Java InputStream Read by Charset getHeaderLen(FileInputStream in, Charset encoding)

Description

get Header Len

License

LGPL

Declaration

private static long getHeaderLen(FileInputStream in, Charset encoding) throws IOException

Method Source Code

//package com.java2s;
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1//  w w w  . j  a va 2 s . c om
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the FRIL Framework.
 *
 * The Initial Developers of the Original Code are
 * The Department of Math and Computer Science, Emory University and 
 * The Centers for Disease Control and Prevention.
 * Portions created by the Initial Developer are Copyright (C) 2008
 * the Initial Developer. All Rights Reserved.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

import java.io.FileInputStream;

import java.io.IOException;
import java.io.InputStream;

import java.nio.charset.Charset;

public class Main {
    private static long getHeaderLen(FileInputStream in, Charset encoding) throws IOException {
        byte[] expectedHeader = getHeader(encoding);
        byte[] magic = new byte[expectedHeader.length];
        int read = readGuaranteed(magic, in);
        if (read != expectedHeader.length) {
            return 0;
        }
        for (int i = 0; i < magic.length; i++) {
            if (magic[i] != expectedHeader[i]) {
                return 0;
            }
        }
        return magic.length;
    }

    private static byte[] getHeader(Charset encoding) {
        byte[] header = null;
        if (encoding.toString().equals("UTF-32LE")) {
            header = new byte[] { (byte) 0xFF, (byte) 0xFE, (byte) 0x00, (byte) 0x00 };
        } else if (encoding.toString().equals("UTF-32BE")) {
            header = new byte[] { (byte) 0x00, (byte) 0x00, (byte) 0xFE, (byte) 0xFF };
        } else if (encoding.toString().equals("UTF-16LE")) {
            header = new byte[] { (byte) 0xFF, (byte) 0xFE };
        } else if (encoding.toString().equals("UTF-16BE")) {
            header = new byte[] { (byte) 0xFE, (byte) 0xFF };
        } else if (encoding.toString().equals("UTF-8")) {
            header = new byte[] { (byte) 0xEF, (byte) 0xBB, (byte) 0xBF };
        } else {
            header = new byte[] {};
        }
        return header;
    }

    private static int readGuaranteed(byte[] magic, InputStream str) throws IOException {
        int read = 0;
        int tmp = 0;
        while ((tmp = str.read(magic, read, magic.length - read)) != -1) {
            read += tmp;
            if (read == magic.length) {
                break;
            }
        }
        return read;
    }
}

Java InputStream Read by Charset getHeaderLen(FileInputStream in, Charset encoding)

Description

License

Declaration

Method Source Code

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