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<?php
namespace Zotlabs\Lib;
/*
* Zotlabs\Lib\Hashpath
*
* Creates hashed directory structures for fast access and resistance to overloading any single directory with files.
*
* Takes a $hash which could be any string
* a $prefix which is where to place the hash directory in the filesystem, default is current directory
* use an empty string for $prefix to place hash directories directly off the root directory
* an optional $depth and $slice (default is 2) to indicate the hash level
* $depth = 1, 256 directories, suitable for < 384K records/files
* $depth = 2, 65536 directories, suitable for < 98M records/files
* $depth = 3, 16777216 directories, suitable for < 2.5B records/files
* ...
* The total number of records anticipated divided by the number of hash directories should generally be kept to
* less than 1500 entries for optimum performance though this varies by operating system and filesystem type.
* ext4 uses 32 bit inode numbers (~4B record limit) so use caution or alternative filesystem types with $depth above 3.
* an optional $mkdir (boolean) to recursively create the directory (ignoring errors) before returning
*
* examples: for a $hash of 'abcdefg' and prefix of 'path' the following paths are returned for $depth = 1 and $depth = 3
* path/7d/7d1a54127b222502f5b79b5fb0803061152a44f92b37e23c6527baf665d4da9a
* path/7d/1a/54/7d1a54127b222502f5b79b5fb0803061152a44f92b37e23c6527baf665d4da9a
*
* see also: boot.php:os_mkdir() - here we provide the equivalent of mkdir -p with permissions of 770.
*
*/
class Hashpath {
static function path($hash, $prefix = '.', $depth = 1, $slice = 2, $mkdir = true, $alg = false) {
if ($alg)
$hash = hash($alg, $hash);
$start = 0;
if ($depth < 1)
$depth = 1;
$sluglen = $depth * $slice;
do {
$slug = substr($hash, $start, $slice);
$prefix .= '/' . $slug;
$start += $slice;
$sluglen -= $slice;
}
while ($sluglen);
if ($mkdir)
os_mkdir($prefix, STORAGE_DEFAULT_PERMISSIONS, true);
return $prefix . '/' . $hash;
}
}
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