HostsFileParser Class — netty Architecture

Source Code

resolver/src/main/java/io/netty/resolver/HostsFileParser.java lines 34–123

public final class HostsFileParser {

    /**
     * Parse hosts file at standard OS location using the systems default {@link Charset} for decoding.
     *
     * @return a {@link HostsFileEntries}
     */
    public static HostsFileEntries parseSilently() {
        return hostsFileEntries(HostsFileEntriesProvider.parser().parseSilently());
    }

    /**
     * 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) {
        return hostsFileEntries(HostsFileEntriesProvider.parser().parseSilently(charsets));
    }

    /**
     * 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 hostsFileEntries(HostsFileEntriesProvider.parser().parse());
    }

    /**
     * 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 hostsFileEntries(HostsFileEntriesProvider.parser().parse(file));
    }

    /**
     * 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 {
        return hostsFileEntries(HostsFileEntriesProvider.parser().parse(file, charsets));
    }

    /**
     * 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 {
        return hostsFileEntries(HostsFileEntriesProvider.parser().parse(reader));
    }

    /**
     * Can't be instantiated.
     */
    private HostsFileParser() {
    }

    @SuppressWarnings("unchecked")
    private static HostsFileEntries hostsFileEntries(HostsFileEntriesProvider provider) {
        return provider == HostsFileEntriesProvider.EMPTY ? HostsFileEntries.EMPTY :
                new HostsFileEntries((Map<String, Inet4Address>) toMapWithSingleValue(provider.ipv4Entries()),
                        (Map<String, Inet6Address>) toMapWithSingleValue(provider.ipv6Entries()));
    }

    private static Map<String, ?> toMapWithSingleValue(Map<String, List<InetAddress>> fromMapWithListValue) {
        Map<String, InetAddress> result = new HashMap<String, InetAddress>(fromMapWithListValue.size());