1 files changed, 192 insertions, 0 deletions
diff --git a/internal/encoding/json/decode_token.go b/internal/encoding/json/decode_token.go
new file mode 100644
index 00000000..50578d65
--- /dev/null
+++ b/internal/encoding/json/decode_token.go
@@ -0,0 +1,192 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+)
+
+// Kind represents a token kind expressible in the JSON format.
+type Kind uint16
+
+const (
+	Invalid Kind = (1 << iota) / 2
+	EOF
+	Null
+	Bool
+	Number
+	String
+	Name
+	ObjectOpen
+	ObjectClose
+	ArrayOpen
+	ArrayClose
+
+	// comma is only for parsing in between tokens and
+	// does not need to be exported.
+	comma
+)
+
+func (k Kind) String() string {
+	switch k {
+	case EOF:
+		return "eof"
+	case Null:
+		return "null"
+	case Bool:
+		return "bool"
+	case Number:
+		return "number"
+	case String:
+		return "string"
+	case ObjectOpen:
+		return "{"
+	case ObjectClose:
+		return "}"
+	case Name:
+		return "name"
+	case ArrayOpen:
+		return "["
+	case ArrayClose:
+		return "]"
+	case comma:
+		return ","
+	}
+	return "<invalid>"
+}
+
+// Token provides a parsed token kind and value.
+//
+// Values are provided by the difference accessor methods. The accessor methods
+// Name, Bool, and ParsedString will panic if called on the wrong kind. There
+// are different accessor methods for the Number kind for converting to the
+// appropriate Go numeric type and those methods have the ok return value.
+type Token struct {
+	// Token kind.
+	kind Kind
+	// pos provides the position of the token in the original input.
+	pos int
+	// raw bytes of the serialized token.
+	// This is a subslice into the original input.
+	raw []byte
+	// boo is parsed boolean value.
+	boo bool
+	// str is parsed string value.
+	str string
+}
+
+// Kind returns the token kind.
+func (t Token) Kind() Kind {
+	return t.kind
+}
+
+// RawString returns the read value in string.
+func (t Token) RawString() string {
+	return string(t.raw)
+}
+
+// Pos returns the token position from the input.
+func (t Token) Pos() int {
+	return t.pos
+}
+
+// Name returns the object name if token is Name, else it panics.
+func (t Token) Name() string {
+	if t.kind == Name {
+		return t.str
+	}
+	panic(fmt.Sprintf("Token is not a Name: %v", t.RawString()))
+}
+
+// Bool returns the bool value if token kind is Bool, else it panics.
+func (t Token) Bool() bool {
+	if t.kind == Bool {
+		return t.boo
+	}
+	panic(fmt.Sprintf("Token is not a Bool: %v", t.RawString()))
+}
+
+// ParsedString returns the string value for a JSON string token or the read
+// value in string if token is not a string.
+func (t Token) ParsedString() string {
+	if t.kind == String {
+		return t.str
+	}
+	panic(fmt.Sprintf("Token is not a String: %v", t.RawString()))
+}
+
+// Float returns the floating-point number if token kind is Number.
+//
+// The floating-point precision is specified by the bitSize parameter: 32 for
+// float32 or 64 for float64. If bitSize=32, the result still has type float64,
+// but it will be convertible to float32 without changing its value. It will
+// return false if the number exceeds the floating point limits for given
+// bitSize.
+func (t Token) Float(bitSize int) (float64, bool) {
+	if t.kind != Number {
+		return 0, false
+	}
+	f, err := strconv.ParseFloat(t.RawString(), bitSize)
+	if err != nil {
+		return 0, false
+	}
+	return f, true
+}
+
+// Int returns the signed integer number if token is Number.
+//
+// The given bitSize specifies the integer type that the result must fit into.
+// It returns false if the number is not an integer value or if the result
+// exceeds the limits for given bitSize.
+func (t Token) Int(bitSize int) (int64, bool) {
+	s, ok := t.getIntStr()
+	if !ok {
+		return 0, false
+	}
+	n, err := strconv.ParseInt(s, 10, bitSize)
+	if err != nil {
+		return 0, false
+	}
+	return n, true
+}
+
+// Uint returns the signed integer number if token is Number.
+//
+// The given bitSize specifies the unsigned integer type that the result must
+// fit into. It returns false if the number is not an unsigned integer value
+// or if the result exceeds the limits for given bitSize.
+func (t Token) Uint(bitSize int) (uint64, bool) {
+	s, ok := t.getIntStr()
+	if !ok {
+		return 0, false
+	}
+	n, err := strconv.ParseUint(s, 10, bitSize)
+	if err != nil {
+		return 0, false
+	}
+	return n, true
+}
+
+func (t Token) getIntStr() (string, bool) {
+	if t.kind != Number {
+		return "", false
+	}
+	parts, ok := parseNumberParts(t.raw)
+	if !ok {
+		return "", false
+	}
+	return normalizeToIntString(parts)
+}
+
+// TokenEquals returns true if given Tokens are equal, else false.
+func TokenEquals(x, y Token) bool {
+	return x.kind == y.kind &&
+		x.pos == y.pos &&
+		bytes.Equal(x.raw, y.raw) &&
+		x.boo == y.boo &&
+		x.str == y.str
+}