Viewing file:  BtRecExample.cpp (4.36 KB) -rw-r--r--
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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997-2004
* Sleepycat Software. All rights reserved.
*
* $Id: BtRecExample.cpp,v 11.26 2004/09/17 22:00:28 mjc Exp $
*/
#include <sys/types.h>
#include <errno.h>
#include <iostream>
#include <iomanip>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <db_cxx.h>
using std::cout;
using std::cerr;
#define DATABASE "access.db"
#define WORDLIST "../test/wordlist"
const char *progname = "BtRecExample"; // Program name.
class BtRecExample
{
public:
BtRecExample(FILE *fp);
~BtRecExample();
void run();
void stats();
void show(const char *msg, Dbt *key, Dbt *data);
private:
Db *dbp;
Dbc *dbcp;
};
BtRecExample::BtRecExample(FILE *fp)
{
char *p, *t, buf[1024], rbuf[1024];
int ret;
// Remove the previous database.
(void)remove(DATABASE);
dbp = new Db(NULL, 0);
dbp->set_error_stream(&cerr);
dbp->set_errpfx(progname);
dbp->set_pagesize(1024); // 1K page sizes.
dbp->set_flags(DB_RECNUM); // Record numbers.
dbp->open(NULL, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664);
//
// Insert records into the database, where the key is the word
// preceded by its record number, and the data is the same, but
// in reverse order.
//
for (int cnt = 1; cnt <= 1000; ++cnt) {
(void)sprintf(buf, "%04d_", cnt);
if (fgets(buf + 4, sizeof(buf) - 4, fp) == NULL)
break;
u_int32_t len = (u_int32_t)strlen(buf);
buf[len - 1] = '\0';
for (t = rbuf, p = buf + (len - 2); p >= buf;)
*t++ = *p--;
*t++ = '\0';
// As a convenience for printing, we include the null terminator
// in the stored data.
//
Dbt key(buf, len);
Dbt data(rbuf, len);
if ((ret = dbp->put(NULL, &key, &data, DB_NOOVERWRITE)) != 0) {
dbp->err(ret, "Db::put");
if (ret != DB_KEYEXIST)
throw DbException(ret);
}
}
}
BtRecExample::~BtRecExample()
{
if (dbcp != 0)
dbcp->close();
dbp->close(0);
delete dbp;
}
//
// Print out the number of records in the database.
//
void BtRecExample::stats()
{
DB_BTREE_STAT *statp;
dbp->stat(NULL, &statp, 0);
cout << progname << ": database contains "
<< (u_long)statp->bt_ndata << " records\n";
// Note: must use free, not delete.
// This struct is allocated by C.
//
free(statp);
}
void BtRecExample::run()
{
db_recno_t recno;
int ret;
char buf[1024];
// Acquire a cursor for the database.
dbp->cursor(NULL, &dbcp, 0);
//
// Prompt the user for a record number, then retrieve and display
// that record.
//
for (;;) {
// Get a record number.
cout << "recno #> ";
cout.flush();
if (fgets(buf, sizeof(buf), stdin) == NULL)
break;
recno = atoi(buf);
//
// Start with a fresh key each time,
// the dbp->get() routine returns
// the key and data pair, not just the key!
//
Dbt key(&recno, sizeof(recno));
Dbt data;
if ((ret = dbcp->get(&key, &data, DB_SET_RECNO)) != 0) {
dbp->err(ret, "DBcursor->get");
throw DbException(ret);
}
// Display the key and data.
show("k/d\t", &key, &data);
// Move the cursor a record forward.
if ((ret = dbcp->get(&key, &data, DB_NEXT)) != 0) {
dbp->err(ret, "DBcursor->get");
throw DbException(ret);
}
// Display the key and data.
show("next\t", &key, &data);
//
// Retrieve the record number for the following record into
// local memory.
//
data.set_data(&recno);
data.set_size(sizeof(recno));
data.set_ulen(sizeof(recno));
data.set_flags(data.get_flags() | DB_DBT_USERMEM);
if ((ret = dbcp->get(&key, &data, DB_GET_RECNO)) != 0) {
if (ret != DB_NOTFOUND && ret != DB_KEYEMPTY) {
dbp->err(ret, "DBcursor->get");
throw DbException(ret);
}
}
else {
cout << "retrieved recno: " << (u_long)recno << "\n";
}
}
dbcp->close();
dbcp = NULL;
}
//
// show --
// Display a key/data pair.
//
void BtRecExample::show(const char *msg, Dbt *key, Dbt *data)
{
cout << msg << (char *)key->get_data()
<< " : " << (char *)data->get_data() << "\n";
}
int
main()
{
FILE *fp;
// Open the word database.
if ((fp = fopen(WORDLIST, "r")) == NULL) {
fprintf(stderr, "%s: open %s: %s\n",
progname, WORDLIST, db_strerror(errno));
return (EXIT_FAILURE);
}
try {
BtRecExample app(fp);
// Close the word database.
(void)fclose(fp);
fp = NULL;
app.stats();
app.run();
}
catch (DbException &dbe) {
cerr << "Exception: " << dbe.what() << "\n";
return (EXIT_FAILURE);
}
return (EXIT_SUCCESS);
}
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