[svn] Document what is meant by "non-printable" in the context of escnonprint.

src/ChangeLog

@@ -1,3 +1,9 @@
+2005-05-05  Hrvoje Niksic  <hniksic@xemacs.org>
+
+	* log.c (copy_and_escape): Replace the FOR_URI argument with a
+	slightly more general mechanism for specifying different kinds of
+	escape.
+
 2005-05-05  Hrvoje Niksic  <hniksic@xemacs.org>
 
 	* ftp-basic.c (ftp_response): Fix printing FTP server response.

src/log.c

@@ -635,46 +635,65 @@ count_nonprint (const char *source)
   return cnt;
 }
 
-/* Copy SOURCE to DEST, escaping non-printable characters.  If FOR_URI
+/* Copy SOURCE to DEST, escaping non-printable characters.
-   is 0, they are escaped as \ooo; otherwise, they are escaped as
+
-   %xx.
+   Non-printable refers to anything outside the non-control ASCII
+   range (32-126) which means that, for example, CR, LF, and TAB are
+   considered non-printable along with ESC and other control chars.
+   This is by design: it makes sure that messages from remote servers
+   cannot be used to deceive the users by mimicking Wget's output.
+   Disallowing non-ASCII characters is another necessary security
+   measure, which makes sure that remote servers cannot garble the
+   screen or guess the local charset and perform homographic attacks.
+
+   Of course, the above means that escnonprint must only be used in
+   decidedly ASCII-only context, such as when printing host names,
+   responses from HTTP headers, messages coming from FTP servers, and
+   the like.
+
+   ESCAPE is the character used to introduce the escape sequence.
+   BASE should be the base of the escape sequence, and must be either
+   8 for octal or 16 for hex.
 
    DEST must point to a location with sufficient room to store an
    encoded version of SOURCE.  */
 
 static void
-copy_and_escape (const char *source, char *dest, int for_uri)
+copy_and_escape (const char *source, char *dest, char escape, int base)
 {
   const char *from;
   char *to;
 
-  /* Copy the string, escaping non-printable chars. */
+  /* Copy the string from SOURCE to DEST, escaping non-printable chars. */
-  if (!for_uri)
+  switch (base)
     {
+    case 8:
       for (from = source, to = dest; *from; from++)
 	if (ISPRINT (*from))
 	  *to++ = *from;
 	else
 	  {
 	    const unsigned char c = *from;
-	    *to++ = '\\';
+	    *to++ = escape;
 	    *to++ = '0' + (c >> 6);
 	    *to++ = '0' + ((c >> 3) & 7);
 	    *to++ = '0' + (c & 7);
 	  }
-    }
+      break;
-  else
+    case 16:
-    {
       for (from = source, to = dest; *from; from++)
 	if (ISPRINT (*from))
 	  *to++ = *from;
 	else
 	  {
 	    const unsigned char c = *from;
-	    *to++ = '%';
+	    *to++ = escape;
 	    *to++ = XNUM_TO_DIGIT (c >> 4);
 	    *to++ = XNUM_TO_DIGIT (c & 0xf);
 	  }
+      break;
+    default:
+      abort ();
     }
   *to = '\0';
 }
@@ -687,10 +706,12 @@ struct ringel {
 static struct ringel ring[RING_SIZE];	/* ring data */
 
 static const char *
-escnonprint_internal (const char *str, int for_uri)
+escnonprint_internal (const char *str, char escape, int base)
 {
   static int ringpos;		        /* current ring position */
 
+  assert (base == 8 || base == 16);
+
   int nprcnt = count_nonprint (str);
   if (nprcnt == 0)
     /* If there are no non-printable chars in STR, don't bother
@@ -702,11 +723,11 @@ escnonprint_internal (const char *str, int for_uri)
        simply r->X instead of ring[ringpos].X. */
     struct ringel *r = ring + ringpos;
 
-    /* Every non-printable character is replaced with "\ooo",
+    /* Every non-printable character is replaced with the escape char
-       i.e. with three *additional* chars (two in URI-mode).  Size
+       and three (or two, depending on BASE) *additional* chars.  Size
-       must also include the length of the original string and an
+       must also include the length of the original string and one
        additional char for the terminating \0. */
-    int needed_size = strlen (str) + 1 + (for_uri ? 2 * nprcnt : 3 * nprcnt);
+    int needed_size = strlen (str) + 1 + (base == 8 ? 3 * nprcnt : 2 * nprcnt);
 
     /* If the current buffer is uninitialized or too small,
        (re)allocate it.  */
@@ -716,7 +737,7 @@ escnonprint_internal (const char *str, int for_uri)
 	r->size = needed_size;
       }
 
-    copy_and_escape (str, r->buffer, for_uri);
+    copy_and_escape (str, r->buffer, escape, base);
     ringpos = (ringpos + 1) % RING_SIZE;
     return r->buffer;
   }
@@ -724,7 +745,8 @@ escnonprint_internal (const char *str, int for_uri)
 
 /* Return a pointer to a static copy of STR with the non-printable
    characters escaped as \ooo.  If there are no non-printable
-   characters in STR, STR is returned.
+   characters in STR, STR is returned.  See copy_and_escape for more
+   information on which characters are considered non-printable.
 
    NOTE: since this function can return a pointer to static data, be
    careful to copy its result before calling it again.  However, to be
@@ -736,12 +758,13 @@ escnonprint_internal (const char *str, int for_uri)
 const char *
 escnonprint (const char *str)
 {
-  return escnonprint_internal (str, 0);
+  return escnonprint_internal (str, '\\', 8);
 }
 
 /* Return a pointer to a static copy of STR with the non-printable
    characters escaped as %XX.  If there are no non-printable
-   characters in STR, STR is returned.
+   characters in STR, STR is returned.  See copy_and_escape for more
+   information on which characters are considered non-printable.
 
    This function returns a pointer to static data which will be
    overwritten by subsequent calls -- see escnonprint for details.  */
@@ -749,7 +772,7 @@ escnonprint (const char *str)
 const char *
 escnonprint_uri (const char *str)
 {
-  return escnonprint_internal (str, 1);
+  return escnonprint_internal (str, '%', 16);
 }
 
 void