root/tags/1.3/wp-admin/includes/taxonomy.php

<?php

//
// Category
//

function category_exists($cat_name) {
    $id = is_term($cat_name, 'category');
    if ( is_array($id) )
        $id = $id['term_id'];
    return $id;
}

function get_category_to_edit( $id ) {
    $category = get_category( $id, OBJECT, 'edit' );
    return $category;
}

function wp_create_category($cat_name) {
    if ( $id = category_exists($cat_name) )
        return $id;

    return wp_insert_category( array('cat_name' => $cat_name) );
}

function wp_create_categories($categories, $post_id = '') {
    $cat_ids = array ();
    foreach ($categories as $category) {
        if ($id = category_exists($category))
            $cat_ids[] = $id;
        else
            if ($id = wp_create_category($category))
                $cat_ids[] = $id;
    }

    if ($post_id)
        wp_set_post_categories($post_id, $cat_ids);

    return $cat_ids;
}

function wp_delete_category($cat_ID) {
    global $wpdb;

    $cat_ID = (int) $cat_ID;
    $default = get_option('default_category');

    // Don't delete the default cat
    if ( $cat_ID == $default )
        return 0;

    return wp_delete_term($cat_ID, 'category', "default=$default");
}

function wp_insert_category($catarr) {
    global $wpdb;

    extract($catarr, EXTR_SKIP);

    if ( trim( $cat_name ) == '' )
        return 0;

    $cat_ID = (int) $cat_ID;

    // Are we updating or creating?
    if ( !empty ($cat_ID) )
        $update = true;
    else
        $update = false;

    $name = $cat_name;
    $description = $category_description;
    $slug = $category_nicename;
    $parent = $category_parent;

    $parent = (int) $parent;
    if ( empty($parent) || !category_exists( $parent ) || ($cat_ID && cat_is_ancestor_of($cat_ID, $parent) ) )
        $parent = 0;

    $args = compact('name', 'slug', 'parent', 'description');

    if ( $update )
        $cat_ID = wp_update_term($cat_ID, 'category', $args);
    else
        $cat_ID = wp_insert_term($cat_name, 'category', $args);

    if ( is_wp_error($cat_ID) )
        return 0;

    return $cat_ID['term_id'];
}

function wp_update_category($catarr) {
    global $wpdb;

    $cat_ID = (int) $catarr['cat_ID'];

    if ( $cat_ID == $catarr['category_parent'] )
        return false;

    // First, get all of the original fields
    $category = get_category($cat_ID, ARRAY_A);

    // Escape data pulled from DB.
    $category = add_magic_quotes($category);

    // Merge old and new fields with new fields overwriting old ones.
    $catarr = array_merge($category, $catarr);

    return wp_insert_category($catarr);
}

//
// Tags
//

function get_tags_to_edit( $post_id ) {
    global $wpdb;

    $post_id = (int) $post_id;
    if ( !$post_id )
        return false;

    $tags = wp_get_post_tags($post_id);

    if ( !$tags )
        return false;

    foreach ( $tags as $tag )
        $tag_names[] = $tag->name;
    $tags_to_edit = join( ', ', $tag_names );
    $tags_to_edit = attribute_escape( $tags_to_edit );
    $tags_to_edit = apply_filters( 'tags_to_edit', $tags_to_edit );
    return $tags_to_edit;
}

function tag_exists($tag_name) {
    return is_term($tag_name, 'post_tag');
}

function wp_create_tag($tag_name) {
    if ( $id = tag_exists($tag_name) )
        return $id;

    return wp_insert_term($tag_name, 'post_tag');
}

?>