root/tags/1.3/wp-includes/category.php

<?php

function get_all_category_ids() {
    global $wpdb;

    if ( ! $cat_ids = wp_cache_get('all_category_ids', 'category') ) {
        $cat_ids = get_terms('category', 'fields=ids&get=all');
        wp_cache_add('all_category_ids', $cat_ids, 'category');
    }

    return $cat_ids;
}

function &get_categories($args = '') {
    $defaults = array('type' => 'category');
    $args = wp_parse_args($args, $defaults);

    $taxonomy = 'category';
    if ( 'link' == $args['type'] )
        $taxonomy = 'link_category';
    $categories = get_terms($taxonomy, $args);

    foreach ( array_keys($categories) as $k )
        _make_cat_compat($categories[$k]);

    return $categories;
}

// Retrieves category data given a category ID or category object.
// Handles category caching.
function &get_category($category, $output = OBJECT, $filter = 'raw') {
    $category = get_term($category, 'category', $output, $filter);
    if ( is_wp_error( $category ) )
        return $category;

    _make_cat_compat($category);

    return $category;
}

function get_category_by_path($category_path, $full_match = true, $output = OBJECT) {
    global $wpdb;
    $category_path = rawurlencode(urldecode($category_path));
    $category_path = str_replace('%2F', '/', $category_path);
    $category_path = str_replace('%20', ' ', $category_path);
    $category_paths = '/' . trim($category_path, '/');
    $leaf_path  = sanitize_title(basename($category_paths));
    $category_paths = explode('/', $category_paths);
    $full_path = '';
    foreach ( (array) $category_paths as $pathdir )
        $full_path .= ( $pathdir != '' ? '/' : '' ) . sanitize_title($pathdir);

    $categories = get_terms('category', "get=all&slug=$leaf_path");

    if ( empty($categories) )
        return NULL;

    foreach ($categories as $category) {
        $path = '/' . $leaf_path;
        $curcategory = $category;
        while ( ($curcategory->parent != 0) && ($curcategory->parent != $curcategory->term_id) ) {
            $curcategory = get_term($curcategory->parent, 'category');
            if ( is_wp_error( $curcategory ) )
                return $curcategory;
            $path = '/' . $curcategory->slug . $path;
        }

        if ( $path == $full_path )
            return get_category($category->term_id, $output);
    }

    // If full matching is not required, return the first cat that matches the leaf.
    if ( ! $full_match )
        return get_category($categories[0]->term_id, $output);

    return NULL;
}

function get_category_by_slug( $slug  ) {
    $category = get_term_by('slug', $slug, 'category');
    if ( $category )
        _make_cat_compat($category);

    return $category;
}

// Get the ID of a category from its name
function get_cat_ID($cat_name='General') {
    global $wpdb;

    $cat = get_term_by('name', $cat_name, 'category');
    if ($cat)
        return $cat->term_id;
    return 0;
}

// Deprecate
function get_catname($cat_ID) {
    return get_cat_name($cat_ID);
}

// Get the name of a category from its ID
function get_cat_name($cat_id) {
    $cat_id = (int) $cat_id;
    $category = &get_category($cat_id);
    return $category->name;
}

function cat_is_ancestor_of($cat1, $cat2) {
    if ( is_int($cat1) )
        $cat1 = & get_category($cat1);
    if ( is_int($cat2) )
        $cat2 = & get_category($cat2);

    if ( !$cat1->term_id || !$cat2->parent )
        return false;

    if ( $cat2->parent == $cat1->term_id )
        return true;

    return cat_is_ancestor_of($cat1, get_category($cat2->parent));
}

function sanitize_category($category, $context = 'display') {
    return sanitize_term($category, 'category', $context);
}

function sanitize_category_field($field, $value, $cat_id, $context) {
    return sanitize_term_field($field, $value, $cat_id, 'category', $context);
}

// Tags

function &get_tags($args = '') {
    global $wpdb, $category_links;

    $key = md5( serialize( $args ) );
    if ( $cache = wp_cache_get( 'get_tags', 'category' ) )
        if ( isset( $cache[ $key ] ) )
            return apply_filters('get_tags', $cache[$key], $args);


    $tags = get_terms('post_tag', $args);

    if ( empty($tags) )
        return array();

    $cache[ $key ] = $tags;
    wp_cache_set( 'get_tags', $cache, 'category' );

    $tags = apply_filters('get_tags', $tags, $args);
    return $tags;
}

function &get_tag($tag, $output = OBJECT, $filter = 'raw') {
    return get_term($tag, 'post_tag', $output, $filter);
}

//
// Cache
//

function update_category_cache() {
    return true;
}

function clean_category_cache($id) {
    clean_term_cache($id, 'category');
}

//
// Private helpers
//

function _make_cat_compat( &$category) {
    if ( is_object($category) ) {
        $category->cat_ID = &$category->term_id;
        $category->category_count = &$category->count;
        $category->category_description = &$category->description;
        $category->cat_name = &$category->name;
        $category->category_nicename = &$category->slug;
        $category->category_parent = &$category->parent;
    } else if ( is_array($category) && isset($category['term_id']) ) {
        $category['cat_ID'] = &$category['term_id'];
        $category['category_count'] = &$category['count'];
        $category['category_description'] = &$category['description'];
        $category['cat_name'] = &$category['name'];
        $category['category_nicename'] = &$category['slug'];
        $category['category_parent'] = &$category['parent'];
    }
}

?>