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pointer.go
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pointer.go
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package jsonpointer
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"strconv"
"strings"
)
type Pointer []string
var ErrInvalidPointerFormat = errors.New("invalid format")
var (
tokenEncoder *strings.Replacer
tokenDecoder *strings.Replacer
)
func init() {
tokenEncoder = strings.NewReplacer("~", "~0", "/", "~1")
tokenDecoder = strings.NewReplacer("~1", "/", "~0", "~")
}
func NewPointer(tokens ...interface{}) Pointer {
return Pointer{}.Child(tokens...)
}
func (p *Pointer) Parse(s string) error {
if len(s) == 0 {
*p = Pointer{}
return nil
}
if s[0] != '/' {
return ErrInvalidPointerFormat
}
parts := strings.Split(s[1:], "/")
tokens := make([]string, len(parts))
for i, part := range parts {
tokens[i] = decodeToken(part)
}
*p = Pointer(tokens)
return nil
}
func (p *Pointer) MustParse(s string) {
if err := p.Parse(s); err != nil {
panic(fmt.Sprintf("invalid json pointer %q: %v", s, err))
}
}
func (p Pointer) String() string {
var buf bytes.Buffer
for _, token := range p {
buf.WriteByte('/')
buf.WriteString(encodeToken(token))
}
return buf.String()
}
func (p Pointer) MarshalJSON() ([]byte, error) {
return json.Marshal(p.String())
}
func (p *Pointer) UnmarshalJSON(data []byte) error {
var s string
if err := json.Unmarshal(data, &s); err != nil {
return err
}
return p.Parse(s)
}
func (p *Pointer) Prepend(tokens ...string) {
*p = append(Pointer(tokens), *p...)
}
func (p *Pointer) Append(tokens ...string) {
*p = append(*p, tokens...)
}
func (p Pointer) Parent() Pointer {
if len(p) == 0 {
panic("empty pointer")
}
return append(Pointer{}, p[:len(p)-1]...)
}
func (p Pointer) Child(tokens ...interface{}) Pointer {
p2 := append(Pointer{}, p...)
for _, token := range tokens {
switch v := token.(type) {
case string:
p2 = append(p2, v)
case int:
p2 = append(p2, strconv.Itoa(v))
case Pointer:
p2 = append(p2, v...)
default:
panic(fmt.Sprintf("invalid json pointer token %#v (%T)",
token, token))
}
}
return p2
}
func (p Pointer) Find(value interface{}) interface{} {
v := value
for _, token := range p {
switch tv := v.(type) {
case []interface{}:
i, err := strconv.ParseInt(token, 10, 64)
if err != nil {
return nil
}
if i < 0 || i >= int64(len(tv)) {
return nil
}
v = tv[i]
case map[string]interface{}:
child, found := tv[token]
if !found {
return nil
}
v = child
default:
return nil
}
}
return v
}
func encodeToken(s string) string {
return tokenEncoder.Replace(s)
}
func decodeToken(s string) string {
return tokenDecoder.Replace(s)
}