I would like to know how I can convert a short ASCII string to a number (int, float, or numeric string). I saw a couple of posts here mentioned perfect hashes which seems like it might be what I need. However, I'm not quite understanding the math for this.
How could you convert an ASCII string into a sequence of numbers and then back to a string?
As a side note, breaking a string down into it's ASCII character numbers is easy enough.
foreach(str_split($string) as $char) $number .= ord($char);
After more reading I came up with this. However, I'm wondering if there are anyways to shorten the number sequence so it's not quite as long.
class intnum
{
public static $charset = array(
32 => ' ', 33 => '!', 34 => '"', 35 => '#', 36 => '$',
37 => '%', 38 => '&', 39 => "'", 40 => '(', 41 => ')',
42 => '*', 43 => '+', 44 => ',', 45 => '-', 46 => '.',
47 => '/', 48 => '0', 49 => '1', 50 => '2', 51 => '3',
52 => '4', 53 => '5', 54 => '6', 55 => '7', 56 => '8',
57 => '9', 58 => ':', 59 => ';', 60 => '<', 61 => '=',
62 => '>', 63 => '?', 64 => '@', 65 => 'A', 66 => 'B',
67 => 'C', 68 => 'D', 69 => 'E', 70 => 'F', 71 => 'G',
72 => 'H', 73 => 'I', 74 => 'J', 75 => 'K', 76 => 'L',
77 => 'M', 78 => 'N', 79 => 'O', 80 => 'P', 81 => 'Q',
82 => 'R', 83 => 'S', 84 => 'T', 85 => 'U', 86 => 'V',
87 => 'W', 88 => 'X', 89 => 'Y', 90 => 'Z', 91 => '[',
92 => '\\', 93 => ']', 94 => '^', 95 => '_', 96 => '`',
97 => 'a', 98 => 'b', 99 => 'c', 100 => 'd', 101 => 'e',
102 => 'f', 103 => 'g', 104 => 'h', 105 => 'i', 106 => 'j',
107 => 'k', 108 => 'l', 109 => 'm', 110 => 'n', 111 => 'o',
112 => 'p', 113 => 'q', 114 => 'r', 115 => 's', 116 => 't',
117 => 'u', 118 => 'v', 119 => 'w', 120 => 'x', 121 => 'y',
122 => 'z', 123 => '{', 124 => '|', 125 => '}'
);
public static function fromNumber($number)
{
$string = '';
while($number)
{
$value = substr($number, 0, 2);
$number = substr($number, 2);
if($value < 32)
{
$value .= substr($number, 0, 1);
$number = substr($number, 1);
}
$string .= self::$charset[ (int) $value];
}
return $string;
}
public static function fromString($string)
{
$number = '';
foreach(str_split($string) as $char) $number .= ord($char);
return $number;
}
}
$string = 'this is my test string to convert';
$number = intnum::fromString($string);
$string = intnum::fromNumber($number);
A string-to-number encoder as one-liner (PHP 5.3 style):
$numbers = implode(array_map(function ($n) { return sprintf('%03d', $n); },
unpack('C*', $str)));
It simply converts every byte into its decimal number equivalent, zero-padding it to a fixed length of 3 digits so it can be unambiguously converted back.
The decoder back to a string:
$str = implode(array_map('chr', str_split($numbers, 3)));
Example text:
Wörks wíth all ストリングズ
087195182114107115032119195173116104032097108108032227130185227131136227131170227131179227130176227130186