| /* DataInput.java -- Interface for reading data from a stream |
| Copyright (C) 1998, 1999, 2001, 2003, 2005 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.io; |
| |
| /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 |
| * "The Java Language Specification", ISBN 0-201-63451-1 |
| * plus online API docs for JDK 1.2 beta from http://www.javasoft.com. |
| * Status: Believed complete and correct. */ |
| |
| /** |
| * This interface is implemented by classes that can data from streams |
| * into Java primitive types. |
| * |
| * @author Aaron M. Renn (arenn@urbanophile.com) |
| * @author Warren Levy (warrenl@cygnus.com) |
| */ |
| public interface DataInput |
| { |
| |
| /** |
| * This method reads a Java boolean value from an input stream. It does |
| * so by reading a single byte of data. If that byte is zero, then the |
| * value returned is <code>false</code>. If the byte is non-zero, then |
| * the value returned is <code>true</code>. |
| * <p> |
| * This method can read a <code>boolean</code> written by an object |
| * implementing the <code>writeBoolean()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The <code>boolean</code> value read |
| * |
| * @exception EOFException If end of file is reached before |
| * reading the boolean |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeBoolean |
| */ |
| boolean readBoolean() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java byte value from an input stream. The value |
| * is in the range of -128 to 127. |
| * <p> |
| * This method can read a <code>byte</code> written by an object |
| * implementing the |
| * <code>writeByte()</code> method in the <code>DataOutput</code> interface. |
| * <p> |
| * @return The <code>byte</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the byte |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeByte |
| */ |
| byte readByte() throws EOFException, IOException; |
| |
| /** |
| * This method reads 8 unsigned bits into a Java <code>int</code> value from |
| * the stream. The value returned is in the range of 0 to 255. |
| * <p> |
| * This method can read an unsigned byte written by an object |
| * implementing the |
| * <code>writeByte()</code> method in the <code>DataOutput</code> |
| * interface. |
| * |
| * @return The unsigned bytes value read as a Java <code>int</code>. |
| * |
| * @exception EOFException If end of file is reached before reading the value |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeByte |
| */ |
| int readUnsignedByte() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java <code>char</code> value from an input stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single 16-bit Java <code>char</code>. The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> represent the |
| * first and second byte read from the stream respectively, they will be |
| * transformed to a <code>char</code> in the following manner: |
| * <p> |
| * <code>(char)((byte1 << 8) + byte2)</code> |
| * <p> |
| * This method can read a <code>char</code> written by an object implementing |
| * the |
| * <code>writeChar()</code> method in the <code>DataOutput</code> interface. |
| * |
| * @return The <code>char</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the char |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeChar |
| */ |
| char readChar() throws EOFException, IOException; |
| |
| /** |
| * This method reads a signed 16-bit value into a Java in from the stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single 16-bit Java <code>short</code>. The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> represent the |
| * first and second byte read from the stream respectively, they will be |
| * transformed to a <code>short</code> in the following manner: |
| * <p> |
| * <code>(short)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))</code> |
| * <p> |
| * The value returned is in the range of -32768 to 32767. |
| * <p> |
| * This method can read a <code>short</code> written by an object |
| * implementing |
| * the <code>writeShort()</code> method in the <code>DataOutput</code> |
| * interface. |
| * |
| * @return The <code>short</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the value |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeShort |
| */ |
| short readShort() throws EOFException, IOException; |
| |
| /** |
| * This method reads 16 unsigned bits into a Java int value from the stream. |
| * It operates by reading two bytes from the stream and converting them to |
| * a single Java <code>int</code>. The two bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> represent the |
| * first and second byte read from the stream respectively, they will be |
| * transformed to an <code>int</code> in the following manner: |
| * <p> |
| * <code>(int)(((byte1 0xFF) << 8) + (byte2 & 0xFF))</code> |
| * <p> |
| * The value returned is in the range of 0 to 65535. |
| * <p> |
| * This method can read an unsigned short written by an object implementing |
| * the <code>writeShort()</code> method in the |
| * <code>DataOutput</code> |
| * interface. |
| * |
| * @return The unsigned short value read as a Java <code>int</code>. |
| * |
| * @exception EOFException If end of file is reached before reading |
| * the value |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeShort |
| */ |
| int readUnsignedShort() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java <code>int</code> value from an input stream |
| * It operates by reading four bytes from the stream and converting them to |
| * a single Java <code>int</code>. The bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> through <code>byte4</code> represent |
| * the first four bytes read from the stream, they will be |
| * transformed to an <code>int</code> in the following manner: |
| * <p> |
| * <code>(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) + |
| * ((byte3 & 0xFF)<< 8) + (byte4 & 0xFF)))</code> |
| * <p> |
| * The value returned is in the range of -2147483648 to 2147483647. |
| * <p> |
| * This method can read an <code>int</code> written by an object |
| * implementing the <code>writeInt()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The <code>int</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the int |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeInt |
| */ |
| int readInt() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java <code>long</code> value from an input stream |
| * It operates by reading eight bytes from the stream and converting them to |
| * a single Java <code>long</code>. The bytes are stored most |
| * significant byte first (i.e., "big endian") regardless of the native |
| * host byte ordering. |
| * <p> |
| * As an example, if <code>byte1</code> through <code>byte8</code> represent |
| * the first eight bytes read from the stream, they will be |
| * transformed to an <code>long</code> in the following manner: |
| * <p> |
| * <code>(long)(((byte1 & 0xFF) << 56) + ((byte2 & 0xFF) << 48) + |
| * ((byte3 & 0xFF) << 40) + ((byte4 & 0xFF) << 32) + |
| * ((byte5 & 0xFF) << 24) + ((byte6 & 0xFF) << 16) + |
| * ((byte7 & 0xFF) << 8) + (byte8 & 0xFF))) |
| * </code> |
| * <p> |
| * The value returned is in the range of -9223372036854775808 to |
| * 9223372036854775807. |
| * <p> |
| * This method can read an <code>long</code> written by an object |
| * implementing the <code>writeLong()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The <code>long</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the long |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeLong |
| */ |
| long readLong() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java float value from an input stream. It operates |
| * by first reading an <code>int</code> value from the stream by calling the |
| * <code>readInt()</code> method in this interface, then converts that |
| * <code>int</code> to a <code>float</code> using the |
| * <code>intBitsToFloat</code> method in the class |
| * <code>java.lang.Float</code>. |
| * <p> |
| * This method can read a <code>float</code> written by an object |
| * implementing |
| * the <code>writeFloat()</code> method in the <code>DataOutput</code> |
| * interface. |
| * |
| * @return The <code>float</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the |
| * float |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeFloat |
| * @see java.lang.Float#intBitsToFloat |
| */ |
| float readFloat() throws EOFException, IOException; |
| |
| /** |
| * This method reads a Java double value from an input stream. It operates |
| * by first reading a <code>long</code> value from the stream by calling the |
| * <code>readLong()</code> method in this interface, then converts that |
| * <code>long</code> to a <code>double</code> using the |
| * <code>longBitsToDouble</code> method in the class |
| * <code>java.lang.Double</code>. |
| * <p> |
| * This method can read a <code>double</code> written by an object |
| * implementing the <code>writeDouble()</code> method in the |
| * <code>DataOutput</code> interface. |
| * |
| * @return The <code>double</code> value read |
| * |
| * @exception EOFException If end of file is reached before reading the |
| * double |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeDouble |
| * @see java.lang.Double#longBitsToDouble |
| */ |
| double readDouble() throws EOFException, IOException; |
| |
| /** |
| * This method reads the next line of text data from an input stream. |
| * It operates by reading bytes and converting those bytes to |
| * <code>char</code> |
| * values by treating the byte read as the low eight bits of the |
| * <code>char</code> and using 0 as the high eight bits. Because of this, |
| * it does not support the full 16-bit Unicode character set. |
| * <P> |
| * The reading of bytes ends when either the end of file or a line terminator |
| * is encountered. The bytes read are then returned as a |
| * <code>String</code>. |
| * A line terminator is a byte sequence consisting of either |
| * <code>\r</code>, <code>\n</code> or <code>\r\n</code>. These termination |
| * charaters are discarded and are not returned as part of the string. |
| * A line is also terminated by an end of file condition. |
| * <p> |
| * |
| * @return The line read as a <code>String</code> |
| * |
| * @exception IOException If an error occurs |
| */ |
| String readLine() throws IOException; |
| |
| /** |
| * This method reads a <code>String</code> from an input stream that is |
| * encoded in a modified UTF-8 format. This format has a leading two byte |
| * sequence that contains the remaining number of bytes to read. |
| * This two byte |
| * sequence is read using the <code>readUnsignedShort()</code> method of this |
| * interface. |
| * |
| * After the number of remaining bytes have been determined, these bytes |
| * are read an transformed into <code>char</code> values. These |
| * <code>char</code> values are encoded in the stream using either a one, |
| * two, or three byte format. |
| * The particular format in use can be determined by examining the first |
| * byte read. |
| * <p> |
| * If the first byte has a high order bit of 0, then |
| * that character consists on only one byte. This character value consists |
| * of seven bits that are at positions 0 through 6 of the byte. As an |
| * example, if <code>byte1</code> is the byte read from the stream, it would |
| * be converted to a <code>char</code> like so: |
| * <p> |
| * <code>(char)byte1</code> |
| * <p> |
| * If the first byte has 110 as its high order bits, then the |
| * character consists of two bytes. The bits that make up the character |
| * value are in positions 0 through 4 of the first byte and bit positions |
| * 0 through 5 of the second byte. (The second byte should have |
| * 10 as its high order bits). These values are in most significant |
| * byte first (i.e., "big endian") order. |
| * <p> |
| * As an example, if <code>byte1</code> and <code>byte2</code> are the first |
| * two bytes read respectively, and the high order bits of them match the |
| * patterns which indicate a two byte character encoding, then they would be |
| * converted to a Java <code>char</code> like so: |
| * <p> |
| * <code>(char)(((byte1 & 0x1F) << 6) + (byte2 & 0x3F))</code> |
| * <p> |
| * If the first byte has a 1110 as its high order bits, then the |
| * character consists of three bytes. The bits that make up the character |
| * value are in positions 0 through 3 of the first byte and bit positions |
| * 0 through 5 of the other two bytes. (The second and third bytes should |
| * have 10 as their high order bits). These values are in most |
| * significant byte first (i.e., "big endian") order. |
| * <p> |
| * As an example, if <code>byte1</code>, <code>byte2</code>, and |
| * <code>byte3</code> are the three bytes read, and the high order bits of |
| * them match the patterns which indicate a three byte character encoding, |
| * then they would be converted to a Java <code>char</code> like so: |
| * |
| * <code> |
| * (char)(((byte1 & 0x0F) << 12) + ((byte2 & 0x3F) + (byte3 & 0x3F)) |
| * </code> |
| * |
| * Note that all characters are encoded in the method that requires the |
| * fewest number of bytes with the exception of the character with the |
| * value of <code>\<llll>u0000</code> which is encoded as two bytes. |
| * This is a modification of the UTF standard used to prevent C language |
| * style <code>NUL</code> values from appearing in the byte stream. |
| * <p> |
| * This method can read data that was written by an object implementing the |
| * <code>writeUTF()</code> method in <code>DataOutput</code>. |
| * |
| * @return The <code>String</code> read |
| * |
| * @exception EOFException If end of file is reached before reading the |
| * String |
| * @exception UTFDataFormatException If the data is not in UTF-8 format |
| * @exception IOException If any other error occurs |
| * |
| * @see DataOutput#writeUTF |
| */ |
| String readUTF() throws EOFException, UTFDataFormatException, IOException; |
| |
| /** |
| * This method reads raw bytes into the passed array until the array is |
| * full. Note that this method blocks until the data is available and |
| * throws an exception if there is not enough data left in the stream to |
| * fill the buffer. Note also that zero length buffers are permitted. |
| * In this case, the method will return immediately without reading any |
| * bytes from the stream. |
| * |
| * @param buf The buffer into which to read the data |
| * |
| * @exception EOFException If end of file is reached before filling the |
| * buffer |
| * @exception IOException If any other error occurs |
| */ |
| void readFully(byte[] buf) throws EOFException, IOException; |
| |
| /** |
| * This method reads raw bytes into the passed array <code>buf</code> |
| * starting |
| * <code>offset</code> bytes into the buffer. The number of bytes read |
| * will be |
| * exactly <code>len</code>. Note that this method blocks until the data is |
| * available and throws an exception if there is not enough data left in |
| * the stream to read <code>len</code> bytes. Note also that zero length |
| * buffers are permitted. In this case, the method will return immediately |
| * without reading any bytes from the stream. |
| * |
| * @param buf The buffer into which to read the data |
| * @param offset The offset into the buffer to start storing data |
| * @param len The number of bytes to read into the buffer |
| * |
| * @exception EOFException If end of file is reached before filling the |
| * buffer |
| * @exception IOException If any other error occurs |
| */ |
| void readFully(byte[] buf, int offset, int len) |
| throws EOFException, IOException; |
| |
| /** |
| * This method skips and discards the specified number of bytes in an |
| * input stream. Note that this method may skip less than the requested |
| * number of bytes. The actual number of bytes skipped is returned. |
| * No bytes are skipped if a negative number is passed to this method. |
| * |
| * @param numBytes The number of bytes to skip |
| * |
| * @return The number of bytes actually skipped, which will always be |
| * <code>numBytes</code> |
| * |
| * @exception EOFException If end of file is reached before all bytes can be |
| * skipped |
| * @exception IOException If any other error occurs |
| */ |
| int skipBytes(int numBytes) throws EOFException, IOException; |
| |
| } // interface DataInput |