serialization library

[Walter Bright]

Bill Baxter wrote:
> How do you fix it?  Very simple really.  Just store the file as a series 
> of chunks with fixed length headers, and each header contains the length 
> of the data in that chunk.  If you get a chunk header with a tag you 
> don't understand, just ignore it.  A particular chunk can have 
> sub-chunks too.

Evolution of a file format:

1.0: Just spew the struct contents out into a file using something like 
fwrite().

2.0: Oops! Need to update 1.0 and retain backwards compatibility. 
Solution: 2.0 files put out 'illegal' values into the 1.0 format to 
signal it's a 2.0 file.

3.0: Doh! Find another set of illegal 2.0 values. This time, get smarter 
and have another field with a version number in it.

4.0: Get smart and implement your suggestion, so you can have both 
backwards and *forwards* compatibility.

Think I'm joking? Just look at a few! Everyone learns this the hard way.

Me, if practical, I like file formats to be in ascii so I can examine 
them easily to see if they're working right.