diff --git a/lib/base64.c b/lib/base64.c
index f3f7298aa..786b0f418 100644
--- a/lib/base64.c
+++ b/lib/base64.c
@@ -64,11 +64,11 @@ static const char b64c[64] =
 
 /* Base64 encode IN array of size INLEN into OUT array. OUT needs
    to be of length >= BASE64_LENGTH(INLEN), and INLEN needs to be
-   a multiple of 3.  */
+   a positive multiple of 3.  */
 static void
 base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out)
 {
-  while (inlen)
+  do
     {
       *out++ = b64c[to_uchar (in[0]) >> 2];
       *out++ = b64c[((to_uchar (in[0]) << 4) + (to_uchar (in[1]) >> 4)) & 0x3f];
@@ -78,6 +78,7 @@ base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out)
       inlen -= 3;
       in += 3;
     }
+  while (inlen);
 }
 
 /* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
@@ -88,6 +89,9 @@ void
 base64_encode (const char *restrict in, size_t inlen,
                char *restrict out, size_t outlen)
 {
+  if (!outlen)
+    return;
+
   /* Note this outlen constraint can be enforced at compile time.
      I.E. that the output buffer is exactly large enough to hold
      the encoded inlen bytes.  The inlen constraints (of corresponding
@@ -101,16 +105,17 @@ base64_encode (const char *restrict in, size_t inlen,
       return;
     }
 
-  while (inlen && outlen)
+  if (inlen)
+   while (true)
     {
       *out++ = b64c[to_uchar (in[0]) >> 2];
       if (!--outlen)
-        break;
+        return;
       *out++ = b64c[((to_uchar (in[0]) << 4)
                        + (--inlen ? to_uchar (in[1]) >> 4 : 0))
                       & 0x3f];
       if (!--outlen)
-        break;
+        return;
       *out++ =
         (inlen
          ? b64c[((to_uchar (in[1]) << 2)
@@ -118,18 +123,17 @@ base64_encode (const char *restrict in, size_t inlen,
                   & 0x3f]
          : '=');
       if (!--outlen)
-        break;
+        return;
       *out++ = inlen ? b64c[to_uchar (in[2]) & 0x3f] : '=';
       if (!--outlen)
+        return;
+      if (inlen <= 1)
         break;
-      if (inlen)
-        inlen--;
-      if (inlen)
-        in += 3;
+      inlen--;
+      in += 3;
     }
 
-  if (outlen)
-    *out = '\0';
+  *out = '\0';
 }
 
 /* Allocate a buffer and store zero terminated base64 encoded data