codec: json: leading zeros are not allowed in decimal numbers

Fixes #408

codec/codec_test.go

@@ -4193,9 +4193,9 @@ func doTestJsonLargeInteger(t *testing.T, h Handle) {
 	var d *Decoder = NewDecoderBytes(nil, jh)
 	for _, v := range []tt{
 		{"0", true, true, 0, 0},
-		{"0000", true, true, 0, 0},
+		{"0000", false, false, 0, 0},
 		{"0.00e+2", true, true, 0, 0},
-		{"000e-2", true, true, 0, 0},
+		{"000e-2", false, false, 0, 0},
 		{"0.00e-2", true, true, 0, 0},
 
 		{"9223372036854775807", true, true, math.MaxInt64, math.MaxInt64},                             // maxint64
@@ -4384,7 +4384,6 @@ func doTestJsonNumberParsing(t *testing.T, h Handle) {
 			}
 			// try decoding it a uint64 or int64
 			fint, ffrac = math.Modf(f)
-			// xdebug2f(">> fint: %v (ffrac: %v) as uint64: %v as float64: %v", fint, ffrac, uint64(fint), float64(uint64(fint)))
 			bv = strconv.AppendFloat(bv[:0], fint, 'E', prec, 64)
 			if f < 0 || fint != float64(uint64(fint)) {
 				goto F64i

codec/decimal.go

@@ -234,6 +234,10 @@ func parseFloat64_custom(b []byte) (f float64, err error) {
 }
 
 func parseUint64_simple(b []byte) (n uint64, ok bool) {
+	if len(b) > 1 && b[0] == '0' { // punt on numbers with leading zeros
+		return
+	}
+
 	var i int
 	var n1 uint64
 	var c uint8
@@ -384,13 +388,23 @@ func readFloat(s []byte, y floatinfo) (r readFloatResult) {
 		i++
 	}
 
-	// we considered punting early if string has length > maxMantDigits, but this doesn't account
+	// considered punting early if string has length > maxMantDigits, but doesn't account
 	// for trailing 0's e.g. 700000000000000000000 can be encoded exactly as it is 7e20
 
 	var nd, ndMant, dp int8
 	var sawdot, sawexp bool
 	var xu uint64
 
+	if i+1 < slen && s[i] == '0' {
+		switch s[i+1] {
+		case '.', 'e', 'E':
+			// ok
+		default:
+			r.bad = true
+			return
+		}
+	}
+
 LOOP:
 	for ; i < slen; i++ {
 		switch s[i] {