Fix fs can't handle large file on 64bit platform

[koichik]

fs.read() and fs.write() can't handle more than 2GB files on 64bit platform.
Also fs.truncate() can't handle more than 4GB files.

Node already has the capability to handle large files.
This patch changes only a parameter check (read/write) and
type conversion from JS's number to C types (truncate).

The testcase only works on 64bit platform, then I put it into test/disabled.

[tshinnic]

Just a note for a future reader...

If you want to return a large integer value from .cc to JS you can't use the commonly-seen method of returning integer values,

    return scope.Close(Integer::New(offs_result));

This will only handle signed 32 bit integer values. Even the added Integer::NewFromUnsigned() will only make unsigned full 32 bit values.

You must switch to using Number::New() to create integer values more than 32 bits. I don't know how large the values can be before truncation occurs, but this is working for me now up past 43 bits:

    return scope.Close(Number::New(offs_result));

[koichik]

Hi, tshinnic.

Because the Write()/Read()'s length is singed int32, they does not return a number bigger than signed int32.
https://github.com/joyent/node/blob/feb26d6c742980b660efc988133640cf14fc67d3/src/node_file.cc#L698
https://github.com/joyent/node/blob/feb26d6c742980b660efc988133640cf14fc67d3/src/node_file.cc#L762

Also the Buffer size is up to signed int32, may be.
https://github.com/joyent/node/blob/5e409c2f1aa94b76f42e58001f7fcd0959a958aa/src/node_buffer.cc#L178

Then I think using Number::New is not a must in this issue.
I agree that we will be necessary when Node supported large Buffer in the future.

[tshinnic]

Agreed, not needed here

I thought to add the note here because I was using your code to update another module for position value input arguments:
baudehlo/node-fs-ext@3ac09b0
and because there I had to also output position values. If people want to know how to do both, here are both answers! :-)

[japj]

can this be closed?

[koichik]

I am going to push this myself :-)
Because v0.5 was released, I merged it into the master (ab68f39).
Please review.