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MDL-41674 backup: Use a trie for grouped path detection.

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This commit is contained in:
Russell Smith 2013-12-08 20:13:59 +11:00 committed by Russell Smith
parent edbcfbd61f
commit 92996836d0
1 changed files with 50 additions and 7 deletions
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57
backup/util/xml/parser/processors/grouped_parser_processor.class.php
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@ -1,5 +1,4 @@
<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
@ -43,6 +42,22 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
protected $groupedpaths; // Paths we are requesting grouped
protected $currentdata; // Where we'll be acummulating data
// We create a array that stores each of the paths in a tree fashion
// like the filesystem. Each element stores all the child elements that are
// part of a full path that builds the grouped parent path we are storing.
// eg Array keys are stored as follows;
// root => a => b
// => b
// => c => d
// => e => f.
// Grouped paths here are; /a/b, /b, /c/d, /c/e/f.
// There are no nested parent paths, that is an enforced rule so
// we store an empty array to designate that the particular XML path element
// is in fact a grouped path.
// eg; $this->groupedparentprefixtree['a']['b'] = array();
/** @var array Search tree storing the grouped paths. */
protected $groupedparentprefixtree;
/**
* Keep cache of parent directory paths for XML parsing.
* @var array
@ -78,6 +93,18 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
throw new progressive_parser_exception('xml_grouped_child_found', $a);
}
$this->groupedpaths[$path] = true;
// We check earlier in the function if there is a parent that is above the path
// to be added so we can be sure no parent exists in the tree.
$patharray = explode('/', $path);
$currentpos = &$this->groupedparentprefixtree;
foreach ($patharray as $item) {
if (!isset($currentpos[$item])) {
$currentpos[$item] = array();
}
// Update the current array position using a reference to allow in-place updates to the array.
$currentpos = &$currentpos[$item];
}
}
parent::add_path($path);
}
@ -162,13 +189,29 @@ abstract class grouped_parser_processor extends simplified_parser_processor {
* false if not
*/
protected function grouped_parent_exists($path) {
$parentpath = $this->get_parent_path($path);
while ($parentpath != '/') {
if ($this->path_is_grouped($parentpath)) {
return $parentpath;
// Search the tree structure to find out if one of the paths
// above the $path is a grouped path.
$patharray = explode('/', $this->get_parent_path($path));
$groupedpath = '';
$currentpos = &$this->groupedparentprefixtree;
foreach ($patharray as $item) {
// When the item isn't set in the array we know
// there is no parent grouped path.
if (!isset($currentpos[$item])) {
return false;
}
$parentpath = $this->get_parent_path($parentpath);
// When we aren't at the start of the path, continue to build
// a string representation of the path that is traversed. We will
// return the grouped path to the caller if we find one.
if ($item != '') {
$groupedpath .= '/'.$item;
}
if ($currentpos[$item] == array()) {
return $groupedpath;
}
$currentpos = &$currentpos[$item];
}
return false;
}