Differencebetween Crc32 and Crc32B

CRC32 In Python (vs CRC32b)

What they are calling "crc32" is the CRC-32/BZIP2 in this catalog. What they are calling "crc32b" is the PKZip CRC-32 (ITU V.42), commonly referred to as simply CRC-32, as it is in that catalog. This use of "crc32" and "crc32b" is apparently a notation invented by the PHP authors.

You can find a set of example hashes on the PHP documentation page for hash(). There the hashes of the string "hello" are calculated, and can be checked against implementations. The catalog I linked uses "123456789" for the checks.

You can easily calculate the BZIP2 CRC yourself. Here is some C code as an example:

uint32_t crc32bzip2(uint32_t crc, void const *mem, size_t len) {
    unsigned char const *data = mem;
    if (data == NULL)
        return 0;
    crc = ~crc;
    while (len--) {
        crc ^= (unsigned)(*data++) << 24;
        for (unsigned k = 0; k < 8; k++)
            crc = crc & 0x80000000 ? (crc << 1) ^ 0x4c11db7 : crc << 1;
    }
    crc = ~crc;
    return crc;
}

If you call that with NULL for the data pointer, it will return the initial value of the CRC, which in this case is zero. Then you can call it with the current CRC and the bytes to update the CRC with, and it will return the resulting CRC.

A Python version that computes the CRC-32/BZIP2 of the bytes from stdin:

#!/usr/local/bin/python3
import sys
a = bytearray(sys.stdin.buffer.read())
crc = 0xffffffff
for x in a:
    crc ^= x << 24;
    for k in range(8):
        crc = (crc << 1) ^ 0x04c11db7 if crc & 0x80000000 else crc << 1
crc = ~crc
crc &= 0xffffffff
print(hex(crc))

crcany will generate more efficient table-based versions (in C) if desired.

php hash('crc32') and crc32() return different value

hash("crc32b", $str) will return the same string as str_pad(dechex(crc32($str)), 8, '0', STR_PAD_LEFT).

See manual and also about difference between crc32 and crc32b

Calculate CRC32b in Java

CRC32b is a coined term if I remember correctly, equal to CRC32 with the 4 bytes reversed.

int crc32b(int crc) {
    ByteBuffer buf = ByteBuffer.allocate(4);
    buf.putInt(crc); // BIG_ENDIAN by default.
    buf.order(ByteOrder.LITTLE_ENDIAN);
    return buf.getInt(0);
}

For instance for input '1':

byte b = (byte) '1';
CRC32 crc = new CRC32();
crc.update(b);

System.out.printf("%x%n", crc.getValue());
int finalCRC = crc32b((int)crc.getValue());
System.out.printf("%x%n", finalCRC);

Output:

83dcefb7
b7efdc83

Given your example the conclusion: java CRC32 (without reversal) is fine.

is there any equivalient php hash crc32b method in c#?

bellow the class used in one of my c# projects :

class CRC32B
    {
        public static int Main(String INPUT)
        {
            // first convert string to byte-array
            String input = INPUT;
            byte[] bytes = new byte[input.Length * sizeof(char)];
            System.Buffer.BlockCopy(input.ToCharArray(), 0, bytes, 0, bytes.Length);

            // then calculate the value
            int crcVal = (int)crc32(input);

            if (crcVal < 0)
            {
                crcVal = crcVal * (-1);
            }

            //Console.WriteLine((int)crcVal);
            return (int)crcVal;
        }

        public static uint crc32(string input)
        {
            var table = new uint[]{
            0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419, 0x706AF48F,
                0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
                0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2,
                0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
                0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
                0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
                0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C,
                0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
                0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423,
                0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
                0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190, 0x01DB7106,
                0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
                0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D,
                0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
                0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
                0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
                0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7,
                0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
                0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA,
                0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
                0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81,
                0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
                0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84,
                0x0D6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
                0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
                0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
                0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E,
                0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
                0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55,
                0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
                0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28,
                0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
                0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A, 0x9C0906A9, 0xEB0E363F,
                0x72076785, 0x05005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
                0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
                0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
                0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69,
                0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
                0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC,
                0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
                0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693,
                0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
                0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
        };

            unchecked
            {
                uint crc = (uint)(((uint)0) ^ (1));
                var len = input.Length;
                for (var i = 0; i < len; i++)
                {
                    crc = (crc >> 8) ^ table[
                        (crc ^ (byte)input[i]) & 0xFF
                ];
                }

                //crc = (uint)(crc ^ (-1));

                if (crc < 0)
                {
                    crc += (uint)4294967296;
                    crc = (uint)(crc ^ (-1));
                }

                return crc;
            }
        }
    }

crc32() vs hash() function differences

The hash() algo that corresponds to the crc32() function is actually 'crc32b' and not 'crc32'. Read the end of the warning on the PHP's manual of the crc32 function.