ;; there, remove it.  We are more tolerant than the RFC in that we
+     ;; endings.
-     ;; tolerate LF-only endings.
+     line)
-     (if (string-suffix? "\r" line)
-         (string-drop-right line 1)
-         line))
     ((line . _)                                ;EOF or missing delimiter
      (bad-header 'read-header-line line))))
 
@@ -184,8 +183,7 @@ was known but the value was invalid.
 Returns the end-of-file object for both values if the end of the message
 body was reached (i.e., a blank line)."
   (let ((line (read-header-line port)))
-    (if (or (string-null? line)
+    (if (string-null? line)
-            (string=? line "\r"))
         (values *eof* *eof*)
         (let* ((delim (or (string-index line #\:)
                           (bad-header '%read line)))

test-suite/tests/rdelim.test

@@ -1,7 +1,7 @@
 ;;;; rdelim.test --- Delimited I/O.      -*- mode: scheme; coding: utf-8; -*-
 ;;;; Ludovic Courtès <ludo@gnu.org>
 ;;;;
-;;;; 	Copyright (C) 2011, 2013, 2014 Free Software Foundation, Inc.
+;;;; 	Copyright (C) 2011, 2013, 2014, 2021 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
@@ -62,6 +62,46 @@
                          (read-line p 'split)))
            (eof-object? (read-line p)))))
 
+  (pass-if "two lines, split, CRLF"
+    (let* ((s "foo\r\nbar\r\n")
+           (p (open-input-string s)))
+      (and (equal? '(("foo" . "\r\n")
+                     ("bar" . "\r\n"))
+                   (list (read-line p 'split)
+                         (read-line p 'split)))
+           (eof-object? (read-line p)))))
+
+  (pass-if "two long lines, split, CRLF"
+    ;; Must be longer than 256 codepoints
+    (let* ((text0 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+           (text1 (string-append text0 text0 text0 text0 text0))
+           (text2 (string-append text1 "\r\n" text1 "\r\n")))
+      (let* ((s text2)
+             (p (open-input-string s)))
+        (and (equal? `((,text1 . "\r\n")
+                       (,text1 . "\r\n"))
+                     (list (read-line p 'split)
+                           (read-line p 'split)))
+             (eof-object? (read-line p))))))
+
+  (pass-if "two lines, split, LS"
+    (let* ((s "foo\u2028bar\u2028")
+           (p (open-input-string s)))
+      (and (equal? '(("foo" . #\x2028)
+                     ("bar" . #\x2028))
+                   (list (read-line p 'split)
+                         (read-line p 'split)))
+           (eof-object? (read-line p)))))
+
+  (pass-if "two lines, split, PS"
+    (let* ((s "foo\u2029bar\u2029")
+           (p (open-input-string s)))
+      (and (equal? '(("foo" . #\x2029)
+                     ("bar" . #\x2029))
+                   (list (read-line p 'split)
+                         (read-line p 'split)))
+           (eof-object? (read-line p)))))
+
   (pass-if "two Greek lines, trim"
     (let* ((s "λαμβδα\nμυ\n")
            (p (open-input-string s)))