Viewing file:  LockExample.cpp (5.03 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: LockExample.cpp,v 11.26 2004/09/17 22:00:28 mjc Exp $
*/
#include <sys/types.h>
#include <errno.h>
#include <iostream>
#include <stdlib.h>
#include <string.h>
#include <db_cxx.h>
using std::cin;
using std::cout;
using std::cerr;
const char *progname = "LockExample"; // Program name.
//
// An example of a program using DBLock and related classes.
//
class LockExample : public DbEnv
{
public:
void run();
int error_code() { return (ecode); }
LockExample(const char *home, u_int32_t maxlocks, int do_unlink);
private:
static const char FileName[];
int ecode;
// no need for copy and assignment
LockExample(const LockExample &);
void operator = (const LockExample &);
};
static int usage(); // forward
int
main(int argc, char *argv[])
{
const char *home;
int do_unlink;
u_int32_t maxlocks;
int i;
home = "TESTDIR";
maxlocks = 0;
do_unlink = 0;
for (int argnum = 1; argnum < argc; ++argnum) {
if (strcmp(argv[argnum], "-h") == 0) {
if (++argnum >= argc)
return (usage());
home = argv[argnum];
}
else if (strcmp(argv[argnum], "-m") == 0) {
if (++argnum >= argc)
return (usage());
if ((i = atoi(argv[argnum])) <= 0)
return (usage());
maxlocks = (u_int32_t)i; /* XXX: possible overflow. */
}
else if (strcmp(argv[argnum], "-u") == 0) {
do_unlink = 1;
}
else {
return (usage());
}
}
try {
int ecode;
if (do_unlink) {
// Create an environment that immediately
// removes all files.
LockExample tmp(home, maxlocks, do_unlink);
if ((ecode = tmp.error_code()) != 0)
return (ecode);
}
LockExample app(home, maxlocks, do_unlink);
if ((ecode = app.error_code()) != 0)
return (ecode);
app.run();
app.close(0);
return (EXIT_SUCCESS);
}
catch (DbException &dbe) {
cerr << "LockExample: " << dbe.what() << "\n";
return (EXIT_FAILURE);
}
}
LockExample::LockExample(const char *home, u_int32_t maxlocks, int do_unlink)
: DbEnv(0)
, ecode(0)
{
int ret;
if (do_unlink) {
if ((ret = remove(home, DB_FORCE)) != 0) {
cerr << progname << ": DbEnv::remove: "
<< strerror(errno) << "\n";
ecode = EXIT_FAILURE;
}
}
else {
set_error_stream(&cerr);
set_errpfx("LockExample");
if (maxlocks != 0)
set_lk_max_locks(maxlocks);
open(home, DB_CREATE | DB_INIT_LOCK, 0);
}
}
void LockExample::run()
{
long held;
size_t len;
u_int32_t locker;
int did_get, ret;
DbLock *locks = 0;
int lockcount = 0;
int lockid = 0;
char objbuf[1024];
//
// Accept lock requests.
//
lock_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, (u_int32_t)strlen(objbuf));
DbLock lock;
ret = lock_get(locker, DB_LOCK_NOWAIT, &dbt,
lock_type, &lock);
did_get = 1;
lockid = lockcount++;
if (locks == NULL) {
locks = new DbLock[1];
}
else {
DbLock *newlocks = new DbLock[lockcount];
for (int lockno = 0;
lockno < lockid; lockno++) {
newlocks[lockno] = locks[lockno];
}
delete locks;
locks = newlocks;
}
locks[lockid] = lock;
} 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)) <= 0);
lockid = strtol(objbuf, NULL, 16);
if (lockid < 0 || lockid >= lockcount) {
cout << "Lock #" << lockid << " out of range\n";
continue;
}
DbLock lock = locks[lockid];
ret = lock_put(&lock);
did_get = 0;
}
switch (ret) {
case 0:
cout << "Lock #" << lockid << " "
<< (did_get ? "granted" : "released")
<< "\n";
held += did_get ? 1 : -1;
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";
if (locks != 0)
delete locks;
}
static int
usage()
{
cerr << "usage: LockExample [-u] [-h home] [-m maxlocks]\n";
return (EXIT_FAILURE);
}
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