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| <?php | |
| function dec_to_n( $dec, $n = 62, $disits = null ) { | |
| if ( !$disits ) { | |
| $disits = array( | |
| '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', | |
| 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', | |
| 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', | |
| 'u', 'v', 'w', 'x', 'y', 'z', | |
| 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', | |
| 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', | |
| 'U', 'V', 'W', 'X', 'Y', 'Z', | |
| ); | |
| } | |
| $max_n = count($disits); | |
| if ( ! (preg_match('/^\d+$/', $n) && $n >= 2 && $n <= $max_n) ) return FALSE; | |
| if ( ! preg_match('/^\d+$/', $dec) ) return FALSE; | |
| if ( $dec == 0 ) return $dec; | |
| $num_str = ''; | |
| while ( $dec !== 0 ) { | |
| $num_str = $disits[$dec % $n] . $num_str; | |
| $dec = (int) ($dec / $n); | |
| } | |
| return $num_str; | |
| } | |
| function n_to_dec( $num_str, $n = 62, $disits = null ) { | |
| if ( !$disits ) { | |
| $disits = array( | |
| '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', | |
| 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', | |
| 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', | |
| 'u', 'v', 'w', 'x', 'y', 'z', | |
| 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', | |
| 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', | |
| 'U', 'V', 'W', 'X', 'Y', 'Z', | |
| ); | |
| } | |
| $max_n = count($disits); | |
| $valids = array(); | |
| for ( $i = 0; $i < $max_n; $i++ ) { | |
| $valids[$disits[$i]] = $i; | |
| } | |
| if ( ! (preg_match('/^\d+$/', $n) && $n >= 2 && $n <= $max_n) ) return FALSE; | |
| if ( ! preg_match('/^[\da-zA-Z]+$/', $num_str) ) return FALSE; | |
| $dec = 0; | |
| for ( $i = 0; $i < strlen($num_str); $i++ ) { | |
| $dec += $valids[ substr($num_str, ($i + 1) * –1, 1) ] * pow( $n, $i ); | |
| } | |
| return $dec; | |
| } |
memo.dogmap.jp 
n_to_dec関数の$valids変数は、array_flip関数で簡単に生成できます。
$valids = array_flip($disits);