source: vendor/3.6.9/source3/lib/dbwrap_rbt.c

/*
   Unix SMB/CIFS implementation.
   Database interface wrapper around red-black trees
   Copyright (C) Volker Lendecke 2007, 2008

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "dbwrap.h"
#include "../lib/util/rbtree.h"

#define DBWRAP_RBT_ALIGN(_size_) (((_size_)+15)&~15)

struct db_rbt_ctx {
        struct rb_root tree;
};

struct db_rbt_rec {
        struct db_rbt_ctx *db_ctx;
        struct db_rbt_node *node;
};

/* The structure that ends up in the tree */

struct db_rbt_node {
        struct rb_node rb_node;
        size_t keysize, valuesize;

        /*
         * key and value are appended implicitly, "data" is only here as a
         * target for offsetof()
         */

        char data[1];
};

/*
 * Hide the ugly pointer calculations in a function
 */

static struct db_rbt_node *db_rbt2node(struct rb_node *node)
{
        return (struct db_rbt_node *)
                ((char *)node - offsetof(struct db_rbt_node, rb_node));
}

/*
 * Compare two keys
 */

static int db_rbt_compare(TDB_DATA a, TDB_DATA b)
{
        int res;

        res = memcmp(a.dptr, b.dptr, MIN(a.dsize, b.dsize));

        if ((res < 0) || ((res == 0) && (a.dsize < b.dsize))) {
                return -1;
        }
        if ((res > 0) || ((res == 0) && (a.dsize > b.dsize))) {
                return 1;
        }
        return 0;
}

/*
 * dissect a db_rbt_node into its implicit key and value parts
 */

static void db_rbt_parse_node(struct db_rbt_node *node,
                              TDB_DATA *key, TDB_DATA *value)
{
        key->dptr = ((uint8 *)node) + offsetof(struct db_rbt_node, data);
        key->dsize = node->keysize;
        value->dptr = key->dptr + node->keysize;
        value->dsize = node->valuesize;
}

static NTSTATUS db_rbt_store(struct db_record *rec, TDB_DATA data, int flag)
{
        struct db_rbt_rec *rec_priv = (struct db_rbt_rec *)rec->private_data;
        struct db_rbt_node *node;

        struct rb_node ** p;
        struct rb_node * parent;

        TDB_DATA this_key, this_val;

        if (rec_priv->node != NULL) {

                /*
                 * The record was around previously
                 */

                db_rbt_parse_node(rec_priv->node, &this_key, &this_val);

                SMB_ASSERT(this_key.dsize == rec->key.dsize);
                SMB_ASSERT(memcmp(this_key.dptr, rec->key.dptr,
                                  this_key.dsize) == 0);

                if (this_val.dsize >= data.dsize) {
                        /*
                         * The new value fits into the old space
                         */
                        memcpy(this_val.dptr, data.dptr, data.dsize);
                        rec_priv->node->valuesize = data.dsize;
                        return NT_STATUS_OK;
                }

                /*
                 * We need to delete the key from the tree and start fresh,
                 * there's not enough space in the existing record
                 */

                rb_erase(&rec_priv->node->rb_node, &rec_priv->db_ctx->tree);

                /*
                 * Keep the existing node around for a while: If the record
                 * existed before, we reference the key data in there.
                 */
        }

        node = (struct db_rbt_node *)talloc_size(rec_priv->db_ctx,
                offsetof(struct db_rbt_node, data) + rec->key.dsize
                + data.dsize);

        if (node == NULL) {
                TALLOC_FREE(rec_priv->node);
                return NT_STATUS_NO_MEMORY;
        }

        ZERO_STRUCT(node->rb_node);

        node->keysize = rec->key.dsize;
        node->valuesize = data.dsize;

        db_rbt_parse_node(node, &this_key, &this_val);

        memcpy(this_key.dptr, rec->key.dptr, node->keysize);
        TALLOC_FREE(rec_priv->node);

        memcpy(this_val.dptr, data.dptr, node->valuesize);

        parent = NULL;
        p = &rec_priv->db_ctx->tree.rb_node;

        while (*p) {
                struct db_rbt_node *r;
                TDB_DATA search_key, search_val;
                int res;

                parent = (*p);

                r = db_rbt2node(*p);

                db_rbt_parse_node(r, &search_key, &search_val);

                res = db_rbt_compare(this_key, search_key);

                if (res == -1) {
                        p = &(*p)->rb_left;
                }
                else if (res == 1) {
                        p = &(*p)->rb_right;
                }
                else {
                        smb_panic("someone messed with the tree");
                }
        }

        rb_link_node(&node->rb_node, parent, p);
        rb_insert_color(&node->rb_node, &rec_priv->db_ctx->tree);

        return NT_STATUS_OK;
}

static NTSTATUS db_rbt_delete(struct db_record *rec)
{
        struct db_rbt_rec *rec_priv = (struct db_rbt_rec *)rec->private_data;

        if (rec_priv->node == NULL) {
                return NT_STATUS_OK;
        }

        rb_erase(&rec_priv->node->rb_node, &rec_priv->db_ctx->tree);
        TALLOC_FREE(rec_priv->node);

        return NT_STATUS_OK;
}

static struct db_record *db_rbt_fetch_locked(struct db_context *db_ctx,
                                             TALLOC_CTX *mem_ctx,
                                             TDB_DATA key)
{
        struct db_rbt_ctx *ctx = talloc_get_type_abort(
                db_ctx->private_data, struct db_rbt_ctx);

        struct db_rbt_rec *rec_priv;
        struct db_record *result;
        struct rb_node *n;
        size_t size;
        bool found = false;
        struct db_rbt_node *r = NULL;
        TDB_DATA search_key = tdb_null, search_val = tdb_null;

        n = ctx->tree.rb_node;

        while (n != NULL) {
                int res;

                r = db_rbt2node(n);

                db_rbt_parse_node(r, &search_key, &search_val);

                res = db_rbt_compare(key, search_key);

                if (res == -1) {
                        n = n->rb_left;
                }
                else if (res == 1) {
                        n = n->rb_right;
                }
                else {
                        found = true;
                        break;
                }
        }

        /*
         * In this low-level routine, play tricks to reduce the number of
         * tallocs to one. Not recommened for general use, but here it pays
         * off.
         */

        size = DBWRAP_RBT_ALIGN(sizeof(struct db_record))
                + sizeof(struct db_rbt_rec);

        if (!found) {
                /*
                 * We need to keep the key around for later store
                 */
                size += key.dsize;
        }

        result = (struct db_record *)talloc_size(mem_ctx, size);
        if (result == NULL) {
                return NULL;
        }

        rec_priv = (struct db_rbt_rec *)
                ((char *)result + DBWRAP_RBT_ALIGN(sizeof(struct db_record)));
        rec_priv->db_ctx = ctx;

        result->store = db_rbt_store;
        result->delete_rec = db_rbt_delete;
        result->private_data = rec_priv;

        if (found) {
                rec_priv->node = r;
                result->key = search_key;
                result->value = search_val;
        }
        else {
                rec_priv->node = NULL;
                result->key.dptr = (uint8 *)
                        ((char *)rec_priv + sizeof(*rec_priv));
                result->key.dsize = key.dsize;
                memcpy(result->key.dptr, key.dptr, key.dsize);

                result->value = tdb_null;
        }

        return result;
}

static int db_rbt_fetch(struct db_context *db, TALLOC_CTX *mem_ctx,
                        TDB_DATA key, TDB_DATA *data)
{
        struct db_rbt_ctx *ctx = talloc_get_type_abort(
                db->private_data, struct db_rbt_ctx);

        struct rb_node *n;
        bool found = false;
        struct db_rbt_node *r = NULL;
        TDB_DATA search_key, search_val;
        uint8_t *result;

        n = ctx->tree.rb_node;

        while (n != NULL) {
                int res;

                r = db_rbt2node(n);

                db_rbt_parse_node(r, &search_key, &search_val);

                res = db_rbt_compare(key, search_key);

                if (res == -1) {
                        n = n->rb_left;
                }
                else if (res == 1) {
                        n = n->rb_right;
                }
                else {
                        found = true;
                        break;
                }
        }

        if (!found) {
                *data = tdb_null;
                return 0;
        }

        result = (uint8 *)talloc_memdup(mem_ctx, search_val.dptr,
                                        search_val.dsize);
        if (result == NULL) {
                return -1;
        }

        data->dptr = result;
        data->dsize = search_val.dsize;
        return 0;
}

static int db_rbt_traverse_internal(struct rb_node *n,
                                    int (*f)(struct db_record *db,
                                             void *private_data),
                                    void *private_data)
{
        struct db_rbt_node *r;
        struct db_record rec;
        int ret;

        if (n == NULL) {
                return 0;
        }

        ret = db_rbt_traverse_internal(n->rb_left, f, private_data);
        if (ret != 0) {
                return ret;
        }

        r = db_rbt2node(n);
        ZERO_STRUCT(rec);
        db_rbt_parse_node(r, &rec.key, &rec.value);

        ret = f(&rec, private_data);
        if (ret != 0) {
                return ret;
        }

        return db_rbt_traverse_internal(n->rb_right, f, private_data);
}

static int db_rbt_traverse(struct db_context *db,
                           int (*f)(struct db_record *db,
                                    void *private_data),
                           void *private_data)
{
        struct db_rbt_ctx *ctx = talloc_get_type_abort(
                db->private_data, struct db_rbt_ctx);

        return db_rbt_traverse_internal(ctx->tree.rb_node, f, private_data);
}

static int db_rbt_get_seqnum(struct db_context *db)
{
        return 0;
}

static int db_rbt_trans_dummy(struct db_context *db)
{
        /*
         * Transactions are pretty pointless in-memory, just return success.
         */
        return 0;
}

struct db_context *db_open_rbt(TALLOC_CTX *mem_ctx)
{
        struct db_context *result;

        result = talloc(mem_ctx, struct db_context);

        if (result == NULL) {
                return NULL;
        }

        result->private_data = TALLOC_ZERO_P(result, struct db_rbt_ctx);

        if (result->private_data == NULL) {
                TALLOC_FREE(result);
                return NULL;
        }

        result->fetch_locked = db_rbt_fetch_locked;
        result->fetch = db_rbt_fetch;
        result->traverse = db_rbt_traverse;
        result->traverse_read = db_rbt_traverse;
        result->get_seqnum = db_rbt_get_seqnum;
        result->transaction_start = db_rbt_trans_dummy;
        result->transaction_commit = db_rbt_trans_dummy;
        result->transaction_cancel = db_rbt_trans_dummy;

        return result;
}