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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1997-2002
* Sleepycat Software. All rights reserved.
*
* $Id: LockExample.java,v 11.8 2002/01/11 15:52:43 bostic Exp $
*/
package com.sleepycat.examples;
import com.sleepycat.db.*;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.PrintStream;
import java.util.Vector;
//
// An example of a program using DbLock and related classes.
//
class LockExample extends DbEnv
{
private static final String progname = "LockExample";
private static final String LOCK_HOME = "TESTDIR";
public LockExample(String home, int maxlocks, boolean do_unlink)
throws DbException, FileNotFoundException
{
super(0);
if (do_unlink) {
remove(home, Db.DB_FORCE);
}
else {
set_error_stream(System.err);
set_errpfx("LockExample");
if (maxlocks != 0)
set_lk_max_locks(maxlocks);
open(home, Db.DB_CREATE|Db.DB_INIT_LOCK, 0);
}
}
// Prompts for a line, and keeps prompting until a non blank
// line is returned. Returns null on error.
//
static public String askForLine(InputStreamReader reader,
PrintStream out, String prompt)
{
String result = "";
while (result != null && result.length() == 0) {
out.print(prompt);
out.flush();
result = getLine(reader);
}
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.
//
static public 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 DbException
{
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 = lock_id();
for (held = 0;;) {
String opbuf = askForLine(in, System.out,
"Operation get/release [get]> ");
if (opbuf == null)
break;
try {
if (opbuf.equals("get")) {
// Acquire a lock.
String objbuf = askForLine(in, System.out,
"input object (text string) to lock> ");
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"));
int lock_type;
if (len <= 1 || lockbuf.equals("read"))
lock_type = Db.DB_LOCK_READ;
else
lock_type = Db.DB_LOCK_WRITE;
Dbt dbt = new Dbt(objbuf.getBytes());
DbLock lock;
did_get = true;
lock = lock_get(locker, Db.DB_LOCK_NOWAIT,
dbt, lock_type);
lockid = locks.size();
locks.addElement(lock);
} else {
// Release a lock.
String objbuf;
objbuf = askForLine(in, System.out,
"input lock to release> ");
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;
DbLock lock = (DbLock)locks.elementAt(lockid);
lock_put(lock);
}
System.out.println("Lock #" + lockid + " " +
(did_get ? "granted" : "released"));
held += did_get ? 1 : -1;
}
catch (DbException dbe) {
switch (dbe.get_errno()) {
case Db.DB_LOCK_NOTGRANTED:
System.out.println("Lock not granted");
break;
case Db.DB_LOCK_DEADLOCK:
System.err.println("LockExample: lock_" +
(did_get ? "get" : "put") +
": returned DEADLOCK");
break;
default:
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[])
{
String 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 = 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 {
if (do_unlink) {
// Create an environment that immediately
// removes all files.
LockExample tmp = new LockExample(home, maxlocks, do_unlink);
}
LockExample app = new LockExample(home, maxlocks, do_unlink);
app.run();
app.close(0);
}
catch (DbException 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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