io.netty.resolver.HostsFileParser Maven / Gradle / Ivy
/*
* Copyright 2015 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.resolver;
import io.netty.util.NetUtil;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.UnstableApi;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Pattern;
import static io.netty.util.internal.ObjectUtil.*;
/**
* A parser for hosts files.
*/
@UnstableApi
public final class HostsFileParser {
private static final String WINDOWS_DEFAULT_SYSTEM_ROOT = "C:\\Windows";
private static final String WINDOWS_HOSTS_FILE_RELATIVE_PATH = "\\system32\\drivers\\etc\\hosts";
private static final String X_PLATFORMS_HOSTS_FILE_PATH = "/etc/hosts";
private static final Pattern WHITESPACES = Pattern.compile("[ \t]+");
private static final InternalLogger logger = InternalLoggerFactory.getInstance(HostsFileParser.class);
private static File locateHostsFile() {
File hostsFile;
if (PlatformDependent.isWindows()) {
hostsFile = new File(System.getenv("SystemRoot") + WINDOWS_HOSTS_FILE_RELATIVE_PATH);
if (!hostsFile.exists()) {
hostsFile = new File(WINDOWS_DEFAULT_SYSTEM_ROOT + WINDOWS_HOSTS_FILE_RELATIVE_PATH);
}
} else {
hostsFile = new File(X_PLATFORMS_HOSTS_FILE_PATH);
}
return hostsFile;
}
/**
* Parse hosts file at standard OS location using the systems default {@link Charset} for decoding.
*
* @return a {@link HostsFileEntries}
*/
public static HostsFileEntries parseSilently() {
return parseSilently(Charset.defaultCharset());
}
/**
* Parse hosts file at standard OS location using the given {@link Charset}s one after each other until
* we were able to parse something or none is left.
*
* @param charsets the {@link Charset}s to try as file encodings when parsing.
* @return a {@link HostsFileEntries}
*/
public static HostsFileEntries parseSilently(Charset... charsets) {
File hostsFile = locateHostsFile();
try {
return parse(hostsFile, charsets);
} catch (IOException e) {
if (logger.isWarnEnabled()) {
logger.warn("Failed to load and parse hosts file at " + hostsFile.getPath(), e);
}
return HostsFileEntries.EMPTY;
}
}
/**
* Parse hosts file at standard OS location using the system default {@link Charset} for decoding.
*
* @return a {@link HostsFileEntries}
* @throws IOException file could not be read
*/
public static HostsFileEntries parse() throws IOException {
return parse(locateHostsFile());
}
/**
* Parse a hosts file using the system default {@link Charset} for decoding.
*
* @param file the file to be parsed
* @return a {@link HostsFileEntries}
* @throws IOException file could not be read
*/
public static HostsFileEntries parse(File file) throws IOException {
return parse(file, Charset.defaultCharset());
}
/**
* Parse a hosts file.
*
* @param file the file to be parsed
* @param charsets the {@link Charset}s to try as file encodings when parsing.
* @return a {@link HostsFileEntries}
* @throws IOException file could not be read
*/
public static HostsFileEntries parse(File file, Charset... charsets) throws IOException {
checkNotNull(file, "file");
checkNotNull(charsets, "charsets");
if (file.exists() && file.isFile()) {
for (Charset charset: charsets) {
HostsFileEntries entries = parse(new BufferedReader(new InputStreamReader(
new FileInputStream(file), charset)));
if (entries != HostsFileEntries.EMPTY) {
return entries;
}
}
}
return HostsFileEntries.EMPTY;
}
/**
* Parse a reader of hosts file format.
*
* @param reader the file to be parsed
* @return a {@link HostsFileEntries}
* @throws IOException file could not be read
*/
public static HostsFileEntries parse(Reader reader) throws IOException {
checkNotNull(reader, "reader");
BufferedReader buff = new BufferedReader(reader);
try {
Map ipv4Entries = new HashMap();
Map ipv6Entries = new HashMap();
String line;
while ((line = buff.readLine()) != null) {
// remove comment
int commentPosition = line.indexOf('#');
if (commentPosition != -1) {
line = line.substring(0, commentPosition);
}
// skip empty lines
line = line.trim();
if (line.isEmpty()) {
continue;
}
// split
List lineParts = new ArrayList();
for (String s: WHITESPACES.split(line)) {
if (!s.isEmpty()) {
lineParts.add(s);
}
}
// a valid line should be [IP, hostname, alias*]
if (lineParts.size() < 2) {
// skip invalid line
continue;
}
byte[] ipBytes = NetUtil.createByteArrayFromIpAddressString(lineParts.get(0));
if (ipBytes == null) {
// skip invalid IP
continue;
}
// loop over hostname and aliases
for (int i = 1; i < lineParts.size(); i ++) {
String hostname = lineParts.get(i);
String hostnameLower = hostname.toLowerCase(Locale.ENGLISH);
InetAddress address = InetAddress.getByAddress(hostname, ipBytes);
if (address instanceof Inet4Address) {
Inet4Address previous = ipv4Entries.put(hostnameLower, (Inet4Address) address);
if (previous != null) {
// restore, we want to keep the first entry
ipv4Entries.put(hostnameLower, previous);
}
} else {
Inet6Address previous = ipv6Entries.put(hostnameLower, (Inet6Address) address);
if (previous != null) {
// restore, we want to keep the first entry
ipv6Entries.put(hostnameLower, previous);
}
}
}
}
return ipv4Entries.isEmpty() && ipv6Entries.isEmpty() ?
HostsFileEntries.EMPTY :
new HostsFileEntries(ipv4Entries, ipv6Entries);
} finally {
try {
buff.close();
} catch (IOException e) {
logger.warn("Failed to close a reader", e);
}
}
}
/**
* Can't be instantiated.
*/
private HostsFileParser() {
}
}