/**
* Converts base-2, base-10, base-16, and binary strings (eg. base-256) to BigIntegers.
*
* If the second parameter - $base - is negative, then it will be assumed that the number's are encoded using
* two's compliment. The sole exception to this is -10, which is treated the same as 10 is.
*
* Here's an example:
* <code>
* <?php
* include('Math/BigInteger.php');
*
* $a = new Math_BigInteger('0x32', 16); // 50 in base-16
*
* echo $a->toString(); // outputs 50
* ?>
* </code>
*
* @param string[optional] $x base-10 number or base-$base number if $base set.
* @param integer[optional] $base
* @return Math_BigInteger
* @access public
*/
public function __construct($x = 0, $base = 10)
{
if (null === self::$mode) {
switch (true) {
case extension_loaded('gmp'):
self::$mode = Math_BigInteger::MODE_GMP;
break;
case extension_loaded('bcmath'):
self::$mode = Math_BigInteger::MODE_BCMATH;
break;
default:
self::$mode = Math_BigInteger::MODE_INTERNAL;
}
}
switch (self::$mode) {
case Math_BigInteger::MODE_GMP:
if (is_resource($x) && get_resource_type($x) == 'GMP integer') {
$this->value = $x;
return;
}
$this->value = gmp_init(0);
break;
case Math_BigInteger::MODE_BCMATH:
$this->value = '0';
break;
default:
$this->value = array();
}
if (empty($x)) {
return;
}
switch ($base) {
case -256:
if (ord($x[0]) & 0x80) {
$x = ~$x;
$this->is_negative = true;
}
case 256:
switch (self::$mode) {
case Math_BigInteger::MODE_GMP:
$sign = $this->is_negative ? '-' : '';
$this->value = gmp_init($sign . '0x' . bin2hex($x));
break;
case Math_BigInteger::MODE_BCMATH:
// round $len to the nearest 4 (thanks, DavidMJ!)
$len = strlen($x) + 3 & 0xfffffffc;
$x = str_pad($x, $len, chr(0), STR_PAD_LEFT);
for ($i = 0; $i < $len; $i += 4) {
$this->value = bcmul($this->value, '4294967296', 0);
// 4294967296 == 2**32
$this->value = bcadd($this->value, 0x1000000 * ord($x[$i]) + (ord($x[$i + 1]) << 16 | ord($x[$i + 2]) << 8 | ord($x[$i + 3])), 0);
}
if ($this->is_negative) {
$this->value = '-' . $this->value;
}
break;
// converts a base-2**8 (big endian / msb) number to base-2**26 (little endian / lsb)
// converts a base-2**8 (big endian / msb) number to base-2**26 (little endian / lsb)
default:
while (strlen($x)) {
$this->value[] = $this->_bytes2int($this->_base256_rshift($x, 26));
}
}
if ($this->is_negative) {
if (self::$mode != Math_BigInteger::MODE_INTERNAL) {
$this->is_negative = false;
}
$temp = $this->add(new Math_BigInteger('-1'));
$this->value = $temp->value;
}
break;
case 16:
case -16:
if ($base > 0 && $x[0] == '-') {
$this->is_negative = true;
$x = substr($x, 1);
}
$x = preg_replace('#^(?:0x)?([A-Fa-f0-9]*).*#', '$1', $x);
$is_negative = false;
if ($base < 0 && hexdec($x[0]) >= 8) {
$this->is_negative = $is_negative = true;
$x = bin2hex(~pack('H*', $x));
}
switch (self::$mode) {
case Math_BigInteger::MODE_GMP:
$temp = $this->is_negative ? '-0x' . $x : '0x' . $x;
$this->value = gmp_init($temp);
$this->is_negative = false;
break;
case Math_BigInteger::MODE_BCMATH:
$x = strlen($x) & 1 ? '0' . $x : $x;
$temp = new Math_BigInteger(pack('H*', $x), 256);
$this->value = $this->is_negative ? '-' . $temp->value : $temp->value;
$this->is_negative = false;
break;
default:
$x = strlen($x) & 1 ? '0' . $x : $x;
$temp = new Math_BigInteger(pack('H*', $x), 256);
$this->value = $temp->value;
}
if ($is_negative) {
$temp = $this->add(new Math_BigInteger('-1'));
$this->value = $temp->value;
}
break;
case 10:
case -10:
$x = preg_replace('#^(-?[0-9]*).*#', '$1', $x);
switch (self::$mode) {
case Math_BigInteger::MODE_GMP:
$this->value = gmp_init($x);
break;
case Math_BigInteger::MODE_BCMATH:
// explicitly casting $x to a string is necessary, here, since doing $x[0] on -1 yields different
// results then doing it on '-1' does (modInverse does $x[0])
$this->value = (string) $x;
break;
default:
$temp = new Math_BigInteger();
// array(10000000) is 10**7 in base-2**26. 10**7 is the closest to 2**26 we can get without passing it.
$multiplier = new Math_BigInteger();
$multiplier->value = array(10000000);
if ($x[0] == '-') {
$this->is_negative = true;
$x = substr($x, 1);
}
$x = str_pad($x, strlen($x) + 6 * strlen($x) % 7, 0, STR_PAD_LEFT);
while (strlen($x)) {
$temp = $temp->multiply($multiplier);
$temp = $temp->add(new Math_BigInteger($this->_int2bytes(substr($x, 0, 7)), 256));
$x = substr($x, 7);
}
$this->value = $temp->value;
}
break;
case 2:
// base-2 support originally implemented by Lluis Pamies - thanks!
// base-2 support originally implemented by Lluis Pamies - thanks!
case -2:
if ($base > 0 && $x[0] == '-') {
$this->is_negative = true;
$x = substr($x, 1);
}
$x = preg_replace('#^([01]*).*#', '$1', $x);
$x = str_pad($x, strlen($x) + 3 * strlen($x) % 4, 0, STR_PAD_LEFT);
$str = '0x';
while (strlen($x)) {
$part = substr($x, 0, 4);
$str .= dechex(bindec($part));
$x = substr($x, 4);
}
if ($this->is_negative) {
$str = '-' . $str;
}
$temp = new Math_BigInteger($str, 8 * $base);
// ie. either -16 or +16
$this->value = $temp->value;
$this->is_negative = $temp->is_negative;
break;
default:
// base not supported, so we'll let $this == 0
}
}
