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