[RESOLVED] Replacing first few bytes of a file

[knucklehead]

Hello!

How could I replace first few bytes of a file with a string of my choice while using chunks-copying method for better handling of large files?

Code I have so far looks similar to this and it's only copying a file so far...

function copyFile($file_in, $file_out) {
    $in = fopen($file_in, 'rb');
    $out = fopen($file_out, 'wb');

while (!feof($in)) {
    if (fwrite($out, fread($in, 1024)) === FALSE) {
        return false;
    }
}

fclose($in);
fclose($out);

return true;
}

Thanks for helping in advance!

[bradgrafelman]

Before your while() loop, fread() the "first few bytes" and do whatever you wish to them (including discarding them entirely), then fwrite() the modified bytes. Your while() loop then remains unchanged (since it's only used to duplicate the rest of the file).

Alternatively, you could do something like: [man]copy/man the in file to the out file destination, [man]fopen/man the out file using the 'c' mode, and then fwrite() the "first few bytes" you wish to overwrite.

[knucklehead]

Hi and thanks for reply!
I did try to put

rewind($out);
fwrite($out, 'my_custom_string');

just after my while loop and it seems it works fine so far... Is that a good approach at all?
I will take a look at your answer and try to play with it a bit, but if the thing I did is acceptable I will mark this as resolved 🙂

Thanks for helping!

[Weedpacket]

Your solution - and bradgrafelman's second suggestion - both assume that your replacement is exactly the same length as what you're replacing. bradgrafelman's first suggestion doesn't have that limitation, and doesn't need the extra rewind/rewrite steps either (and will therefore work on streams that can't be rewound).

[knucklehead]

Ok, thanks for this great info and helping with this. I'm marking it resolved and will try to implement bradgrafelman's first solution as suggested to avoid potential problems 🙂