Times are progressing and society is developing. The emergence of 64-bit machines has caused the shift calculation to no longer easily overflow. This is certainly a happy thing. However, during the system migration, 64-bit machines were suddenly discovered. The result obtained by the hash function was actually different from the 32-bit result. I was shocked and quickly studied the algorithm and found that it was a problem with the shift operation sign.
I had no choice but to judge the system and rewrite the algorithm for 64-bit machines. The code is as follows:
if (exec("getconf LONG_BIT") == "32") { function _hash($apszData = "", $MAX_TABLE_NUM = 0) { $_hash = $x = $i = 0; for($i = 0; $i < strlen($apszData); $i++) { $_hash = ($_hash << 4) + ord($apszData[$i]); if (($x = $_hash &0xF0000000) != 0) { $_hash ^= ($x >> 24); $_hash &= ~$x; } } return ($_hash &0x7FFFFFFF) % $MAX_TABLE_NUM + 1; } } else { function _hash($apszData = "", $MAX_TABLE_NUM = 0) { $hash = $x = $i = 0; for($i = 0; $i < strlen($apszData); $i++) { $hash = ($hash << 4) + ((ord($apszData[$i])) << 32); if (($x = $hash &0xF000000000000000) != 0) { $hash ^= $x >> 24; $hash &= (~$x) &0xFFFFFFFF00000000; } } $ret = ($hash &0x7FFFFFFF00000000) % ($MAX_TABLE_NUM << 32) + (1 << 32); $ret >>= 32; $ret &= 0xFFFFFFFF; return $ret; } }