<?php
/** @package    php-gpg::GPG */

/** seed rand */
list($gpg_usec, $gpg_sec) = explode(' ', microtime());
srand((float) $gpg_sec + ((float) $gpg_usec * 100000));

/**
 * @package    php-gpg::GPG
 */
class GPG_Utility
{
	
	static function starts_with($haystack, $needle)
	{
		return $needle === "" || strpos($haystack, $needle) === 0;
	}
	
	static function B0($x) {
		return ($x & 0xff);
	}
	
	static function B1($x) {
		return (($x >> 0x8) & 0xff);
	}
	
	static function B2($x) {
		return (($x >> 0x10) & 0xff);
	}
	
	static function B3($x) {
		return (($x >> 0x18) & 0xff);
	}
	
	static function zshift($x, $s) {
		$res = $x >> $s;
		
		$pad = 0;
		for ($i = 0; $i < 32 - $s; $i++) $pad += (1 << $i);
		
		return $res & $pad;
	}
	
	static function pack_octets($octets)
	{
		$i = 0;
		$j = 0;
		$len = count($octets);
		$b = array_fill(0, $len / 4, 0);
		
		if (!$octets || $len % 4) return;
		
		for ($i = 0, $j = 0; $j < $len; $j += 4) {
			$b[$i++] = $octets[$j] | ($octets[$j + 1] << 0x8) | ($octets[$j + 2] << 0x10) | ($octets[$j + 3] << 0x18);
			
		}
		
		return $b;  
	}
	
	static function unpack_octets($packed)
	{
		$j = 0;
		$i = 0;
		$l = count($packed);
		$r = array_fill(0, $l * 4, 0);
		
		for ($j = 0; $j < $l; $j++) {
			$r[$i++] = GPG_Utility::B0($packed[$j]);
			$r[$i++] = GPG_Utility::B1($packed[$j]);
			$r[$i++] = GPG_Utility::B2($packed[$j]);
			$r[$i++] = GPG_Utility::B3($packed[$j]);
		}
		
		return $r;
	}




	static function hex2bin($h)
	{
		if(strlen($h) % 2) $h += "0";

		$r = "";
		for($i = 0; $i < strlen($h); $i += 2) {
			$r .= chr(intval($h[$i], 16) * 16 + intval($h[$i + 1], 16));
		}

		return $r;
	}

	static function crc24($data)
	{
		$crc = 0xb704ce;

		for($n = 0; $n < strlen($data); $n++) {
			$crc ^= (ord($data[$n]) & 0xff) << 0x10;
			for($i = 0; $i < 8; $i++) {
				$crc <<= 1;
				if($crc & 0x1000000) $crc ^= 0x1864cfb;
			}       
		}
	    
		return
			chr(($crc >> 0x10) & 0xff) .
			chr(($crc >> 0x8) & 0xff) .
			chr($crc & 0xff);
	}

	static function s_random($len, $textmode)
	{
		$r = "";
		for($i = 0; $i < $len;)
		{
			$t = rand(0, 0xff);
			if($t == 0 && $textmode) continue;
			$i++;

			$r .= chr($t);
		}

		return $r;
	}

	static function c_random() {
		return round(rand(0, 0xff));
	}

}
?>