JSON(2)JSON(2)NAME
json: readjson, writejson, JValue - read, write and represent values in
JavaScript Object Notation
SYNOPSIS
include "json.m";
json := load JSON JSON->PATH;
JValue: adt {
pick{
Object =>
mem: cyclic list of (string, ref JValue);
Array =>
a: cyclic array of ref JValue;
String =>
s: string;
Int =>
value: big;
Real =>
value: real;
True or
False or
Null =>
}
isarray: fn(v: self ref JValue): int;
isfalse: fn(v: self ref JValue): int;
isint: fn(v: self ref JValue): int;
isnull: fn(v: self ref JValue): int;
isnumber: fn(v: self ref JValue): int;
isobject: fn(v: self ref JValue): int;
isreal: fn(v: self ref JValue): int;
isstring: fn(v: self ref JValue): int;
istrue: fn(v: self ref JValue): int;
copy: fn(v: self ref JValue): ref Jvalue;
eq: fn(v: self ref JValue, v: ref JValue): int;
get: fn(v: self ref JValue, mem: string): ref JValue;
set: fn(v: self ref JValue, mem: string, value: ref JValue);
text: fn(v: self ref JValue): string;
};
init: fn(bufio: Bufio);
readjson: fn(input: ref Bufio->Iobuf): (ref JValue, string);
writejson: fn(output: ref Bufio->Iobuf, val: ref JValue): int;
jvarray: fn(a: array of ref JValue): ref JValue.Array;
jvbig: fn(b: big): ref JValue.Int;
jvfalse: fn(): ref JValue.False;
jvint: fn(i: int): ref JValue.Int;
jvnull: fn(): ref JValue.Null;
jvobject: fn(m: list of (string, ref JValue)): ref JValue.Object;
jvreal: fn(r: real): ref JValue.Real;
jvstring: fn(s: string): ref JValue.String;
jvtrue: fn(): ref JValue.True;
DESCRIPTIONJSON provides value representations, and encoding and decoding opera‐
tions for the JavaScript Object Notation (JSON) described by Internet
RFC4627 and summarised in json(6).
Init must be called before invoking any other operation of the module.
The bufio parameter must refer to the instance of bufio(2) that pro‐
vides the Iobuf parameters used for input and output.
JValue is the internal representation of values transmitted by the JSON
encoding. They are distinguished in a pick adt:
JValue.False
Represents the value false.
JValue.Null
Represents a null value of any type.
JValue.True
Represents the value true.
JValue.Int
Represents as a Limbo big a JavaScript number with no fractional
part.
JValue.Real
Represents as a Limbo real a JavaScript number with a fractional
part.
JValue.String
Represents a JavaScript string of Unicode characters from
+U'0000' to +U'FFFF'.
JValue.Array
Represents a JavaScript array of values of any type.
JValue.Object
Represents a tuple of (member/property name, value) pairs corre‐
sponding to the value of a JavaScript object, or an associative
array or table, indexed by strings. The member names must be
unique within a value.
Readjson reads a single value in JSON format from the input stream and
returns a tuple (val, err). On success, val is a JValue that repre‐
sents the value successfully read. If an error occurs, val is nil and
err contains a diagnostic.
Writejson writes to the output stream in JSON format a representation
of the value v. It returns 0 on success and -1 on error (setting the
system error string).
The easiest way to create a new JValue for subsequent output is with
one of the module-level functions jvarray, jvint, jvobject, jvstring,
and so on. As values of a pick adt, a JValue can be inspected using
Limbo's tagof operator and the appropriate variant accessed using a
pick statement. JValue also supports several groups of common opera‐
tions, for smaller, tidier code. First, the set of enquiry functions
v.isX() return true if the value v is an instance of the JavaScript
type X (array, int, object, real, string, etc). A numeric value is
either int or real. The other operations are:
v.copy()
Return a (reference to) a copy of value v. The copying is not
recursive.
v.eq(w)
Return true if the values of v and w are equal, including the
values of corresponding subcomponents, recursively
v.get(mem)
Return the value associated with the member named mem in v;
return null if there is none.
v.set(mem, value)
Adds or changes the value associated with the member named mem
in v, which must be a JValue.Object( raises exception json: set
non-object otherwise).
v.text()
Return a string containing the JSON representation of v.
SOURCE
/appl/lib/json.b
SEE ALSOsexprs(2), ubfa(2), json(6), sexprs(6), ubfa(6)
D Crockford, ``The application/json Media Type for JavaScript Object
Notation (JSON)'', RFC4627.
JSON(2)