io.crlf: add a word that reads an optional CR.

basis/io/crlf/crlf-docs.factor

@@ -9,4 +9,8 @@ HELP: crlf
 
 HELP: read-crlf
 { $values { "seq" sequence } }
-{ $description "Reads until the next CRLF (carriage return followed by line feed) from the current input stream, throwing an error if there is not a CRLF remaining, or if CR is present without immediately being followed by LF." } ;
+{ $description "Reads until the next CRLF (carriage return followed by line feed) from the current input stream, throwing an error if CR is present without immediately being followed by LF." } ;
+
+HELP: read-?crlf
+{ $values { "seq" sequence } }
+{ $description "Reads until the next LF (line feed) or CRLF (carriage return followed by line feed) from the current input stream, throwing an error if CR is present without immediately being followed by LF." } ;

basis/io/crlf/crlf-tests.factor

@@ -6,3 +6,8 @@ USING: io.crlf tools.test io.streams.string io ;
 [ "Hello, world.\r" [ read-crlf ] with-string-reader ] must-fail
 [ f ] [ "" [ read-crlf ] with-string-reader ] unit-test
 [ "" ] [ "\r\n" [ read-crlf ] with-string-reader ] unit-test
+
+[ "foo\r" [ read-?crlf ] with-string-reader ] must-fail
+[ f ] [ "" [ read-?crlf ] with-string-reader ] unit-test
+[ "" ] [ "\n" [ read-?crlf ] with-string-reader ] unit-test
+[ "foo" ] [ "foo\n" [ read-?crlf ] with-string-reader ] unit-test

basis/io/crlf/crlf.factor

@@ -9,3 +9,7 @@ IN: io.crlf
 : read-crlf ( -- seq )
     "\r" read-until
     [ CHAR: \r assert= read1 CHAR: \n assert= ] [ f like ] if* ;
+
+: read-?crlf ( -- seq )
+    "\r\n" read-until
+    [ CHAR: \r = [ read1 CHAR: \n assert= ] when ] [ f like ] if* ;