utils: Do not return eof if matched at beginning.

* email/utils.scm (read-while, read-bytes-till): Do not return eof if
matched at beginning. Return empty string or bytevector respectively.
* tests/utils.scm ("read-bytes-till returns empty bytevector on match
at beginning", "read-while returns empty string on match at
beginning"): New tests.

1 files changed, 12 insertions, 1 deletions

diff --git a/tests/utils.scm b/tests/utils.scm
index 7681c72..ce8fdb2 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -1,5 +1,5 @@
 ;;; guile-email --- Guile email parser
-;;; Copyright © 2019 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2019, 2020 Arun Isaac <arunisaac@systemreboot.net>
 ;;;
 ;;; This file is part of guile-email.
 ;;;
@@ -35,4 +35,15 @@
    (call-with-input-string ""
      (cut read-while <> read identity))))
 
+(test-equal "read-bytes-till returns empty bytevector on match at beginning"
+  (call-with-port (open-bytevector-input-port #vu8(1 2 3))
+    (cut read-bytes-till <> #vu8(1 2)))
+  #vu8())
+
+(test-equal "read-while returns empty string on match at beginning"
+  (call-with-input-string "foo\nbar"
+    (lambda (port)
+      (read-while port get-line (negate (cut string-prefix? "foo" <>)))))
+  "")
+
 (test-end "utils")