Re: Compiled chunk loading cross platform

[RLake@...]

> I'm having a strange problem with loading my
compiled chunks on a
> different platform.

<SNIP>

> What I'd like to know is whether there are any
structure packing settings,
> alignment issues, or other general things to
be aware of when loading
> compiled lua scripts.

The main thing to be aware of is line-end conversion
on platforms which
distinguish between text and binary files. If you
are using standard C
libraries to read a file of byte-code and your standard
C library cares
about line-endings, you must open in mode "rb"
to avoid data corruption.

> My PS2 loading code is as simple as loading the
script
> into a buffer, concatenating a NULL character to the end of it (to
make sure
> text buffers are NULL terminated), and passing that buffer off to
> lua_dobuffer.

The NUL termination is unnecessary, and the compiled
script may have
internal NULs. What does your call to lua_dobuffer
look like? If it is lua_dobuffer(L, buff, strlen(buff),
"name");
then buff's length will be computed incorrectly (since
strlen
stops at the first NUL) and Lua will undoubtedly report
a premature
end of file.

> Also, how is Lua detecting the end of file? I
don't see any
> obvious record of the file size internal to the format, I don't pass
the
> size to lua_dobuffer, and I don't see an obvious EOF character, so
I assume
> some parse logic determines when there is no more data to read...?

It is very standard marshalling code. The demarshaller
knows how long
scalar datatypes are (and this information is coded
into the header to
ensure that the sizes are compatible); compound datatypes
like strings
and tables are prefixed with their element counts.
The marshalled script
contains a single root object which is a compound
object; the demarshaller
recursively reads this object and all of its subobjects
until it is done.
If it runs out of data before it finishes, it reports
premature end of file.