在PHP中交换文本的字节

Question

I basically need to port this piece of code to php

for (i = 0; i < 128/4; i++)
    data32[i] = bswap_32(data32[i]);

But, there is no bswap function in php.

Would someone be kind enough to provide me with something that could solve the problem?

Answer 1

This should do it (untested):

function bswap_32($j)
{
    return (($j & 255) << 24) | (($j & 0xff00) << 8) |
           (($j & 0xff0000) >> 8) | (($j & 0xff000000) >> 24);
}

Or, if there is a sign extension problem, this should resolve it:

function bswap_32($j)
{
    return (($j & 255) << 24) | (($j & 0xff00) << 8) |
           (($j & 0xff0000) >> 8) | (255 & (($j & 0xff000000) >> 24));
}