457 lines
19 KiB
Java
457 lines
19 KiB
Java
/* DataInput.java -- Interface for reading data from a stream
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Copyright (C) 1998, 1999, 2001, 2003, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.io;
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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* Status: Believed complete and correct. */
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/**
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* This interface is implemented by classes that can data from streams
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* into Java primitive types.
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Warren Levy (warrenl@cygnus.com)
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*/
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public interface DataInput
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{
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/**
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* This method reads a Java boolean value from an input stream. It does
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* so by reading a single byte of data. If that byte is zero, then the
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* value returned is <code>false</code>. If the byte is non-zero, then
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* the value returned is <code>true</code>.
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* <p>
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* This method can read a <code>boolean</code> written by an object
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* implementing the <code>writeBoolean()</code> method in the
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* <code>DataOutput</code> interface.
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*
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* @return The <code>boolean</code> value read
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*
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* @exception EOFException If end of file is reached before
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* reading the boolean
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeBoolean
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*/
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boolean readBoolean() throws EOFException, IOException;
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/**
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* This method reads a Java byte value from an input stream. The value
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* is in the range of -128 to 127.
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* <p>
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* This method can read a <code>byte</code> written by an object
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* implementing the
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* <code>writeByte()</code> method in the <code>DataOutput</code> interface.
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* <p>
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* @return The <code>byte</code> value read
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*
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* @exception EOFException If end of file is reached before reading the byte
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeByte
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*/
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byte readByte() throws EOFException, IOException;
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/**
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* This method reads 8 unsigned bits into a Java <code>int</code> value from
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* the stream. The value returned is in the range of 0 to 255.
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* <p>
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* This method can read an unsigned byte written by an object
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* implementing the
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* <code>writeByte()</code> method in the <code>DataOutput</code>
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* interface.
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*
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* @return The unsigned bytes value read as a Java <code>int</code>.
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*
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* @exception EOFException If end of file is reached before reading the value
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeByte
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*/
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int readUnsignedByte() throws EOFException, IOException;
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/**
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* This method reads a Java <code>char</code> value from an input stream.
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* It operates by reading two bytes from the stream and converting them to
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* a single 16-bit Java <code>char</code>. The two bytes are stored most
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* significant byte first (i.e., "big endian") regardless of the native
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* host byte ordering.
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* <p>
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* As an example, if <code>byte1</code> and <code>byte2</code> represent the
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* first and second byte read from the stream respectively, they will be
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* transformed to a <code>char</code> in the following manner:
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* <p>
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* <code>(char)((byte1 << 8) + byte2)</code>
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* <p>
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* This method can read a <code>char</code> written by an object implementing
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* the
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* <code>writeChar()</code> method in the <code>DataOutput</code> interface.
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*
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* @return The <code>char</code> value read
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*
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* @exception EOFException If end of file is reached before reading the char
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeChar
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*/
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char readChar() throws EOFException, IOException;
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/**
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* This method reads a signed 16-bit value into a Java in from the stream.
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* It operates by reading two bytes from the stream and converting them to
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* a single 16-bit Java <code>short</code>. The two bytes are stored most
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* significant byte first (i.e., "big endian") regardless of the native
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* host byte ordering.
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* <p>
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* As an example, if <code>byte1</code> and <code>byte2</code> represent the
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* first and second byte read from the stream respectively, they will be
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* transformed to a <code>short</code> in the following manner:
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* <p>
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* <code>(short)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))</code>
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* <p>
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* The value returned is in the range of -32768 to 32767.
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* <p>
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* This method can read a <code>short</code> written by an object
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* implementing
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* the <code>writeShort()</code> method in the <code>DataOutput</code>
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* interface.
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*
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* @return The <code>short</code> value read
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*
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* @exception EOFException If end of file is reached before reading the value
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeShort
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*/
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short readShort() throws EOFException, IOException;
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/**
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* This method reads 16 unsigned bits into a Java int value from the stream.
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* It operates by reading two bytes from the stream and converting them to
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* a single Java <code>int</code>. The two bytes are stored most
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* significant byte first (i.e., "big endian") regardless of the native
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* host byte ordering.
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* <p>
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* As an example, if <code>byte1</code> and <code>byte2</code> represent the
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* first and second byte read from the stream respectively, they will be
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* transformed to an <code>int</code> in the following manner:
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* <p>
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* <code>(int)(((byte1 0xFF) << 8) + (byte2 & 0xFF))</code>
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* <p>
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* The value returned is in the range of 0 to 65535.
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* <p>
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* This method can read an unsigned short written by an object implementing
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* the <code>writeShort()</code> method in the
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* <code>DataOutput</code>
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* interface.
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*
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* @return The unsigned short value read as a Java <code>int</code>.
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*
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* @exception EOFException If end of file is reached before reading
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* the value
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeShort
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*/
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int readUnsignedShort() throws EOFException, IOException;
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/**
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* This method reads a Java <code>int</code> value from an input stream
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* It operates by reading four bytes from the stream and converting them to
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* a single Java <code>int</code>. The bytes are stored most
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* significant byte first (i.e., "big endian") regardless of the native
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* host byte ordering.
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* <p>
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* As an example, if <code>byte1</code> through <code>byte4</code> represent
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* the first four bytes read from the stream, they will be
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* transformed to an <code>int</code> in the following manner:
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* <p>
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* <code>(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) +
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* ((byte3 & 0xFF)<< 8) + (byte4 & 0xFF)))</code>
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* <p>
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* The value returned is in the range of -2147483648 to 2147483647.
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* <p>
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* This method can read an <code>int</code> written by an object
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* implementing the <code>writeInt()</code> method in the
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* <code>DataOutput</code> interface.
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*
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* @return The <code>int</code> value read
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*
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* @exception EOFException If end of file is reached before reading the int
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeInt
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*/
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int readInt() throws EOFException, IOException;
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/**
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* This method reads a Java <code>long</code> value from an input stream
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* It operates by reading eight bytes from the stream and converting them to
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* a single Java <code>long</code>. The bytes are stored most
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* significant byte first (i.e., "big endian") regardless of the native
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* host byte ordering.
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* <p>
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* As an example, if <code>byte1</code> through <code>byte8</code> represent
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* the first eight bytes read from the stream, they will be
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* transformed to an <code>long</code> in the following manner:
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* <p>
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* <code>(long)(((byte1 & 0xFF) << 56) + ((byte2 & 0xFF) << 48) +
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* ((byte3 & 0xFF) << 40) + ((byte4 & 0xFF) << 32) +
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* ((byte5 & 0xFF) << 24) + ((byte6 & 0xFF) << 16) +
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* ((byte7 & 0xFF) << 8) + (byte8 & 0xFF)))
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* </code>
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* <p>
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* The value returned is in the range of -9223372036854775808 to
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* 9223372036854775807.
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* <p>
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* This method can read an <code>long</code> written by an object
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* implementing the <code>writeLong()</code> method in the
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* <code>DataOutput</code> interface.
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*
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* @return The <code>long</code> value read
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*
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* @exception EOFException If end of file is reached before reading the long
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeLong
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*/
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long readLong() throws EOFException, IOException;
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/**
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* This method reads a Java float value from an input stream. It operates
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* by first reading an <code>int</code> value from the stream by calling the
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* <code>readInt()</code> method in this interface, then converts that
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* <code>int</code> to a <code>float</code> using the
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* <code>intBitsToFloat</code> method in the class
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* <code>java.lang.Float</code>.
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* <p>
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* This method can read a <code>float</code> written by an object
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* implementing
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* the <code>writeFloat()</code> method in the <code>DataOutput</code>
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* interface.
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*
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* @return The <code>float</code> value read
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*
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* @exception EOFException If end of file is reached before reading the
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* float
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeFloat
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* @see java.lang.Float#intBitsToFloat
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*/
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float readFloat() throws EOFException, IOException;
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/**
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* This method reads a Java double value from an input stream. It operates
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* by first reading a <code>long</code> value from the stream by calling the
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* <code>readLong()</code> method in this interface, then converts that
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* <code>long</code> to a <code>double</code> using the
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* <code>longBitsToDouble</code> method in the class
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* <code>java.lang.Double</code>.
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* <p>
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* This method can read a <code>double</code> written by an object
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* implementing the <code>writeDouble()</code> method in the
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* <code>DataOutput</code> interface.
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*
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* @return The <code>double</code> value read
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*
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* @exception EOFException If end of file is reached before reading the
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* double
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeDouble
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* @see java.lang.Double#longBitsToDouble
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*/
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double readDouble() throws EOFException, IOException;
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/**
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* This method reads the next line of text data from an input stream.
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* It operates by reading bytes and converting those bytes to
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* <code>char</code>
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* values by treating the byte read as the low eight bits of the
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* <code>char</code> and using 0 as the high eight bits. Because of this,
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* it does not support the full 16-bit Unicode character set.
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* <P>
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* The reading of bytes ends when either the end of file or a line terminator
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* is encountered. The bytes read are then returned as a
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* <code>String</code>.
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* A line terminator is a byte sequence consisting of either
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* <code>\r</code>, <code>\n</code> or <code>\r\n</code>. These termination
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* charaters are discarded and are not returned as part of the string.
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* A line is also terminated by an end of file condition.
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* <p>
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*
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* @return The line read as a <code>String</code>
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*
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* @exception IOException If an error occurs
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*/
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String readLine() throws IOException;
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/**
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* This method reads a <code>String</code> from an input stream that is
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* encoded in a modified UTF-8 format. This format has a leading two byte
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* sequence that contains the remaining number of bytes to read.
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* This two byte
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* sequence is read using the <code>readUnsignedShort()</code> method of this
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* interface.
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*
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* After the number of remaining bytes have been determined, these bytes
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* are read an transformed into <code>char</code> values. These
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* <code>char</code> values are encoded in the stream using either a one,
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* two, or three byte format.
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* The particular format in use can be determined by examining the first
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* byte read.
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* <p>
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* If the first byte has a high order bit of 0, then
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* that character consists on only one byte. This character value consists
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* of seven bits that are at positions 0 through 6 of the byte. As an
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* example, if <code>byte1</code> is the byte read from the stream, it would
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* be converted to a <code>char</code> like so:
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* <p>
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* <code>(char)byte1</code>
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* <p>
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* If the first byte has 110 as its high order bits, then the
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* character consists of two bytes. The bits that make up the character
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* value are in positions 0 through 4 of the first byte and bit positions
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* 0 through 5 of the second byte. (The second byte should have
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* 10 as its high order bits). These values are in most significant
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* byte first (i.e., "big endian") order.
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* <p>
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* As an example, if <code>byte1</code> and <code>byte2</code> are the first
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* two bytes read respectively, and the high order bits of them match the
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* patterns which indicate a two byte character encoding, then they would be
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* converted to a Java <code>char</code> like so:
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* <p>
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* <code>(char)(((byte1 & 0x1F) << 6) + (byte2 & 0x3F))</code>
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* <p>
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* If the first byte has a 1110 as its high order bits, then the
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* character consists of three bytes. The bits that make up the character
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* value are in positions 0 through 3 of the first byte and bit positions
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* 0 through 5 of the other two bytes. (The second and third bytes should
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* have 10 as their high order bits). These values are in most
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* significant byte first (i.e., "big endian") order.
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* <p>
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* As an example, if <code>byte1</code>, <code>byte2</code>, and
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* <code>byte3</code> are the three bytes read, and the high order bits of
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* them match the patterns which indicate a three byte character encoding,
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* then they would be converted to a Java <code>char</code> like so:
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*
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* <code>
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* (char)(((byte1 & 0x0F) << 12) + ((byte2 & 0x3F) + (byte3 & 0x3F))
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* </code>
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*
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* Note that all characters are encoded in the method that requires the
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* fewest number of bytes with the exception of the character with the
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* value of <code>\<llll>u0000</code> which is encoded as two bytes.
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* This is a modification of the UTF standard used to prevent C language
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* style <code>NUL</code> values from appearing in the byte stream.
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* <p>
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* This method can read data that was written by an object implementing the
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* <code>writeUTF()</code> method in <code>DataOutput</code>.
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*
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* @return The <code>String</code> read
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*
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* @exception EOFException If end of file is reached before reading the
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* String
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* @exception UTFDataFormatException If the data is not in UTF-8 format
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* @exception IOException If any other error occurs
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*
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* @see DataOutput#writeUTF
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*/
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String readUTF() throws EOFException, UTFDataFormatException, IOException;
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/**
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* This method reads raw bytes into the passed array until the array is
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* full. Note that this method blocks until the data is available and
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* throws an exception if there is not enough data left in the stream to
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* fill the buffer. Note also that zero length buffers are permitted.
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* In this case, the method will return immediately without reading any
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* bytes from the stream.
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*
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* @param buf The buffer into which to read the data
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*
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* @exception EOFException If end of file is reached before filling the
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* buffer
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* @exception IOException If any other error occurs
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*/
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void readFully(byte[] buf) throws EOFException, IOException;
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/**
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* This method reads raw bytes into the passed array <code>buf</code>
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* starting
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* <code>offset</code> bytes into the buffer. The number of bytes read
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* will be
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* exactly <code>len</code>. Note that this method blocks until the data is
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* available and throws an exception if there is not enough data left in
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* the stream to read <code>len</code> bytes. Note also that zero length
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* buffers are permitted. In this case, the method will return immediately
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* without reading any bytes from the stream.
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*
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* @param buf The buffer into which to read the data
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* @param offset The offset into the buffer to start storing data
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* @param len The number of bytes to read into the buffer
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*
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* @exception EOFException If end of file is reached before filling the
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* buffer
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* @exception IOException If any other error occurs
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*/
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void readFully(byte[] buf, int offset, int len)
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throws EOFException, IOException;
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/**
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* This method skips and discards the specified number of bytes in an
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* input stream. Note that this method may skip less than the requested
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* number of bytes. The actual number of bytes skipped is returned.
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* No bytes are skipped if a negative number is passed to this method.
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*
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* @param numBytes The number of bytes to skip
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*
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* @return The number of bytes actually skipped, which will always be
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* <code>numBytes</code>
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*
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* @exception EOFException If end of file is reached before all bytes can be
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* skipped
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* @exception IOException If any other error occurs
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*/
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int skipBytes(int numBytes) throws EOFException, IOException;
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} // interface DataInput
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