如何在PHP中实现zlib的crc32_combine()函数?
How to implement zlib's crc32_combine() function in PHP?
我正在尝试在 PHP 中创建 crc32_combine 函数,但我不完全理解它是 source in zlib library。
我需要这个:
<?php
$crc_a = crc32('a');
$crc_aa = crc32('aa');
$crc_aa === crc32_combine($crc_a, $crc_a, 1); // should result in TRUE
我有:
<?php
define('GF2_DIM', 32);
function gf2_matrix_times($mat, $vec) {
$sum = 0;
while ($vec) {
if ($vec & 1) {
$sum ^= $mat;
}
$vec >>= 1;
$mat++;
}
return $sum;
}
function gf2_matrix_square(&$square, &$mat) {
for ($n = 0; $n < GF2_DIM; $n++) {
$square[$n] = gf2_matrix_times($mat, $mat[$n]);
}
}
function crc32_combine($crc1, $crc2, $len2) {
$even = array_fill(0, GF2_DIM, 0);
$odd = array_fill(0, GF2_DIM, 0);
/* degenerate case (also disallow negative lengths) */
if ($len2 <= 0) {
return $crc1;
}
/* put operator for one zero bit in odd */
$odd[0] = 0xedb88320; /* CRC-32 polynomial */
$row = 1;
for ($n = 1; $n < GF2_DIM; $n++) {
$odd[$n] = $row;
$row <<= 1;
}
/* put operator for two zero bits in even */
gf2_matrix_square($even, $odd);
/* put operator for four zero bits in odd */
gf2_matrix_square($odd, $even);
/* apply len2 zeros to crc1 (first square will put the operator for one
zero byte, eight zero bits, in even) */
do {
/* apply zeros operator for this bit of len2 */
gf2_matrix_square($even, $odd);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($even, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
if ($len2 == 0) {
break;
}
/* another iteration of the loop with odd and even swapped */
gf2_matrix_square($odd, $even);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($odd, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
} while ($len2 != 0);
/* return combined crc */
$crc1 ^= $crc2;
return $crc1;
}
我认为 gf2_matrix_times 函数是错误的,因为 $mat 是一个数组,但我不知道如何重写它。
我让代码正常工作:
<?php
define('GF2_DIM', 32);
function gf2_matrix_times($mat, $vec) {
$i = 0;
$sum = 0;
while ($vec) {
if ($vec & 1) {
$sum ^= $mat[$i];
}
$vec >>= 1;
$i++;
}
return $sum;
}
function gf2_matrix_square(&$square, &$mat) {
for ($n = 0; $n < GF2_DIM; $n++) {
$square[$n] = gf2_matrix_times($mat, $mat[$n]);
}
}
function crc32_combine($crc1, $crc2, $len2) {
$even = array_fill(0, GF2_DIM, 0);
$odd = array_fill(0, GF2_DIM, 0);
/* degenerate case (also disallow negative lengths) */
if ($len2 <= 0) {
return $crc1;
}
/* put operator for one zero bit in odd */
$odd[0] = 0xedb88320; /* CRC-32 polynomial */
$row = 1;
for ($n = 1; $n < GF2_DIM; $n++) {
$odd[$n] = $row;
$row <<= 1;
}
/* put operator for two zero bits in even */
gf2_matrix_square($even, $odd);
/* put operator for four zero bits in odd */
gf2_matrix_square($odd, $even);
/* apply len2 zeros to crc1 (first square will put the operator for one
zero byte, eight zero bits, in even) */
do {
/* apply zeros operator for this bit of len2 */
gf2_matrix_square($even, $odd);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($even, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
if ($len2 == 0) {
break;
}
/* another iteration of the loop with odd and even swapped */
gf2_matrix_square($odd, $even);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($odd, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
} while ($len2 != 0);
/* return combined crc */
$crc1 ^= $crc2;
return $crc1;
}
我正在尝试在 PHP 中创建 crc32_combine 函数,但我不完全理解它是 source in zlib library。
我需要这个:
<?php
$crc_a = crc32('a');
$crc_aa = crc32('aa');
$crc_aa === crc32_combine($crc_a, $crc_a, 1); // should result in TRUE
我有:
<?php
define('GF2_DIM', 32);
function gf2_matrix_times($mat, $vec) {
$sum = 0;
while ($vec) {
if ($vec & 1) {
$sum ^= $mat;
}
$vec >>= 1;
$mat++;
}
return $sum;
}
function gf2_matrix_square(&$square, &$mat) {
for ($n = 0; $n < GF2_DIM; $n++) {
$square[$n] = gf2_matrix_times($mat, $mat[$n]);
}
}
function crc32_combine($crc1, $crc2, $len2) {
$even = array_fill(0, GF2_DIM, 0);
$odd = array_fill(0, GF2_DIM, 0);
/* degenerate case (also disallow negative lengths) */
if ($len2 <= 0) {
return $crc1;
}
/* put operator for one zero bit in odd */
$odd[0] = 0xedb88320; /* CRC-32 polynomial */
$row = 1;
for ($n = 1; $n < GF2_DIM; $n++) {
$odd[$n] = $row;
$row <<= 1;
}
/* put operator for two zero bits in even */
gf2_matrix_square($even, $odd);
/* put operator for four zero bits in odd */
gf2_matrix_square($odd, $even);
/* apply len2 zeros to crc1 (first square will put the operator for one
zero byte, eight zero bits, in even) */
do {
/* apply zeros operator for this bit of len2 */
gf2_matrix_square($even, $odd);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($even, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
if ($len2 == 0) {
break;
}
/* another iteration of the loop with odd and even swapped */
gf2_matrix_square($odd, $even);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($odd, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
} while ($len2 != 0);
/* return combined crc */
$crc1 ^= $crc2;
return $crc1;
}
我认为 gf2_matrix_times 函数是错误的,因为 $mat 是一个数组,但我不知道如何重写它。
我让代码正常工作:
<?php
define('GF2_DIM', 32);
function gf2_matrix_times($mat, $vec) {
$i = 0;
$sum = 0;
while ($vec) {
if ($vec & 1) {
$sum ^= $mat[$i];
}
$vec >>= 1;
$i++;
}
return $sum;
}
function gf2_matrix_square(&$square, &$mat) {
for ($n = 0; $n < GF2_DIM; $n++) {
$square[$n] = gf2_matrix_times($mat, $mat[$n]);
}
}
function crc32_combine($crc1, $crc2, $len2) {
$even = array_fill(0, GF2_DIM, 0);
$odd = array_fill(0, GF2_DIM, 0);
/* degenerate case (also disallow negative lengths) */
if ($len2 <= 0) {
return $crc1;
}
/* put operator for one zero bit in odd */
$odd[0] = 0xedb88320; /* CRC-32 polynomial */
$row = 1;
for ($n = 1; $n < GF2_DIM; $n++) {
$odd[$n] = $row;
$row <<= 1;
}
/* put operator for two zero bits in even */
gf2_matrix_square($even, $odd);
/* put operator for four zero bits in odd */
gf2_matrix_square($odd, $even);
/* apply len2 zeros to crc1 (first square will put the operator for one
zero byte, eight zero bits, in even) */
do {
/* apply zeros operator for this bit of len2 */
gf2_matrix_square($even, $odd);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($even, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
if ($len2 == 0) {
break;
}
/* another iteration of the loop with odd and even swapped */
gf2_matrix_square($odd, $even);
if ($len2 & 1) {
$crc1 = gf2_matrix_times($odd, $crc1);
}
$len2 >>= 1;
/* if no more bits set, then done */
} while ($len2 != 0);
/* return combined crc */
$crc1 ^= $crc2;
return $crc1;
}