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;
Page 1 Plan 9 (printed 11/23/24)
JSON(2) JSON(2)
jvreal: fn(r: real): ref JValue.Real;
jvstring: fn(s: string): ref JValue.String;
jvtrue: fn(): ref JValue.True;
DESCRIPTION
JSON provides value representations, and encoding and decod-
ing operations 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 provides 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 corresponding 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 represents the value successfully read. If an
error occurs, val is nil and err contains a diagnostic.
Page 2 Plan 9 (printed 11/23/24)
JSON(2) JSON(2)
Writejson writes to the output stream in JSON format a rep-
resentation 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 operations, 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, includ-
ing the values of corresponding subcomponents, recur-
sively
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 ALSO
sexprs(2), ubfa(2), json(6), sexprs(6), ubfa(6)
D Crockford, ``The application/json Media Type for
JavaScript Object Notation (JSON)'', RFC4627.
Page 3 Plan 9 (printed 11/23/24)