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116 lines
5.4 KiB
116 lines
5.4 KiB
// Copyright 2023 The Go Authors. All rights reserved. |
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// Use of this source code is governed by a BSD-style |
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// license that can be found in the LICENSE file. |
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//go:build goexperiment.jsonv2 |
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// Package jsontext implements syntactic processing of JSON |
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// as specified in RFC 4627, RFC 7159, RFC 7493, RFC 8259, and RFC 8785. |
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// JSON is a simple data interchange format that can represent |
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// primitive data types such as booleans, strings, and numbers, |
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// in addition to structured data types such as objects and arrays. |
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// |
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// This package (encoding/json/jsontext) is experimental, |
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// and not subject to the Go 1 compatibility promise. |
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// It only exists when building with the GOEXPERIMENT=jsonv2 environment variable set. |
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// Most users should use [encoding/json]. |
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// |
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// The [Encoder] and [Decoder] types are used to encode or decode |
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// a stream of JSON tokens or values. |
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// |
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// # Tokens and Values |
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// |
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// A JSON token refers to the basic structural elements of JSON: |
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// |
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// - a JSON literal (i.e., null, true, or false) |
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// - a JSON string (e.g., "hello, world!") |
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// - a JSON number (e.g., 123.456) |
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// - a begin or end delimiter for a JSON object (i.e., '{' or '}') |
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// - a begin or end delimiter for a JSON array (i.e., '[' or ']') |
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// |
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// A JSON token is represented by the [Token] type in Go. Technically, |
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// there are two additional structural characters (i.e., ':' and ','), |
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// but there is no [Token] representation for them since their presence |
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// can be inferred by the structure of the JSON grammar itself. |
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// For example, there must always be an implicit colon between |
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// the name and value of a JSON object member. |
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// |
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// A JSON value refers to a complete unit of JSON data: |
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// |
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// - a JSON literal, string, or number |
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// - a JSON object (e.g., `{"name":"value"}`) |
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// - a JSON array (e.g., `[1,2,3,]`) |
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// |
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// A JSON value is represented by the [Value] type in Go and is a []byte |
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// containing the raw textual representation of the value. There is some overlap |
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// between tokens and values as both contain literals, strings, and numbers. |
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// However, only a value can represent the entirety of a JSON object or array. |
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// |
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// The [Encoder] and [Decoder] types contain methods to read or write the next |
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// [Token] or [Value] in a sequence. They maintain a state machine to validate |
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// whether the sequence of JSON tokens and/or values produces a valid JSON. |
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// [Options] may be passed to the [NewEncoder] or [NewDecoder] constructors |
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// to configure the syntactic behavior of encoding and decoding. |
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// |
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// # Terminology |
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// |
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// The terms "encode" and "decode" are used for syntactic functionality |
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// that is concerned with processing JSON based on its grammar, and |
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// the terms "marshal" and "unmarshal" are used for semantic functionality |
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// that determines the meaning of JSON values as Go values and vice-versa. |
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// This package (i.e., [jsontext]) deals with JSON at a syntactic layer, |
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// while [encoding/json/v2] deals with JSON at a semantic layer. |
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// The goal is to provide a clear distinction between functionality that |
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// is purely concerned with encoding versus that of marshaling. |
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// For example, one can directly encode a stream of JSON tokens without |
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// needing to marshal a concrete Go value representing them. |
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// Similarly, one can decode a stream of JSON tokens without |
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// needing to unmarshal them into a concrete Go value. |
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// |
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// This package uses JSON terminology when discussing JSON, which may differ |
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// from related concepts in Go or elsewhere in computing literature. |
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// |
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// - a JSON "object" refers to an unordered collection of name/value members. |
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// - a JSON "array" refers to an ordered sequence of elements. |
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// - a JSON "value" refers to either a literal (i.e., null, false, or true), |
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// string, number, object, or array. |
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// |
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// See RFC 8259 for more information. |
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// |
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// # Specifications |
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// |
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// Relevant specifications include RFC 4627, RFC 7159, RFC 7493, RFC 8259, |
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// and RFC 8785. Each RFC is generally a stricter subset of another RFC. |
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// In increasing order of strictness: |
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// |
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// - RFC 4627 and RFC 7159 do not require (but recommend) the use of UTF-8 |
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// and also do not require (but recommend) that object names be unique. |
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// - RFC 8259 requires the use of UTF-8, |
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// but does not require (but recommends) that object names be unique. |
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// - RFC 7493 requires the use of UTF-8 |
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// and also requires that object names be unique. |
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// - RFC 8785 defines a canonical representation. It requires the use of UTF-8 |
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// and also requires that object names be unique and in a specific ordering. |
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// It specifies exactly how strings and numbers must be formatted. |
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// |
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// The primary difference between RFC 4627 and RFC 7159 is that the former |
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// restricted top-level values to only JSON objects and arrays, while |
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// RFC 7159 and subsequent RFCs permit top-level values to additionally be |
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// JSON nulls, booleans, strings, or numbers. |
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// |
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// By default, this package operates on RFC 7493, but can be configured |
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// to operate according to the other RFC specifications. |
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// RFC 7493 is a stricter subset of RFC 8259 and fully compliant with it. |
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// In particular, it makes specific choices about behavior that RFC 8259 |
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// leaves as undefined in order to ensure greater interoperability. |
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// |
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// # Security Considerations |
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// |
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// See the "Security Considerations" section in [encoding/json/v2]. |
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package jsontext |
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// requireKeyedLiterals can be embedded in a struct to require keyed literals. |
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type requireKeyedLiterals struct{} |
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// nonComparable can be embedded in a struct to prevent comparability. |
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type nonComparable [0]func()
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