Rearranging data in files

There is an array of numbers, divided into partitions containing the same number of elements (as an output of array_chunk()). They are written into separate files, file 1.txt contains the first chunk, 2.txt - the second and so on. And now I want these files to contain a different number of elements of the initial array. Of course, I can read them into one arra开发者_开发知识库y and split it again, but it requires quite a large amount of memory. Could you please help me with a more efficient solution? (The number of files and the size of the last are stored separately) I have no other ideas...

Do you know what the different number is? If you do, then you can easily read data in, and then whenever you fill a chunk write data out. In pseudo-code:

for each original file:
    for each record:
        add record to buffer
        if buffer is desired size:
            write new file
            clear buffer
write new file

Obviously you'll need to keep new files separate from old ones. And then, once you've rewritten the data, you can swap them out somehow. (I would personally suggest having two directories, then rename directories after you're done.)

If you don't know what the size of your chunks should be (for instance you want a specific number of files) then first do whatever work it needs to figure that out, then proceed with the original solution.