Hi!
I've written a JSON dumper and parser some time ago
and haven't got around finishing it up for more smooth
usage. As I'm currenlty quite busy with my studies
I probably wont get around fixing the remaining issues:
- Unicode handling is not implemented and not really taken
care of, this means you can probably only send ascii JSON
around.
Unicode needs to be implemented and somehow taken care of
before this implementation can be called a real JSON dumper/parser.
- Also the handling of the '\uXXXX' escaping in JSON needs some
thought and implementation (I'm not very familiar with the code anymore
atm.)
- Maybe also the datatypes for json objects and arrays could be made
configurable
somehow. It's currently limited to generating Dictionary and
OrderedCollection
from a JSON string.
The dumping works for Dictionaries and SequenceableCollection.
- The dumping of floats is currently just done by: (self asFloat)
printString
I don't know whether that always gives a JSON compatible representation.
I only remember that I was too lazy to write a float dumper back then.
Someone should take a look at this or at least keep it in mind.
So, before the code gets lost I've attached it to this mail (json.st).
There are some comments in the code and I hope it's mostly understandable.
When I have more time for coding I'll probably fix the issues, but I don't see
that in the near future (~3-4 months).
If anyone is interested feel free to fix the issues (just drop a mail to the ML
if you have done so, so that I don't fix already fixed things :).
Here is a short example:
~/devel/smalltalk# gst
GNU Smalltalk ready
st> FileStream fileIn: 'json.st'!
FileStream
st> JSONDumper toJSON: 'fooo'!
'"fooo"'
st> JSONDumper fromJSON: '{"a":"b"}'!
Dictionary new: 32 "<0x2ad8f4e93be0>"
st> (JSONDumper fromJSON: '{"a":"b"}') at: 'a'!
'b'
Greetings,
Robin
Object subclass: #JSONDumper
instanceVariableNames: ''
classVariableNames: ''
poolDictionaries: ''
category: nil !
ReadWriteStream subclass: #JSONTokenStream
instanceVariableNames: ''
classVariableNames: ''
poolDictionaries: ''
category: nil !
JSONDumper comment:
'I read and write data structures (currently build of OrderedCollection and
Dictionary)
from and to JSON (Java Script Object Notation). Note: I will behave badly with
circular
data structures.' !
JSONTokenStream comment:
'I''m a helper class for JSONDumper. I know what is considered whitespace
for JSON and have some helper methods JSONDumper uses.' !
!JSONTokenStream methodsFor: 'json'!
peekNonJSONWhitespace
"I'm peeking for the next non-whitespace character and will drop all
whitespace in front of it"
| c |
[
c := self peek.
c = (Character space)
or: [ c = (Character tab)
or: [ c = (Character lf)
or: [ c = (Character cr)]]]
] whileTrue: [
self next
].
^self peek
!
skipNonJSONWhitespace
"I will skil all whitespace characters in the stream until i hit some
non-ws. character"
self nextNonJSONWhitespace.
^self
!
nextNonJSONWhitespace
"I'm returning the next non-whitespace character"
| c |
self peekNonJSONWhitespace.
c := self next.
c isNil ifTrue: [ ^self error: 'expected character but found end of stream'
].
^c
! !
!JSONDumper class methodsFor: 'json'!
toJSON: anObject
"I'm returning a JSON string which represents the object."
^anObject toJSON
!
fromJSON: string
"I'm responsible for decoding the JSON string to objects."
^self fromJSONStream: (JSONTokenStream on: string)
! !
!JSONDumper class methodsFor: 'private'!
fromJSONStream: stream
"I decode a json stream to a value, which will be one of: nil,
true, false, OrderedCollection, Dictionary, String or Number
(i will return Integer or Float depending on the input)."
| c |
c := stream peekNonJSONWhitespace.
(c = $n) ifTrue: [ stream next: 4. ^nil ].
(c = $t) ifTrue: [ stream next: 4. ^true ].
(c = $f) ifTrue: [ stream next: 5. ^false ].
(c = ${) ifTrue: [ ^self objectFromJSONStream: stream ].
(c = $[) ifTrue: [ ^self arrayFromJSONStream: stream ].
(c = $") ifTrue: [ ^self stringFromJSONStream: stream ].
^self numberFromJSONStream: stream
!
arrayFromJSONStream: stream
"I decode JSON arrays from the stream and will return a OrderedCollection
for them."
| c obj value |
obj := OrderedCollection new.
stream skipNonJSONWhitespace.
c := stream peekNonJSONWhitespace.
[ ((c = $]) not) or: [ c = $, ] ] whileTrue: [
(c = $,) ifTrue: [ stream skip: 1. ].
value := self fromJSONStream: stream.
obj add: value.
c := stream peekNonJSONWhitespace.
].
stream skipNonJSONWhitespace.
^obj
!
objectFromJSONStream: stream
"I decode JSON objects from the stream and will return a Dictionary
containing all the key/value pairs."
| c obj key value |
obj := Dictionary new.
stream skipNonJSONWhitespace.
c := stream peekNonJSONWhitespace.
[ (c = $}) not or: [ c = $, ] ] whileTrue: [
(c = $,) ifTrue: [ stream skip: 1. ].
key := self stringFromJSONStream: stream.
c := stream nextNonJSONWhitespace.
c = $: ifFalse: [
self error: ('unexpected character found where name-seperator '':''
expected, found: %1' bindWith: c)
].
value := self fromJSONStream: stream.
obj at: key put: value.
c := stream peekNonJSONWhitespace.
].
stream skipNonJSONWhitespace.
^obj
!
stringFromJSONStream: stream
"I'm extracting a JSON string from the stream and return them as String."
| c obj str |
str := WriteStream on: (String new).
stream skipNonJSONWhitespace.
c := stream nextNonJSONWhitespace.
[ c = $" ] whileFalse: [
c = $\
ifTrue: [
c := stream next.
c isNil ifTrue:
[ ^self error: 'expected character, found end of stream' ].
c = $u
ifTrue: [ str nextPut: ((Integer readFrom: (ReadStream on:
(stream next: 4)) radix: 16) asCharacter) ];
ifFalse: [ str nextPut: c ].
];
ifFalse: [ str nextPut: c ].
c := stream nextNonJSONWhitespace.
].
^str contents
!
numberFromJSONStream: stream
"I'm extracting a number in JSON format from the stream and return Integer
or Float depending on the input."
| c num sgn int intexp frac exp isfloat |
num := WriteStream on: (String new).
isfloat := false.
sgn := 1.
int := 0.
intexp := 1.
c := stream peek.
(c isNil) ifTrue: [ ^self error: 'expected number or -sign, but found end of
stream' ].
c = $- ifTrue: [ sgn := -1. stream next. ].
c := stream peek.
(c isNil) ifTrue: [ ^self error: 'expected number, but found end of stream'
].
[ c notNil and: [ c isDigit ] ] whileTrue: [
stream next.
int := sgn * (c digitValue) + (int * 10).
c := stream peek
].
(c isNil) ifTrue: [ ^int ].
c = $. ifTrue: [
stream next.
isfloat := true.
[ c := stream peek. c notNil and: [ c isDigit ] ] whileTrue: [
sgn := sgn / 10.
int := sgn * (c digitValue) + int.
stream next
]
].
exp := 0.
((c = $e) or: [ c = $E ]) ifTrue: [
stream next.
c := stream peek.
(c isNil) ifTrue: [ ^int ].
sgn := 1.
c = $+ ifTrue: [ sgn := 1. stream next ].
c = $- ifTrue: [ sgn := -1. stream next ].
[ c := stream peek. c notNil and: [ c isDigit ] ] whileTrue: [
exp := (c digitValue) + (exp * 10).
stream next
].
(1 to: exp) do: [ :i |
sgn > 0
ifTrue: [
int := int * 10.
];
ifFalse: [
int := int / 10.
]
]
].
isfloat ifTrue: [ ^int asFloat ];
ifFalse: [ ^int asInteger ]
! !
!Number methodsFor: 'json'!
toJSON
"I return the Number in a JSON compatible format as String."
^(self asFloat) printString
! !
!Integer methodsFor: 'json'!
toJSON
"I return the Integer in a JSON compatible format as String."
^self printString
! !
!Dictionary methodsFor: 'json'!
toJSON
"I encode my contents (key/value pairs) to a JSON object and return it as
String."
| ws f |
ws := WriteStream on: (String new).
ws nextPut: ${.
f := true.
self keysAndValuesDo: [ :key :val |
f ifFalse: [ ws nextPut: $, ].
ws nextPutAll: (key toJSON).
ws nextPut: $:.
ws nextPutAll: val toJSON.
f := false
].
ws nextPut: $}.
^ws contents
! !
!String methodsFor: 'json'!
toJSON
"I will encode me as JSON String and return a String containing my encoded
version."
| i c rs ws |
rs := ReadStream on: self.
ws := WriteStream on: (String new).
[ c := rs next. c notNil ] whileTrue: [
i := c asInteger.
(((i = 16r20
or: [ i = 16r21 ])
or: [ i >= 16r23 and: [ i <= 16r5B ] ])
or: [ i >= 16r5D ])
ifTrue: [ ws nextPut: c ];
ifFalse: [ | f |
f := false.
ws nextPut: $\.
i = 16r22 ifTrue: [ f := true. ws nextPut: c ].
i = 16r5C ifTrue: [ f := true. ws nextPut: c ].
i = 16r2F ifTrue: [ f := true. ws nextPut: c ].
i = 16r08 ifTrue: [ f := true. ws nextPut: $b ].
i = 16r0C ifTrue: [ f := true. ws nextPut: $f ].
i = 16r0A ifTrue: [ f := true. ws nextPut: $n ].
i = 16r0D ifTrue: [ f := true. ws nextPut: $r ].
i = 16r09 ifTrue: [ f := true. ws nextPut: $t ].
f ifFalse: [ ^self error: ('Unrecognized character found while
encoding string to JSON, character: %1' bindWith: c) ]
]
].
^('"', (ws contents), '"')
! !
!SequenceableCollection methodsFor: 'json'!
toJSON
"I'm returning a JSON encoding of my contents as String."
| ws f |
ws := WriteStream on: (String new).
ws nextPut: $[.
f := true.
self do: [ :val |
f ifFalse: [ ws nextPut: $, ].
ws nextPutAll: (val toJSON).
f := false
].
ws nextPut: $].
^ws contents
! !
!UndefinedObject methodsFor: 'json'!
toJSON
"I'm returning my corresponding value as JSON String."
^'null'
! !
!True methodsFor: 'json'!
toJSON
"I'm returning the JSON String for trueness."
^'true'
! !
!False methodsFor: 'json'!
toJSON
"I'm returning the JSON String for falseness."
^'false'
! !
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