Fix invalid pointer arithmetic.

[nmh] / sbr / base64.c

diff --git a/sbr/base64.c b/sbr/base64.c
index 995f955692d4fec5b69384c9cef30cc48d0bbaba..cbd225dee062c60fa42ebb8415350bc17cb4f835 100644 (file)
--- a/sbr/base64.c
+++ b/sbr/base64.c
@@ -13,6 +13,17 @@
 static const char nib2b64[0x40+1] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
+/*
+ * Copy data from one file to another, converting to base64-encoding.
+ *
+ * Arguments include:
+ *
+ * in          - Input filehandle (unencoded data)
+ * out         - Output filename (base64-encoded data)
+ * crlf                - If set, output encoded CRLF for every LF on input.
+ *
+ * Returns OK on success, NOTOK otherwise.
+ */
 int
 writeBase64aux (FILE *in, FILE *out, int crlf)
 {
@@ -227,7 +238,13 @@ static const unsigned char b642nib[0x80] = {
 
 /*
  * Decode a base64 string.  The result, decoded, must be freed by the caller.
- * See description of arguments with declaration in h/prototypes.h.
+ *
+ * encoded      - the string to be decoded
+ * decoded      - the decoded bytes
+ * len          - number of decoded bytes
+ * skip-crs     - non-zero for text content, and for which CR's should be
+ *                skipped
+ * digest       - for an MD5 digest, it can be null
  */
 int
 decodeBase64 (const char *encoded, unsigned char **decoded, size_t *len,
@@ -307,12 +324,9 @@ test_end:
     }
 
     if (! self_delimiting  &&  bitno != 18) {
-        int i;
-
         /* Show some context for the error. */
-        for (i = 0; i < 20  &&  cp > encoded; ++i, --cp) {}
-        inform("premature ending (bitno %d) near %s", bitno,
-                cp ? cp : encoded);
+        cp -= min(cp - encoded, 20);
+        inform("premature ending (bitno %d) near %s", bitno, cp);
         charstring_free (decoded_c);
         *decoded = NULL;