| /* |
| * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.io; |
| |
| /** |
| * The {@code DataInput} interface provides |
| * for reading bytes from a binary stream and |
| * reconstructing from them data in any of |
| * the Java primitive types. There is also |
| * a |
| * facility for reconstructing a {@code String} |
| * from data in |
| * <a href="#modified-utf-8">modified UTF-8</a> |
| * format. |
| * <p> |
| * It is generally true of all the reading |
| * routines in this interface that if end of |
| * file is reached before the desired number |
| * of bytes has been read, an {@code EOFException} |
| * (which is a kind of {@code IOException}) |
| * is thrown. If any byte cannot be read for |
| * any reason other than end of file, an {@code IOException} |
| * other than {@code EOFException} is |
| * thrown. In particular, an {@code IOException} |
| * may be thrown if the input stream has been |
| * closed. |
| * |
| * <h3><a name="modified-utf-8">Modified UTF-8</a></h3> |
| * <p> |
| * Implementations of the DataInput and DataOutput interfaces represent |
| * Unicode strings in a format that is a slight modification of UTF-8. |
| * (For information regarding the standard UTF-8 format, see section |
| * <i>3.9 Unicode Encoding Forms</i> of <i>The Unicode Standard, Version |
| * 4.0</i>). |
| * Note that in the following table, the most significant bit appears in the |
| * far left-hand column. |
| * |
| * <blockquote> |
| * <table border="1" cellspacing="0" cellpadding="8" |
| * summary="Bit values and bytes"> |
| * <tr> |
| * <th colspan="9"><span style="font-weight:normal"> |
| * All characters in the range {@code '\u005Cu0001'} to |
| * {@code '\u005Cu007F'} are represented by a single byte:</span></th> |
| * </tr> |
| * <tr> |
| * <td></td> |
| * <th colspan="8" id="bit_a">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1_a">Byte 1</th> |
| * <td><center>0</center> |
| * <td colspan="7"><center>bits 6-0</center> |
| * </tr> |
| * <tr> |
| * <th colspan="9"><span style="font-weight:normal"> |
| * The null character {@code '\u005Cu0000'} and characters |
| * in the range {@code '\u005Cu0080'} to {@code '\u005Cu07FF'} are |
| * represented by a pair of bytes:</span></th> |
| * </tr> |
| * <tr> |
| * <td></td> |
| * <th colspan="8" id="bit_b">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1_b">Byte 1</th> |
| * <td><center>1</center> |
| * <td><center>1</center> |
| * <td><center>0</center> |
| * <td colspan="5"><center>bits 10-6</center> |
| * </tr> |
| * <tr> |
| * <th id="byte2_a">Byte 2</th> |
| * <td><center>1</center> |
| * <td><center>0</center> |
| * <td colspan="6"><center>bits 5-0</center> |
| * </tr> |
| * <tr> |
| * <th colspan="9"><span style="font-weight:normal"> |
| * {@code char} values in the range {@code '\u005Cu0800'} |
| * to {@code '\u005CuFFFF'} are represented by three bytes:</span></th> |
| * </tr> |
| * <tr> |
| * <td></td> |
| * <th colspan="8"id="bit_c">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1_c">Byte 1</th> |
| * <td><center>1</center> |
| * <td><center>1</center> |
| * <td><center>1</center> |
| * <td><center>0</center> |
| * <td colspan="4"><center>bits 15-12</center> |
| * </tr> |
| * <tr> |
| * <th id="byte2_b">Byte 2</th> |
| * <td><center>1</center> |
| * <td><center>0</center> |
| * <td colspan="6"><center>bits 11-6</center> |
| * </tr> |
| * <tr> |
| * <th id="byte3">Byte 3</th> |
| * <td><center>1</center> |
| * <td><center>0</center> |
| * <td colspan="6"><center>bits 5-0</center> |
| * </tr> |
| * </table> |
| * </blockquote> |
| * <p> |
| * The differences between this format and the |
| * standard UTF-8 format are the following: |
| * <ul> |
| * <li>The null byte {@code '\u005Cu0000'} is encoded in 2-byte format |
| * rather than 1-byte, so that the encoded strings never have |
| * embedded nulls. |
| * <li>Only the 1-byte, 2-byte, and 3-byte formats are used. |
| * <li><a href="../lang/Character.html#unicode">Supplementary characters</a> |
| * are represented in the form of surrogate pairs. |
| * </ul> |
| * @author Frank Yellin |
| * @see java.io.DataInputStream |
| * @see java.io.DataOutput |
| * @since JDK1.0 |
| */ |
| public |
| interface DataInput { |
| /** |
| * Reads some bytes from an input |
| * stream and stores them into the buffer |
| * array {@code b}. The number of bytes |
| * read is equal |
| * to the length of {@code b}. |
| * <p> |
| * This method blocks until one of the |
| * following conditions occurs: |
| * <ul> |
| * <li>{@code b.length} |
| * bytes of input data are available, in which |
| * case a normal return is made. |
| * |
| * <li>End of |
| * file is detected, in which case an {@code EOFException} |
| * is thrown. |
| * |
| * <li>An I/O error occurs, in |
| * which case an {@code IOException} other |
| * than {@code EOFException} is thrown. |
| * </ul> |
| * <p> |
| * If {@code b} is {@code null}, |
| * a {@code NullPointerException} is thrown. |
| * If {@code b.length} is zero, then |
| * no bytes are read. Otherwise, the first |
| * byte read is stored into element {@code b[0]}, |
| * the next one into {@code b[1]}, and |
| * so on. |
| * If an exception is thrown from |
| * this method, then it may be that some but |
| * not all bytes of {@code b} have been |
| * updated with data from the input stream. |
| * |
| * @param b the buffer into which the data is read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| void readFully(byte b[]) throws IOException; |
| |
| /** |
| * |
| * Reads {@code len} |
| * bytes from |
| * an input stream. |
| * <p> |
| * This method |
| * blocks until one of the following conditions |
| * occurs: |
| * <ul> |
| * <li>{@code len} bytes |
| * of input data are available, in which case |
| * a normal return is made. |
| * |
| * <li>End of file |
| * is detected, in which case an {@code EOFException} |
| * is thrown. |
| * |
| * <li>An I/O error occurs, in |
| * which case an {@code IOException} other |
| * than {@code EOFException} is thrown. |
| * </ul> |
| * <p> |
| * If {@code b} is {@code null}, |
| * a {@code NullPointerException} is thrown. |
| * If {@code off} is negative, or {@code len} |
| * is negative, or {@code off+len} is |
| * greater than the length of the array {@code b}, |
| * then an {@code IndexOutOfBoundsException} |
| * is thrown. |
| * If {@code len} is zero, |
| * then no bytes are read. Otherwise, the first |
| * byte read is stored into element {@code b[off]}, |
| * the next one into {@code b[off+1]}, |
| * and so on. The number of bytes read is, |
| * at most, equal to {@code len}. |
| * |
| * @param b the buffer into which the data is read. |
| * @param off an int specifying the offset into the data. |
| * @param len an int specifying the number of bytes to read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| void readFully(byte b[], int off, int len) throws IOException; |
| |
| /** |
| * Makes an attempt to skip over |
| * {@code n} bytes |
| * of data from the input |
| * stream, discarding the skipped bytes. However, |
| * it may skip |
| * over some smaller number of |
| * bytes, possibly zero. This may result from |
| * any of a |
| * number of conditions; reaching |
| * end of file before {@code n} bytes |
| * have been skipped is |
| * only one possibility. |
| * This method never throws an {@code EOFException}. |
| * The actual |
| * number of bytes skipped is returned. |
| * |
| * @param n the number of bytes to be skipped. |
| * @return the number of bytes actually skipped. |
| * @exception IOException if an I/O error occurs. |
| */ |
| int skipBytes(int n) throws IOException; |
| |
| /** |
| * Reads one input byte and returns |
| * {@code true} if that byte is nonzero, |
| * {@code false} if that byte is zero. |
| * This method is suitable for reading |
| * the byte written by the {@code writeBoolean} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the {@code boolean} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| boolean readBoolean() throws IOException; |
| |
| /** |
| * Reads and returns one input byte. |
| * The byte is treated as a signed value in |
| * the range {@code -128} through {@code 127}, |
| * inclusive. |
| * This method is suitable for |
| * reading the byte written by the {@code writeByte} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the 8-bit value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| byte readByte() throws IOException; |
| |
| /** |
| * Reads one input byte, zero-extends |
| * it to type {@code int}, and returns |
| * the result, which is therefore in the range |
| * {@code 0} |
| * through {@code 255}. |
| * This method is suitable for reading |
| * the byte written by the {@code writeByte} |
| * method of interface {@code DataOutput} |
| * if the argument to {@code writeByte} |
| * was intended to be a value in the range |
| * {@code 0} through {@code 255}. |
| * |
| * @return the unsigned 8-bit value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| int readUnsignedByte() throws IOException; |
| |
| /** |
| * Reads two input bytes and returns |
| * a {@code short} value. Let {@code a} |
| * be the first byte read and {@code b} |
| * be the second byte. The value |
| * returned |
| * is: |
| * <pre>{@code (short)((a << 8) | (b & 0xff)) |
| * }</pre> |
| * This method |
| * is suitable for reading the bytes written |
| * by the {@code writeShort} method of |
| * interface {@code DataOutput}. |
| * |
| * @return the 16-bit value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| short readShort() throws IOException; |
| |
| /** |
| * Reads two input bytes and returns |
| * an {@code int} value in the range {@code 0} |
| * through {@code 65535}. Let {@code a} |
| * be the first byte read and |
| * {@code b} |
| * be the second byte. The value returned is: |
| * <pre>{@code (((a & 0xff) << 8) | (b & 0xff)) |
| * }</pre> |
| * This method is suitable for reading the bytes |
| * written by the {@code writeShort} method |
| * of interface {@code DataOutput} if |
| * the argument to {@code writeShort} |
| * was intended to be a value in the range |
| * {@code 0} through {@code 65535}. |
| * |
| * @return the unsigned 16-bit value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| int readUnsignedShort() throws IOException; |
| |
| /** |
| * Reads two input bytes and returns a {@code char} value. |
| * Let {@code a} |
| * be the first byte read and {@code b} |
| * be the second byte. The value |
| * returned is: |
| * <pre>{@code (char)((a << 8) | (b & 0xff)) |
| * }</pre> |
| * This method |
| * is suitable for reading bytes written by |
| * the {@code writeChar} method of interface |
| * {@code DataOutput}. |
| * |
| * @return the {@code char} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| char readChar() throws IOException; |
| |
| /** |
| * Reads four input bytes and returns an |
| * {@code int} value. Let {@code a-d} |
| * be the first through fourth bytes read. The value returned is: |
| * <pre>{@code |
| * (((a & 0xff) << 24) | ((b & 0xff) << 16) | |
| * ((c & 0xff) << 8) | (d & 0xff)) |
| * }</pre> |
| * This method is suitable |
| * for reading bytes written by the {@code writeInt} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the {@code int} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| int readInt() throws IOException; |
| |
| /** |
| * Reads eight input bytes and returns |
| * a {@code long} value. Let {@code a-h} |
| * be the first through eighth bytes read. |
| * The value returned is: |
| * <pre>{@code |
| * (((long)(a & 0xff) << 56) | |
| * ((long)(b & 0xff) << 48) | |
| * ((long)(c & 0xff) << 40) | |
| * ((long)(d & 0xff) << 32) | |
| * ((long)(e & 0xff) << 24) | |
| * ((long)(f & 0xff) << 16) | |
| * ((long)(g & 0xff) << 8) | |
| * ((long)(h & 0xff))) |
| * }</pre> |
| * <p> |
| * This method is suitable |
| * for reading bytes written by the {@code writeLong} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the {@code long} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| long readLong() throws IOException; |
| |
| /** |
| * Reads four input bytes and returns |
| * a {@code float} value. It does this |
| * by first constructing an {@code int} |
| * value in exactly the manner |
| * of the {@code readInt} |
| * method, then converting this {@code int} |
| * value to a {@code float} in |
| * exactly the manner of the method {@code Float.intBitsToFloat}. |
| * This method is suitable for reading |
| * bytes written by the {@code writeFloat} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the {@code float} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| float readFloat() throws IOException; |
| |
| /** |
| * Reads eight input bytes and returns |
| * a {@code double} value. It does this |
| * by first constructing a {@code long} |
| * value in exactly the manner |
| * of the {@code readLong} |
| * method, then converting this {@code long} |
| * value to a {@code double} in exactly |
| * the manner of the method {@code Double.longBitsToDouble}. |
| * This method is suitable for reading |
| * bytes written by the {@code writeDouble} |
| * method of interface {@code DataOutput}. |
| * |
| * @return the {@code double} value read. |
| * @exception EOFException if this stream reaches the end before reading |
| * all the bytes. |
| * @exception IOException if an I/O error occurs. |
| */ |
| double readDouble() throws IOException; |
| |
| /** |
| * Reads the next line of text from the input stream. |
| * It reads successive bytes, converting |
| * each byte separately into a character, |
| * until it encounters a line terminator or |
| * end of |
| * file; the characters read are then |
| * returned as a {@code String}. Note |
| * that because this |
| * method processes bytes, |
| * it does not support input of the full Unicode |
| * character set. |
| * <p> |
| * If end of file is encountered |
| * before even one byte can be read, then {@code null} |
| * is returned. Otherwise, each byte that is |
| * read is converted to type {@code char} |
| * by zero-extension. If the character {@code '\n'} |
| * is encountered, it is discarded and reading |
| * ceases. If the character {@code '\r'} |
| * is encountered, it is discarded and, if |
| * the following byte converts  to the |
| * character {@code '\n'}, then that is |
| * discarded also; reading then ceases. If |
| * end of file is encountered before either |
| * of the characters {@code '\n'} and |
| * {@code '\r'} is encountered, reading |
| * ceases. Once reading has ceased, a {@code String} |
| * is returned that contains all the characters |
| * read and not discarded, taken in order. |
| * Note that every character in this string |
| * will have a value less than {@code \u005Cu0100}, |
| * that is, {@code (char)256}. |
| * |
| * @return the next line of text from the input stream, |
| * or {@code null} if the end of file is |
| * encountered before a byte can be read. |
| * @exception IOException if an I/O error occurs. |
| */ |
| String readLine() throws IOException; |
| |
| /** |
| * Reads in a string that has been encoded using a |
| * <a href="#modified-utf-8">modified UTF-8</a> |
| * format. |
| * The general contract of {@code readUTF} |
| * is that it reads a representation of a Unicode |
| * character string encoded in modified |
| * UTF-8 format; this string of characters |
| * is then returned as a {@code String}. |
| * <p> |
| * First, two bytes are read and used to |
| * construct an unsigned 16-bit integer in |
| * exactly the manner of the {@code readUnsignedShort} |
| * method . This integer value is called the |
| * <i>UTF length</i> and specifies the number |
| * of additional bytes to be read. These bytes |
| * are then converted to characters by considering |
| * them in groups. The length of each group |
| * is computed from the value of the first |
| * byte of the group. The byte following a |
| * group, if any, is the first byte of the |
| * next group. |
| * <p> |
| * If the first byte of a group |
| * matches the bit pattern {@code 0xxxxxxx} |
| * (where {@code x} means "may be {@code 0} |
| * or {@code 1}"), then the group consists |
| * of just that byte. The byte is zero-extended |
| * to form a character. |
| * <p> |
| * If the first byte |
| * of a group matches the bit pattern {@code 110xxxxx}, |
| * then the group consists of that byte {@code a} |
| * and a second byte {@code b}. If there |
| * is no byte {@code b} (because byte |
| * {@code a} was the last of the bytes |
| * to be read), or if byte {@code b} does |
| * not match the bit pattern {@code 10xxxxxx}, |
| * then a {@code UTFDataFormatException} |
| * is thrown. Otherwise, the group is converted |
| * to the character: |
| * <pre>{@code (char)(((a & 0x1F) << 6) | (b & 0x3F)) |
| * }</pre> |
| * If the first byte of a group |
| * matches the bit pattern {@code 1110xxxx}, |
| * then the group consists of that byte {@code a} |
| * and two more bytes {@code b} and {@code c}. |
| * If there is no byte {@code c} (because |
| * byte {@code a} was one of the last |
| * two of the bytes to be read), or either |
| * byte {@code b} or byte {@code c} |
| * does not match the bit pattern {@code 10xxxxxx}, |
| * then a {@code UTFDataFormatException} |
| * is thrown. Otherwise, the group is converted |
| * to the character: |
| * <pre>{@code |
| * (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F)) |
| * }</pre> |
| * If the first byte of a group matches the |
| * pattern {@code 1111xxxx} or the pattern |
| * {@code 10xxxxxx}, then a {@code UTFDataFormatException} |
| * is thrown. |
| * <p> |
| * If end of file is encountered |
| * at any time during this entire process, |
| * then an {@code EOFException} is thrown. |
| * <p> |
| * After every group has been converted to |
| * a character by this process, the characters |
| * are gathered, in the same order in which |
| * their corresponding groups were read from |
| * the input stream, to form a {@code String}, |
| * which is returned. |
| * <p> |
| * The {@code writeUTF} |
| * method of interface {@code DataOutput} |
| * may be used to write data that is suitable |
| * for reading by this method. |
| * @return a Unicode string. |
| * @exception EOFException if this stream reaches the end |
| * before reading all the bytes. |
| * @exception IOException if an I/O error occurs. |
| * @exception UTFDataFormatException if the bytes do not represent a |
| * valid modified UTF-8 encoding of a string. |
| */ |
| String readUTF() throws IOException; |
| } |
