| /* |
| ******************************************************************************* |
| * Copyright (C) 1996-2004, International Business Machines Corporation and * |
| * others. All Rights Reserved. * |
| ******************************************************************************* |
| */ |
| package com.ibm.icu.impl; |
| |
| import java.io.InputStream; |
| import java.io.DataInputStream; |
| import java.io.IOException; |
| import java.util.Arrays; |
| |
| public final class ICUBinary |
| { |
| // public inner interface ------------------------------------------------ |
| |
| /** |
| * Special interface for data authentication |
| */ |
| public static interface Authenticate |
| { |
| /** |
| * Method used in ICUBinary.readHeader() to provide data format |
| * authentication. |
| * @param version version of the current data |
| * @return true if dataformat is an acceptable version, false otherwise |
| */ |
| public boolean isDataVersionAcceptable(byte version[]); |
| } |
| |
| // public methods -------------------------------------------------------- |
| |
| /** |
| * <p>ICU data header reader method. |
| * Takes a ICU generated big-endian input stream, parse the ICU standard |
| * file header and authenticates them.</p> |
| * <p>Header format: |
| * <ul> |
| * <li> Header size (char) |
| * <li> Magic number 1 (byte) |
| * <li> Magic number 2 (byte) |
| * <li> Rest of the header size (char) |
| * <li> Reserved word (char) |
| * <li> Big endian indicator (byte) |
| * <li> Character set family indicator (byte) |
| * <li> Size of a char (byte) for c++ and c use |
| * <li> Reserved byte (byte) |
| * <li> Data format identifier (4 bytes), each ICU data has its own |
| * identifier to distinguish them. [0] major [1] minor |
| * [2] milli [3] micro |
| * <li> Data version (4 bytes), the change version of the ICU data |
| * [0] major [1] minor [2] milli [3] micro |
| * <li> Unicode version (4 bytes) this ICU is based on. |
| * </ul> |
| * </p> |
| * <p> |
| * Example of use:<br> |
| * <pre> |
| * try { |
| * FileInputStream input = new FileInputStream(filename); |
| * If (Utility.readICUDataHeader(input, dataformat, dataversion, |
| * unicode) { |
| * System.out.println("Verified file header, this is a ICU data file"); |
| * } |
| * } catch (IOException e) { |
| * System.out.println("This is not a ICU data file"); |
| * } |
| * </pre> |
| * </p> |
| * @param inputStream input stream that contains the ICU data header |
| * @param dataFormatIDExpected Data format expected. An array of 4 bytes |
| * information about the data format. |
| * E.g. data format ID 1.2.3.4. will became an array of |
| * {1, 2, 3, 4} |
| * @param authenticate user defined extra data authentication. This value |
| * can be null, if no extra authentication is needed. |
| * @exception IOException thrown if there is a read error or |
| * when header authentication fails. |
| * @draft 2.1 |
| */ |
| public static final byte[] readHeader(InputStream inputStream, |
| byte dataFormatIDExpected[], |
| Authenticate authenticate) |
| throws IOException |
| { |
| DataInputStream input = new DataInputStream(inputStream); |
| char headersize = input.readChar(); |
| int readcount = 2; |
| //reading the header format |
| byte magic1 = input.readByte(); |
| readcount ++; |
| byte magic2 = input.readByte(); |
| readcount ++; |
| if (magic1 != MAGIC1 || magic2 != MAGIC2) { |
| throw new IOException(MAGIC_NUMBER_AUTHENTICATION_FAILED_); |
| } |
| |
| input.readChar(); // reading size |
| readcount += 2; |
| input.readChar(); // reading reserved word |
| readcount += 2; |
| byte bigendian = input.readByte(); |
| readcount ++; |
| byte charset = input.readByte(); |
| readcount ++; |
| byte charsize = input.readByte(); |
| readcount ++; |
| input.readByte(); // reading reserved byte |
| readcount ++; |
| |
| byte dataFormatID[] = new byte[4]; |
| input.readFully(dataFormatID); |
| readcount += 4; |
| byte dataVersion[] = new byte[4]; |
| input.readFully(dataVersion); |
| readcount += 4; |
| byte unicodeVersion[] = new byte[4]; |
| input.readFully(unicodeVersion); |
| readcount += 4; |
| if (headersize < readcount) { |
| throw new IOException("Internal Error: Header size error"); |
| } |
| input.skipBytes(headersize - readcount); |
| |
| if (bigendian != BIG_ENDIAN_ || charset != CHAR_SET_ |
| || charsize != CHAR_SIZE_ |
| || !Arrays.equals(dataFormatIDExpected, dataFormatID) |
| || (authenticate != null |
| && !authenticate.isDataVersionAcceptable(dataVersion))) { |
| throw new IOException(HEADER_AUTHENTICATION_FAILED_); |
| } |
| return unicodeVersion; |
| } |
| |
| // private variables ------------------------------------------------- |
| |
| /** |
| * Magic numbers to authenticate the data file |
| */ |
| private static final byte MAGIC1 = (byte)0xda; |
| private static final byte MAGIC2 = (byte)0x27; |
| |
| /** |
| * File format authentication values |
| */ |
| private static final byte BIG_ENDIAN_ = 1; |
| private static final byte CHAR_SET_ = 0; |
| private static final byte CHAR_SIZE_ = 2; |
| |
| /** |
| * Error messages |
| */ |
| private static final String MAGIC_NUMBER_AUTHENTICATION_FAILED_ = |
| "ICU data file error: Not an ICU data file"; |
| private static final String HEADER_AUTHENTICATION_FAILED_ = |
| "ICU data file error: Header authentication failed, please check if you have a valid ICU data file"; |
| } |