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package java.io;
A ByteArrayInputStream
contains
an internal buffer that contains bytes that
may be read from the stream. An internal
counter keeps track of the next byte to
be supplied by the read
method.
Closing a ByteArrayInputStream has no effect. The methods in
this class can be called after the stream has been closed without
generating an IOException.
Author: Arthur van Hoff See Also: Since: JDK1.0
/**
* A <code>ByteArrayInputStream</code> contains
* an internal buffer that contains bytes that
* may be read from the stream. An internal
* counter keeps track of the next byte to
* be supplied by the <code>read</code> method.
* <p>
* Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an <tt>IOException</tt>.
*
* @author Arthur van Hoff
* @see java.io.StringBufferInputStream
* @since JDK1.0
*/
public
class ByteArrayInputStream extends InputStream {
An array of bytes that was provided
by the creator of the stream. Elements buf[0]
through buf[count-1]
are the
only bytes that can ever be read from the
stream; element buf[pos]
is
the next byte to be read.
/**
* An array of bytes that was provided
* by the creator of the stream. Elements <code>buf[0]</code>
* through <code>buf[count-1]</code> are the
* only bytes that can ever be read from the
* stream; element <code>buf[pos]</code> is
* the next byte to be read.
*/
protected byte buf[];
The index of the next character to read from the input stream buffer.
This value should always be nonnegative
and not larger than the value of count
.
The next byte to be read from the input stream buffer
will be buf[pos]
.
/**
* The index of the next character to read from the input stream buffer.
* This value should always be nonnegative
* and not larger than the value of <code>count</code>.
* The next byte to be read from the input stream buffer
* will be <code>buf[pos]</code>.
*/
protected int pos;
The currently marked position in the stream.
ByteArrayInputStream objects are marked at position zero by
default when constructed. They may be marked at another
position within the buffer by the mark()
method.
The current buffer position is set to this point by the
reset()
method.
If no mark has been set, then the value of mark is the offset
passed to the constructor (or 0 if the offset was not supplied).
Since: JDK1.1
/**
* The currently marked position in the stream.
* ByteArrayInputStream objects are marked at position zero by
* default when constructed. They may be marked at another
* position within the buffer by the <code>mark()</code> method.
* The current buffer position is set to this point by the
* <code>reset()</code> method.
* <p>
* If no mark has been set, then the value of mark is the offset
* passed to the constructor (or 0 if the offset was not supplied).
*
* @since JDK1.1
*/
protected int mark = 0;
The index one greater than the last valid character in the input
stream buffer.
This value should always be nonnegative
and not larger than the length of buf
.
It is one greater than the position of
the last byte within buf
that
can ever be read from the input stream buffer.
/**
* The index one greater than the last valid character in the input
* stream buffer.
* This value should always be nonnegative
* and not larger than the length of <code>buf</code>.
* It is one greater than the position of
* the last byte within <code>buf</code> that
* can ever be read from the input stream buffer.
*/
protected int count;
Creates a ByteArrayInputStream
so that it uses buf
as its
buffer array.
The buffer array is not copied.
The initial value of pos
is 0
and the initial value
of count
is the length of
buf
.
Params: - buf – the input buffer.
/**
* Creates a <code>ByteArrayInputStream</code>
* so that it uses <code>buf</code> as its
* buffer array.
* The buffer array is not copied.
* The initial value of <code>pos</code>
* is <code>0</code> and the initial value
* of <code>count</code> is the length of
* <code>buf</code>.
*
* @param buf the input buffer.
*/
public ByteArrayInputStream(byte buf[]) {
this.buf = buf;
this.pos = 0;
this.count = buf.length;
}
Creates ByteArrayInputStream
that uses buf
as its
buffer array. The initial value of pos
is offset
and the initial value
of count
is the minimum of offset+length
and buf.length
.
The buffer array is not copied. The buffer's mark is
set to the specified offset.
Params: - buf – the input buffer.
- offset – the offset in the buffer of the first byte to read.
- length – the maximum number of bytes to read from the buffer.
/**
* Creates <code>ByteArrayInputStream</code>
* that uses <code>buf</code> as its
* buffer array. The initial value of <code>pos</code>
* is <code>offset</code> and the initial value
* of <code>count</code> is the minimum of <code>offset+length</code>
* and <code>buf.length</code>.
* The buffer array is not copied. The buffer's mark is
* set to the specified offset.
*
* @param buf the input buffer.
* @param offset the offset in the buffer of the first byte to read.
* @param length the maximum number of bytes to read from the buffer.
*/
public ByteArrayInputStream(byte buf[], int offset, int length) {
this.buf = buf;
this.pos = offset;
this.count = Math.min(offset + length, buf.length);
this.mark = offset;
}
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 read
method
cannot block.
Returns: the next byte of data, or -1
if the end of the
stream has been reached.
/**
* Reads the next byte of data from this input stream. The value
* byte is returned as an <code>int</code> in the range
* <code>0</code> to <code>255</code>. If no byte is available
* because the end of the stream has been reached, the value
* <code>-1</code> is returned.
* <p>
* This <code>read</code> method
* cannot block.
*
* @return the next byte of data, or <code>-1</code> if the end of the
* stream has been reached.
*/
public synchronized int read() {
return (pos < count) ? (buf[pos++] & 0xff) : -1;
}
Reads up to len
bytes of data into an array of bytes
from this input stream.
If pos
equals count
,
then -1
is returned to indicate
end of file. Otherwise, the number k
of bytes read is equal to the smaller of
len
and count-pos
.
If k
is positive, then bytes
buf[pos]
through buf[pos+k-1]
are copied into b[off]
through
b[off+k-1]
in the manner performed
by System.arraycopy
. The
value k
is added into pos
and k
is returned.
This read
method cannot block.
Params: - b – the buffer into which the data is read.
- off – the start offset in the destination array
b
- len – the maximum number of bytes read.
Throws: - NullPointerException – If
b
is null
. - IndexOutOfBoundsException – If
off
is negative,
len
is negative, or len
is greater than
b.length - off
Returns: 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.
/**
* Reads up to <code>len</code> bytes of data into an array of bytes
* from this input stream.
* If <code>pos</code> equals <code>count</code>,
* then <code>-1</code> is returned to indicate
* end of file. Otherwise, the number <code>k</code>
* of bytes read is equal to the smaller of
* <code>len</code> and <code>count-pos</code>.
* If <code>k</code> is positive, then bytes
* <code>buf[pos]</code> through <code>buf[pos+k-1]</code>
* are copied into <code>b[off]</code> through
* <code>b[off+k-1]</code> in the manner performed
* by <code>System.arraycopy</code>. The
* value <code>k</code> is added into <code>pos</code>
* and <code>k</code> is returned.
* <p>
* This <code>read</code> method cannot block.
*
* @param b the buffer into which the data is read.
* @param off the start offset in the destination array <code>b</code>
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of
* the stream has been reached.
* @exception NullPointerException If <code>b</code> is <code>null</code>.
* @exception IndexOutOfBoundsException If <code>off</code> is negative,
* <code>len</code> is negative, or <code>len</code> is greater than
* <code>b.length - off</code>
*/
public synchronized int read(byte b[], int off, int len) {
if (b == null) {
throw new NullPointerException();
} else if (off < 0 || len < 0 || len > b.length - off) {
throw new IndexOutOfBoundsException();
}
if (pos >= count) {
return -1;
}
int avail = count - pos;
if (len > avail) {
len = avail;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, b, off, len);
pos += len;
return len;
}
Skips n
bytes of input from this input stream. Fewer
bytes might be skipped if the end of the input stream is reached.
The actual number k
of bytes to be skipped is equal to the smaller
of n
and count-pos
.
The value k
is added into pos
and k
is returned.
Params: - n – the number of bytes to be skipped.
Returns: the actual number of bytes skipped.
/**
* Skips <code>n</code> bytes of input from this input stream. Fewer
* bytes might be skipped if the end of the input stream is reached.
* The actual number <code>k</code>
* of bytes to be skipped is equal to the smaller
* of <code>n</code> and <code>count-pos</code>.
* The value <code>k</code> is added into <code>pos</code>
* and <code>k</code> is returned.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
*/
public synchronized long skip(long n) {
long k = count - pos;
if (n < k) {
k = n < 0 ? 0 : n;
}
pos += k;
return k;
}
Returns the number of remaining bytes that can be read (or skipped over)
from this input stream.
The value returned is count - pos
,
which is the number of bytes remaining to be read from the input buffer.
Returns: the number of remaining bytes that can be read (or skipped
over) from this input stream without blocking.
/**
* Returns the number of remaining bytes that can be read (or skipped over)
* from this input stream.
* <p>
* The value returned is <code>count - pos</code>,
* which is the number of bytes remaining to be read from the input buffer.
*
* @return the number of remaining bytes that can be read (or skipped
* over) from this input stream without blocking.
*/
public synchronized int available() {
return count - pos;
}
Tests if this InputStream
supports mark/reset. The
markSupported
method of ByteArrayInputStream
always returns true
.
Since: JDK1.1
/**
* Tests if this <code>InputStream</code> supports mark/reset. The
* <code>markSupported</code> method of <code>ByteArrayInputStream</code>
* always returns <code>true</code>.
*
* @since JDK1.1
*/
public boolean markSupported() {
return true;
}
Set the current marked position in the stream.
ByteArrayInputStream objects are marked at position zero by
default when constructed. They may be marked at another
position within the buffer by this method.
If no mark has been set, then the value of the mark is the
offset passed to the constructor (or 0 if the offset was not
supplied).
Note: The readAheadLimit
for this class
has no meaning.
Since: JDK1.1
/**
* Set the current marked position in the stream.
* ByteArrayInputStream objects are marked at position zero by
* default when constructed. They may be marked at another
* position within the buffer by this method.
* <p>
* If no mark has been set, then the value of the mark is the
* offset passed to the constructor (or 0 if the offset was not
* supplied).
*
* <p> Note: The <code>readAheadLimit</code> for this class
* has no meaning.
*
* @since JDK1.1
*/
public void mark(int readAheadLimit) {
mark = pos;
}
Resets the buffer to the marked position. The marked position
is 0 unless another position was marked or an offset was specified
in the constructor.
/**
* Resets the buffer to the marked position. The marked position
* is 0 unless another position was marked or an offset was specified
* in the constructor.
*/
public synchronized void reset() {
pos = mark;
}
Closing a ByteArrayInputStream has no effect. The methods in
this class can be called after the stream has been closed without
generating an IOException.
/**
* Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in
* this class can be called after the stream has been closed without
* generating an <tt>IOException</tt>.
*/
public void close() throws IOException {
}
}