Function truncateMidEscape

json_fuzz_test.go:649–676

truncateMidEscape cuts inside a \uXXXX escape sequence. This is the truncated_escape_sequence class: the parser's Unescape routine must detect the truncated escape and return MalformedStringEscapeError.

(r *rand.Rand, data []byte)

// truncated_escape_sequence class: the parser's Unescape routine must
// detect the truncated escape and return MalformedStringEscapeError.
func truncateMidEscape(r *rand.Rand, data []byte) []byte {
	var cuts []int
	for i := 0; i+1 < len(data); i++ {
		if data[i] != '\\' || data[i+1] != 'u' {
			continue
		}
		// \uXXXX is 6 bytes. Cut somewhere in [i+2, i+6).
		lo := i + 2
		hi := i + 6
		if hi > len(data) {
			hi = len(data)
		}
		if hi > lo {
			cuts = append(cuts, lo+r.Intn(hi-lo))
		}
	}
	if len(cuts) == 0 {
		// No \u escape present; inject a truncated one and exercise the path.
		out := make([]byte, 0, len(data)+5)
		out = append(out, data...)
		out = append(out, '"', '\\', 'u', '3', '0')
		return out
	}
	cut := cuts[r.Intn(len(cuts))]
	out := make([]byte, cut)
	copy(out, data[:cut])
	return out
}

// truncateMidElement cuts inside an array element, after a '[' or ','. The
// truncated_mid_element class: the parser must not read past the cut when