add read/writePointer to be used in threads (de)serializePointer

[BTNC]

Hi,

Added read/writePointer together with a test case 'readWritePointer' in test/test_sharedmem.lua. The implementation of (de)serializePointer in threads will be replaced with these new functions instead of relying on readWriteLong/Double.

Travis-ci fail for osx with following error during test, but the compilation does succeed.
/Users/travis/torch/install/bin/luajit: /Users/travis/torch/install/share/lua/5.1/torch/init.lua:13: cannot load '/Users/travis/torch/install/lib/lua/5.1/libtorch.so'

Thanks,

[soumith]

thanks. dont worry about the OSX build, it's been failing on travis, i have to take a look at it.

[gchanan]

do we need to declare this for all File types, or can it just be in MemoryFile? Seems only useful there.

I haven't thought through if this complicates the implementation; have you considered it?

[gchanan]

nit: rename convenient to convenience.

[gchanan]

here too.

[BTNC]

Yes, it seems only useful for MemoryFile. However if remove this from DiskFile, it would be against the purpose of virtual table and will complicate the implementation and maintenance. By using virtual table (as in c++), it is not expected some sub class have null function pointers in virtual table. To remove this from DiskFile, the function pointers have to be initialized as null pointers and the callers have to check if the function pointers are null pointers before calling them. This special logic will make the implementation less straightforward and less maintainable. Besides, it will add unnecessary null pointer check for the normal case, the MemoryFile case.