Implement 'string-utf8-length' and 'scm_c_string_utf8_length'.

* libguile/strings.c (utf8_length, scm_c_string_utf8_length)
  (scm_string_utf8_length): New functions.
* libguile/strings.h (scm_c_string_utf8_length, scm_string_utf8_length):
  New prototypes.
* doc/ref/api-data.texi (Bytevectors as Strings): Add docs.
* doc/ref/guile.texi: Update manual copyright date to 2015.
* test-suite/tests/strings.test (string-utf8-length): Add tests.

doc/ref/api-data.texi

@@ -1,6 +1,6 @@
 @c -*-texinfo-*-
 @c This is part of the GNU Guile Reference Manual.
-@c Copyright (C)  1996, 1997, 2000-2004, 2006-2014
+@c Copyright (C)  1996, 1997, 2000-2004, 2006-2015
 @c   Free Software Foundation, Inc.
 @c See the file guile.texi for copying conditions.
 
@@ -4983,6 +4983,12 @@ in one of the most commonly available encoding formats.
 @result{} #vu8(99 97 102 195 169)
 @end lisp
 
+@deftypefn {Scheme Procedure} {} string-utf8-length str
+@deftypefnx {C function} SCM scm_string_utf8_length (str)
+@deftypefnx {C function} size_t scm_c_string_utf8_length (str)
+Return the number of bytes in the UTF-8 representation of @var{str}.
+@end deftypefn
+
 @deffn {Scheme Procedure} string->utf8 str
 @deffnx {Scheme Procedure} string->utf16 str [endianness]
 @deffnx {Scheme Procedure} string->utf32 str [endianness]

doc/ref/guile.texi

@@ -14,7 +14,7 @@
 This manual documents Guile version @value{VERSION}.
 
 Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2009,
-2010, 2011, 2012, 2013, 2014 Free Software Foundation.
+2010, 2011, 2012, 2013, 2014, 2015 Free Software Foundation.
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or

libguile/strings.c

@@ -1,5 +1,5 @@
 /* Copyright (C) 1995, 1996, 1998, 2000, 2001, 2004, 2006,
- *   2008-2015 Free Software Foundation, Inc.
+ *   2008-2016 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
@@ -2065,6 +2065,38 @@ u32_u8_length_in_bytes (const scm_t_uint32 *str, size_t len)
   return ret;
 }
 
+static size_t
+utf8_length (SCM str)
+{
+  if (scm_i_is_narrow_string (str))
+    return latin1_u8_strlen ((scm_t_uint8 *) scm_i_string_chars (str),
+                             scm_i_string_length (str));
+  else
+    return u32_u8_length_in_bytes
+      ((scm_t_uint32 *) scm_i_string_wide_chars (str),
+       scm_i_string_length (str));
+}
+
+size_t
+scm_c_string_utf8_length (SCM string)
+#define FUNC_NAME "scm_c_string_utf8_length"
+{
+  SCM_VALIDATE_STRING (1, string);
+  return utf8_length (string);
+}
+#undef FUNC_NAME
+
+SCM_DEFINE (scm_string_utf8_length, "string-utf8-length", 1, 0, 0,
+	    (SCM string),
+	    "Returns the number of bytes in the UTF-8 representation of "
+            "@var{string}.")
+#define FUNC_NAME s_scm_string_utf8_length
+{
+  SCM_VALIDATE_STRING (1, string);
+  return scm_from_size_t (utf8_length (string));
+}
+#undef FUNC_NAME
+
 char *
 scm_to_utf8_stringn (SCM str, size_t *lenp)
 #define FUNC_NAME "scm_to_utf8_stringn"

libguile/strings.h

@@ -3,7 +3,8 @@
 #ifndef SCM_STRINGS_H
 #define SCM_STRINGS_H
 
-/* Copyright (C) 1995,1996,1997,1998,2000,2001, 2004, 2005, 2006, 2008, 2009, 2010, 2011, 2013 Free Software Foundation, Inc.
+/* Copyright (C) 1995-1998, 2000, 2001, 2004-2006, 2008-2011, 2013,
+ *   2015-2016 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
@@ -107,6 +108,7 @@ SCM_API SCM scm_string_p (SCM x);
 SCM_API SCM scm_string (SCM chrs);
 SCM_API SCM scm_make_string (SCM k, SCM chr);
 SCM_API SCM scm_string_length (SCM str);
+SCM_API SCM scm_string_utf8_length (SCM str);
 SCM_API SCM scm_string_bytes_per_char (SCM str);
 SCM_API SCM scm_string_ref (SCM str, SCM k);
 SCM_API SCM scm_string_set_x (SCM str, SCM k, SCM chr);
@@ -120,6 +122,7 @@ SCM_API SCM scm_from_stringn (const char *str, size_t len, const char *encoding,
                               scm_t_string_failed_conversion_handler handler);
 SCM_API SCM scm_c_make_string (size_t len, SCM chr);
 SCM_API size_t scm_c_string_length (SCM str);
+SCM_API size_t scm_c_string_utf8_length (SCM str);
 SCM_API size_t scm_c_symbol_length (SCM sym);
 SCM_API SCM scm_c_string_ref (SCM str, size_t pos);
 SCM_API void scm_c_string_set_x (SCM str, size_t pos, SCM chr);

test-suite/tests/strings.test

@@ -1,8 +1,8 @@
 ;;;; strings.test --- test suite for Guile's string functions    -*- scheme -*-
 ;;;; Jim Blandy <jimb@red-bean.com> --- August 1999
 ;;;;
-;;;; Copyright (C) 1999, 2001, 2004, 2005, 2006, 2008, 2009, 2010,
+;;;; Copyright (C) 1999, 2001, 2004-2006, 2008-2011, 2013,
-;;;;   2011, 2013 Free Software Foundation, Inc.
+;;;;   2015 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
@@ -457,6 +457,22 @@
   (pass-if "compatibility composition is equal?"
     (equal? (string-normalize-nfkc "\u1e9b\u0323") "\u1e69")))
 
+;;
+;; string-utf8-length
+;;
+
+(with-test-prefix "string-utf8-length"
+
+  (pass-if-exception "wrong type argument"
+      exception:wrong-type-arg
+    (string-utf8-length 50))
+
+  (pass-if-equal 0 (string-utf8-length ""))
+  (pass-if-equal 1 (string-utf8-length "\0"))
+  (pass-if-equal 5 (string-utf8-length "hello"))
+  (pass-if-equal 7 (string-utf8-length "helloλ"))
+  (pass-if-equal 9 (string-utf8-length "ሠላም")))
+
 ;;
 ;; string-ref
 ;;