зеркало из https://github.com/mozilla/pjs.git
198 строки
5.4 KiB
Java
198 строки
5.4 KiB
Java
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/* -*- Mode: java; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* The contents of this file are subject to the Mozilla Public License
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* Version 1.0 (the "License"); you may not use this file except in
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* compliance with the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS"
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* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
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* the License for the specific language governing rights and limitations
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* under the License.
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*
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* The Original Code is the Grendel mail/news client.
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*
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* The Initial Developer of the Original Code is Netscape Communications
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* Corporation. Portions created by Netscape are Copyright (C) 1997
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* Netscape Communications Corporation. All Rights Reserved.
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*
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* Created: Terry Weissman <terry@netscape.com>, 26 Sep 1997.
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*/
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package grendel.storage.intertwingle;
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import calypso.util.Assert;
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import calypso.util.NullJavaEnumeration;
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import java.io.File;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.util.Enumeration;
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import java.util.Hashtable;
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import java.util.NoSuchElementException;
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/** This is a completely wretched thing that implements a RDF-ish database.
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It works by generating zillions of tiny files. We should never ever really
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use this; it's just for playing. If we actually ever do ship this, I will
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be forced to spend the rest of my life hunting down every copy on every
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machine in the world and eradicating it. */
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final class HackDB extends BaseDB {
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private File top;
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private File tmpfile;
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private Hashtable slotdirs = new Hashtable();
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private Hashtable reverseslotdirs = new Hashtable();
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HackDB(File f) throws IOException {
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top = f;
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ensureDirectory(top);
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tmpfile = new File(top, "--tmp--");
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}
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private void ensureDirectory(File f) throws IOException {
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if (!f.exists()) f.mkdirs();
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if (!f.isDirectory()) {
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throw new IOException("Must be a directory: " + f);
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}
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}
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private File findSlotFile(String name, boolean reverse) throws IOException {
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Hashtable table = (reverse ? reverseslotdirs : slotdirs);
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File result = (File) table.get(name);
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if (result == null) {
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result = new File(top, reverse ? "reverse-" + name : name);
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ensureDirectory(result);
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table.put(name, result);
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}
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return result;
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}
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private void putone(File dir, String name, String value) throws IOException {
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File n = new File(dir, name);
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RandomAccessFile file = new RandomAccessFile(n, "rw");
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String line;
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long length = file.length();
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while (file.getFilePointer() < length) {
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line = file.readUTF();
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if (line.equals(value)) {
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file.close();
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return;
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}
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}
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file.writeUTF(value);
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file.close();
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}
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private void nukeone(File dir, String name, String value)
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throws IOException
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{
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File n = new File(dir, name);
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if (!n.exists()) return;
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RandomAccessFile file = new RandomAccessFile(n, "r");
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tmpfile.delete();
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RandomAccessFile out = new RandomAccessFile(tmpfile, "rw");
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long length = file.length();
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boolean found = false;
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int count = 0;
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while (file.getFilePointer() < length) {
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String line = file.readUTF();
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if (line.equals(value)) {
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found = true;
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} else {
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out.writeUTF(line);
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count++;
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}
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}
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file.close();
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out.close();
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if (found) {
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n.delete();
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if (count > 0) {
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tmpfile.renameTo(n);
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} else {
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tmpfile.delete();
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}
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} else {
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tmpfile.delete();
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}
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}
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public synchronized void assert(String name, String slot, String value)
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throws IOException
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{
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File s = findSlotFile(slot, false);
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File r = findSlotFile(slot, true);
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putone(s, name, value);
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putone(r, value, name);
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}
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public synchronized void unassert(String name, String slot, String value)
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throws IOException
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{
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File s = findSlotFile(slot, false);
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File r = findSlotFile(slot, true);
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nukeone(s, name, value);
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nukeone(r, value, name);
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}
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public synchronized String findFirst(String name, String slot,
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boolean reverse) throws IOException {
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File f = new File(findSlotFile(slot, reverse), name);
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if (!f.exists()) return null;
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RandomAccessFile fid = new RandomAccessFile(f, "r");
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String line = null;
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if (fid.length() > 0) {
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line = fid.readUTF();
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}
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fid.close();
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return line;
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}
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public Enumeration findAll(String name, String slot, boolean reverse)
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throws IOException
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{
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File f = new File(findSlotFile(slot, reverse), name);
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if (!f.exists()) return NullJavaEnumeration.kInstance;
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final RandomAccessFile thefid = new RandomAccessFile(f, "r");
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return new Enumeration() {
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RandomAccessFile fid = thefid;
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String next = null;
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public boolean hasMoreElements() {
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if (next != null) return true;
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if (fid == null) return false;
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try {
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next = fid.readUTF();
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} catch (IOException e) {
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next = null;
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}
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if (next == null) {
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try {
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fid.close();
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} catch (IOException e) {
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}
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fid = null;
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return false;
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}
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return true;
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}
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public Object nextElement() throws NoSuchElementException {
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if (!hasMoreElements()) throw new NoSuchElementException();
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String result = next;
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next = null;
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return result;
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}
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};
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}
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};
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