fix and enhance stringToCm to parse LOC RR optional fields (#1148)

Automatically submitted.

parse_test.go

@@ -415,6 +415,67 @@ func TestParseLOC(t *testing.T) {
 	}
 }
 
+// this tests a subroutine for the LOC RR parser.  It's complicated enough to test separately.
+func TestStringToCm(t *testing.T) {
+	tests := []struct {
+		// Test description: the input token and the expected return values from stringToCm.
+		token string
+		e     uint8
+		m     uint8
+		ok    bool
+	}{
+		{"100", 4, 1, true},
+		{"0100", 4, 1, true}, // leading 0 (allowed)
+		{"100.99", 4, 1, true},
+		{"90000000", 9, 9, true},
+		{"90000000.00", 9, 9, true},
+		{"0", 0, 0, true},
+		{"0.00", 0, 0, true},
+		{"0.01", 0, 1, true},
+		{".01", 0, 1, true}, // empty 'meter' part (allowed)
+		{"0.1", 1, 1, true},
+
+		// out of range (too large)
+		{"90000001", 0, 0, false},
+		{"90000000.01", 0, 0, false},
+
+		// more than 2 digits in 'cmeter' part
+		{"0.000", 0, 0, false},
+		{"0.001", 0, 0, false},
+		{"0.999", 0, 0, false},
+		// with plus or minus sign (disallowed)
+		{"-100", 0, 0, false},
+		{"+100", 0, 0, false},
+		{"0.-10", 0, 0, false},
+		{"0.+10", 0, 0, false},
+		{"0a.00", 0, 0, false}, // invalid string for 'meter' part
+		{".1x", 0, 0, false},   // invalid string for 'cmeter' part
+		{".", 0, 0, false},     // empty 'cmeter' part (disallowed)
+		{"1.", 0, 0, false},    // ditto
+		{"m", 0, 0, false},     // only the "m" suffix
+	}
+	for _, tc := range tests {
+		tc := tc
+		t.Run(tc.token, func(t *testing.T) {
+			// In all cases the expected result is the same with or without the 'm' suffix.
+			// So we test both cases using the same test code.
+			for _, sfx := range []string{"", "m"} {
+				token := tc.token + sfx
+				e, m, ok := stringToCm(token)
+				if ok != tc.ok {
+					t.Fatal("unexpected validation result")
+				}
+				if m != tc.m {
+					t.Fatalf("Expected %d, got %d", tc.m, m)
+				}
+				if e != tc.e {
+					t.Fatalf("Expected %d, got %d", tc.e, e)
+				}
+			}
+		})
+	}
+}
+
 func TestParseDS(t *testing.T) {
 	dt := map[string]string{
 		"example.net. 3600 IN DS 40692 12 3 22261A8B0E0D799183E35E24E2AD6BB58533CBA7E3B14D659E9CA09B 2071398F": "example.net.\t3600\tIN\tDS\t40692 12 3 22261A8B0E0D799183E35E24E2AD6BB58533CBA7E3B14D659E9CA09B2071398F",

scan.go

@@ -1210,11 +1210,29 @@ func stringToCm(token string) (e, m uint8, ok bool) {
 		if cmeters, err = strconv.Atoi(s[1]); err != nil {
 			return
 		}
+		// There's no point in having more than 2 digits in this part, and would rather make the implementation complicated ('123' should be treated as '12').
+		// So we simply reject it.
+		// We also make sure the first character is a digit to reject '+-' signs.
+		if len(s[1]) > 2 || s[1][0] < '0' || s[1][0] > '9' {
+			return
+		}
+		if len(s[1]) == 1 {
+			// 'nn.1' must be treated as 'nn-meters and 10cm, not 1cm.
+			cmeters *= 10
+		}
+		if len(s[0]) == 0 {
+			// This will allow omitting the 'meter' part, like .01 (meaning 0.01m = 1cm).
+			break
+		}
 		fallthrough
 	case 1:
 		if meters, err = strconv.Atoi(s[0]); err != nil {
 			return
 		}
+		// RFC1876 states the max value is 90000000.00.  The latter two conditions enforce it.
+		if s[0][0] < '0' || s[0][0] > '9' || meters > 90000000 || (meters == 90000000 && cmeters != 0) {
+			return
+		}
 	case 0:
 		// huh?
 		return 0, 0, false
@@ -1227,13 +1245,10 @@ func stringToCm(token string) (e, m uint8, ok bool) {
 		e = 0
 		val = cmeters
 	}
-	for val > 10 {
+	for val >= 10 {
 		e++
 		val /= 10
 	}
-	if e > 9 {
-		ok = false
-	}
 	m = uint8(val)
 	return
 }