1 files changed, 55 insertions, 0 deletions
diff --git a/Zotlabs/Lib/Hashpath.php b/Zotlabs/Lib/Hashpath.php
new file mode 100644
index 000000000..f3b25d2b6
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+++ b/Zotlabs/Lib/Hashpath.php
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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;
+	}
+}