www.pudn.com > j2me_cldc-1_1-fcs-src-winunix.rar > DataInputStream.java
/*
* Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*/
package java.io;
/**
* A data input stream lets an application read primitive Java data
* types from an underlying input stream in a machine-independent
* way. An application uses a data output stream to write data that
* can later be read by a data input stream.
*
* @author unascribed
* @version 12/17/01 (CLDC 1.1)
* @see java.io.DataOutputStream
* @since JDK1.0, CLDC 1.0
*/
public
class DataInputStream extends InputStream implements DataInput {
/**
* The input stream.
*/
protected InputStream in;
/**
* Creates a DataInputStream
* and saves its argument, the input stream
* in, for later use.
*
* @param in the input stream.
*/
public DataInputStream(InputStream in) {
this.in = in;
}
/**
* Reads the next byte of data from this input stream. The value
* byte is returned as an int in the range
* 0 to 255. If no byte is available
* because the end of the stream has been reached, the value
* -1 is returned. This method blocks until input data
* is available, the end of the stream is detected, or an exception
* is thrown.
*
* This method
* simply performs in.read() and returns the result.
*
* @return the next byte of data, or -1 if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
*/
public int read() throws IOException {
return in.read();
}
/**
* See the general contract of the read
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @param b the buffer into which the data is read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end
* of the stream has been reached.
* @exception IOException if an I/O error occurs.
* @see java.io.InputStream#read(byte[], int, int)
*/
public final int read(byte b[]) throws IOException {
return in.read(b, 0, b.length);
}
/**
* Reads up to len bytes of data from this input stream
* into an array of bytes. This method blocks until some input is
* available.
*
* This method simply performs in.read(b, off, len)
* and returns the result.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* the stream has been reached.
* @exception IOException if an I/O error occurs.
*/
public final int read(byte b[], int off, int len) throws IOException {
return in.read(b, off, len);
}
/**
* See the general contract of the readFully
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @param b the buffer into which the data is read.
* @exception EOFException if this input stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte b[]) throws IOException {
readFully(b, 0, b.length);
}
/**
* See the general contract of the readFully
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @param b the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the number of bytes to read.
* @exception EOFException if this input stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
public final void readFully(byte b[], int off, int len) throws IOException {
if (len < 0) {
throw new IndexOutOfBoundsException();
}
int n = 0;
while (n < len) {
int count = read(b, off + n, len - n);
if (count < 0) {
throw new EOFException();
}
n += count;
}
}
/**
* See the general contract of the skipBytes
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public final int skipBytes(int n) throws IOException {
int total = 0;
int cur = 0;
while ((total 0)) {
total += cur;
}
return total;
}
/**
* See the general contract of the readBoolean
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the boolean value read.
* @exception EOFException if this input stream has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final boolean readBoolean() throws IOException {
int ch = read();
if (ch < 0) {
throw new EOFException();
}
return (ch != 0);
}
/**
* See the general contract of the readByte
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next byte of this input stream as a signed 8-bit
* byte.
* @exception EOFException if this input stream has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final byte readByte() throws IOException {
int ch = read();
if (ch < 0) {
throw new EOFException();
}
return (byte)(ch);
}
/**
* See the general contract of the readUnsignedByte
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next byte of this input stream, interpreted as an
* unsigned 8-bit number.
* @exception EOFException if this input stream has reached the end.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedByte() throws IOException {
int ch = read();
if (ch < 0) {
throw new EOFException();
}
return ch;
}
/**
* See the general contract of the readShort
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next two bytes of this input stream, interpreted as a
* signed 16-bit number.
* @exception EOFException if this input stream reaches the end before
* reading two bytes.
* @exception IOException if an I/O error occurs.
*/
public final short readShort() throws IOException {
return (short)readUnsignedShort();
}
/**
* See the general contract of the readUnsignedShort
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next two bytes of this input stream, interpreted as an
* unsigned 16-bit integer.
* @exception EOFException if this input stream reaches the end before
* reading two bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readUnsignedShort() throws IOException {
int ch1 = read();
int ch2 = read();
if ((ch1 | ch2) < 0) {
throw new EOFException();
}
return (ch1 << 8) + (ch2 << 0);
}
/**
* See the general contract of the readChar
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next two bytes of this input stream as a Unicode
* character.
* @exception EOFException if this input stream reaches the end before
* reading two bytes.
* @exception IOException if an I/O error occurs.
*/
public final char readChar() throws IOException {
return (char)readUnsignedShort();
}
/**
* See the general contract of the readInt
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next four bytes of this input stream, interpreted as an
* int.
* @exception EOFException if this input stream reaches the end before
* reading four bytes.
* @exception IOException if an I/O error occurs.
*/
public final int readInt() throws IOException {
int ch1 = read();
int ch2 = read();
int ch3 = read();
int ch4 = read();
if ((ch1 | ch2 | ch3 | ch4) < 0) {
throw new EOFException();
}
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}
/**
* See the general contract of the readLong
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next eight bytes of this input stream, interpreted as a
* long.
* @exception EOFException if this input stream reaches the end before
* reading eight bytes.
* @exception IOException if an I/O error occurs.
*/
public final long readLong() throws IOException {
return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
}
/**
* See the general contract of the readFloat
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next four bytes of this input stream, interpreted as a
* float.
* @exception EOFException if this input stream reaches the end before
* reading four bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.DataInputStream#readInt()
* @see java.lang.Float#intBitsToFloat(int)
* @since CLDC 1.1
*/
public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}
/**
* See the general contract of the readDouble
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return the next eight bytes of this input stream, interpreted as a
* double.
* @exception EOFException if this input stream reaches the end before
* reading eight bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.DataInputStream#readLong()
* @see java.lang.Double#longBitsToDouble(long)
* @since CLDC 1.1
*/
public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
/**
* See the general contract of the readUTF
* method of DataInput.
*
* Bytes for this operation are read from the contained
* input stream.
*
* @return a Unicode string.
* @exception EOFException if this input stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
* @see java.io.DataInputStream#readUTF(java.io.DataInput)
*/
public final String readUTF() throws IOException {
return readUTF(this);
}
/**
* Reads from the
* stream in a representation
* of a Unicode character string encoded in
* Java modified UTF-8 format; this string
* of characters is then returned as a String.
* The details of the modified UTF-8 representation
* are exactly the same as for the readUTF
* method of DataInput.
*
* @param in a data input stream.
* @return a Unicode string.
* @exception EOFException if the input stream reaches the end
* before 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 Unicode string.
* @see java.io.DataInputStream#readUnsignedShort()
*/
public final static String readUTF(DataInput in) throws IOException {
int utflen = in.readUnsignedShort();
char str[] = new char[utflen];
byte bytearr [] = new byte[utflen];
int c, char2, char3;
int count = 0;
int strlen = 0;
in.readFully(bytearr, 0, utflen);
while (count < utflen) {
c = (int) bytearr[count] & 0xff;
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
/* 0xxxxxxx*/
count++;
str[strlen++] = (char)c;
break;
case 12: case 13:
/* 110x xxxx 10xx xxxx*/
count += 2;
if (count > utflen)
throw new UTFDataFormatException();
char2 = (int) bytearr[count-1];
if ((char2 & 0xC0) != 0x80)
throw new UTFDataFormatException();
str[strlen++] = (char)(((c & 0x1F) << 6) | (char2 & 0x3F));
break;
case 14:
/* 1110 xxxx 10xx xxxx 10xx xxxx */
count += 3;
if (count > utflen)
throw new UTFDataFormatException();
char2 = (int) bytearr[count-2];
char3 = (int) bytearr[count-1];
if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
throw new UTFDataFormatException();
str[strlen++] = (char)(((c & 0x0F) << 12) |
((char2 & 0x3F) << 6) |
((char3 & 0x3F) << 0));
break;
default:
/* 10xx xxxx, 1111 xxxx */
throw new UTFDataFormatException();
}
}
// The number of chars produced may be less than utflen
return new String(str, 0, strlen);
}
/**
* Skips over and discards n bytes of data from the
* input stream. The skip method may, for a variety of
* reasons, end up skipping over some smaller number of bytes,
* possibly 0. The actual number of bytes skipped is
* returned.
*
* This method
* simply performs in.skip(n).
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public long skip(long n) throws IOException {
return in.skip(n);
}
/**
* Returns the number of bytes that can be read from this input
* stream without blocking.
*
* This method simply performs in.available() and
* returns the result.
*
* @return the number of bytes that can be read from the input stream
* without blocking.
* @exception IOException if an I/O error occurs.
*/
public int available() throws IOException {
return in.available();
}
/**
* Closes this input stream and releases any system resources
* associated with the stream.
* This
* method simply performs in.close().
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {
in.close();
}
/**
* Marks the current position in this input stream. A subsequent
* call to the reset method repositions this stream at
* the last marked position so that subsequent reads re-read the same bytes.
*
* The readlimit argument tells this input stream to
* allow that many bytes to be read before the mark position gets
* invalidated.
*
* This method simply performs in.mark(readlimit).
*
* @param readlimit the maximum limit of bytes that can be read before
* the mark position becomes invalid.
*/
public synchronized void mark(int readlimit) {
in.mark(readlimit);
}
/**
* Repositions this stream to the position at the time the
* mark method was last called on this input stream.
*
* This method
* simply performs in.reset().
*
* Stream marks are intended to be used in
* situations where you need to read ahead a little to see what's in
* the stream. Often this is most easily done by invoking some
* general parser. If the stream is of the type handled by the
* parse, it just chugs along happily. If the stream is not of
* that type, the parser should toss an exception when it fails.
* If this happens within readlimit bytes, it allows the outer
* code to reset the stream and try another parser.
*
* @exception IOException if the stream has not been marked or if the
* mark has been invalidated.
*/
public synchronized void reset() throws IOException {
in.reset();
}
/**
* Tests if this input stream supports the mark
* and reset methods.
* This method
* simply performs in.markSupported().
*
* @return true if this stream type supports the
* mark and reset method;
* false otherwise.
*/
public boolean markSupported() {
return in.markSupported();
}
}