fix scm_to_utf8_stringn for wide strings to NUL-append the strings

* libguile/strings.c (u32_u8_strlen, scm_to_utf8_stringn): Sigh, fix the
  u32-to-u8 optimization to ensure that the utf8 string is
  NUL-terminated.

diff --git a/libguile/strings.c b/libguile/strings.c
index 494a658..a9e5afe 100644 (file)
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -1874,6 +1874,39 @@ latin1_to_u8 (const scm_t_uint8 *str, size_t latin_len,
   return u8_result;
 }
 
+/* From RFC 3629:
+
+   Char. number range  |        UTF-8 octet sequence
+      (hexadecimal)    |              (binary)
+   --------------------+---------------------------------------------
+   0000 0000-0000 007F | 0xxxxxxx
+   0000 0080-0000 07FF | 110xxxxx 10xxxxxx
+   0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
+   0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+*/
+
+static size_t
+u32_u8_strlen (const scm_t_uint32 *str, size_t len)
+{
+  size_t ret, i;
+
+  for (i = 0, ret = 0; i < len; i++)
+    {
+      scm_t_uint32 c = str[i];
+
+      if (c <= 0x7f)
+        ret += 1;
+      else if (c <= 0x7ff)
+        ret += 2;
+      else if (c <= 0xffff)
+        ret += 3;
+      else
+        ret += 4;
+    }
+
+  return ret;
+}
+
 char *
 scm_to_utf8_stringn (SCM str, size_t *lenp)
 {
@@ -1882,9 +1915,39 @@ scm_to_utf8_stringn (SCM str, size_t *lenp)
                                   scm_i_string_length (str),
                                   NULL, lenp);
   else
-    return (char *) u32_to_u8 ((scm_t_uint32*)scm_i_string_wide_chars (str),
-                               scm_i_string_length (str),
-                               NULL, lenp);
+    {
+      scm_t_uint8 *buf, *ret;
+      size_t len, allocated;
+
+      len = u32_u8_strlen ((scm_t_uint32*)scm_i_string_wide_chars (str),
+                           scm_i_string_length (str));
+      allocated = len + 1;
+      buf = scm_malloc (allocated);
+
+      ret = u32_to_u8 ((scm_t_uint32*)scm_i_string_wide_chars (str),
+                       scm_i_string_length (str), buf, &len);
+
+      if (ret == buf && len + 1 == allocated)
+        {
+          ret[len] = 0;
+          return (char *) ret;
+        }
+
+      /* An error: a bad codepoint.  */
+      {
+        int saved_errno = errno;
+
+        free (buf);
+        if (!saved_errno)
+          abort ();
+
+        scm_decoding_error ("scm_to_utf8_stringn", errno,
+                            "invalid codepoint in string", str);
+
+        /* Not reached.  */
+        return NULL;
+      }
+    }
 }
 
 scm_t_wchar *