<?php
function string_shift_left($input, $inputlen, $bits, &$output = null)
{
$skip = (int) ($bits / 8);
$copylen = (int) ($inputlen - $skip);
$offset = ($bits % 8) & 0xff;
$mask = (0xff >> $offset) << (8 - $offset);
$output = str_pad('', $inputlen + 1, "\x00");
echo "$skip $copylen $offset $mask\n";
if ($offset == 0) {
/* Shifting multiples of 8 allows us to simply copy the relevant bytes */
for ($i = 0; $i < $copylen; $i++) {
$output[$i] = $input[$i + $skip];
}
return;
}
for ($i = 0; $i < $copylen; $i++) {
$left = (ord($input[$i + $skip]) << $offset);
$right = (ord($input[$i + $skip + 1]) & $mask) >> $offset;
printf("%02x ", $left | $right);
$output[$i] = chr($left | $right);
}
}
//0b000100010001000100000000;
$str = "abc\x00";
$bits = 2;
string_shift_left($str, strlen($str) - 1, $bits, $output);
for ($i = 0; $i < strlen($output); $i++) {
printf("\n%02x", ord($output[$i]));
}
preferences:
40.51 ms | 402 KiB | 5 Q