MpoolExample.cpp

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1997-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: MpoolExample.cpp,v 12.1 2005/06/16 20:22:14 bostic Exp $
 */

#include <sys/types.h>

#include <errno.h>
#include <fcntl.h>
#include <iostream>
#include <fstream>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <db_cxx.h>

using std::cout;
using std::cerr;
using std::ios;
using std::ofstream;

#define MPOOL   "mpool"

int init(const char *, int, int);
int run(DB_ENV *, int, int, int);

static int usage();

const char *progname = "MpoolExample";                  // Program name.

class MpoolExample : public DbEnv
{
public:
        MpoolExample();
        int initdb(const char *home, int cachesize);
        int run(int hits, int pagesize, int npages);

private:
        static const char FileName[];

        // no need for copy and assignment
        MpoolExample(const MpoolExample &);
        void operator = (const MpoolExample &);
};

int main(int argc, char *argv[])
{
        int ret;
        int cachesize = 20 * 1024;
        int hits = 1000;
        int npages = 50;
        int pagesize = 1024;

        for (int i = 1; i < argc; ++i) {
                if (strcmp(argv[i], "-c") == 0) {
                        if ((cachesize = atoi(argv[++i])) < 20 * 1024)
                                usage();
                }
                else if (strcmp(argv[i], "-h") == 0) {
                        if ((hits = atoi(argv[++i])) <= 0)
                                usage();
                }
                else if (strcmp(argv[i], "-n") == 0) {
                        if ((npages = atoi(argv[++i])) <= 0)
                                usage();
                }
                else if (strcmp(argv[i], "-p") == 0) {
                        if ((pagesize = atoi(argv[++i])) <= 0)
                                usage();
                }
                else {
                        usage();
                }
        }

        // Initialize the file.
        if ((ret = init(MPOOL, pagesize, npages)) != 0)
                return (ret);

        try {
                MpoolExample app;

                cout << progname
                     << ": cachesize: " << cachesize
                     << "; pagesize: " << pagesize
                     << "; N pages: " << npages << "\n";

                if ((ret = app.initdb(NULL, cachesize)) != 0)
                        return (ret);
                if ((ret = app.run(hits, pagesize, npages)) != 0)
                        return (ret);
                cout << "MpoolExample: completed\n";
                return (EXIT_SUCCESS);
        }
        catch (DbException &dbe) {
                cerr << "MpoolExample: " << dbe.what() << "\n";
                return (EXIT_FAILURE);
        }
}

//
// init --
//      Create a backing file.
//
int
init(const char *file, int pagesize, int npages)
{
        // Create a file with the right number of pages, and store a page
        // number on each page.
        ofstream of(file, ios::out | ios::binary);

        if (of.fail()) {
                cerr << "MpoolExample: " << file << ": open failed\n";
                return (EXIT_FAILURE);
        }
        char *p = new char[pagesize];
        memset(p, 0, pagesize);

        // The pages are numbered from 0.
        for (int cnt = 0; cnt <= npages; ++cnt) {
                *(db_pgno_t *)p = cnt;
                of.write(p, pagesize);
                if (of.fail()) {
                        cerr << "MpoolExample: " << file << ": write failed\n";
                        return (EXIT_FAILURE);
                }
        }
        delete [] p;
        return (EXIT_SUCCESS);
}

static int
usage()
{
        cerr << "usage: MpoolExample [-c cachesize] "
             << "[-h hits] [-n npages] [-p pagesize]\n";
        return (EXIT_FAILURE);
}

// Note: by using DB_CXX_NO_EXCEPTIONS, we get explicit error returns
// from various methods rather than exceptions so we can report more
// information with each error.
//
MpoolExample::MpoolExample()
:       DbEnv(DB_CXX_NO_EXCEPTIONS)
{
}

int MpoolExample::initdb(const char *home, int cachesize)
{
        set_error_stream(&cerr);
        set_errpfx("MpoolExample");
        set_cachesize(0, cachesize, 0);

        open(home, DB_CREATE | DB_INIT_MPOOL, 0);
        return (EXIT_SUCCESS);
}

//
// run --
//      Get a set of pages.
//
int
MpoolExample::run(int hits, int pagesize, int npages)
{
        db_pgno_t pageno;
        int cnt, ret;
        void *p;

        // Open the file in the environment.
        DbMpoolFile *mfp;

        if ((ret = memp_fcreate(&mfp, 0)) != 0) {
                cerr << "MpoolExample: memp_fcreate failed: "
                     << strerror(ret) << "\n";
                return (EXIT_FAILURE);
        }
        mfp->open(MPOOL, 0, 0, pagesize);

        cout << "retrieve " << hits << " random pages... ";

        srand((unsigned int)time(NULL));
        for (cnt = 0; cnt < hits; ++cnt) {
                pageno = (rand() % npages) + 1;
                if ((ret = mfp->get(&pageno, 0, &p)) != 0) {
                        cerr << "MpoolExample: unable to retrieve page "
                             << (unsigned long)pageno << ": "
                             << strerror(ret) << "\n";
                        return (EXIT_FAILURE);
                }
                if (*(db_pgno_t *)p != pageno) {
                        cerr << "MpoolExample: wrong page retrieved ("
                             << (unsigned long)pageno << " != "
                             << *(int *)p << ")\n";
                        return (EXIT_FAILURE);
                }
                if ((ret = mfp->put(p, 0)) != 0) {
                        cerr << "MpoolExample: unable to return page "
                             << (unsigned long)pageno << ": "
                             << strerror(ret) << "\n";
                        return (EXIT_FAILURE);
                }
        }

        cout << "successful.\n";

        // Close the pool.
        if ((ret = close(0)) != 0) {
                cerr << "MpoolExample: " << strerror(ret) << "\n";
                return (EXIT_FAILURE);
        }
        return (EXIT_SUCCESS);
}

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