json source pure

JSON Parser

The JSON parser is a package that provides functionality for parsing and processing JSON strings. This package accepts JSON strings as byte slices.

Currently, gno does not support the reflect package, so it cannot retrieve type information at runtime. Therefore, it is designed to infer and handle type information when parsing JSON strings using a state machine approach.

After passing through the state machine, JSON strings are represented as the Node type. The Node type represents nodes for JSON data, including various types such as ObjectNode, ArrayNode, StringNode, NumberNode, BoolNode, and NullNode.

This package provides methods for manipulating, searching, and extracting the Node type.

State Machine

To parse JSON strings, a finite state machine approach is used. The state machine transitions to the next state based on the current state and the input character while parsing the JSON string. Through this method, type information can be inferred and processed without reflect, and the amount of parser code can be significantly reduced.

The image below shows the state transitions of the state machine according to the states and input characters.

stateDiagram-v2
    [*] --> __: Start
    __ --> ST: String
    __ --> MI: Number
    __ --> ZE: Zero
    __ --> IN: Integer
    __ --> T1: Boolean (true)
    __ --> F1: Boolean (false)
    __ --> N1: Null
    __ --> ec: Empty Object End
    __ --> cc: Object End
    __ --> bc: Array End
    __ --> co: Object Begin
    __ --> bo: Array Begin
    __ --> cm: Comma
    __ --> cl: Colon
    __ --> OK: Success/End
    ST --> OK: String Complete
    MI --> OK: Number Complete
    ZE --> OK: Zero Complete
    IN --> OK: Integer Complete
    T1 --> OK: True Complete
    F1 --> OK: False Complete
    N1 --> OK: Null Complete
    ec --> OK: Empty Object Complete
    cc --> OK: Object Complete
    bc --> OK: Array Complete
    co --> OB: Inside Object
    bo --> AR: Inside Array
    cm --> KE: Expecting New Key
    cm --> VA: Expecting New Value
    cl --> VA: Expecting Value
    OB --> ST: String in Object (Key)
    OB --> ec: Empty Object
    OB --> cc: End Object
    AR --> ST: String in Array
    AR --> bc: End Array
    KE --> ST: String as Key
    VA --> ST: String as Value
    VA --> MI: Number as Value
    VA --> T1: True as Value
    VA --> F1: False as Value
    VA --> N1: Null as Value
    OK --> [*]: End

Examples

This package provides parsing functionality along with encoding and decoding functionality. The following examples demonstrate how to use this package.

Decoding

Decoding (or Unmarshaling) is the functionality that converts an input byte slice JSON string into a Node type.

The converted Node type allows you to modify the JSON data or search and extract data that meets specific conditions.

 1package main
 2
 3import (
 4    "gno.land/p/demo/json"
 5    "gno.land/p/nt/ufmt/v0"
 6)
 7
 8func main() {
 9    node, err := json.Unmarshal([]byte(`{"foo": "var"}`))
10    if err != nil {
11        ufmt.Errorf("error: %v", err)
12    }
13
14    ufmt.Sprintf("node: %v", node)
15}

Encoding

Encoding (or Marshaling) is the functionality that converts JSON data represented as a Node type into a byte slice JSON string.

⚠️ Caution: Converting a large Node type into a JSON string may impact performance. or might be cause unexpected behavior.

 1package main
 2
 3import (
 4    "gno.land/p/demo/json"
 5    "gno.land/p/nt/ufmt/v0"
 6)
 7
 8func main() {
 9    node := ObjectNode("", map[string]*Node{
10        "foo": StringNode("foo", "bar"),
11        "baz": NumberNode("baz", 100500),
12        "qux": NullNode("qux"),
13    })
14
15    b, err := json.Marshal(node)
16    if err != nil {
17        ufmt.Errorf("error: %v", err)
18    }
19
20    ufmt.Sprintf("json: %s", string(b))
21}

Searching

Once the JSON data converted into a Node type, you can search and extract data that satisfy specific conditions. For example, you can find data with a specific type or data with a specific key.

To use this functionality, you can use methods in the GetXXX prefixed methods. The MustXXX methods also provide the same functionality as the former methods, but they will panic if data doesn't satisfies the condition.

Here is an example of finding data with a specific key. For more examples, please refer to the node.gno file.

 1package main
 2
 3import (
 4    "gno.land/p/demo/json"
 5    "gno.land/p/nt/ufmt/v0"
 6)
 7
 8func main() {
 9    root, err := Unmarshal([]byte(`{"foo": true, "bar": null}`))
10    if err != nil {
11        ufmt.Errorf("error: %v", err)
12    }
13
14    value, err := root.GetKey("foo")
15    if err != nil {
16        ufmt.Errorf("error occurred while getting key, %s", err)
17    }
18
19    if value.MustBool() != true {
20        ufmt.Errorf("value is not true")
21    }
22
23    value, err = root.GetKey("bar")
24    if err != nil {
25        t.Errorf("error occurred while getting key, %s", err)
26    }
27
28    _, err = root.GetKey("baz")
29    if err == nil {
30        t.Errorf("key baz is not exist. must be failed")
31    }
32}

Contributing

Please submit any issues or pull requests for this package through the GitHub repository at gnolang/gno.

 1const (
 2	C_SPACE Classes = iota /* space */
 3	C_WHITE                /* other whitespace */
 4	C_LCURB                /* {  */
 5	C_RCURB                /* } */
 6	C_LSQRB                /* [ */
 7	C_RSQRB                /* ] */
 8	C_COLON                /* : */
 9	C_COMMA                /* , */
10	C_QUOTE                /* " */
11	C_BACKS                /* \ */
12	C_SLASH                /* / */
13	C_PLUS                 /* + */
14	C_MINUS                /* - */
15	C_POINT                /* . */
16	C_ZERO                 /* 0 */
17	C_DIGIT                /* 123456789 */
18	C_LOW_A                /* a */
19	C_LOW_B                /* b */
20	C_LOW_C                /* c */
21	C_LOW_D                /* d */
22	C_LOW_E                /* e */
23	C_LOW_F                /* f */
24	C_LOW_L                /* l */
25	C_LOW_N                /* n */
26	C_LOW_R                /* r */
27	C_LOW_S                /* s */
28	C_LOW_T                /* t */
29	C_LOW_U                /* u */
30	C_ABCDF                /* ABCDF */
31	C_E                    /* E */
32	C_ETC                  /* everything else */
33)

source

enum classes

 1const (
 2	GO States = iota /* start    */
 3	OK               /* ok       */
 4	OB               /* object   */
 5	KE               /* key      */
 6	CO               /* colon    */
 7	VA               /* value    */
 8	AR               /* array    */
 9	ST               /* string   */
10	ES               /* escape   */
11	U1               /* u1       */
12	U2               /* u2       */
13	U3               /* u3       */
14	U4               /* u4       */
15	MI               /* minus    */
16	ZE               /* zero     */
17	IN               /* integer  */
18	DT               /* dot      */
19	FR               /* fraction */
20	E1               /* e        */
21	E2               /* ex       */
22	E3               /* exp      */
23	T1               /* tr       */
24	T2               /* tru      */
25	T3               /* true     */
26	F1               /* fa       */
27	F2               /* fal      */
28	F3               /* fals     */
29	F4               /* false    */
30	N1               /* nu       */
31	N2               /* nul      */
32	N3               /* null     */
33)

source

The state codes.

 1const (
 2	NotExist ValueType = iota
 3	String
 4	Number
 5	Float
 6	Object
 7	Array
 8	Boolean
 9	Null
10	Unknown
11)

source

 1var AsciiClasses = [128]Classes{
 2
 3	__, __, __, __, __, __, __, __,
 4	__, C_WHITE, C_WHITE, __, __, C_WHITE, __, __,
 5	__, __, __, __, __, __, __, __,
 6	__, __, __, __, __, __, __, __,
 7
 8	C_SPACE, C_ETC, C_QUOTE, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
 9	C_ETC, C_ETC, C_ETC, C_PLUS, C_COMMA, C_MINUS, C_POINT, C_SLASH,
10	C_ZERO, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT,
11	C_DIGIT, C_DIGIT, C_COLON, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
12
13	C_ETC, C_ABCDF, C_ABCDF, C_ABCDF, C_ABCDF, C_E, C_ABCDF, C_ETC,
14	C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
15	C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
16	C_ETC, C_ETC, C_ETC, C_LSQRB, C_BACKS, C_RSQRB, C_ETC, C_ETC,
17
18	C_ETC, C_LOW_A, C_LOW_B, C_LOW_C, C_LOW_D, C_LOW_E, C_LOW_F, C_ETC,
19	C_ETC, C_ETC, C_ETC, C_ETC, C_LOW_L, C_ETC, C_LOW_N, C_ETC,
20	C_ETC, C_ETC, C_LOW_R, C_LOW_S, C_LOW_T, C_LOW_U, C_ETC, C_ETC,
21	C_ETC, C_ETC, C_ETC, C_LCURB, C_ETC, C_RCURB, C_ETC, C_ETC,
22}

source

AsciiClasses array maps the 128 ASCII characters into character classes.

 1var QuoteAsciiClasses = [128]Classes{
 2
 3	__, __, __, __, __, __, __, __,
 4	__, C_WHITE, C_WHITE, __, __, C_WHITE, __, __,
 5	__, __, __, __, __, __, __, __,
 6	__, __, __, __, __, __, __, __,
 7
 8	C_SPACE, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_QUOTE,
 9	C_ETC, C_ETC, C_ETC, C_PLUS, C_COMMA, C_MINUS, C_POINT, C_SLASH,
10	C_ZERO, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT, C_DIGIT,
11	C_DIGIT, C_DIGIT, C_COLON, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
12
13	C_ETC, C_ABCDF, C_ABCDF, C_ABCDF, C_ABCDF, C_E, C_ABCDF, C_ETC,
14	C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
15	C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC, C_ETC,
16	C_ETC, C_ETC, C_ETC, C_LSQRB, C_BACKS, C_RSQRB, C_ETC, C_ETC,
17
18	C_ETC, C_LOW_A, C_LOW_B, C_LOW_C, C_LOW_D, C_LOW_E, C_LOW_F, C_ETC,
19	C_ETC, C_ETC, C_ETC, C_ETC, C_LOW_L, C_ETC, C_LOW_N, C_ETC,
20	C_ETC, C_ETC, C_LOW_R, C_LOW_S, C_LOW_T, C_LOW_U, C_ETC, C_ETC,
21	C_ETC, C_ETC, C_ETC, C_LCURB, C_ETC, C_RCURB, C_ETC, C_ETC,
22}

source

QuoteAsciiClasses is a HACK for single quote from AsciiClasses

 1var StateTransitionTable = [31][31]States{
 2
 3	{GO, GO, co, __, bo, __, __, __, ST, __, __, __, MI, __, ZE, IN, __, __, __, __, __, F1, __, N1, __, __, T1, __, __, __, __},
 4	{OK, OK, __, cc, __, bc, __, cm, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
 5	{OB, OB, __, ec, __, __, __, __, ST, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
 6	{KE, KE, __, __, __, __, __, __, ST, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
 7	{CO, CO, __, __, __, __, cl, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
 8	{VA, VA, co, __, bo, __, __, __, ST, __, __, __, MI, __, ZE, IN, __, __, __, __, __, F1, __, N1, __, __, T1, __, __, __, __},
 9	{AR, AR, co, __, bo, bc, __, __, ST, __, __, __, MI, __, ZE, IN, __, __, __, __, __, F1, __, N1, __, __, T1, __, __, __, __},
10	{ST, __, ST, ST, ST, ST, ST, ST, qt, ES, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST, ST},
11	{__, __, __, __, __, __, __, __, ST, ST, ST, __, __, __, __, __, __, ST, __, __, __, ST, __, ST, ST, __, ST, U1, __, __, __},
12	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, U2, U2, U2, U2, U2, U2, U2, U2, __, __, __, __, __, __, U2, U2, __},
13	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, U3, U3, U3, U3, U3, U3, U3, U3, __, __, __, __, __, __, U3, U3, __},
14	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, U4, U4, U4, U4, U4, U4, U4, U4, __, __, __, __, __, __, U4, U4, __},
15	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, ST, ST, ST, ST, ST, ST, ST, ST, __, __, __, __, __, __, ST, ST, __},
16	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, ZE, IN, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
17	{OK, OK, __, cc, __, bc, __, cm, __, __, __, __, __, DT, __, __, __, __, __, __, E1, __, __, __, __, __, __, __, __, E1, __},
18	{OK, OK, __, cc, __, bc, __, cm, __, __, __, __, __, DT, IN, IN, __, __, __, __, E1, __, __, __, __, __, __, __, __, E1, __},
19	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, FR, FR, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
20	{OK, OK, __, cc, __, bc, __, cm, __, __, __, __, __, __, FR, FR, __, __, __, __, E1, __, __, __, __, __, __, __, __, E1, __},
21	{__, __, __, __, __, __, __, __, __, __, __, E2, E2, __, E3, E3, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
22	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, E3, E3, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
23	{OK, OK, __, cc, __, bc, __, cm, __, __, __, __, __, __, E3, E3, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
24	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, T2, __, __, __, __, __, __},
25	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, T3, __, __, __},
26	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, OK, __, __, __, __, __, __, __, __, __, __},
27	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, F2, __, __, __, __, __, __, __, __, __, __, __, __, __, __},
28	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, F3, __, __, __, __, __, __, __, __},
29	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, F4, __, __, __, __, __},
30	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, OK, __, __, __, __, __, __, __, __, __, __},
31	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, N2, __, __, __},
32	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, N3, __, __, __, __, __, __, __, __},
33	{__, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, OK, __, __, __, __, __, __, __, __},
34}

source

StateTransitionTable is the state transition table takes the current state and the current symbol, and returns either a new state or an action. An action is represented as a negative number. A JSON text is accepted if at the end of the text the state is OK and if the mode is DONE.

1func Indent(data []byte, indent string) ([]byte, error)

source

IndentJSON formats the JSON data with the specified indentation.

1func Marshal(node *Node) ([]byte, error)

source

Marshal returns the JSON encoding of a Node.

1func ParseBoolLiteral(data []byte) (bool, error)

source

ParseBoolLiteral parses a boolean value from the given byte slice.

1func ParsePath(path string) ([]string, error)

source

ParsePath takes a JSONPath string and returns a slice of strings representing the path segments.

1func ParseStringLiteral(data []byte) (string, error)

source

PaseStringLiteral parses a string from the given byte slice.

1func Unescape(input, output []byte) ([]byte, error)

source

Unescape takes an input byte slice, processes it to Unescape certain characters, and writes the result into an output byte slice.

it returns the processed slice and any error encountered during the Unescape operation.

1func Unquote(s []byte, border byte) (string, bool)

source

Unquote takes a byte slice and unquotes it by removing the surrounding quotes and unescaping the contents.

1func ArrayNode(key string, value []*Node) *Node

source

ArrayNode creates a new array type node.

If the given value is nil, it creates an empty array node.

Usage:

Example

1root := ArrayNode("", []*Node{StringNode("", "foo"), NumberNode("", 1)})
2if root == nil {
3	t.Errorf("ArrayNode returns nil")
4}

1func BoolNode(key string, value bool) *Node

source

BoolNode creates a new given boolean value node.

Usage:

Example

1root := BoolNode("", true)
2if root == nil {
3	t.Errorf("BoolNode returns nil")
4}

1func Must(root *Node, expect error) *Node

source

Must panics if the given node is not fulfilled the expectation. Usage:

Example

1node := Must(Unmarshal([]byte(`{"key": "value"}`))

1func NewNode(prev *Node, b *buffer, typ ValueType, key **string) (*Node, error)

source

NewNode creates a new node instance with the given parent node, buffer, type, and key.

1func NullNode(key string) *Node

source

NullNode creates a new null type node.

Usage:

Example

1_ := NullNode("")

1func NumberNode(key string, value float64) *Node

source

NumberNode creates a new number type node.

Usage:

Example

1root := NumberNode("", 1)
2if root == nil {
3	t.Errorf("NumberNode returns nil")
4}

1func ObjectNode(key string, value map[string]*Node) *Node

source

ObjectNode creates a new object type node.

If the given value is nil, it creates an empty object node.

next is a map of key and value pairs of the object.

1func StringNode(key string, value string) *Node

source

StringNode creates a new string type node.

Usage:

Example

1root := StringNode("", "foo")
2if root == nil {
3	t.Errorf("StringNode returns nil")
4}

1func Unmarshal(data []byte) (*Node, error)

source

Unmarshal parses the JSON-encoded data and returns a Node. The data must be a valid JSON-encoded value.

Usage:

Example

1node, err := json.Unmarshal([]byte(`{"key": "value"}`))
2if err != nil {
3	ufmt.Println(err)
4}
5println(node) // {"key": "value"}

1func UnmarshalSafe(data []byte) (*Node, error)

source

UnmarshalSafe parses the JSON-encoded data and returns a Node.

1func Builder() *NodeBuilder

source

1type ArrayBuilder struct {
2	nodes []*Node
3}

source

1func (ab *ArrayBuilder) WriteArray(fn func(*ArrayBuilder)) *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteBool(value bool) *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteInt(value int) *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteNull() *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteNumber(value float64) *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteObject(fn func(*NodeBuilder)) *ArrayBuilder

source

1func (ab *ArrayBuilder) WriteString(value string) *ArrayBuilder

source

1type Classes int8

source

 1type Node struct {
 2	prev     *Node            // prev is the parent node of the current node.
 3	next     map[string]*Node // next is the child nodes of the current node.
 4	key      *string          // key holds the key of the current node in the parent node.
 5	data     []byte           // byte slice of JSON data
 6	value    any              // value holds the value of the current node.
 7	nodeType ValueType        // NodeType holds the type of the current node. (Object, Array, String, Number, Boolean, Null)
 8	index    *int             // index holds the index of the current node in the parent array node.
 9	borders  [2]int           // borders stores the start and end index of the current node in the data.
10	modified bool             // modified indicates the current node is changed or not.
11}

source

Node represents a JSON node.

1func (n *Node) AppendArray(value ...*Node) error

source

AppendArray appends the given values to the current array node.

If the current node is not array type, it returns an error.

Example 1:

Example

1root := Must(Unmarshal([]byte(`[{"foo":"bar"}]`)))
2if err := root.AppendArray(NullNode("")); err != nil {
3	t.Errorf("should not return error: %s", err)
4}
5
6result: [{"foo":"bar"}, null]

Example 2:

Example

1root := Must(Unmarshal([]byte(`["bar", "baz"]`)))
2err := root.AppendArray(NumberNode("", 1), StringNode("", "foo"))
3if err != nil {
4	t.Errorf("AppendArray returns error: %v", err)
5 }
6
7result: ["bar", "baz", 1, "foo"]

1func (n *Node) AppendObject(key string, value *Node) error

source

AppendObject appends the given key and value to the current object node.

If the current node is not object type, it returns an error.

1func (n *Node) ArrayEach(callback func(i int, target *Node))

source

ArrayEach executes the callback for each element in the JSON array.

Usage:

Example

1jsonArrayNode.ArrayEach(func(i int, valueNode *Node) {
2    ufmt.Println(i, valueNode)
3})

1func (n *Node) Changed() bool

source

Changed checks the current node is changed or not.

1func (n *Node) Delete() error

source

Delete removes the current node from the parent node.

Usage:

Example

1root := Unmarshal([]byte(`{"key": "value"}`))
2if err := root.MustKey("key").Delete(); err != nil {
3	t.Errorf("Delete returns error: %v", err)
4}
5
6result: {} (empty object)

1func (n *Node) DeleteIndex(idx int) error

source

DeleteIndex removes the array element at the given index.

1func (n *Node) Empty() bool

source

Empty returns true if the current node is empty.

1func (n *Node) GetArray() ([]*Node, error)

source

GetArray returns the array value if current node is array type.

Usage:

Example

 1	root := Must(Unmarshal([]byte(`["foo", 1]`)))
 2	arr, err := root.GetArray()
 3	if err != nil {
 4		t.Errorf("GetArray returns error: %v", err)
 5	}
 6
 7	for _, val := range arr {
 8		println(val)
 9	}
10
11 result: "foo", 1

1func (n *Node) GetBool() (bool, error)

source

GetBool returns the boolean value if current node is boolean type.

Usage:

Example

1root := Unmarshal([]byte("true"))
2val, err := root.GetBool()
3if err != nil {
4	t.Errorf("GetBool returns error: %v", err)
5}
6println(val) // true

1func (n *Node) GetIndex(idx int) (*Node, error)

source

GetIndex returns the array element at the given index.

if the index is negative, it returns the index is from the end of the array.

1func (n *Node) GetKey(key string) (*Node, error)

source

GetKey returns the value of the given key from the current object node.

1func (n *Node) GetNull() (any, error)

source

GetNull returns the null value if current node is null type.

Usage:

Example

1root := Unmarshal([]byte("null"))
2val, err := root.GetNull()
3if err != nil {
4	t.Errorf("GetNull returns error: %v", err)
5}
6if val != nil {
7	t.Errorf("GetNull returns wrong result: %v", val)
8}

1func (n *Node) GetNumeric() (float64, error)

source

GetNumeric returns the numeric (int/float) value if current node is number type.

Usage:

Example

1root := Unmarshal([]byte("10.5"))
2val, err := root.GetNumeric()
3if err != nil {
4	t.Errorf("GetNumeric returns error: %v", err)
5}
6println(val) // 10.5

1func (n *Node) GetObject() (map[string]*Node, error)

source

GetObject returns the object value if current node is object type.

Usage:

Example

1root := Must(Unmarshal([]byte(`{"key": "value"}`)))
2obj, err := root.GetObject()
3if err != nil {
4	t.Errorf("GetObject returns error: %v", err)
5}
6
7result: map[string]*Node{"key": StringNode("key", "value")}

1func (n *Node) GetString() (string, error)

source

GetString returns the string value if current node is string type.

Usage:

Example

 1root, err := Unmarshal([]byte("foo"))
 2if err != nil {
 3	t.Errorf("Error on Unmarshal(): %s", err)
 4}
 5
 6str, err := root.GetString()
 7if err != nil {
 8	t.Errorf("should retrieve string value: %s", err)
 9}
10
11println(str) // "foo"

1func (n *Node) HasKey(key string) bool

source

HasKey checks the current node has the given key or not.

1func (n *Node) Index() int

source

Index returns the index of the current node in the parent array node.

Usage:

Example

1root := ArrayNode("", []*Node{StringNode("", "foo"), NumberNode("", 1)})
2if root == nil {
3	t.Errorf("ArrayNode returns nil")
4}
5
6if root.MustIndex(1).Index() != 1 {
7	t.Errorf("Index returns wrong index: %d", root.MustIndex(1).Index())
8}

We can also use the index to the byte slice of the JSON data directly.

Example:

Example

1root := Unmarshal([]byte(`["foo", 1]`))
2if root == nil {
3	t.Errorf("Unmarshal returns nil")
4}
5
6if string(root.MustIndex(1).source()) != "1" {
7	t.Errorf("source returns wrong result: %s", root.MustIndex(1).source())
8}

1func (n *Node) IsArray() bool

source

IsArray returns true if the current node is array type.

1func (n *Node) IsBool() bool

source

IsBool returns true if the current node is boolean type.

1func (n *Node) IsNull() bool

source

IsNull returns true if the current node is null type.

1func (n *Node) IsNumber() bool

source

IsNumber returns true if the current node is number type.

1func (n *Node) IsObject() bool

source

IsObject returns true if the current node is object type.

1func (n *Node) IsString() bool

source

IsString returns true if the current node is string type.

1func (n *Node) Key() string

source

Key returns the key of the current node.

1func (n *Node) MustArray() []*Node

source

MustArray returns the array value if current node is array type.

It panics if the current node is not array type.

1func (n *Node) MustBool() bool

source

MustBool returns the boolean value if current node is boolean type.

It panics if the current node is not boolean type.

1func (n *Node) MustIndex(expectIdx int) *Node

source

MustIndex returns the array element at the given index.

If the index is negative, it returns the index is from the end of the array. Also, it panics if the index is not found.

check the Index method for detailed usage.

1func (n *Node) MustKey(key string) *Node

source

MustKey returns the value of the given key from the current object node.

1func (n *Node) MustNull() any

source

MustNull returns the null value if current node is null type.

It panics if the current node is not null type.

1func (n *Node) MustNumeric() float64

source

MustNumeric returns the numeric (int/float) value if current node is number type.

It panics if the current node is not number type.

1func (n *Node) MustObject() map[string]*Node

source

MustObject returns the object value if current node is object type.

It panics if the current node is not object type.

1func (n *Node) MustString() string

source

MustString returns the string value if current node is string type.

It panics if the current node is not string type.

1func (n *Node) ObjectEach(callback func(key string, value *Node))

source

ObjectEach executes the callback for each key-value pair in the JSON object.

Usage:

Example

1jsonObjectNode.ObjectEach(func(key string, valueNode *Node) {
2    ufmt.Println(key, valueNode)
3})

1func (n *Node) Path() string

source

Path builds the path of the current node.

For example:

Example

1{ "key": { "sub": [ "val1", "val2" ] }}

The path of "val2" is: $.key.sub[1]

1func (n *Node) Size() int

source

Size returns the size (length) of the current array node.

Usage:

Example

1root := ArrayNode("", []*Node{StringNode("", "foo"), NumberNode("", 1)})
2if root == nil {
3	t.Errorf("ArrayNode returns nil")
4}
5
6if root.Size() != 2 {
7	t.Errorf("ArrayNode returns wrong size: %d", root.Size())
8}

1func (n *Node) String() string

source

String converts the node to a string representation.

1func (n *Node) Type() ValueType

source

Type returns the type (ValueType) of the current node.

1func (n *Node) UniqueKeyLists() []string

source

UniqueKeyLists traverses the current JSON nodes and collects all the unique keys.

1func (n *Node) Value() (value any, err error)

source

Value returns the value of the current node.

Usage:

Example

1root := Unmarshal([]byte(`{"key": "value"}`))
2val, err := root.MustKey("key").Value()
3if err != nil {
4	t.Errorf("Value returns error: %v", err)
5}
6
7result: "value"

1type NodeBuilder struct {
2	node *Node
3}

source

1func (b *NodeBuilder) Node() *Node

source

1func (b *NodeBuilder) WriteArray(key string, fn func(*ArrayBuilder)) *NodeBuilder

source

1func (b *NodeBuilder) WriteBool(key string, value bool) *NodeBuilder

source

1func (b *NodeBuilder) WriteNull(key string) *NodeBuilder

source

1func (b *NodeBuilder) WriteNumber(key string, value float64) *NodeBuilder

source

1func (b *NodeBuilder) WriteObject(key string, fn func(*NodeBuilder)) *NodeBuilder

source

1func (b *NodeBuilder) WriteString(key, value string) *NodeBuilder

source

1type States int8

source

1type ValueType int

source

1func (v ValueType) String() string

source

bytes stdlib
errors stdlib
gno.land/p/nt/ufmt/v0 package
io stdlib
strconv stdlib
strings stdlib
unicode/utf8 stdlib

Readme View source

JSON Parser

State Machine

Examples

Decoding

Encoding

Searching

Contributing

Constants 3

Variables 3

Functions 18

Types 6

Methods on ArrayBuilder

Methods on Node

Methods on NodeBuilder

Methods on ValueType

Imports 7

Source Files 24