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/*

This is not an official specification document, and usage is restricted.

NOTICE


(c) 2005-2007 Sun Microsystems, Inc. All Rights Reserved.

Neither this file nor any files generated from it describe a complete specification, and they may only be used as described below. For example, no permission is given for you to incorporate this file, in whole or in part, in an implementation of a Java specification.

Sun Microsystems Inc. owns the copyright in this file and it is provided to you for informative, as opposed to normative, use. The file and any files generated from it may be used to generate other informative documentation, such as a unified set of documents of API signatures for a platform that includes technologies expressed as Java APIs. The file may also be used to produce "compilation stubs," which allow applications to be compiled and validated for such platforms.

Any work generated from this file, such as unified javadocs or compiled stub files, must be accompanied by this notice in its entirety.

This work corresponds to the API signatures of JSR 219: Foundation Profile 1.1. In the event of a discrepency between this work and the JSR 219 specification, which is available at http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence. */ package java.io; /** * The 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 String * from data in Java modified UTF-8 format. *

* 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 EOFException * (which is a kind of IOException) * is thrown. If any byte cannot be read for * any reason other than end of file, an IOException * other than EOFException is * thrown. In particular, an IOException * may be thrown if the input stream has been * closed. * * @author Frank Yellin * @version 1.16, 02/02/00 * @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 b. The number of bytes * read is equal * to the length of b. *

* This method blocks until one of the * following conditions occurs:

*

    *
  • b.length * bytes of input data are available, in which * case a normal return is made. * *
  • End of * file is detected, in which case an EOFException * is thrown. * *
  • An I/O error occurs, in * which case an IOException other * than EOFException is thrown. *
*

* If b is null, * a NullPointerException is thrown. * If b.length is zero, then * no bytes are read. Otherwise, the first * byte read is stored into element b[0], * the next one into b[1], and * so on. * If an exception is thrown from * this method, then it may be that some but * not all bytes of 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. */ public void readFully(byte[] b) throws IOException; /** * Reads len * bytes from * an input stream. *

* This method * blocks until one of the following conditions * occurs:

*

    *
  • len bytes * of input data are available, in which case * a normal return is made. * *
  • End of file * is detected, in which case an EOFException * is thrown. * *
  • An I/O error occurs, in * which case an IOException other * than EOFException is thrown. *
*

* If b is null, * a NullPointerException is thrown. * If off is negative, or len * is negative, or off+len is * greater than the length of the array b, * then an IndexOutOfBoundsException * is thrown. * If len is zero, * then no bytes are read. Otherwise, the first * byte read is stored into element b[off], * the next one into b[off+1], * and so on. The number of bytes read is, * at most, equal to 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. */ public void readFully(byte[] b, int off, int len) throws IOException; /** * Makes an attempt to skip over * 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 n bytes * have been skipped is * only one possibility. * This method never throws an 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. */ public int skipBytes(int n) throws IOException; /** * Reads one input byte and returns * true if that byte is nonzero, * false if that byte is zero. * This method is suitable for reading * the byte written by the writeBoolean * method of interface DataOutput. * * @return the boolean value read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public boolean readBoolean() throws IOException; /** * Reads and returns one input byte. * The byte is treated as a signed value in * the range -128 through 127, * inclusive. * This method is suitable for * reading the byte written by the writeByte * method of interface 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. */ public byte readByte() throws IOException; /** * Reads one input byte, zero-extends * it to type int, and returns * the result, which is therefore in the range * 0 * through 255. * This method is suitable for reading * the byte written by the writeByte * method of interface DataOutput * if the argument to writeByte * was intended to be a value in the range * 0 through 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. */ public int readUnsignedByte() throws IOException; /** * Reads two input bytes and returns * a short value. Let a * be the first byte read and b * be the second byte. The value * returned * is: *

(short)((a << 8) * | (b & 0xff))
     * 
* This method * is suitable for reading the bytes written * by the writeShort method of * interface 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. */ public short readShort() throws IOException; /** * Reads two input bytes and returns * an int value in the range 0 * through 65535. Let a * be the first byte read and * b * be the second byte. The value returned is: *

(((a & 0xff) << 8) | (b & 0xff))
     * 
* This method is suitable for reading the bytes * written by the writeShort method * of interface DataOutput if * the argument to writeShort * was intended to be a value in the range * 0 through 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. */ public int readUnsignedShort() throws IOException; /** * Reads an input char and returns the char value. * A Unicode char is made up of two bytes. * Let a * be the first byte read and b * be the second byte. The value * returned is: *

(char)((a << 8) | (b & 0xff))
     * 
* This method * is suitable for reading bytes written by * the writeChar method of interface * DataOutput. * * @return the Unicode char read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public char readChar() throws IOException; /** * Reads four input bytes and returns an * int value. Let a * be the first byte read, b be * the second byte, c be the third * byte, * and d be the fourth * byte. The value returned is: *

     * 
     * (((a & 0xff) << 24) | ((b & 0xff) << 16) |
     *  ((c & 0xff) << 8) | (d & 0xff))
     * 
* This method is suitable * for reading bytes written by the writeInt * method of interface DataOutput. * * @return the int value read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public int readInt() throws IOException; /** * Reads eight input bytes and returns * a long value. Let a * be the first byte read, b be * the second byte, c be the third * byte, d * be the fourth byte, * e be the fifth byte, f * be the sixth byte, g be the * seventh byte, * and h be the * eighth byte. The value returned is: *

 
     * (((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)))
     * 
*

* This method is suitable * for reading bytes written by the writeLong * method of interface DataOutput. * * @return the long value read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public long readLong() throws IOException; /** * Reads four input bytes and returns * a float value. It does this * by first constructing an int * value in exactly the manner * of the readInt * method, then converting this int * value to a float in * exactly the manner of the method Float.intBitsToFloat. * This method is suitable for reading * bytes written by the writeFloat * method of interface DataOutput. * * @return the float value read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public float readFloat() throws IOException; /** * Reads eight input bytes and returns * a double value. It does this * by first constructing a long * value in exactly the manner * of the readlong * method, then converting this long * value to a double in exactly * the manner of the method Double.longBitsToDouble. * This method is suitable for reading * bytes written by the writeDouble * method of interface DataOutput. * * @return the double value read. * @exception EOFException if this stream reaches the end before reading * all the bytes. * @exception IOException if an I/O error occurs. */ public 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 String. Note * that because this * method processes bytes, * it does not support input of the full Unicode * character set. *

* If end of file is encountered * before even one byte can be read, then null * is returned. Otherwise, each byte that is * read is converted to type char * by zero-extension. If the character '\n' * is encountered, it is discarded and reading * ceases. If the character '\r' * is encountered, it is discarded and, if * the following byte converts to the * character '\n', then that is * discarded also; reading then ceases. If * end of file is encountered before either * of the characters '\n' and * '\r' is encountered, reading * ceases. Once reading has ceased, a 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 \u0100, * that is, (char)256. * * @return the next line of text from the input stream, * or null if the end of file is * encountered before a byte can be read. * @exception IOException if an I/O error occurs. */ public String readLine() throws IOException; /** * Reads in a string that has been encoded using a modified UTF-8 format. * The general contract of readUTF * is that it reads a representation of a Unicode * character string encoded in Java modified * UTF-8 format; this string of characters * is then returned as a String. *

* First, two bytes are read and used to * construct an unsigned 16-bit integer in * exactly the manner of the readUnsignedShort * method . This integer value is called the * UTF length 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. *

* If the first byte of a group * matches the bit pattern 0xxxxxxx * (where x means "may be 0 * or 1"), then the group consists * of just that byte. The byte is zero-extended * to form a character. *

* If the first byte * of a group matches the bit pattern 110xxxxx, * then the group consists of that byte a * and a second byte b. If there * is no byte b (because byte * a was the last of the bytes * to be read), or if byte b does * not match the bit pattern 10xxxxxx, * then a UTFDataFormatException * is thrown. Otherwise, the group is converted * to the character:

*

(char)(((a& 0x1F) << 6) | (b & 0x3F))
     * 
* If the first byte of a group * matches the bit pattern 1110xxxx, * then the group consists of that byte a * and two more bytes b and c. * If there is no byte c (because * byte a was one of the last * two of the bytes to be read), or either * byte b or byte c * does not match the bit pattern 10xxxxxx, * then a UTFDataFormatException * is thrown. Otherwise, the group is converted * to the character:

*


     * (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
     * 
* If the first byte of a group matches the * pattern 1111xxxx or the pattern * 10xxxxxx, then a UTFDataFormatException * is thrown. *

* If end of file is encountered * at any time during this entire process, * then an EOFException is thrown. *

* 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 String, * which is returned. *

* The writeUTF * method of interface 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 UTF-8 encoding of a string. */ public String readUTF() throws IOException; }





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