simplify id_decode()

src/id.c

@@ -28,6 +28,7 @@
 
 #include <string.h>
 #include <errno.h>
+#include <stdint.h>
 
 #include "vmod_blobcode.h"
 
@@ -69,23 +70,24 @@ id_decode(const enum encoding enc,
 	  ssize_t n, const char *restrict const p, va_list ap)
 {
 	char *dest = buf;
-	size_t len, outlen = 0;
+	size_t outlen = 0, c = SIZE_MAX;
 
 	(void) enc;
 	AN(buf);
 
-	for (const char *s = p; s != vrt_magic_string_end;
+	if (n >= 0)
+		c = n;
+
+	for (const char *s = p; c > 0 && s != vrt_magic_string_end;
 	     s = va_arg(ap, const char *)) {
+		size_t len;
+
 		if (s == NULL || *s == '\0')
 			continue;
 		len = strlen(s);
-		if (n >= 0) {
-			if (n == 0)
-				break;
-			if (len > n)
-				len = n;
-			n -= len;
-		}
+		if (len > c)
+			len = c;
+		c -= len;
 		if ((outlen += len) > buflen) {
 			errno = ENOMEM;
 			return -1;