service/vendor/github.com/bytedance/sonic/ast/visitor.go

316 lines
9.2 KiB
Go

/*
* Copyright 2021 ByteDance Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ast
import (
`encoding/json`
`github.com/bytedance/sonic/internal/native/types`
)
// Visitor handles the callbacks during preorder traversal of a JSON AST.
//
// According to the JSON RFC8259, a JSON AST can be defined by
// the following rules without separator / whitespace tokens.
//
// JSON-AST = value
// value = false / null / true / object / array / number / string
// object = begin-object [ member *( member ) ] end-object
// member = string value
// array = begin-array [ value *( value ) ] end-array
//
type Visitor interface {
// OnNull handles a JSON null value.
OnNull() error
// OnBool handles a JSON true / false value.
OnBool(v bool) error
// OnString handles a JSON string value.
OnString(v string) error
// OnInt64 handles a JSON number value with int64 type.
OnInt64(v int64, n json.Number) error
// OnFloat64 handles a JSON number value with float64 type.
OnFloat64(v float64, n json.Number) error
// OnObjectBegin handles the beginning of a JSON object value with a
// suggested capacity that can be used to make your custom object container.
//
// After this point the visitor will receive a sequence of callbacks like
// [string, value, string, value, ......, ObjectEnd].
//
// Note:
// 1. This is a recursive definition which means the value can
// also be a JSON object / array described by a sequence of callbacks.
// 2. The suggested capacity will be 0 if current object is empty.
// 3. Currently sonic use a fixed capacity for non-empty object (keep in
// sync with ast.Node) which might not be very suitable. This may be
// improved in future version.
OnObjectBegin(capacity int) error
// OnObjectKey handles a JSON object key string in member.
OnObjectKey(key string) error
// OnObjectEnd handles the ending of a JSON object value.
OnObjectEnd() error
// OnArrayBegin handles the beginning of a JSON array value with a
// suggested capacity that can be used to make your custom array container.
//
// After this point the visitor will receive a sequence of callbacks like
// [value, value, value, ......, ArrayEnd].
//
// Note:
// 1. This is a recursive definition which means the value can
// also be a JSON object / array described by a sequence of callbacks.
// 2. The suggested capacity will be 0 if current array is empty.
// 3. Currently sonic use a fixed capacity for non-empty array (keep in
// sync with ast.Node) which might not be very suitable. This may be
// improved in future version.
OnArrayBegin(capacity int) error
// OnArrayEnd handles the ending of a JSON array value.
OnArrayEnd() error
}
// VisitorOptions contains all Visitor's options. The default value is an
// empty VisitorOptions{}.
type VisitorOptions struct {
// OnlyNumber indicates parser to directly return number value without
// conversion, then the first argument of OnInt64 / OnFloat64 will always
// be zero.
OnlyNumber bool
}
var defaultVisitorOptions = &VisitorOptions{}
// Preorder decodes the whole JSON string and callbacks each AST node to visitor
// during preorder traversal. Any visitor method with an error returned will
// break the traversal and the given error will be directly returned. The opts
// argument can be reused after every call.
func Preorder(str string, visitor Visitor, opts *VisitorOptions) error {
if opts == nil {
opts = defaultVisitorOptions
}
// process VisitorOptions first to guarantee that all options will be
// constant during decoding and make options more readable.
var (
optDecodeNumber = !opts.OnlyNumber
)
tv := &traverser{
parser: Parser{
s: str,
noLazy: true,
skipValue: false,
},
visitor: visitor,
}
if optDecodeNumber {
tv.parser.decodeNumber(true)
}
err := tv.decodeValue()
if optDecodeNumber {
tv.parser.decodeNumber(false)
}
return err
}
type traverser struct {
parser Parser
visitor Visitor
}
// NOTE: keep in sync with (*Parser).Parse method.
func (self *traverser) decodeValue() error {
switch val := self.parser.decodeValue(); val.Vt {
case types.V_EOF:
return types.ERR_EOF
case types.V_NULL:
return self.visitor.OnNull()
case types.V_TRUE:
return self.visitor.OnBool(true)
case types.V_FALSE:
return self.visitor.OnBool(false)
case types.V_STRING:
return self.decodeString(val.Iv, val.Ep)
case types.V_DOUBLE:
return self.visitor.OnFloat64(val.Dv,
json.Number(self.parser.s[val.Ep:self.parser.p]))
case types.V_INTEGER:
return self.visitor.OnInt64(val.Iv,
json.Number(self.parser.s[val.Ep:self.parser.p]))
case types.V_ARRAY:
return self.decodeArray()
case types.V_OBJECT:
return self.decodeObject()
default:
return types.ParsingError(-val.Vt)
}
}
// NOTE: keep in sync with (*Parser).decodeArray method.
func (self *traverser) decodeArray() error {
sp := self.parser.p
ns := len(self.parser.s)
/* check for EOF */
self.parser.p = self.parser.lspace(sp)
if self.parser.p >= ns {
return types.ERR_EOF
}
/* check for empty array */
if self.parser.s[self.parser.p] == ']' {
self.parser.p++
if err := self.visitor.OnArrayBegin(0); err != nil {
return err
}
return self.visitor.OnArrayEnd()
}
/* allocate array space and parse every element */
if err := self.visitor.OnArrayBegin(_DEFAULT_NODE_CAP); err != nil {
return err
}
for {
/* decode the value */
if err := self.decodeValue(); err != nil {
return err
}
self.parser.p = self.parser.lspace(self.parser.p)
/* check for EOF */
if self.parser.p >= ns {
return types.ERR_EOF
}
/* check for the next character */
switch self.parser.s[self.parser.p] {
case ',':
self.parser.p++
case ']':
self.parser.p++
return self.visitor.OnArrayEnd()
default:
return types.ERR_INVALID_CHAR
}
}
}
// NOTE: keep in sync with (*Parser).decodeObject method.
func (self *traverser) decodeObject() error {
sp := self.parser.p
ns := len(self.parser.s)
/* check for EOF */
self.parser.p = self.parser.lspace(sp)
if self.parser.p >= ns {
return types.ERR_EOF
}
/* check for empty object */
if self.parser.s[self.parser.p] == '}' {
self.parser.p++
if err := self.visitor.OnObjectBegin(0); err != nil {
return err
}
return self.visitor.OnObjectEnd()
}
/* allocate object space and decode each pair */
if err := self.visitor.OnObjectBegin(_DEFAULT_NODE_CAP); err != nil {
return err
}
for {
var njs types.JsonState
var err types.ParsingError
/* decode the key */
if njs = self.parser.decodeValue(); njs.Vt != types.V_STRING {
return types.ERR_INVALID_CHAR
}
/* extract the key */
idx := self.parser.p - 1
key := self.parser.s[njs.Iv:idx]
/* check for escape sequence */
if njs.Ep != -1 {
if key, err = unquote(key); err != 0 {
return err
}
}
if err := self.visitor.OnObjectKey(key); err != nil {
return err
}
/* expect a ':' delimiter */
if err = self.parser.delim(); err != 0 {
return err
}
/* decode the value */
if err := self.decodeValue(); err != nil {
return err
}
self.parser.p = self.parser.lspace(self.parser.p)
/* check for EOF */
if self.parser.p >= ns {
return types.ERR_EOF
}
/* check for the next character */
switch self.parser.s[self.parser.p] {
case ',':
self.parser.p++
case '}':
self.parser.p++
return self.visitor.OnObjectEnd()
default:
return types.ERR_INVALID_CHAR
}
}
}
// NOTE: keep in sync with (*Parser).decodeString method.
func (self *traverser) decodeString(iv int64, ep int) error {
p := self.parser.p - 1
s := self.parser.s[iv:p]
/* fast path: no escape sequence */
if ep == -1 {
return self.visitor.OnString(s)
}
/* unquote the string */
out, err := unquote(s)
if err != 0 {
return err
}
return self.visitor.OnString(out)
}