We Keep Coding

Generate code from antlr tokens

We are currently working on trying to generate a new code using antlr. We have a grammar file that pretty much can recognize everything. Now, our problem is that we want to be able to create code again using the tokens that we generate to create this new file.
We have a .txt file with our tokens that looks like this:
[#0,0:6=' ',<75>,channel=1,1:0]
[#1,7:20='IDENTIFICATION',<6>,1:7]
[#2,21:21=' ',<75>,channel=1,1:21]
[#3,22:29='DIVISION',<4>,1:22]
[#4,30:30='.',<3>,1:30]
[#5,31:40='\n \t ',<75>,channel=1,1:31]
[#6,41:50='PROGRAM-ID',<16>,2:9]
[#7,51:51='.',<3>,2:19]
[#8,52:52=' ',<75>,channel=1,2:20]
[#9,53:59='testpro',<76>,2:21]
[#10,60:60='.',<3>,2:28]
[#11,61:70='\n \t ',<75>,channel=1,2:29]
[#12,71:76='AUTHOR',<31>,3:9]
[#13,77:77='.',<3>,3:15]
Or is there another way to create the old code using tokens?
Thanks in advance, Viktor

The most straight forward way to make the lexer output portable is to serialize the tokenized output of the lexer for transport and storage. You could equally serialize the entire parser generated parse tree. In either case, you will be capturing the full text of the source input.
The intrinsic complexity of the lexer stream object is a single class. The parse tree object complexity is also quite small, involving just a handful of standard classes. Consequently, the complexity of the serialization & deserialization is almost entirely a linear function of size of the parsed source input.
Google Gson is a simple-to-use, relatively fast Java object serialization library.
If your parser is generating some intermediate representation of the parsed source input, you could directly transport the IR using a defined record serialization library like Google FlatBuffers to save & restore IR model instances.

JSON parsing in java

I have no idea how to parse JSON in java(or anything else). I've seen some tutorials but I can't get it straight.
I am trying to get title="Fabiola Jean and Laurent Lundy commented on a photo that you're tagged". All I need is to know how to create a getTitle() method
this is the JSON I want to parse:
Connection[data=[Notification[id=notif__161136848 metadata=null
title=Fabiola Jean and Laurent Lundy commented on a photo that you're tagged in. type=null]]
nextPageUrl=https://graph.facebook.com/811204509/notifications?fields
=title&value=1&format=json&redirect=1&access_token=MY_TOKEN&__paging_token=
notif__161136848
previousPageUrl=https://graph.facebook.com/811204509/notifications?fields=title
&value=1&format=json&redirect=1&access_token=MY_TOKEN&limit=5000&since=1342109329&
__paging_token=notif__161136848&__previous=1 next=true previous=true]

First, the code you put in your question is absolutely not valid JSON. I'm not quite sure what it is, and it does not appear to be easily parsable.
Assuming you are trying to parse actual JSON you almost certainly want to use a 3rd party library instead of writing the code using string manipulation functions.
Gson would be my first recommendation, and Jackson is another alternative you might want to look at.

Good way to serialize array in Java that is readable from Python?

I have some Java's serialized objects (arrays of doubles) in MySql database fields that I generated previously. Now I needed to read them from Python and I have just realized that it is probably not possible to do directly.
Then I tried to convert them to strings in java (simply comma delimited), and manually parse them from Python. But, it turned out that parsing from Python works painfully slow this way. Is there any better way for serializing arrays that is compatible between Java and Python?
Edit: Sorry, my parsing code was the problem, of course. I replaced it with this:
stringList = string.split(', ')
svdVector = [float(x) for x in stringList]
..and now it is almost instant for my case of 1000x1000 doubles. Although it still feels wrong to store doubles as strings instead of binary, but since it's easy to code and runs fast enough, it is fine.

Python comes with modules for CSV files, XML, and JSON, so one of those would likely do the trick quite well.

If you really want to try binary serialization, check out the built-in struct and array modules for help with interpreting the data in Python.

JSON-lib escaping / preserving strings

I am using JSON-lib library for java http://json-lib.sourceforge.net
I just want to add simple string which can look like JSON (but i do not want library to automatically figure out that it might be json and just to treat it as string). Looking into source of library I can't find the way to do it without ugly hacks.
example:
JSONObject object = new JSONObject();
String chatMessageFromUser = "{\"dont\":\"treat it as json\"}";
object.put("myString", chatMessageFromUser);
object.toString() will give us {"myString":{"dont":"treat it as json"}}
and i want just to have {"myString":"{\"dont\":\"treat it as json\"}"}
How to achieve it without modifying source code ? I am using this piece of code as transport for chat messages from users - so it works OK for normal chat messages, but when user will enter JSON format as message it will break it because of default behavior of JSON-lib described here.

If I understand question correctly, I think json-lib is unique in its assumption of a String being passed needing to be parsed. Other libs typically treat it as String to include (with escaping of double-quotes and backslashes as necessary), i.e. work as you would expect.
So you may want to consider other libraries: I would recommend Jackson, Gson also works.

json-simple offers a JSONObject.escape() method.

Developing a (file) exchange format for java

I want to come up with a binary format for passing data between application instances in a form of POFs (Plain Old Files ;)).
Prerequisites:
should be cross-platform
information to be persisted includes a single POJO & arbitrary byte[]s (files actually, the POJO stores it's names in a String[])
only sequential access is required
should be a way to check data consistency
should be small and fast
should prevent an average user with archiver + notepad from modifying the data
Currently I'm using DeflaterOutputStream + OutputStreamWriter together with InflaterInputStream + InputStreamReader to save/restore objects serialized with XStream, one object per file. Readers/Writers use UTF8.
Now, need to extend this to support the previously described.
My idea of format:
{serialized to XML object}
{delimiter}
{String file name}{delimiter}{byte[] file data}
{delimiter}
{another String file name}{delimiter}{another byte[] file data}
...
{delimiter}
{delimiter}
{MD5 hash for the entire file}
Does this look sane?
What would you use for a delimiter and how would you determine it?
The right way to calculate MD5 in this case?
What would you suggest to read on the subject?
TIA.

It looks INsane.
why invent a new file format?
why try to prevent only stupid users from changing file?
why use a binary format ( hard to compress ) ?
why use a format that cannot be parsed while being received? (receiver has to receive entire file before being able to act on the file. )
XML is already a serialization format that is compressable. So you are serializing a serialized format.

Would serialization of the model (if you are into MVC) not be another way? I'd prefer to use things in the language (or standard libraries) rather then roll my own if possible. The only issue I can see with that is that the file size may be larger than you want.

1) Does this look sane?
It looks fairly sane. However, if you are going to invent your own format rather than just using Java serialization then you should have a good reason. Do you have any good reasons (they do exist in some cases)? One of the standard reasons for using XStream is to make the result human readable, which a binary format immediately loses. Do you have a good reason for a binary format rather than a human readable one? See this question for why human readable is good (and bad).
Wouldn't it be easier just to put everything in a signed jar. There are already standard Java libraries and tools to do this, and you get compression and verification provided.
2) What would you use for a delimiter and how determine it?
Rather than a delimiter I'd explicitly store the length of each block before the block. It's just as easy, and prevents you having to escape the delimiter if it comes up on its own.
3) The right way to calculate MD5 in this case?
There is example code here which looks sensible.
4) What would you suggest to read on the subject?
On the subject of serialization? I'd read about the Java serialization, JSON, and XStream serialization so I understood the pros and cons of each, especially the benefits of human readable files. I'd also look at a classic file format, for example from Microsoft, to understand possible design decisions from back in the days that every byte mattered, and how these have been extended. For example: The WAV file format.

Let's see this should be pretty straightforward.
Prerequisites:
0. should be cross-platform
1. information to be persisted includes a single POJO & arbitrary byte[]s (files actually, the POJO stores it's names in a String[])
2. only sequential access is required
3. should be a way to check data consistency
4. should be small and fast
5. should prevent an average user with archiver + notepad from modifying the data
Well guess what, you pretty much have it already, it's built-in the platform already:Object Serialization
If you need to reduce the amount of data sent in the wire and provide a custom serialization ( for instance you can sent only 1,2,3 for a given object without using the attribute name or nothing similar, and read them in the same sequence, ) you can use this somehow "Hidden feature"
If you really need it in "text plain" you can also encode it, it takes almost the same amount of bytes.
For instance this bean:
import java.io.*;
public class SimpleBean implements Serializable {
private String website = "http://stackoverflow.com";
public String toString() {
return website;
}
}
Could be represented like this:
rO0ABXNyAApTaW1wbGVCZWFuPB4W2ZRCqRICAAFMAAd3ZWJzaXRldAASTGphdmEvbGFuZy9TdHJpbmc7eHB0ABhodHRwOi8vc3RhY2tvdmVyZmxvdy5jb20=
See this answer
Additionally, if you need a sounded protocol you can also check to Protobuf, Google's internal exchange format.

You could use a zip (rar / 7z / tar.gz / ...) library. Many exists, most are well tested and it'll likely save you some time.
Possibly not as much fun though.

I agree in that it doesn't really sound like you need a new format, or a binary one.
If you truly want a binary format, why not consider one of these first:
Binary XML (fast infoset, Bnux)
Hessian
google packet buffers
But besides that, many textual formats should work just fine (or perhaps better) too; easier to debug, extensive tool support, compresses to about same size as binary (binary compresses poorly, and information theory suggests that for same effective information, same compression rate is achieved -- and this has been true in my testing).
So perhaps also consider:
Json works well; binary support via base64 (with, say, http://jackson.codehaus.org/)
XML not too bad either; efficient streaming parsers, some with base64 support (http://woodstox.codehaus.org/, "typed access API" under 'org.codehaus.stax2.typed.TypedXMLStreamReader').
So it kind of sounds like you just want to build something of your own. Nothing wrong with that, as a hobby, but if so you need to consider it as such.
It likely is not a requirement for the system you are building.

Perhaps you could explain how this is better than using an existing file format such as JAR.
Most standard files formats of this type just use CRC as its faster to calculate. MD5 is more appropriate if you want to prevent deliberate modification.

Bencode could be the way to go.
Here's an excellent implementation by Daniel Spiewak.
Unfortunately, bencode spec doesn't support utf8 which is a showstopper for me.
Might come to this later but currently xml seems like a better choice (with blobs serialized as a Map).