simplify base64_decode()

src/base64.c

@@ -132,11 +132,15 @@ base64_decode(const enum encoding dec, char *restrict const buf,
 	char *dest = buf;
 	unsigned u = 0, term = 0;
 	int n = 0;
+	size_t len = SIZE_MAX;
 
 	AN(buf);
 	AN(alpha);
 
-	for (const char *s = p; s != vrt_magic_string_end;
+	if (inlen >= 0)
+		len = inlen;
+
+	for (const char *s = p; len > 0 && s != vrt_magic_string_end;
 	     s = va_arg(ap, const char *)) {
 		if (s == NULL)
 			continue;
@@ -144,7 +148,7 @@ base64_decode(const enum encoding dec, char *restrict const buf,
 			errno = EINVAL;
 			return -1;
 		}
-		while (*s && (inlen == -1 || inlen > 0)) {
+		while (*s && len) {
 			while (n < 4) {
 				char b = alpha->i64[(unsigned) *s++];
 				u <<= 6;
@@ -158,11 +162,8 @@ base64_decode(const enum encoding dec, char *restrict const buf,
 					continue;
 				}
 				u |= (unsigned) b;
-				if (inlen != -1) {
-					--inlen;
-					if (inlen == 0)
-						break;
-				}
+				if (--len == 0)
+					break;
 				if (!*s)
 					break;
 			}
@@ -172,8 +173,6 @@ base64_decode(const enum encoding dec, char *restrict const buf,
 				n = 0;
 			}
 		}
-		if (inlen != -1 && inlen == 0)
-			break;
 	}
 	if (n) {
 		if (!alpha->padding)