| /* |
| * Copyright (c) 1995, 2006, 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</code> 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</code> |
| * 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</code> |
| * (which is a kind of <code>IOException</code>) |
| * is thrown. If any byte cannot be read for |
| * any reason other than end of file, an <code>IOException</code> |
| * other than <code>EOFException</code> is |
| * thrown. In particular, an <code>IOException</code> |
| * may be thrown if the input stream has been |
| * closed. |
| * |
| * <h4><a name="modified-utf-8">Modified UTF-8</a></h4> |
| * <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 tables, the most significant bit appears in the |
| * far left-hand column. |
| * <p> |
| * All characters in the range <code>'\u0001'</code> to |
| * <code>'\u007F'</code> are represented by a single byte: |
| * |
| * <blockquote> |
| * <table border="1" cellspacing="0" cellpadding="8" width="50%" |
| * summary="Bit values and bytes"> |
| * <tr> |
| * <td></td> |
| * <th id="bit">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1">Byte 1</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>0</center> |
| * <td colspan="7"><center>bits 6-0</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * </table> |
| * </blockquote> |
| * |
| * <p> |
| * The null character <code>'\u0000'</code> and characters in the |
| * range <code>'\u0080'</code> to <code>'\u07FF'</code> are |
| * represented by a pair of bytes: |
| * |
| * <blockquote> |
| * <table border="1" cellspacing="0" cellpadding="8" width="50%" |
| * summary="Bit values and bytes"> |
| * <tr> |
| * <td></td> |
| * <th id="bit">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1">Byte 1</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>1</center> |
| * <td width="12%"><center>0</center> |
| * <td colspan="5"><center>bits 10-6</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * <tr> |
| * <th id="byte2">Byte 2</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>0</center> |
| * <td colspan="6"><center>bits 5-0</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * </table> |
| * </blockquote> |
| * |
| * <br> |
| * <code>char</code> values in the range <code>'\u0800'</code> to |
| * <code>'\uFFFF'</code> are represented by three bytes: |
| * |
| * <blockquote> |
| * <table border="1" cellspacing="0" cellpadding="8" width="50%" |
| * summary="Bit values and bytes"> |
| * <tr> |
| * <td></td> |
| * <th id="bit">Bit Values</th> |
| * </tr> |
| * <tr> |
| * <th id="byte1">Byte 1</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>1</center> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>0</center> |
| * <td colspan="4"><center>bits 15-12</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * <tr> |
| * <th id="byte2">Byte 2</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>0</center> |
| * <td colspan="6"><center>bits 11-6</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * <tr> |
| * <th id="byte3">Byte 3</th> |
| * <td> |
| * <table border="1" cellspacing="0" width="100%"> |
| * <tr> |
| * <td width="12%"><center>1</center> |
| * <td width="13%"><center>0</center> |
| * <td colspan="6"><center>bits 5-0</center> |
| * </tr> |
| * </table> |
| * </td> |
| * </tr> |
| * </table> |
| * </blockquote> |
| * |
| * <p> |
| * The differences between this format and the |
| * standard UTF-8 format are the following: |
| * <ul> |
| * <li>The null byte <code>'\u0000'</code> 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</code>. The number of bytes |
| * read is equal |
| * to the length of <code>b</code>. |
| * <p> |
| * This method blocks until one of the |
| * following conditions occurs:<p> |
| * <ul> |
| * <li><code>b.length</code> |
| * 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</code> |
| * is thrown. |
| * |
| * <li>An I/O error occurs, in |
| * which case an <code>IOException</code> other |
| * than <code>EOFException</code> is thrown. |
| * </ul> |
| * <p> |
| * If <code>b</code> is <code>null</code>, |
| * a <code>NullPointerException</code> is thrown. |
| * If <code>b.length</code> is zero, then |
| * no bytes are read. Otherwise, the first |
| * byte read is stored into element <code>b[0]</code>, |
| * the next one into <code>b[1]</code>, and |
| * so on. |
| * If an exception is thrown from |
| * this method, then it may be that some but |
| * not all bytes of <code>b</code> 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</code> |
| * bytes from |
| * an input stream. |
| * <p> |
| * This method |
| * blocks until one of the following conditions |
| * occurs:<p> |
| * <ul> |
| * <li><code>len</code> 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</code> |
| * is thrown. |
| * |
| * <li>An I/O error occurs, in |
| * which case an <code>IOException</code> other |
| * than <code>EOFException</code> is thrown. |
| * </ul> |
| * <p> |
| * If <code>b</code> is <code>null</code>, |
| * a <code>NullPointerException</code> is thrown. |
| * If <code>off</code> is negative, or <code>len</code> |
| * is negative, or <code>off+len</code> is |
| * greater than the length of the array <code>b</code>, |
| * then an <code>IndexOutOfBoundsException</code> |
| * is thrown. |
| * If <code>len</code> is zero, |
| * then no bytes are read. Otherwise, the first |
| * byte read is stored into element <code>b[off]</code>, |
| * the next one into <code>b[off+1]</code>, |
| * and so on. The number of bytes read is, |
| * at most, equal to <code>len</code>. |
| * |
| * @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</code> 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</code> bytes |
| * have been skipped is |
| * only one possibility. |
| * This method never throws an <code>EOFException</code>. |
| * 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</code> if that byte is nonzero, |
| * <code>false</code> if that byte is zero. |
| * This method is suitable for reading |
| * the byte written by the <code>writeBoolean</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @return the <code>boolean</code> 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</code> through <code>127</code>, |
| * inclusive. |
| * This method is suitable for |
| * reading the byte written by the <code>writeByte</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @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</code>, and returns |
| * the result, which is therefore in the range |
| * <code>0</code> |
| * through <code>255</code>. |
| * This method is suitable for reading |
| * the byte written by the <code>writeByte</code> |
| * method of interface <code>DataOutput</code> |
| * if the argument to <code>writeByte</code> |
| * was intended to be a value in the range |
| * <code>0</code> through <code>255</code>. |
| * |
| * @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</code> value. Let <code>a</code> |
| * be the first byte read and <code>b</code> |
| * be the second byte. The value |
| * returned |
| * is: |
| * <p><pre><code>(short)((a << 8) | (b & 0xff)) |
| * </code></pre> |
| * This method |
| * is suitable for reading the bytes written |
| * by the <code>writeShort</code> method of |
| * interface <code>DataOutput</code>. |
| * |
| * @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</code> value in the range <code>0</code> |
| * through <code>65535</code>. Let <code>a</code> |
| * be the first byte read and |
| * <code>b</code> |
| * be the second byte. The value returned is: |
| * <p><pre><code>(((a & 0xff) << 8) | (b & 0xff)) |
| * </code></pre> |
| * This method is suitable for reading the bytes |
| * written by the <code>writeShort</code> method |
| * of interface <code>DataOutput</code> if |
| * the argument to <code>writeShort</code> |
| * was intended to be a value in the range |
| * <code>0</code> through <code>65535</code>. |
| * |
| * @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</code> value. |
| * Let <code>a</code> |
| * be the first byte read and <code>b</code> |
| * be the second byte. The value |
| * returned is: |
| * <p><pre><code>(char)((a << 8) | (b & 0xff)) |
| * </code></pre> |
| * This method |
| * is suitable for reading bytes written by |
| * the <code>writeChar</code> method of interface |
| * <code>DataOutput</code>. |
| * |
| * @return the <code>char</code> 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</code> value. Let <code>a-d</code> |
| * be the first through fourth bytes read. The value returned is: |
| * <p><pre> |
| * <code> |
| * (((a & 0xff) << 24) | ((b & 0xff) << 16) | |
| *  ((c & 0xff) << 8) | (d & 0xff)) |
| * </code></pre> |
| * This method is suitable |
| * for reading bytes written by the <code>writeInt</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @return the <code>int</code> 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</code> value. Let <code>a-h</code> |
| * be the first through eighth bytes read. |
| * The value returned is: |
| * <p><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))) |
| * </code></pre> |
| * <p> |
| * This method is suitable |
| * for reading bytes written by the <code>writeLong</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @return the <code>long</code> 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</code> value. It does this |
| * by first constructing an <code>int</code> |
| * value in exactly the manner |
| * of the <code>readInt</code> |
| * method, then converting this <code>int</code> |
| * value to a <code>float</code> in |
| * exactly the manner of the method <code>Float.intBitsToFloat</code>. |
| * This method is suitable for reading |
| * bytes written by the <code>writeFloat</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @return the <code>float</code> 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</code> value. It does this |
| * by first constructing a <code>long</code> |
| * value in exactly the manner |
| * of the <code>readlong</code> |
| * method, then converting this <code>long</code> |
| * value to a <code>double</code> in exactly |
| * the manner of the method <code>Double.longBitsToDouble</code>. |
| * This method is suitable for reading |
| * bytes written by the <code>writeDouble</code> |
| * method of interface <code>DataOutput</code>. |
| * |
| * @return the <code>double</code> 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</code>. 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</code> |
| * is returned. Otherwise, each byte that is |
| * read is converted to type <code>char</code> |
| * by zero-extension. If the character <code>'\n'</code> |
| * is encountered, it is discarded and reading |
| * ceases. If the character <code>'\r'</code> |
| * is encountered, it is discarded and, if |
| * the following byte converts  to the |
| * character <code>'\n'</code>, then that is |
| * discarded also; reading then ceases. If |
| * end of file is encountered before either |
| * of the characters <code>'\n'</code> and |
| * <code>'\r'</code> is encountered, reading |
| * ceases. Once reading has ceased, a <code>String</code> |
| * 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>\u0100</code>, |
| * that is, <code>(char)256</code>. |
| * |
| * @return the next line of text from the input stream, |
| * or <CODE>null</CODE> 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</code> |
| * 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</code>. |
| * <p> |
| * First, two bytes are read and used to |
| * construct an unsigned 16-bit integer in |
| * exactly the manner of the <code>readUnsignedShort</code> |
| * 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</code> |
| * (where <code>x</code> means "may be <code>0</code> |
| * or <code>1</code>"), 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</code>, |
| * then the group consists of that byte <code>a</code> |
| * and a second byte <code>b</code>. If there |
| * is no byte <code>b</code> (because byte |
| * <code>a</code> was the last of the bytes |
| * to be read), or if byte <code>b</code> does |
| * not match the bit pattern <code>10xxxxxx</code>, |
| * then a <code>UTFDataFormatException</code> |
| * is thrown. Otherwise, the group is converted |
| * to the character:<p> |
| * <pre><code>(char)(((a& 0x1F) << 6) | (b & 0x3F)) |
| * </code></pre> |
| * If the first byte of a group |
| * matches the bit pattern <code>1110xxxx</code>, |
| * then the group consists of that byte <code>a</code> |
| * and two more bytes <code>b</code> and <code>c</code>. |
| * If there is no byte <code>c</code> (because |
| * byte <code>a</code> was one of the last |
| * two of the bytes to be read), or either |
| * byte <code>b</code> or byte <code>c</code> |
| * does not match the bit pattern <code>10xxxxxx</code>, |
| * then a <code>UTFDataFormatException</code> |
| * is thrown. Otherwise, the group is converted |
| * to the character:<p> |
| * <pre><code> |
| * (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F)) |
| * </code></pre> |
| * If the first byte of a group matches the |
| * pattern <code>1111xxxx</code> or the pattern |
| * <code>10xxxxxx</code>, then a <code>UTFDataFormatException</code> |
| * is thrown. |
| * <p> |
| * If end of file is encountered |
| * at any time during this entire process, |
| * then an <code>EOFException</code> 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</code>, |
| * which is returned. |
| * <p> |
| * The <code>writeUTF</code> |
| * method of interface <code>DataOutput</code> |
| * 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; |
| } |
