BigTell seems to move the file pointer to the beginning
No, in BigTell(), the last arguments both to seek and to SetFilePointer() is 1, not 0, so those calls both seek 0 bytes from the current position; that is, neither call should reset the file position. The call to seek is there for the side effect of flushing read/write buffers and the call to SetFilePointer() is there for the side effect of obtaining the current position, even if it is past the 4GB mark.

In other words, BigTell() should act just like tell except that it works far past the 4GB mark and so returns the current position as an 8-byte string instead of as an integer.

And thanks for replying. It got me to test the code and find a typo in BigSeek() [I forgot to rename one instance of $posHigh to $posHi] and to update the original code to fix that.

I try to use something along the lines of "00010000" for the beginning of the next 4Gb segment.
Actually it would be pack( "NN", 1, 0 ) which is "\0\0\0\01\0\0\0\0" for the start of the 4GB segment.

What read call do I use from here to actually read in that segment?
I was thinking you could just use normal Perl I/O operations. But now that you mention it I guess I do recall hearing that those don't work at least some of the time. I'd think that at least sysread would work, but I've certainly been wrong before and it would take me a while to generate a 5GB file in order to test that. It makes some sense that buffered I/O operations could fail, but I was surprised to hear that just reading a huge file like a stream (even with buffering) fails.

Though you could certainly use ReadFile() [and WriteFile()] from Win32API::File. Note that if you do need to use those, then you might also need to comment out the calls to seek in both BigSeek() and BigTell() as those might also break in such cases.

        - tye (but my friends call me "Tye")

In reply to (tye)Re2: 4Gb filesize limit by tye
in thread 4Gb filesize limit by ruffing

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