parser - Cryo

import std::json::parser; · source

Free Functions

`function parse(text: Str) -> Result<JsonValue, JsonError>;`

Parse a complete JSON document. Returns the parsed value on success, or a JsonError pointing at the first byte that failed to parse. Trailing whitespace is allowed; trailing non-whitespace produces JsonErrorKind::TrailingData.

The parser is single-pass recursive descent over a borrowed Str, and it is RFC 8259 strict: no trailing commas, no unquoted keys, no comments. String literals decode \X and \uXXXX escapes, and UTF-16 surrogate pairs are recombined; a lone surrogate is InvalidUnicode.

MAX_DEPTH caps combined object and array nesting at 256. The default is generous for hand-authored data and tight enough that a malicious megabyte of [[[...]]] cannot exhaust the stack.

The Parser struct behind parse is public but is an implementation detail; drive the free function.

Constants

const MAX_DEPTH: u64 = 256;
const HT:        u8  = 9;
const LF:        u8  = 10;
const CR:        u8  = 13;
const SPACE:     u8  = 32;
const QUOTE:     u8  = 34;
const PLUS:      u8  = 43;
const COMMA:     u8  = 44;
const MINUS:     u8  = 45;
const DOT:       u8  = 46;
const ZERO:      u8  = 48;
const NINE:      u8  = 57;
const COLON:     u8  = 58;
const UPPER_A:   u8  = 65;
const UPPER_E:   u8  = 69;
const UPPER_F:   u8  = 70;
const LBRACK:    u8  = 91;
const BACKSLASH: u8  = 92;
const RBRACK:    u8  = 93;
const LOWER_A:   u8  = 97;
const LOWER_B:   u8  = 98;
const LOWER_E:   u8  = 101;
const LOWER_F:   u8  = 102;
const LOWER_L:   u8  = 108;
const LOWER_N:   u8  = 110;
const LOWER_R:   u8  = 114;
const LOWER_S:   u8  = 115;
const LOWER_T:   u8  = 116;
const LOWER_U:   u8  = 117;
const LBRACE:    u8  = 123;
const RBRACE:    u8  = 125;

const NAME: Type = value;

At module level, a true compile-time constant, conventionally SCREAMING_SNAKE_CASE. (mut at module level declares mutable global state instead.)

language reference

const MAX_DEPTH: u64 = 256;

primitive u64

64-bit unsigned integer.

primitive type

const HT: u8 = 9;

primitive u8

8-bit unsigned integer.

primitive type

const LF: u8 = 10;

const CR: u8 = 13;

const SPACE: u8 = 32;

const QUOTE: u8 = 34;

const PLUS: u8 = 43;

const COMMA: u8 = 44;

const MINUS: u8 = 45;

const DOT: u8 = 46;

const ZERO: u8 = 48;

const NINE: u8 = 57;

const COLON: u8 = 58;

const UPPER_A: u8 = 65;

const UPPER_E: u8 = 69;

const UPPER_F: u8 = 70;

const LBRACK: u8 = 91;

const BACKSLASH: u8 = 92;

const RBRACK: u8 = 93;

const LOWER_A: u8 = 97;

const LOWER_B: u8 = 98;

const LOWER_E: u8 = 101;

const LOWER_F: u8 = 102;

const LOWER_L: u8 = 108;

const LOWER_N: u8 = 110;

const LOWER_R: u8 = 114;

const LOWER_S: u8 = 115;

const LOWER_T: u8 = 116;

const LOWER_U: u8 = 117;

const LBRACE: u8 = 123;

const RBRACE: u8 = 125;

import a::b;
import a::b::{ X, Y };
import a::b as c;
import a::b::*;

Brings a module, or selected items from it, into scope. One path per declaration: use the brace form for several items, as to alias, and * for everything public (prefer the brace form; wildcards invite name collisions).

language reference

namespace std;

std: the Cryo standard library.

module page

namespace std::json;

json: RFC 8259 JSON parser and serializer.

module page

namespace std::json::parser;

Recursive-descent JSON parser.

module page

function name<T>(param: Type) -> Ret { ... }

Declares a function. Parameters are written name: Type and are never inferred; the return type follows -> and defaults to void. Declaration order does not matter: every signature is collected before any body is checked, so functions may call each other freely and recurse.

language reference

function parse(text: Str) -> Result<JsonValue, JsonError>

(parameter) text: Str

type struct Str {
    bytes: u8*;
    length: u64;
}

Str: a borrowed UTF-8 string slice.

std::collections::str

type enum Result<T, E> {
    Ok(T);
    Err(E);
}

Result: a value that may be an error.

std::core::result

type enum JsonValue {
    Null;
    Bool(boolean);
    Number(JsonNumber);
    String(String);
    Array(Array<JsonValue>);
    Object(JsonObject);
}

One JSON value. Recursive through Array and Object.

std::json::value

type struct JsonError {
    kind: JsonErrorKind;
    line: u64;
    column: u64;
    offset: u64;
    msg: String;
}

std::json::error

type enum JsonErrorKind {
    UnexpectedEof;
    UnexpectedChar;
    InvalidNumber;
    InvalidEscape;
    InvalidUnicode;
    DepthExceeded;
    TrailingData;
    KeyNotString;
    OutOfMemory;
}

Closed set of failure kinds the JSON parser produces. New kinds are rare; most failures fold into one of these.

std::json::error

JsonErrorKind::TrailingData

Garbage after the top-level value.

std::json::error

JsonErrorKind::InvalidUnicode

A \uXXXX sequence is malformed or names an unpaired surrogate.

std::json::error

const MAX_DEPTH: u64 = 256;

std::json::parser

type struct Parser {
    src: u8*;
    len: u64;
    pos: u64;
    line: u64;
    column: u64;
    depth: u64;
}

Recursive-descent JSON parser.

std::json::parser

function parse(text: Str) -> Result<JsonValue, JsonError>

std::json::parser

Free Functions#

function parse(text: Str) -> Result<JsonValue, JsonError>;#

Constants#

Free Functions

`function parse(text: Str) -> Result<JsonValue, JsonError>;`

Constants