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<?php
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @package Avro
*/
/**
* Methods for handling 64-bit operations using the GMP extension.
*
* This is a naive and hackish implementation that is intended
* to work well enough to support Avro. It has not been tested
* beyond what's needed to decode and encode long values.
*
* @package Avro
*/
class AvroGMP {
/**
* @var resource memoized GMP resource for zero
*/
private static $gmp_0;
/**
* @returns resource GMP resource for zero
*/
private static function gmp_0()
{
if (!isset(self::$gmp_0))
self::$gmp_0 = gmp_init('0');
return self::$gmp_0;
}
/**
* @var resource memoized GMP resource for one (1)
*/
private static $gmp_1;
/**
* @returns resource GMP resource for one (1)
*/
private static function gmp_1()
{
if (!isset(self::$gmp_1))
self::$gmp_1 = gmp_init('1');
return self::$gmp_1;
}
/**
* @var resource memoized GMP resource for two (2)
*/
private static $gmp_2;
/**
* @returns resource GMP resource for two (2)
*/
private static function gmp_2()
{
if (!isset(self::$gmp_2))
self::$gmp_2 = gmp_init('2');
return self::$gmp_2;
}
/**
* @var resource memoized GMP resource for 0x7f
*/
private static $gmp_0x7f;
/**
* @returns resource GMP resource for 0x7f
*/
private static function gmp_0x7f()
{
if (!isset(self::$gmp_0x7f))
self::$gmp_0x7f = gmp_init('0x7f');
return self::$gmp_0x7f;
}
/**
* @var resource memoized GMP resource for 64-bit ~0x7f
*/
private static $gmp_n0x7f;
/**
* @returns resource GMP resource for 64-bit ~0x7f
*/
private static function gmp_n0x7f()
{
if (!isset(self::$gmp_n0x7f))
self::$gmp_n0x7f = gmp_init('0xffffffffffffff80');
return self::$gmp_n0x7f;
}
/**
* @var resource memoized GMP resource for 64-bits of 1
*/
private static $gmp_0xfs;
/**
* @returns resource GMP resource for 64-bits of 1
*/
private static function gmp_0xfs()
{
if (!isset(self::$gmp_0xfs))
self::$gmp_0xfs = gmp_init('0xffffffffffffffff');
return self::$gmp_0xfs;
}
/**
* @param GMP resource
* @returns GMP resource 64-bit two's complement of input.
*/
static function gmp_twos_complement($g)
{
return gmp_neg(gmp_sub(gmp_pow(self::gmp_2(), 64), $g));
}
/**
* @interal Only works up to shift 63 (doesn't wrap bits around).
* @param resource|int|string $g
* @param int $shift number of bits to shift left
* @returns resource $g shifted left
*/
static function shift_left($g, $shift)
{
if (0 == $shift)
return $g;
if (0 > gmp_sign($g))
$g = self::gmp_twos_complement($g);
$m = gmp_mul($g, gmp_pow(self::gmp_2(), $shift));
$m = gmp_and($m, self::gmp_0xfs());
if (gmp_testbit($m, 63))
$m = gmp_neg(gmp_add(gmp_and(gmp_com($m), self::gmp_0xfs()),
self::gmp_1()));
return $m;
}
/**
* Arithmetic right shift
* @param resource|int|string $g
* @param int $shift number of bits to shift right
* @returns resource $g shifted right $shift bits
*/
static function shift_right($g, $shift)
{
if (0 == $shift)
return $g;
if (0 <= gmp_sign($g))
$m = gmp_div($g, gmp_pow(self::gmp_2(), $shift));
else // negative
{
$g = gmp_and($g, self::gmp_0xfs());
$m = gmp_div($g, gmp_pow(self::gmp_2(), $shift));
$m = gmp_and($m, self::gmp_0xfs());
for ($i = 63; $i >= (63 - $shift); $i--)
gmp_setbit($m, $i);
$m = gmp_neg(gmp_add(gmp_and(gmp_com($m), self::gmp_0xfs()),
self::gmp_1()));
}
return $m;
}
/**
* @param int|str $n integer (or string representation of integer) to encode
* @return string $bytes of the long $n encoded per the Avro spec
*/
static function encode_long($n)
{
$g = gmp_init($n);
$g = gmp_xor(self::shift_left($g, 1),
self::shift_right($g, 63));
$bytes = '';
while (0 != gmp_cmp(self::gmp_0(), gmp_and($g, self::gmp_n0x7f())))
{
$bytes .= chr(gmp_intval(gmp_and($g, self::gmp_0x7f())) | 0x80);
$g = self::shift_right($g, 7);
}
$bytes .= chr(gmp_intval($g));
return $bytes;
}
/**
* @param int[] $bytes array of ascii codes of bytes to decode
* @return string represenation of decoded long.
*/
static function decode_long_from_array($bytes)
{
$b = array_shift($bytes);
$g = gmp_init($b & 0x7f);
$shift = 7;
while (0 != ($b & 0x80))
{
$b = array_shift($bytes);
$g = gmp_or($g, self::shift_left(($b & 0x7f), $shift));
$shift += 7;
}
$val = gmp_xor(self::shift_right($g, 1), gmp_neg(gmp_and($g, 1)));
return gmp_strval($val);
}
}
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