crc32

    (PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

    crc32 — 计算一个字符串的 crc32 多项式

    说明

    crc32(string $string): int

    生成 string 的 32 位循环冗余校验和多项式。这通常用于检查正在传输的数据是否完整。

    警告

    由于 PHP 的整数类型是有符号的，所以在 32 位系统上许多 crc32 校验和将产生负整数。不过在 64 位上所有 crc32() 的结果将都是正整数。

    因此需要使用 sprintf() 或 printf() 的“%u”格式标志符获取十进制格式的无符号 crc32 校验和的字符串表示形式。

    对于十六进制的校验和可以使用 sprintf() 或 printf() 的“%x”格式标志符或 dechex() 转换程序，这两个函数负责将 crc32() 结果转为无符号整数。

    64 位的设备也会返回负数，更高的结果值会破坏十六进制转换，因为负数会得到额外的 0xFFFFFFFF######## 偏移量。由于十六进制似乎是最常见的用例，所以决定不破坏该原则，即使从 32 位移动到 64 位时破坏了大约 50% 的十进制直接比较。

    回想一下，让函数返回整数可能不是最好的主意，而立即返回十六进制的字符串（例如 md5()）可能是更好的开始。

    可移植方案可以考虑通用的 hash()。hash("crc32b", $str) 返回跟 str_pad(dechex(crc32($str)), 8, '0', STR_PAD_LEFT) 相同的字符串。

    参数

    string

    要校验的数据。

    返回值

    以整数形式返回 string 的 crc32 校验和。

    示例

    示例 #1 显示 crc32 校验和

    示例中演示了如何使用 printf() 函数打印转换后的校验和：

    <?php
    $checksum     = crc32("The quick brown fox jumped over the lazy dog.");
    printf("%u\n", $checksum);
    ?>

    参见

    • hash() - 生成散列值（消息摘要）
    • md5() - 计算字符串的 MD5 散列值
    • sha1() - 计算字符串的 sha1 散列值

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    ＋添加备注

    用户贡献的备注 22 notes

    up
    24
    jian at theorchard dot com
    14 years ago
    This function returns an unsigned integer from a 64-bit Linux platform. It does return the signed integer from other 32-bit platforms even a 64-bit Windows one.

    The reason is because the two constants PHP_INT_SIZE and PHP_INT_MAX have different values on the 64-bit Linux platform.

    I've created a work-around function to handle this situation.

    <?php
    function get_signed_int($in) {
    $int_max = pow(2, 31)-1;
    if (    $in > $int_max){
    $out = $in - $int_max * 2 - 2;
    }
    else {
    $out = $in;
    }
    return     $out;
    }
    ?>

    Hope this helps.
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    11
    i at morfi dot ru
    11 years ago
    Implementation crc64() in php 64bit

    <?php

    /**
    * @return array
    */
    function crc64Table()
    {
    $crc64tab = [];

    // ECMA polynomial
    $poly64rev = (0xC96C5795 << 32) | 0xD7870F42;

    // ISO polynomial
    // $poly64rev = (0xD8 << 56);

    for ($i = 0; $i < 256; $i++)
    {
    for (    $part = $i, $bit = 0; $bit < 8; $bit++) {
    if (    $part & 1) {
    $part = (($part >> 1) & ~(0x8 << 60)) ^ $poly64rev;
    } else {
    $part = ($part >> 1) & ~(0x8 << 60);
    }
    }

    $crc64tab[$i] = $part;
    }

    return     $crc64tab;
    }

    /**
    * @param string $string
    * @param string $format
    * @return mixed
    *
    * Formats:
    * crc64('php'); // afe4e823e7cef190
    * crc64('php', '0x%x'); // 0xafe4e823e7cef190
    * crc64('php', '0x%X'); // 0xAFE4E823E7CEF190
    * crc64('php', '%d'); // -5772233581471534704 signed int
    * crc64('php', '%u'); // 12674510492238016912 unsigned int
    */
    function crc64($string, $format = '%x')
    {
    static     $crc64tab;

    if (    $crc64tab === null) {
    $crc64tab = crc64Table();
    }

    $crc = 0;

    for (    $i = 0; $i < strlen($string); $i++) {
    $crc = $crc64tab[($crc ^ ord($string[$i])) & 0xff] ^ (($crc >> 8) & ~(0xff << 56));
    }

    return     sprintf($format, $crc);
    }
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    9
    JS at JavsSys dot Org
    11 years ago
    The khash() function by sukitsupaluk has two problems, it does not use all 62 characters from the $map set and when corrected it then produces different results on 64-bit compared to 32-bit PHP systems.

    Here is my modified version :

    <?php

    /**
    * Small sample convert crc32 to character map
    * Based upon http://www.php.net/manual/en/function.crc32.php#105703
    * (Modified to now use all characters from $map)
    * (Modified to be 32-bit PHP safe)
    */
    function khash($data)
    {
    static     $map = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $hash = bcadd(sprintf('%u',crc32($data)) , 0x100000000);
    $str = "";
    do
    {
    $str = $map[bcmod($hash, 62) ] . $str;
    $hash = bcdiv($hash, 62);
    }
    while (    $hash >= 1);
    return     $str;
    }
    //-----------------------------------------------------------------------------------
    $test = array(null, true, false, 0, "0", 1, "1", "2", "3", "ab", "abc", "abcd",
    "abcde", "abcdefoo", "248840027", "1365848013", // time()
    "9223372035488927794", // PHP_INT_MAX-time()
    "901131979", // mt_rand()
    "Sat, 13 Apr 2013 10:13:33 +0000" // gmdate('r')
    );
    $out = array();
    foreach (    $test as $s)
    {
    $out[] = khash($s) . ": " . $s;
    }
    print     "<h3>khash() -- maps a crc32 result into a (62-character) result</h3>";
    print     '<pre>';
    var_dump($out);
    print     "\n\n\$GLOBALS['raw_crc32']:\n";
    var_dump($GLOBALS['raw_crc32']);
    print     '</pre><hr>';
    flush();
    $pefile = __FILE__;
    print     "<h3>$pefile</h3>";
    ob_end_flush();
    flush();
    highlight_file($pefile);
    print     "<hr>";
    //-----------------------------------------------------------------------------------
    /* CURRENT output
    array(19) {
    [0]=>
    string(8) "4GFfc4: "
    [1]=>
    string(9) "76nO4L: 1"
    [2]=>
    string(8) "4GFfc4: "
    [3]=>
    string(9) "9aGcIp: 0"
    [4]=>
    string(9) "9aGcIp: 0"
    [5]=>
    string(9) "76nO4L: 1"
    [6]=>
    string(9) "76nO4L: 1"
    [7]=>
    string(9) "5b8iNn: 2"
    [8]=>
    string(9) "6HmfFN: 3"
    [9]=>
    string(10) "7ADPD7: ab"
    [10]=>
    string(11) "5F0aUq: abc"
    [11]=>
    string(12) "92kWw9: abcd"
    [12]=>
    string(13) "78hcpf: abcde"
    [13]=>
    string(16) "9eBVPB: abcdefoo"
    [14]=>
    string(17) "5TjOuZ: 248840027"
    [15]=>
    string(18) "5eNliI: 1365848013"
    [16]=>
    string(27) "4Q00e5: 9223372035488927794"
    [17]=>
    string(17) "6DUX8V: 901131979"
    [18]=>
    string(39) "5i2aOW: Sat, 13 Apr 2013 10:13:33 +0000"
    }
    */
    //-----------------------------------------------------------------------------------

    ?>
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    10
    Bulk at bulksplace dot com
    19 years ago
    A faster way I've found to return CRC values of larger files, is instead of using the file()/implode() method used below, is to us file_get_contents() (PHP 4 >= 4.3.0) which uses memory mapping techniques if supported by your OS to enhance performance. Here's my example function:

    <?php
    // $file is the path to the file you want to check.
    function file_crc($file)
    {
    $file_string = file_get_contents($file);

    $crc = crc32($file_string);

    return     sprintf("%u", $crc);
    }

    $file_to_crc = /home/path/to/file.jpg;

    echo     file_crc($file_to_crc); // Outputs CRC value for given file.
    ?>

    I've found in testing this method is MUCH faster for larger binary files.
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    8
    slimshady451
    17 years ago
    I see a lot of function for crc32_file, but for php version >= 5.1.2 don't forget you can use this :

    <?php
    function crc32_file($filename)
    {
    return     hash_file ('CRC32', $filename , FALSE );
    }
    ?>

    Using crc32(file_get_contents($filename)) will use too many memory on big file so don't use it.
    up
    6
    same
    20 years ago
    bit by bit crc32 computation

    <?php

    function bitbybit_crc32($str,$first_call=false){

    //reflection in 32 bits of crc32 polynomial 0x04C11DB7
    $poly_reflected=0xEDB88320;

    //=0xFFFFFFFF; //keep track of register value after each call
    static $reg=0xFFFFFFFF;

    //initialize register on first call
    if($first_call) $reg=0xFFFFFFFF;

    $n=strlen($str);
    $zeros=$n<4 ? $n : 4;

    //xor first $zeros=min(4,strlen($str)) bytes into the register
    for($i=0;$i<$zeros;$i++)
    $reg^=ord($str{$i})<<$i*8;

    //now for the rest of the string
    for($i=4;$i<$n;$i++){
    $next_char=ord($str{$i});
    for(    $j=0;$j<8;$j++)
    $reg=(($reg>>1&0x7FFFFFFF)|($next_char>>$j&1)<<0x1F)
    ^(    $reg&1)*$poly_reflected;
    }

    //put in enough zeros at the end
    for($i=0;$i<$zeros*8;$i++)
    $reg=($reg>>1&0x7FFFFFFF)^($reg&1)*$poly_reflected;

    //xor the register with 0xFFFFFFFF
    return ~$reg;
    }

    $str="123456789"; //whatever
    $blocksize=4; //whatever

    for($i=0;$i<strlen($str);$i+=$blocksize) $crc=bitbybit_crc32(substr($str,$i,$blocksize),!$i);

    ?>
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    5
    dave at jufer dot info
    16 years ago
    This function returns the same int value on a 64 bit mc. like the crc32() function on a 32 bit mc.

    <?php
    function crcKw($num){
    $crc = crc32($num);
    if(    $crc & 0x80000000){
    $crc ^= 0xffffffff;
    $crc += 1;
    $crc = -$crc;
    }
    return     $crc;
    }
    ?>
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    3
    Clifford dot ct at gmail dot com
    12 years ago
    The crc32() function can return a signed integer in certain environments. Assuming that it will always return an unsigned integer is not portable.

    Depending on your desired behavior, you should probably use sprintf() on the result or the generic hash() instead. Also note that integer arithmetic operators do not have the precision to work correctly with the integer output.
    up
    3
    alban dot lopez+php [ at ] gmail dot com
    12 years ago
    I made this code to verify Transmition with Vantage Pro2 ( weather station ) based on CRC16-CCITT standard.

    <?php
    // CRC16-CCITT validator
    $crc_table = array(
    0x0, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
    0x1231, 0x210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
    0x2462, 0x3443, 0x420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0xa50, 0x3a33, 0x2a12,
    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0xc60, 0x1c41,
    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0xe70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
    0x1080, 0xa1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
    0x2b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
    0x26d3, 0x36f2, 0x691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x8e1, 0x3882, 0x28a3,
    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0xaf1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0xcc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0xed1, 0x1ef0);

    $test = chr(0xC6).chr(0xCE).chr(0xA2).chr(0x03); // CRC16-CCITT = 0xE2B4
    genCRC ($test);

    function     genCRC (&$ptr)
    {
    $crc = 0x0000;
    $crc_table = $GLOBALS['crc_table'];
    for (    $i = 0; $i < strlen($ptr); $i++)
    $crc = $crc_table[(($crc>>8) ^ ord($ptr[$i]))] ^ (($crc<<8) & 0x00FFFF);
    return     $crc;
    }
    ?>
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    3
    arachnid at notdot dot net
    20 years ago
    Note that the CRC32 algorithm should NOT be used for cryptographic purposes, or in situations where a hostile/untrusted user is involved, as it is far too easy to generate a hash collision for CRC32 (two different binary strings that have the same CRC32 hash). Instead consider SHA-1 or MD5.
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    2
    spectrumizer at cycos dot net
    21 years ago
    Here is a tested and working CRC16-Algorithm:

    <?php
    function crc16($string) {
    $crc = 0xFFFF;
    for (    $x = 0; $x < strlen ($string); $x++) {
    $crc = $crc ^ ord($string[$x]);
    for (    $y = 0; $y < 8; $y++) {
    if ((    $crc & 0x0001) == 0x0001) {
    $crc = (($crc >> 1) ^ 0xA001);
    } else {     $crc = $crc >> 1; }
    }
    }
    return     $crc;
    }
    ?>

    Regards,
    Mario
    up
    4
    roberto at spadim dot com dot br
    18 years ago
    MODBUS RTU, CRC16,
    input-> modbus rtu string
    output -> 2bytes string, in correct modbus order

    <?php
    function crc16($string,$length=0){

    $auchCRCHi=array( 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
    0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81,
    0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
    0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
    0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
    0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
    0x40);
    $auchCRCLo=array( 0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4,
    0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
    0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD,
    0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7,
    0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
    0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE,
    0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2,
    0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
    0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB,
    0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91,
    0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
    0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88,
    0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80,
    0x40);
    $length =($length<=0?strlen($string):$length);
    $uchCRCHi =0xFF;
    $uchCRCLo =0xFF;
    $uIndex =0;
    for (    $i=0;$i<$length;$i++){
    $uIndex =$uchCRCLo ^ ord(substr($string,$i,1));
    $uchCRCLo =$uchCRCHi ^ $auchCRCHi[$uIndex];
    $uchCRCHi =$auchCRCLo[$uIndex] ;
    }
    return(    chr($uchCRCLo).chr($uchCRCHi));
    }
    ?>
    up
    2
    sukitsupaluk at hotmail dot com
    13 years ago
    small sample convert crc32 to character map

    <?php

    function khash($data) {
    static     $map="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $hash=crc32($data)+0x100000000;
    $str = "";
    do {
    $str = $map[31+ ($hash % 31)] . $str;
    $hash /= 31;
    } while(    $hash >= 1);
    return     $str;
    }
    $test= array(null,TRUE,FALSE,0,"0",1,"1","2","3","ab","abc","abcd","abcde","abcdefoo");
    $out = array();
    foreach(    $test as $s)
    {
    $out[]=khash($s).": ". $s;
    }
    var_dump($out);

    /*
    output:
    array
    0 => string 'zVvOYTv: ' (length=9)
    1 => string 'xKDKKL8: 1' (length=10)
    2 => string 'zVvOYTv: ' (length=9)
    3 => string 'zOKCQxh: 0' (length=10)
    4 => string 'zOKCQxh: 0' (length=10)
    5 => string 'xKDKKL8: 1' (length=10)
    6 => string 'xKDKKL8: 1' (length=10)
    7 => string 'AFSzIAO: 2' (length=10)
    8 => string 'BXGSvQJ: 3' (length=10)
    9 => string 'xZWOQSu: ab' (length=11)
    10 => string 'AVAwHOR: abc' (length=12)
    11 => string 'zKASNE1: abcd' (length=13)
    12 => string 'xLCTOV7: abcde' (length=14)
    13 => string 'zQLzKMt: abcdefoo' (length=17)

    */

    ?>
    up
    1
    chernyshevsky at hotmail dot com
    14 years ago
    The crc32_combine() function provided by petteri at qred dot fi has a bug that causes an infinite loop, a shift operation on a 32-bit signed int might never reach zero. Replacing the function gf2_matrix_times() with the following seems to fix it:

    <?php
    function gf2_matrix_times($mat, $vec)
    {
    $sum=0;
    $i=0;

    while (    $vec) {
    if (    $vec & 1) {
    $sum ^= $mat[$i];
    }
    $vec = ($vec >> 1) & 0x7FFFFFFF;
    $i++;
    }
    return     $sum;
    }
    ?>

    Otherwise, it's probably the best solution if you can't use hash_file(). Using a 1meg read buffer, the function only takes twice as long to process a 300meg files than hash_file() in my test.
    up
    1
    berna (at) gensis (dot) com (dot) br
    15 years ago
    For those who want a more familiar return value for the function:

    <?php
    function strcrc32($text) {
    $crc = crc32($text);
    if (    $crc & 0x80000000) {
    $crc ^= 0xffffffff;
    $crc += 1;
    $crc = -$crc;
    }
    return     $crc;
    }
    ?>

    And to show the result in Hex string:

    <?php
    function int32_to_hex($value) {
    $value &= 0xffffffff;
    return     str_pad(strtoupper(dechex($value)), 8, "0", STR_PAD_LEFT);
    }
    ?>
    up
    1
    arris at zsolttech dot com
    13 years ago
    not found anywhere crc64 based on http://bioinfadmin.cs.ucl.ac.uk/downloads/crc64/crc64.c .

    (use gmp module)

    <?php

    /* OLDCRC */
    define('POLY64REV', "d800000000000000");
    define('INITIALCRC', "0000000000000000");
    define('TABLELEN', 256);
    /* NEWCRC */
    // define('POLY64REV', "95AC9329AC4BC9B5");
    // define('INITIALCRC', "FFFFFFFFFFFFFFFF");

    if(function_exists('gmp_init')){
    class     CRC64{

    private static     $CRCTable = array();

    public static function     encode($seq){

    $crc = gmp_init(INITIALCRC, 16);
    $init = FALSE;
    $poly64rev = gmp_init(POLY64REV, 16);

    if (!    $init)
    {
    $init = TRUE;
    for (    $i = 0; $i < TABLELEN; $i++)
    {
    $part = gmp_init($i, 10);
    for (    $j = 0; $j < 8; $j++)
    {
    if (    gmp_strval(gmp_and($part, "0x1")) != "0"){
    // if (gmp_testbit($part, 1)){ /* PHP 5 >= 5.3.0, untested */
    $part = gmp_xor(gmp_div_q($part, "2"), $poly64rev);
    } else {
    $part = gmp_div_q($part, "2");
    }
    }
    self::$CRCTable[$i] = $part;
    }
    }

    for(    $k = 0; $k < strlen($seq); $k++){
    $tmp_gmp_val = gmp_init(ord($seq[$k]), 10);
    $tableindex = gmp_xor(gmp_and($crc, "0xff"), $tmp_gmp_val);
    $crc = gmp_div_q($crc, "256");
    $crc = gmp_xor($crc, self::$CRCTable[gmp_strval($tableindex, 10)]);
    }

    $res = gmp_strval($crc, 16);

    return     $res;
    }
    }
    } else {
    die(    "Please install php-gmp package!!!");
    }
    ?>
    up
    1
    quix at free dot fr
    21 years ago
    I needed the crc32 of a file that was pretty large, so I didn't want to read it into memory.
    So I made this:

    <?php
    $GLOBALS    ['__crc32_table']=array(); // Lookup table array
    __crc32_init_table();

    function     __crc32_init_table() { // Builds lookup table array
    // This is the official polynomial used by
    // CRC-32 in PKZip, WinZip and Ethernet.
    $polynomial = 0x04c11db7;

    // 256 values representing ASCII character codes.
    for($i=0;$i <= 0xFF;++$i) {
    $GLOBALS['__crc32_table'][$i]=(__crc32_reflect($i,8) << 24);
    for(    $j=0;$j < 8;++$j) {
    $GLOBALS['__crc32_table'][$i]=(($GLOBALS['__crc32_table'][$i] << 1) ^
    ((    $GLOBALS['__crc32_table'][$i] & (1 << 31))?$polynomial:0));
    }
    $GLOBALS['__crc32_table'][$i] = __crc32_reflect($GLOBALS['__crc32_table'][$i], 32);
    }
    }

    function     __crc32_reflect($ref, $ch) { // Reflects CRC bits in the lookup table
    $value=0;

    // Swap bit 0 for bit 7, bit 1 for bit 6, etc.
    for($i=1;$i<($ch+1);++$i) {
    if(    $ref & 1) $value |= (1 << ($ch-$i));
    $ref = (($ref >> 1) & 0x7fffffff);
    }
    return     $value;
    }

    function     __crc32_string($text) { // Creates a CRC from a text string
    // Once the lookup table has been filled in by the two functions above,
    // this function creates all CRCs using only the lookup table.

    // You need unsigned variables because negative values
    // introduce high bits where zero bits are required.
    // PHP doesn't have unsigned integers:
    // I've solved this problem by doing a '&' after a '>>'.

    // Start out with all bits set high.
    $crc=0xffffffff;
    $len=strlen($text);

    // Perform the algorithm on each character in the string,
    // using the lookup table values.
    for($i=0;$i < $len;++$i) {
    $crc=(($crc >> 8) & 0x00ffffff) ^ $GLOBALS['__crc32_table'][($crc & 0xFF) ^ ord($text{$i})];
    }

    // Exclusive OR the result with the beginning value.
    return $crc ^ 0xffffffff;
    }

    function     __crc32_file($name) { // Creates a CRC from a file
    // Info: look at __crc32_string

    // Start out with all bits set high.
    $crc=0xffffffff;

    if((    $fp=fopen($name,'rb'))===false) return false;

    // Perform the algorithm on each character in file
    for(;;) {
    $i=@fread($fp,1);
    if(    strlen($i)==0) break;
    $crc=(($crc >> 8) & 0x00ffffff) ^ $GLOBALS['__crc32_table'][($crc & 0xFF) ^ ord($i)];
    }

    @    fclose($fp);

    // Exclusive OR the result with the beginning value.
    return $crc ^ 0xffffffff;
    }
    ?>
    up
    1
    Ren
    17 years ago
    Dealing with 32 bit unsigned values overflowing 32 bit php signed values can be done by adding 0x10000000 to any unexpected negative result, rather than using sprintf.

    $i = crc32('1');
    printf("%u\n", $i);
    if (0 > $i)
    {
    // Implicitly casts i as float, and corrects this sign.
    $i += 0x100000000;
    }
    var_dump($i);

    Outputs:

    2212294583
    float(2212294583)
    up
    0
    dotg at mail dot ru
    7 years ago
    crc32() on php 32bit and 64 bit not equal in some values

    i use abs for result in positive for 32 bit

    not equal
    <?=abs(crc32(1));?>
    64 bit
    2212294583
    32 bit
    2082672713

    equal
    <?=abs(crc32(3));?>
    64 bit
    1842515611
    32 bit
    1842515611
    up
    0
    toggio at writeme dot com
    8 years ago
    A faster implementation of modbus CRC16

    function crc16($data)
    {
    $crc = 0xFFFF;
    for ($i = 0; $i < strlen($data); $i++)
    {
    $crc ^=ord($data[$i]);

    for ($j = 8; $j !=0; $j--)
    {
    if (($crc & 0x0001) !=0)
    {
    $crc >>= 1;
    $crc ^= 0xA001;
    }
    else
    $crc >>= 1;
    }
    }
    return $crc;
    }
    up
    -1
    mail at tristansmis dot nl
    17 years ago
    I used the abs value of this function on a 32-bit system. When porting the code to a 64-bit system I’ve found that the value is different. The following code has the same outcome on both systems.
    <?php

    $crc     = abs(crc32($string));
    if(     $crc & 0x80000000){
    $crc ^= 0xffffffff;
    $crc += 1;
    }

    /* Old solution
    * $crc = abs(crc32($string))
    */

    ?>
    up
    -2
    gabri dot ns at gmail dot com
    14 years ago
    if you are looking for a fast function to hash a file, take a look at
    http://www.php.net/manual/en/function.hash-file.php
    this is crc32 file checker based on a CRC32 guide
    it have performance at ~ 625 KB/s on my 2.2GHz Turion
    far slower than hash_file('crc32b','filename.ext')
    <?php
    function crc32_file ($filename)
    {
    $f = @fopen($filename,'rb');
    if (!    $f) return false;

    static     $CRC32Table, $Reflect8Table;
    if (!isset(    $CRC32Table))
    {
    $Polynomial = 0x04c11db7;
    $topBit = 1 << 31;

    for(    $i = 0; $i < 256; $i++)
    {
    $remainder = $i << 24;
    for (    $j = 0; $j < 8; $j++)
    {
    if (    $remainder & $topBit)
    $remainder = ($remainder << 1) ^ $Polynomial;
    else     $remainder = $remainder << 1;
    }

    $CRC32Table[$i] = $remainder;

    if (isset(    $Reflect8Table[$i])) continue;
    $str = str_pad(decbin($i), 8, '0', STR_PAD_LEFT);
    $num = bindec(strrev($str));
    $Reflect8Table[$i] = $num;
    $Reflect8Table[$num] = $i;
    }
    }

    $remainder = 0xffffffff;
    while (    $data = fread($f,1024))
    {
    $len = strlen($data);
    for (    $i = 0; $i < $len; $i++)
    {
    $byte = $Reflect8Table[ord($data[$i])];
    $index = (($remainder >> 24) & 0xff) ^ $byte;
    $crc = $CRC32Table[$index];
    $remainder = ($remainder << 8) ^ $crc;
    }
    }

    $str = decbin($remainder);
    $str = str_pad($str, 32, '0', STR_PAD_LEFT);
    $remainder = bindec(strrev($str));
    return     $remainder ^ 0xffffffff;
    }
    ?>

    <?php
    $a     = microtime();
    echo     dechex(crc32_file('filename.ext'))."\n";
    $b = microtime();
    echo     array_sum(explode(' ',$b)) - array_sum(explode(' ',$a))."\n";
    ?>
    Output:
    ec7369fe
    2.384134054184 (or similiar)
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