sdbm.c

一套很值得分析的短信SMS开发源代码。是我今年早些时候从taobao上买来的。但我现在也没看完（先说清楚

/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: [e-mail]
 * ex-public domain, ported to APR for Apache 2
 * core routines
 */

#include "apr.h"
#include "apr_file_io.h"
#include "apr_strings.h"
#include "apr_errno.h"
#include "apr_sdbm.h"

#include "sdbm_tune.h"
#include "sdbm_pair.h"
#include "sdbm_private.h"

#include <string.h>     /* for memset() */
#include <stdlib.h>     /* for malloc() and free() */

/*
 * forward
 */
static int getdbit (apr_sdbm_t *, long);
static apr_status_t setdbit(apr_sdbm_t *, long);
static apr_status_t getpage(apr_sdbm_t *db, long);
static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db);
static apr_status_t makroom(apr_sdbm_t *, long, int);

/*
 * useful macros
 */
#define bad(x)		((x).dptr == NULL || (x).dsize <= 0)
#define exhash(item)	sdbm_hash((item).dptr, (item).dsize)

/* ### Does anything need these externally? */
#define sdbm_dirfno(db)	((db)->dirf)
#define sdbm_pagfno(db)	((db)->pagf)

#define OFF_PAG(off)	(apr_off_t) (off) * PBLKSIZ
#define OFF_DIR(off)	(apr_off_t) (off) * DBLKSIZ

static long masks[] = {
        000000000000, 000000000001, 000000000003, 000000000007,
        000000000017, 000000000037, 000000000077, 000000000177,
        000000000377, 000000000777, 000000001777, 000000003777,
        000000007777, 000000017777, 000000037777, 000000077777,
        000000177777, 000000377777, 000000777777, 000001777777,
        000003777777, 000007777777, 000017777777, 000037777777,
        000077777777, 000177777777, 000377777777, 000777777777,
        001777777777, 003777777777, 007777777777, 017777777777
};

const apr_sdbm_datum_t sdbm_nullitem = { NULL, 0 };

static apr_status_t database_cleanup(void *data)
{
    apr_sdbm_t *db = data;

    /*
     * Can't rely on apr_sdbm_unlock, since it will merely
     * decrement the refcnt if several locks are held.
     */
    if (db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK))
        (void) apr_file_unlock(db->dirf);
    (void) apr_file_close(db->dirf);
    (void) apr_file_close(db->pagf);
    free(db);

    return APR_SUCCESS;
}

static apr_status_t prep(apr_sdbm_t **pdb, const char *dirname, const char *pagname,
                         apr_int32_t flags, apr_fileperms_t perms, apr_pool_t *p)
{
    apr_sdbm_t *db;
    apr_status_t status;

    *pdb = NULL;

    db = malloc(sizeof(*db));
    memset(db, 0, sizeof(*db));

    db->pool = p;

    /*
     * adjust user flags so that WRONLY becomes RDWR, 
     * as required by this package. Also set our internal
     * flag for RDONLY if needed.
     */
    if (!(flags & APR_WRITE)) {
        db->flags |= SDBM_RDONLY;
    }

    /*
     * adjust the file open flags so that we handle locking
     * on our own (don't rely on any locking behavior within
     * an apr_file_t, in case it's ever introduced, and set
     * our own flag.
     */
    if (flags & APR_SHARELOCK) {
        db->flags |= SDBM_SHARED;
        flags &= ~APR_SHARELOCK;
    }

    flags |= APR_BINARY | APR_READ;

    /*
     * open the files in sequence, and stat the dirfile.
     * If we fail anywhere, undo everything, return NULL.
     */

    if ((status = apr_file_open(&db->dirf, dirname, flags, perms, p))
                != APR_SUCCESS)
        goto error;

    if ((status = apr_file_open(&db->pagf, pagname, flags, perms, p))
                != APR_SUCCESS)
        goto error;

    if ((status = apr_sdbm_lock(db, (db->flags & SDBM_RDONLY) 
                                        ? APR_FLOCK_SHARED
                                        : APR_FLOCK_EXCLUSIVE))
                != APR_SUCCESS)
        goto error;

    /* apr_pcalloc zeroed the buffers
     * apr_sdbm_lock stated the dirf->size and invalidated the cache
     */

    /*
     * if we are opened in SHARED mode, unlock ourself 
     */
    if (db->flags & SDBM_SHARED)
        if ((status = apr_sdbm_unlock(db)) != APR_SUCCESS)
            goto error;

    /* make sure that we close the database at some point */
    apr_pool_cleanup_register(p, db, database_cleanup, apr_pool_cleanup_null);

    /* Done! */
    *pdb = db;
    return APR_SUCCESS;

error:
    if (db->dirf && db->pagf)
        (void) apr_sdbm_unlock(db);
    if (db->dirf != NULL)
        (void) apr_file_close(db->dirf);
    if (db->pagf != NULL) {
        (void) apr_file_close(db->pagf);
    }
    free(db);
    return status;
}

APU_DECLARE(apr_status_t) apr_sdbm_open(apr_sdbm_t **db, const char *file, 
                                        apr_int32_t flags, 
                                        apr_fileperms_t perms, apr_pool_t *p)
{
    char *dirname = apr_pstrcat(p, file, APR_SDBM_DIRFEXT, NULL);
    char *pagname = apr_pstrcat(p, file, APR_SDBM_PAGFEXT, NULL);
    
    return prep(db, dirname, pagname, flags, perms, p);
}

APU_DECLARE(apr_status_t) apr_sdbm_close(apr_sdbm_t *db)
{
    return apr_pool_cleanup_run(db->pool, db, database_cleanup);
}

APU_DECLARE(apr_status_t) apr_sdbm_fetch(apr_sdbm_t *db, apr_sdbm_datum_t *val,
                                         apr_sdbm_datum_t key)
{
    apr_status_t status;
    
    if (db == NULL || bad(key))
        return APR_EINVAL;

    if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
        return status;

    if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
        *val = getpair(db->pagbuf, key);
        /* ### do we want a not-found result? */
    }

    (void) apr_sdbm_unlock(db);

    return status;
}

static apr_status_t write_page(apr_sdbm_t *db, const char *buf, long pagno)
{
    apr_status_t status;
    apr_off_t off = OFF_PAG(pagno);
    
    if ((status = apr_file_seek(db->pagf, APR_SET, &off)) == APR_SUCCESS)
        status = apr_file_write_full(db->pagf, buf, PBLKSIZ, NULL);

    return status;
}

APU_DECLARE(apr_status_t) apr_sdbm_delete(apr_sdbm_t *db, 
                                          const apr_sdbm_datum_t key)
{
    apr_status_t status;
    
    if (db == NULL || bad(key))
        return APR_EINVAL;
    if (apr_sdbm_rdonly(db))
        return APR_EINVAL;
    
    if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
        return status;

    if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
        if (!delpair(db->pagbuf, key))
            /* ### should we define some APRUTIL codes? */
            status = APR_EGENERAL;
        else
            status = write_page(db, db->pagbuf, db->pagbno);
    }

    (void) apr_sdbm_unlock(db);

    return status;
}

APU_DECLARE(apr_status_t) apr_sdbm_store(apr_sdbm_t *db, apr_sdbm_datum_t key,
                                         apr_sdbm_datum_t val, int flags)
{
    int need;
    register long hash;
    apr_status_t status;
    
    if (db == NULL || bad(key))
        return APR_EINVAL;
    if (apr_sdbm_rdonly(db))
        return APR_EINVAL;
    need = key.dsize + val.dsize;
    /*
     * is the pair too big (or too small) for this database ??
     */
    if (need < 0 || need > PAIRMAX)
        return APR_EINVAL;

    if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
        return status;

    if ((status = getpage(db, (hash = exhash(key)))) == APR_SUCCESS) {

        /*
         * if we need to replace, delete the key/data pair
         * first. If it is not there, ignore.
         */
        if (flags == APR_SDBM_REPLACE)
            (void) delpair(db->pagbuf, key);
        else if (!(flags & APR_SDBM_INSERTDUP) && duppair(db->pagbuf, key)) {
            status = APR_EEXIST;
            goto error;
        }
        /*
         * if we do not have enough room, we have to split.
         */
        if (!fitpair(db->pagbuf, need))
            if ((status = makroom(db, hash, need)) != APR_SUCCESS)
                goto error;
        /*
         * we have enough room or split is successful. insert the key,
         * and update the page file.
         */
        (void) putpair(db->pagbuf, key, val);

        status = write_page(db, db->pagbuf, db->pagbno);
    }

error: