JsonValue structv0.1.0

pub struct JsonValue {
    pub kind: JsonKind;
    // private fields
}

Move-only, because it owns strings and nested values. The allocator it was built with is carried along, so a subtree can be released without the caller having to remember where it came from — which is what makes a document assembled from several sources safe to take apart. The tag is inspected with Kind and the payload read with the matching accessor; asking for the wrong one reports failure rather than reinterpreting the bytes.

Fields

Associated functions

Null

pub func Null(allocator: Allocator) -> JsonValue

The literal null.

Returns: the null value

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Boolean

pub func Boolean(
    allocator: Allocator,
    value: bool
) -> JsonValue

A boolean value.

Returns: that boolean as a value

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Number

pub func Number(
    allocator: Allocator,
    text: char8[..]
) -> JsonValue ! TextError

A number, from the text it was written with.

Returns: that text as a number value, or the null value when the allocator refused

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Text

pub func Text(
    allocator: Allocator,
    value: char8[..]
) -> JsonValue ! TextError

A string value.

Returns: that text as a string value, or the null value when the allocator refused

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Array

pub func Array(allocator: Allocator) -> JsonValue

An empty array.

Returns: an empty array

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Object

pub func Object(allocator: Allocator) -> JsonValue

An empty object.

Returns: an empty object

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Methods

Kind

pub func Kind(self: &JsonValue) -> JsonKind

Which kind this value is.

Returns: which of the six JSON kinds this is

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IsNull

pub func IsNull(self: &JsonValue) -> bool

Whether this is null.

Returns: whether this is the null value

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AsBoolean

pub func AsBoolean(
    self: &JsonValue,
    result: *var bool
) -> bool

The boolean payload, or false when this is not a boolean — which Kind distinguishes from a genuine false.

Returns: whether this is a boolean

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AsNumber

pub func AsNumber(self: &JsonValue) -> *JsonNumber

The number payload, borrowed.

Returns: the number, or null when this is not one

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AsText

pub func AsText(self: &JsonValue) -> StringView

The string payload, or an empty view when this is not a string.

Returns: the string, or an empty view when this is not one

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Length

pub func Length(self: &JsonValue) -> uint

How many elements an array holds, or members an object holds; zero for anything else.

Returns: how many elements or members this holds; zero for anything else

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Push

pub func Push(
    self: &var JsonValue,
    value: JsonValue
) -> bool

Appends value to an array, taking ownership of it. Reports false when this is not an array or the allocator refused; value is consumed either way, so a caller does not have to decide who owns it on failure.

Returns: whether the element was appended

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Insert

pub func Insert(
    self: &var JsonValue,
    name: String,
    value: JsonValue
) -> bool

Appends a member to an object, taking ownership of both name and value. The order members are added in is the order they are kept and written, which is what makes a document round-trip recognisably. Nothing here rejects a duplicate name — that policy lives in the parser, where the caller can choose it.

Returns: whether the member was added

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At

pub func At(self: &JsonValue, index: uint) -> *JsonValue

The element at index, borrowed, or null when there is none.

Returns: the element at index, or null when there is none

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Find

pub func Find(
    self: &JsonValue,
    name: StringView
) -> *JsonValue

The value of the member named name, borrowed, or null when there is none. With duplicate names present — which only a permissive parser policy allows — this finds the first, since that is the one a reader encounters.

Returns: the first member with that name, or null when there is none

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MemberAt

pub func MemberAt(
    self: &JsonValue,
    index: uint
) -> *JsonMember

The member at index, borrowed, or null when there is none.

Returns: the member at index, or null when there is none

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RemoveFirst

pub func RemoveFirst(
    self: &var JsonValue,
    name: StringView
) -> bool

Removes the first member named name, if there is one. Used by the duplicate-name policy that keeps the last occurrence: dropping the earlier one is what keeps the object a map rather than a list that happens to repeat itself. The members after it are popped and pushed back rather than shifted, because shifting would move owning values around inside the vector, and a move out of a container is the one thing the ownership rules will not allow silently. Duplicates are rare enough that the cost never matters.

Returns: whether a member with that name was removed

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Destructor

func ~JsonValue(self: &var JsonValue)

Releases everything this value owns. Written out rather than left to the compiler, because a value owns its strings and its children own theirs: the recursion here is the shape of the document, and stating it makes the ownership of a nested tree something a reader can check.

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Related

JsonKind

pub enum JsonKind: int32 {
    Null = 0,
    Boolean = 1,
    Number = 2,
    Text = 3,
    Array = 4,
    Object = 5
}

Which kind of JSON value this is.

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Cases

JsonMember

pub struct JsonMember {
    pub name: String;
    pub value: JsonValue;
}

A name-value pair inside an object.

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Fields

Destructor

~JsonMember

func ~JsonMember(self: &var JsonMember)

Releases the member's name and value.

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