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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997-2009 Oracle. All rights reserved.
*
* $Id$
*/
package db;
import com.sleepycat.db.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintStream;
import java.util.Vector;
//
// An example of a program using Lock and related classes.
//
class LockExample {
private static final String progname = "LockExample";
private static final File LOCK_HOME = new File("TESTDIR");
Environment dbenv;
public LockExample(File home, int maxlocks, boolean do_unlink)
throws DatabaseException, FileNotFoundException {
if (do_unlink) {
Environment.remove(home, true, null);
}
EnvironmentConfig config = new EnvironmentConfig();
config.setErrorStream(System.err);
config.setErrorPrefix("LockExample");
config.setMaxLocks(maxlocks);
config.setAllowCreate(true);
config.setInitializeLocking(true);
dbenv = new Environment(home, config);
}
public void close() throws DatabaseException {
dbenv.close();
}
// Prompts for a line, returning the default answer if a blank
// line is entered.
//
public static String askForLine(InputStreamReader reader,
PrintStream out, String prompt,
String defaultAnswer) {
String result;
do {
if (defaultAnswer != null)
out.print(prompt + " [" + defaultAnswer + "] >");
else
out.print(prompt);
out.flush();
result = getLine(reader);
if (result == null || result.length() == 0)
result = defaultAnswer;
} while (result == null);
return result;
}
// Not terribly efficient, but does the job.
// Works for reading a line from stdin or a file.
// Returns null on EOF. If EOF appears in the middle
// of a line, returns that line, then null on next call.
//
public static String getLine(InputStreamReader reader) {
StringBuffer b = new StringBuffer();
int c;
try {
while ((c = reader.read()) != -1 && c != '\n')
if (c != '\r')
b.append((char)c);
} catch (IOException ioe) {
c = -1;
}
if (c == -1 && b.length() == 0)
return null;
else
return b.toString();
}
public void run() throws DatabaseException {
long held;
int len = 0, locker;
int ret;
boolean did_get = false;
int lockid = 0;
InputStreamReader in = new InputStreamReader(System.in);
Vector locks = new Vector();
//
// Accept lock requests.
//
locker = dbenv.createLockerID();
for (held = 0;;) {
String opbuf = askForLine(in, System.out,
"Operation get/release", "get");
if (opbuf == null)
break;
try {
if (opbuf.equals("get") || opbuf.equals("vget")) {
// Acquire a lock.
String objbuf = askForLine(in, System.out,
"input object (text string) to lock> ", null);
if (objbuf == null)
break;
String lockbuf;
do {
lockbuf = askForLine(in, System.out,
"lock type read/write", "read");
if (lockbuf == null)
break;
len = lockbuf.length();
} while (len >= 1 &&
!lockbuf.equals("read") &&
!lockbuf.equals("write"));
LockRequestMode lock_type;
if (len <= 1 || lockbuf.equals("read"))
lock_type = LockRequestMode.READ;
else
lock_type = LockRequestMode.WRITE;
DatabaseEntry entry = new DatabaseEntry(objbuf.getBytes());
Lock lock;
if (opbuf.equals("get")) {
did_get = true;
lock = dbenv.getLock(locker, true, entry, lock_type);
} else {
LockRequest req = new LockRequest(
LockOperation.GET, lock_type, entry, null);
LockRequest[] reqs = { req };
dbenv.lockVector(locker, true, reqs);
lock = req.getLock();
System.out.println("Got lock: " + lock);
}
lockid = locks.size();
locks.addElement(lock);
} else {
// Release a lock.
String objbuf;
objbuf = askForLine(in, System.out,
"input lock to release> ", null);
if (objbuf == null)
break;
lockid = Integer.parseInt(objbuf, 16);
if (lockid < 0 || lockid >= locks.size()) {
System.out.println("Lock #" + lockid + " out of range");
continue;
}
did_get = false;
Lock lock = (Lock)locks.elementAt(lockid);
dbenv.putLock(lock);
}
System.out.println("Lock #" + lockid + " " +
(did_get ? "granted" : "released"));
held += did_get ? 1 : -1;
} catch (LockNotGrantedException lnge) {
System.err.println("Lock not granted");
} catch (DeadlockException de) {
System.err.println("LockExample: lock_" +
(did_get ? "get" : "put") +
": returned DEADLOCK");
} catch (DatabaseException dbe) {
System.err.println("LockExample: lock_get: " + dbe.toString());
}
}
System.out.println();
System.out.println("Closing lock region " + String.valueOf(held) +
" locks held");
}
private static void usage() {
System.err.println("usage: LockExample [-u] [-h home] [-m maxlocks]");
System.exit(1);
}
public static void main(String[] argv) {
File home = LOCK_HOME;
boolean do_unlink = false;
int maxlocks = 0;
for (int i = 0; i < argv.length; ++i) {
if (argv[i].equals("-h")) {
if (++i >= argv.length)
usage();
home = new File(argv[i]);
} else if (argv[i].equals("-m")) {
if (++i >= argv.length)
usage();
try {
maxlocks = Integer.parseInt(argv[i]);
} catch (NumberFormatException nfe) {
usage();
}
} else if (argv[i].equals("-u")) {
do_unlink = true;
} else {
usage();
}
}
try {
LockExample app = new LockExample(home, maxlocks, do_unlink);
app.run();
app.close();
} catch (DatabaseException dbe) {
System.err.println(progname + ": " + dbe.toString());
} catch (Throwable t) {
System.err.println(progname + ": " + t.toString());
}
System.out.println("LockExample completed");
}
}
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