Micro-blog Short link algorithm php version

idea:

1) will be long Web site MD5 generated 32-bit signature string, divided into 4 paragraphs, 8 bytes per paragraph;

2 to the four-segment loop, take 8 bytes, consider him as 16-string and 0X3FFFFFFF (30-bit 1) and operation, that is, more than 30-bit ignore processing;

3 The 30 bits are divided into 6 segments, each 5 digit number is taken as the index of the alphabet to obtain the specific characters, and then the 6-bit string is obtained.

4) The total MD5 string can obtain 4 6-bit strings; Taking any one inside can be used as the short URL of this long URL;

Here is the PHP code:

function Shorturl ($url = ', $prefix = ', $suffix = ') {
$base = Array (
' 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 ', ' 0 ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ');

$hex = MD5 ($prefix. $url. $suffix);
$hexLen = strlen ($hex);
$subHexLen = $hexLen/8;
$output = Array ();

for ($i = 0; $i < $subHexLen; $i + +) {
$subHex = substr ($hex, $i * 8, 8);
$int = 0X3FFFFFFF & (1 * (' 0x '. $subHex));
$out = ';
for ($j = 0; $j < 6; $j + +) {
$val = 0x0000001f & $int;
$out. = $base 32[$val];
$int = $int >> 5;
}
$output [] = $out;
}
return $output;
}

$urls = Shorturl (' http://www.php100.com ');
Var_dump ($urls);