gecko-dev/db/examples_cxx/LockExample.cpp
1998-10-15 03:56:37 +00:00

199 lines
4.7 KiB
C++

/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997, 1998
* Sleepycat Software. All rights reserved.
*
* @(#)LockExample.cpp 10.5 (Sleepycat) 4/10/98
*/
#include "config.h"
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <errno.h>
#include <iostream.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#endif
#include <db_cxx.h>
#define LOCK_HOME "/var/tmp/lock"
char *progname = "LockExample"; // Program name.
//
// An example of a program using DBLock and related classes.
//
class LockExample : public DbEnv
{
public:
void run();
LockExample(const char *home);
private:
static const char FileName[];
// no need for copy and assignment
LockExample(const LockExample &);
operator = (const LockExample &);
};
static void usage(); // forward
int
main(int argc, char *argv[])
{
const char *home = LOCK_HOME;
int do_unlink = 0;
for (int i = 1; i < argc; ++i) {
if (strcmp(argv[i], "-h") == 0) {
home = argv[++i];
}
else if (strcmp(argv[i], "-u") == 0) {
do_unlink = 1;
}
else {
usage();
}
}
try {
if (do_unlink) {
LockExample temp(home);
DbLockTab::unlink(home, 1, &temp);
}
LockExample app(home);
app.run();
return 0;
}
catch (DbException &dbe) {
cerr << "AccessExample: " << dbe.what() << "\n";
return 1;
}
}
LockExample::LockExample(const char *home)
: DbEnv(home, 0, DB_CREATE|DB_INIT_LOCK)
{
set_error_stream(&cerr);
set_errpfx("LockExample");
}
void LockExample::run()
{
long held;
u_int32_t len, locker;
int did_get, ret;
char objbuf[1024];
unsigned int lockid = 0;
DbLockTab *lockTable = get_lk_info();
if (!lockTable) {
cerr << "LockExample: lock table not initialized\n";
return;
}
//
// Accept lock requests.
//
lockTable->id(&locker);
for (held = 0;;) {
cout << "Operation get/release [get]> ";
cout.flush();
char opbuf[16];
cin.getline(opbuf, sizeof(opbuf));
if (cin.eof())
break;
if ((len = strlen(opbuf)) <= 1 || strcmp(opbuf, "get") == 0) {
// Acquire a lock.
cout << "input object (text string) to lock> ";
cout.flush();
cin.getline(objbuf, sizeof(objbuf));
if (cin.eof())
break;
if ((len = strlen(objbuf)) <= 0)
continue;
char lockbuf[16];
do {
cout << "lock type read/write [read]> ";
cout.flush();
cin.getline(lockbuf, sizeof(lockbuf));
if (cin.eof())
break;
len = strlen(lockbuf);
} while (len >= 1 &&
strcmp(lockbuf, "read") != 0 &&
strcmp(lockbuf, "write") != 0);
db_lockmode_t lock_type;
if (len <= 1 || strcmp(lockbuf, "read") == 0)
lock_type = DB_LOCK_READ;
else
lock_type = DB_LOCK_WRITE;
Dbt dbt(objbuf, strlen(objbuf));
DbLock lock;
ret = lockTable->get(locker,
DB_LOCK_NOWAIT, &dbt, lock_type, &lock);
lockid = lock.get_lock_id();
did_get = 1;
} else {
// Release a lock.
do {
cout << "input lock to release> ";
cout.flush();
cin.getline(objbuf, sizeof(objbuf));
if (cin.eof())
break;
} while ((len = strlen(objbuf)) <= 1);
lockid = strtoul(objbuf, NULL, 16);
DbLock lock(lockid);
ret = lock.put(lockTable);
did_get = 0;
}
switch (ret) {
case 0:
cout << "Lock 0x" << hex << lockid << " "
<< (did_get ? "granted" : "released")
<< "\n";
held += did_get ? 1 : -1;
break;
case DB_LOCK_NOTHELD:
cout << "You do not hold the lock " << lockid << "\n";
break;
case DB_LOCK_NOTGRANTED:
cout << "Lock not granted\n";
break;
case DB_LOCK_DEADLOCK:
cerr << "LockExample: lock_"
<< (did_get ? "get" : "put")
<< ": " << "returned DEADLOCK";
break;
default:
cerr << "LockExample: lock_get: %s",
strerror(errno);
}
}
cout << "\n";
cout << "Closing lock region " << held << " locks held\n";
}
static void
usage()
{
cerr << "usage: LockExample [-u] [-h home]\n";
exit(1);
}