fuzz: prefer longer inputs

In general, the fuzzer does minimizes test cases.
Therefore, the fuzzing code barely sees long inputs.
Consequently, we have to tell the fuzzer that we like
long input values.

Author: Andreas Auernhammer

fuzz.go

@@ -61,6 +61,8 @@ func init() {
 	wStream = NewStream(c20p1305, BufSize)
 }
 
+var maxDataLen int
+
 func FuzzAll(data []byte) int {
 	v := FuzzReader(data)
 	v += FuzzReadByte(data)
@@ -69,6 +71,11 @@ func FuzzAll(data []byte) int {
 	v += FuzzWrite(data)
 	v += FuzzWriteByte(data)
 	v += FuzzReadFrom(data)
+
+	if len(data) > maxDataLen { // Prefer longer inputs
+		maxDataLen = len(data)
+		v += 1
+	}
 	return v
 }