Documents

The example parses the people document in your selected format. It then reads Ada's age through the document nodes. Typed reads give you these values without serializing the document.

Example

Read Ada's age

people_text holds this document:

edn

287 B

{:#_ada {:name "Ada"
         :role "engineer"
         :age  36}
 :#_bob {:name   "Bob"
         :role   "engineer"
         :age    41
         :mentor {:#link "#_ada"}}
 :#_cy  {:name "Cy"
         :role "designer"
         :age  29}
 :#_tx  {:author "smoke"
         :reason "seed"}}

rust

176 B

let people = stardust::parse(people_text, Format::EDN)?;
let ada = people.member(people.root()?, "#_ada")?;
let age = people.member(ada, "age")?;
let result = people.i64(age)?;

Result / 11 B

{:value 36}

Numbers

A document number is an i64 integer or a finite f64 value. The number type defines both.

An integer read requires an integer node. A floating-point node can cause the read to fail.
Choose the typed read that matches the node that you read.

Operations

Operation	Returns	Summary
parse	document	parse(text, format) returns an owned document.
Document::root	node	document.root() returns the root node ID.
Document::count	count	document.count() returns the number of nodes.
Document::read	node_view	document.read(id) returns a node view: kind, boolean, parent, position, first_child, next_sibling, key and text.
Document::read_many	node_views	document.read_many(start, capacity) reads consecutive node views.
Document::member	node	document.member(id, key) returns the first matching object member ID.
Document::children	node_views	document.children(id) iterates the node views of a node's children in order.
Document::members	node_views	document.members(id) iterates the members of an object node in order, each with its key.
Document::i64	integer	Read an exact signed integer.
Document::f64	real	Read a finite floating-point number.
Document::close	none	Release the document handle.

parse

rust

72 B

pub fn parse(text: impl AsRef<[u8]>, format: Format) -> Result<Document>

Parameters

Parameter	Type	Ownership	Default	Meaning
`text`	`impl AsRef<[u8]>`	Value	Required	Encoded input bytes in the selected format. TRON is binary.
`format`	`Format`	Value	Required	The codec to use for this operation.

Errors

Status	When
`Status::INVALID_JSON`	JSON text is malformed
`Status::INVALID_ARGUMENT`	the text is malformed, the format is unknown or a number is outside `i64` or finite `f64`
`Status::OUT_OF_MEMORY`	native memory is exhausted

Examples

Parse the shared DUST expression fixture

expression holds these bytes:

text

278 B

// One expression built once and evaluated against several inputs. The
// evaluate examples load this file, build `expression`, evaluate it with each
// of `inputs` in order and compare each result with `expected`.
expression [+ ?x 1]
inputs     [{x 1} {x 41}]
expected   [2 42]

rust

56 B

let result = stardust::parse(expression, Format::DUST)?;

Result / 330 B

{:value {:$comment   "One expression built once and evaluated against several inputs. The\nevaluate examples load this file, build `expression`, evaluate it with each\nof `inputs` in order and compare each result with `expected`."
         :expression ["+" ?x 1]
         :inputs     [{:x 1} {:x 41}]
         :expected   [2 42]}}

Report a malformed byte at offset zero

malformed holds these bytes:

text

1 B

rust

60 B

let result = stardust::parse(malformed, Format::DUST).err();

Result / 204 B

{:value {:code    "invalid_dust"
         :message "Invalid_Syntax at offset 0"
         :path    nil
         :field   nil
         :entity  nil
         :offset  0
         :status  "invalid_argument"}}

Report malformed DUST

malformed holds these bytes:

text

1 B

rust

60 B

let result = stardust::parse(malformed, Format::DUST).err();

Result / 204 B

{:value {:code    "invalid_dust"
         :message "Unexpected_End at offset 2"
         :path    nil
         :field   nil
         :entity  nil
         :offset  2
         :status  "invalid_argument"}}

C exports: stardust_parse, stardust_document_error

Document::read

rust

54 B

pub fn read(&self, id: NodeId) -> Result<NodeView<'_>>

Parameters

Parameter	Type	Ownership	Default	Meaning
`self`	`&Self`	Borrowed for the call	Required	The document owner for this operation. Keep it alive during the call.
`id`	`NodeId`	Value	Required	A node ID within the receiver document.

Errors

Close consumes this owner. Rust ownership prevents later access. Thus, the safe API does not report closed for this receiver.

Status	When
`Status::INVALID_ARGUMENT`	id is not a node of the document

Notes

Text contains string values. Read numbers with i64 or f64.

Examples

document/read

input_text holds this document:

edn

7 B

{:x 41}

rust

95 B

let input = stardust::parse(input_text, Format::EDN)?;
let result = input.read(input.root()?)?;

Result / 218 B

{:value {:kind         "object"
         :boolean      false
         :parent       nil
         :position     0
         :first_child  1
         :next_sibling nil
         :key          ""
         :text         ""}}

C exports: stardust_document_read_many

Document::read_many

rust

82 B

pub fn read_many(&self, start: NodeId, capacity: i64) -> Result<Vec<NodeView<'_>>>

Parameters

Parameter	Type	Ownership	Default	Meaning
`self`	`&Self`	Borrowed for the call	Required	The document owner for this operation. Keep it alive during the call.
`start`	`NodeId`	Value	Required	The first node ID of the consecutive read.
`capacity`	`i64`	Value	Required	The maximum number of node views to read. For output slices, the call uses the caller's slice length.

Errors

Close consumes this owner. Rust ownership prevents later access. Thus, the safe API does not report closed for this receiver.

Status	When
`Status::INVALID_ARGUMENT`	start is past the last node or capacity is negative

Examples

document/read_many

input_text holds this document:

edn

7 B

{:x 41}

rust

169 B

let input = stardust::parse(input_text, Format::EDN)?;
let views = input.read_many(input.root()?, 1)?;
let result = views.into_iter().next().ok_or("missing node view")?;

Result / 218 B

{:value {:kind         "object"
         :boolean      false
         :parent       nil
         :position     0
         :first_child  1
         :next_sibling nil
         :key          ""
         :text         ""}}

C exports: stardust_document_read_many

Status	When
`Status::NOT_FOUND`	the object has no member with the key
`Status::INVALID_ARGUMENT`	id is not an object node of the document

Document::children

rust

50 B

pub fn children(&self, id: NodeId) -> Children<'_>

Parameters

Parameter	Type	Ownership	Default	Meaning
`self`	`&Self`	Borrowed for the call	Required	The document owner for this operation. Keep it alive during the call.
`id`	`NodeId`	Value	Required	A node ID within the receiver document.

Errors

Close consumes this owner. Rust ownership prevents later access. Thus, the safe API does not report closed for this receiver.

Status	When
`Status::INVALID_ARGUMENT`	id is not a node of the document

Notes

Keep the document open during iteration. A scalar has no children. A read failure is reported once and ends iteration.

Examples

document/children

seed_text holds this document:

edn

287 B

{:#_ada {:name "Ada"
         :role "engineer"
         :age  36}
 :#_bob {:name   "Bob"
         :role   "engineer"
         :age    41
         :mentor {:#link "#_ada"}}
 :#_cy  {:name "Cy"
         :role "designer"
         :age  29}
 :#_tx  {:author "smoke"
         :reason "seed"}}

rust

196 B

let seed = stardust::parse(seed_text, Format::EDN)?;
let mut result = 0i64;
let mut children = seed.children(seed.root()?);
while let Some(child) = children.next() {
    child?;
    result += 1;
}

Result / 10 B

{:value 4}

C exports: stardust_document_read_many

Document::members

rust

48 B

pub fn members(&self, id: NodeId) -> Members<'_>

Parameters

Parameter	Type	Ownership	Default	Meaning
`self`	`&Self`	Borrowed for the call	Required	The document owner for this operation. Keep it alive during the call.
`id`	`NodeId`	Value	Required	A node ID within the receiver document.

Errors

Close consumes this owner. Rust ownership prevents later access. Thus, the safe API does not report closed for this receiver.

Status	When
`Status::INVALID_ARGUMENT`	id is not an object node of the document

Notes

Duplicate keys appear in document order. Keep the document open during iteration. A read failure is reported once and ends iteration.

Examples

document/members

seed_text holds this document:

edn

287 B

{:#_ada {:name "Ada"
         :role "engineer"
         :age  36}
 :#_bob {:name   "Bob"
         :role   "engineer"
         :age    41
         :mentor {:#link "#_ada"}}
 :#_cy  {:name "Cy"
         :role "designer"
         :age  29}
 :#_tx  {:author "smoke"
         :reason "seed"}}

rust

166 B

let seed = stardust::parse(seed_text, Format::EDN)?;
let (key, _view) = seed.members(seed.root()?).next().ok_or("no members")??;
let result = key.as_bytes().to_vec();

Result / 24 B

{:value {:text "#_ada"}}

C exports: stardust_document_read_many

Status	When
`Status::INVALID_ARGUMENT`	the node is not an integer number

Status	When
`Status::INVALID_ARGUMENT`	the node is not a number or its value overflows `f64`

Parameter	Type	Ownership	Default	Meaning
`self`	`Self`	Consumed owner	Required	The document owner to release. Do not use it after this call.

node_view

This record contains the result of read and read_many. The key and text fields are owned strings and remain valid after the document closes.

Field	Type	Unit	Absent	Meaning
`kind`	`Kind`	None	—	—
`boolean`	`bool`	None	—	True only for true.
`parent`	`Option<NodeId>`	None	None	—
`position`	`u32`	Count	—	Index within the parent container.
`first_child`	`Option<NodeId>`	None	None	—
`next_sibling`	`Option<NodeId>`	None	None	—
`key`	`&'a str`	None	—	Member key of an object member, else empty.
`text`	`&'a str`	None	—	Value of a string, else empty. It can contain NUL.

This record supplies a node for add and add_many. The number field holds a typed i64 or f64 value. Go uses I64/F64, Rust and Odin use Number, Clojure uses long or double, and Python uses int or float. This value sets the ABI number kind and the integer or real field.

Field	Type	Absent	Meaning
`parent`	`Option<NodeId>`	None	—
`kind`	`Kind`	—	—
`boolean`	`bool`	—	Value of a boolean node.
`number`	`Number`	—	Value of a number node.
`key`	`&'a str`	—	Member key when the parent is an object.
`text`	`&'a str`	—	Value of a string node.