/*
* Copyright (c) 1999, 2007, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package javax.imageio.stream;
import java.io.DataInput;
import java.io.IOException;
import java.nio.ByteOrder;
/**
* A seekable input stream interface for use by
* <code>ImageReader</code>s. Various input sources, such as
* <code>InputStream</code>s and <code>File</code>s,
* as well as future fast I/O sources may be "wrapped" by a suitable
* implementation of this interface for use by the Image I/O API.
*
* @see ImageInputStreamImpl
* @see FileImageInputStream
* @see FileCacheImageInputStream
* @see MemoryCacheImageInputStream
*
*/
public interface ImageInputStream extends DataInput {
/**
* Sets the desired byte order for future reads of data values
* from this stream. For example, the sequence of bytes '0x01
* 0x02 0x03 0x04' if read as a 4-byte integer would have the
* value '0x01020304' using network byte order and the value
* '0x04030201' under the reverse byte order.
*
* <p> The enumeration class <code>java.nio.ByteOrder</code> is
* used to specify the byte order. A value of
* <code>ByteOrder.BIG_ENDIAN</code> specifies so-called
* big-endian or network byte order, in which the high-order byte
* comes first. Motorola and Sparc processors store data in this
* format, while Intel processors store data in the reverse
* <code>ByteOrder.LITTLE_ENDIAN</code> order.
*
* <p> The byte order has no effect on the results returned from
* the <code>readBits</code> method (or the value written by
* <code>ImageOutputStream.writeBits</code>).
*
* @param byteOrder one of <code>ByteOrder.BIG_ENDIAN</code> or
* <code>java.nio.ByteOrder.LITTLE_ENDIAN</code>, indicating whether
* network byte order or its reverse will be used for future
* reads.
*
* @see java.nio.ByteOrder
* @see #getByteOrder
* @see #readBits(int)
*/
void setByteOrder(ByteOrder byteOrder);
/**
* Returns the byte order with which data values will be read from
* this stream as an instance of the
* <code>java.nio.ByteOrder</code> enumeration.
*
* @return one of <code>ByteOrder.BIG_ENDIAN</code> or
* <code>ByteOrder.LITTLE_ENDIAN</code>, indicating which byte
* order is being used.
*
* @see java.nio.ByteOrder
* @see #setByteOrder
*/
ByteOrder getByteOrder();
/**
* Reads a single byte from the stream and returns it as an
* integer between 0 and 255. If the end of the stream is
* reached, -1 is returned.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a byte value from the stream, as an int, or -1 to
* indicate EOF.
*
* @exception IOException if an I/O error occurs.
*/
int read() throws IOException;
/**
* Reads up to <code>b.length</code> bytes from the stream, and
* stores them into <code>b</code> starting at index 0. The
* number of bytes read is returned. If no bytes can be read
* because the end of the stream has been reached, -1 is returned.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param b an array of bytes to be written to.
*
* @return the number of bytes actually read, or <code>-1</code>
* to indicate EOF.
*
* @exception NullPointerException if <code>b</code> is
* <code>null</code>.
*
* @exception IOException if an I/O error occurs.
*/
int read(byte[] b) throws IOException;
/**
* Reads up to <code>len</code> bytes from the stream, and stores
* them into <code>b</code> starting at index <code>off</code>.
* The number of bytes read is returned. If no bytes can be read
* because the end of the stream has been reached, <code>-1</code>
* is returned.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param b an array of bytes to be written to.
* @param off the starting position within <code>b</code> to write to.
* @param len the maximum number of <code>byte</code>s to read.
*
* @return the number of bytes actually read, or <code>-1</code>
* to indicate EOF.
*
* @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>off +
* len</code> is greater than <code>b.length</code>.
* @exception IOException if an I/O error occurs.
*/
int read(byte[] b, int off, int len) throws IOException;
/**
* Reads up to <code>len</code> bytes from the stream, and
* modifies the supplied <code>IIOByteBuffer</code> to indicate
* the byte array, offset, and length where the data may be found.
* The caller should not attempt to modify the data found in the
* <code>IIOByteBuffer</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param buf an IIOByteBuffer object to be modified.
* @param len the maximum number of <code>byte</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>len</code> is
* negative.
* @exception NullPointerException if <code>buf</code> is
* <code>null</code>.
*
* @exception IOException if an I/O error occurs.
*/
void readBytes(IIOByteBuffer buf, int len) throws IOException;
/**
* Reads a byte from the stream and returns a <code>boolean</code>
* value of <code>true</code> if it is nonzero, <code>false</code>
* if it is zero.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a boolean value from the stream.
*
* @exception EOFException if the end of the stream is reached.
* @exception IOException if an I/O error occurs.
*/
boolean readBoolean() throws IOException;
/**
* Reads a byte from the stream and returns it as a
* <code>byte</code> value. Byte values between <code>0x00</code>
* and <code>0x7f</code> represent integer values between
* <code>0</code> and <code>127</code>. Values between
* <code>0x80</code> and <code>0xff</code> represent negative
* values from <code>-128</code> to <code>/1</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a signed byte value from the stream.
*
* @exception EOFException if the end of the stream is reached.
* @exception IOException if an I/O error occurs.
*/
byte readByte() throws IOException;
/**
* Reads a byte from the stream, and (conceptually) converts it to
* an int, masks it with <code>0xff</code> in order to strip off
* any sign-extension bits, and returns it as a <code>byte</code>
* value.
*
* <p> Thus, byte values between <code>0x00</code> and
* <code>0x7f</code> are simply returned as integer values between
* <code>0</code> and <code>127</code>. Values between
* <code>0x80</code> and <code>0xff</code>, which normally
* represent negative <code>byte</code>values, will be mapped into
* positive integers between <code>128</code> and
* <code>255</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return an unsigned byte value from the stream.
*
* @exception EOFException if the end of the stream is reached.
* @exception IOException if an I/O error occurs.
*/
int readUnsignedByte() throws IOException;
/**
* Reads two bytes from the stream, and (conceptually)
* concatenates them according to the current byte order, and
* returns the result as a <code>short</code> value.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a signed short value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
short readShort() throws IOException;
/**
* Reads two bytes from the stream, and (conceptually)
* concatenates them according to the current byte order, converts
* the resulting value to an <code>int</code>, masks it with
* <code>0xffff</code> in order to strip off any sign-extension
* buts, and returns the result as an unsigned <code>int</code>
* value.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return an unsigned short value from the stream, as an int.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
int readUnsignedShort() throws IOException;
/**
* Equivalent to <code>readUnsignedShort</code>, except that the
* result is returned using the <code>char</code> datatype.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return an unsigned char value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #readUnsignedShort
*/
char readChar() throws IOException;
/**
* Reads 4 bytes from the stream, and (conceptually) concatenates
* them according to the current byte order and returns the result
* as an <code>int</code>.
*
* <p> The bit offset within the stream is ignored and treated as
* though it were zero.
*
* @return a signed int value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
int readInt() throws IOException;
/**
* Reads 4 bytes from the stream, and (conceptually) concatenates
* them according to the current byte order, converts the result
* to a long, masks it with <code>0xffffffffL</code> in order to
* strip off any sign-extension bits, and returns the result as an
* unsigned <code>long</code> value.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return an unsigned int value from the stream, as a long.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
long readUnsignedInt() throws IOException;
/**
* Reads 8 bytes from the stream, and (conceptually) concatenates
* them according to the current byte order and returns the result
* as a <code>long</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a signed long value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
long readLong() throws IOException;
/**
* Reads 4 bytes from the stream, and (conceptually) concatenates
* them according to the current byte order and returns the result
* as a <code>float</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a float value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
float readFloat() throws IOException;
/**
* Reads 8 bytes from the stream, and (conceptually) concatenates
* them according to the current byte order and returns the result
* as a <code>double</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a double value from the stream.
*
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*
* @see #getByteOrder
*/
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
* <code>String</code>. Note that because this method processes
* bytes, it does not support input of the full Unicode character
* set.
*
* <p> If end of file is encountered before even one byte can be
* read, then <code>null</code> is returned. Otherwise, each byte
* that is read is converted to type <code>char</code> by
* zero-extension. If the character <code>'\n'</code> is
* encountered, it is discarded and reading ceases. If the
* character <code>'\r'</code> is encountered, it is discarded
* and, if the following byte converts to the character
* <code>'\n'</code>, then that is discarded also; reading then
* ceases. If end of file is encountered before either of the
* characters <code>'\n'</code> and <code>'\r'</code> is
* encountered, reading ceases. Once reading has ceased, a
* <code>String</code> 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
* <code>\u0100</code>, that is, <code>(char)256</code>.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @return a String containing a line of text from the stream.
*
* @exception IOException if an I/O error occurs.
*/
String readLine() throws IOException;
/**
* Reads in a string that has been encoded using a
* <a href="../../../java/io/DataInput.html#modified-utf-8">modified
* UTF-8</a>
* format. The general contract of <code>readUTF</code> is that
* it reads a representation of a Unicode character string encoded
* in modified UTF-8 format; this string of characters is
* then returned as a <code>String</code>.
*
* <p> First, two bytes are read and used to construct an unsigned
* 16-bit integer in the manner of the
* <code>readUnsignedShort</code> method, using network byte order
* (regardless of the current byte order setting). This integer
* value is called the <i>UTF length</i> 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.
*
* <p> If the first byte of a group matches the bit pattern
* <code>0xxxxxxx</code> (where <code>x</code> means "may be
* <code>0</code> or <code>1</code>"), then the group consists of
* just that byte. The byte is zero-extended to form a character.
*
* <p> If the first byte of a group matches the bit pattern
* <code>110xxxxx</code>, then the group consists of that byte
* <code>a</code> and a second byte <code>b</code>. If there is no
* byte <code>b</code> (because byte <code>a</code> was the last
* of the bytes to be read), or if byte <code>b</code> does not
* match the bit pattern <code>10xxxxxx</code>, then a
* <code>UTFDataFormatException</code> is thrown. Otherwise, the
* group is converted to the character:
*
* <p> <pre><code>
* (char)(((a& 0x1F) << 6) | (b & 0x3F))
* </code></pre>
*
* If the first byte of a group matches the bit pattern
* <code>1110xxxx</code>, then the group consists of that byte
* <code>a</code> and two more bytes <code>b</code> and
* <code>c</code>. If there is no byte <code>c</code> (because
* byte <code>a</code> was one of the last two of the bytes to be
* read), or either byte <code>b</code> or byte <code>c</code>
* does not match the bit pattern <code>10xxxxxx</code>, then a
* <code>UTFDataFormatException</code> is thrown. Otherwise, the
* group is converted to the character:
*
* <p> <pre><code>
* (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
* </code></pre>
*
* If the first byte of a group matches the pattern
* <code>1111xxxx</code> or the pattern <code>10xxxxxx</code>,
* then a <code>UTFDataFormatException</code> is thrown.
*
* <p> If end of file is encountered at any time during this
* entire process, then an <code>EOFException</code> is thrown.
*
* <p> 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 <code>String</code>, which is returned.
*
* <p> The current byte order setting is ignored.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* <p><strong>Note:</strong> This method should not be used in
* the implementation of image formats that use standard UTF-8,
* because the modified UTF-8 used here is incompatible with
* standard UTF-8.
*
* @return a String read from the stream.
*
* @exception EOFException if this stream reaches the end
* before reading all the bytes.
* @exception UTFDataFormatException if the bytes do not represent a
* valid modified UTF-8 encoding of a string.
* @exception IOException if an I/O error occurs.
*/
String readUTF() throws IOException;
/**
* Reads <code>len</code> bytes from the stream, and stores them
* into <code>b</code> starting at index <code>off</code>.
* If the end of the stream is reached, an <code>EOFException</code>
* will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param b an array of bytes to be written to.
* @param off the starting position within <code>b</code> to write to.
* @param len the maximum number of <code>byte</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>b.length</code>.
* @exception NullPointerException if <code>b</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(byte[] b, int off, int len) throws IOException;
/**
* Reads <code>b.length</code> bytes from the stream, and stores them
* into <code>b</code> starting at index <code>0</code>.
* If the end of the stream is reached, an <code>EOFException</code>
* will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param b an array of <code>byte</code>s.
*
* @exception NullPointerException if <code>b</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(byte[] b) throws IOException;
/**
* Reads <code>len</code> shorts (signed 16-bit integers) from the
* stream according to the current byte order, and
* stores them into <code>s</code> starting at index
* <code>off</code>. If the end of the stream is reached, an
* <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param s an array of shorts to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>short</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>s.length</code>.
* @exception NullPointerException if <code>s</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(short[] s, int off, int len) throws IOException;
/**
* Reads <code>len</code> chars (unsigned 16-bit integers) from the
* stream according to the current byte order, and
* stores them into <code>c</code> starting at index
* <code>off</code>. If the end of the stream is reached, an
* <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param c an array of chars to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>char</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>c.length</code>.
* @exception NullPointerException if <code>c</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(char[] c, int off, int len) throws IOException;
/**
* Reads <code>len</code> ints (signed 32-bit integers) from the
* stream according to the current byte order, and
* stores them into <code>i</code> starting at index
* <code>off</code>. If the end of the stream is reached, an
* <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param i an array of ints to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>int</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>i.length</code>.
* @exception NullPointerException if <code>i</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(int[] i, int off, int len) throws IOException;
/**
* Reads <code>len</code> longs (signed 64-bit integers) from the
* stream according to the current byte order, and
* stores them into <code>l</code> starting at index
* <code>off</code>. If the end of the stream is reached, an
* <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param l an array of longs to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>long</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>l.length</code>.
* @exception NullPointerException if <code>l</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(long[] l, int off, int len) throws IOException;
/**
* Reads <code>len</code> floats (32-bit IEEE single-precision
* floats) from the stream according to the current byte order,
* and stores them into <code>f</code> starting at
* index <code>off</code>. If the end of the stream is reached,
* an <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param f an array of floats to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>float</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>f.length</code>.
* @exception NullPointerException if <code>f</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(float[] f, int off, int len) throws IOException;
/**
* Reads <code>len</code> doubles (64-bit IEEE double-precision
* floats) from the stream according to the current byte order,
* and stores them into <code>d</code> starting at
* index <code>off</code>. If the end of the stream is reached,
* an <code>EOFException</code> will be thrown.
*
* <p> The bit offset within the stream is reset to zero before
* the read occurs.
*
* @param d an array of doubles to be written to.
* @param off the starting position withinb to write to.
* @param len the maximum number of <code>double</code>s to read.
*
* @exception IndexOutOfBoundsException if <code>off</code> is
* negative, <code>len</code> is negative, or <code>off +
* len</code> is greater than <code>d.length</code>.
* @exception NullPointerException if <code>d</code> is
* <code>null</code>.
* @exception EOFException if the stream reaches the end before
* reading all the bytes.
* @exception IOException if an I/O error occurs.
*/
void readFully(double[] d, int off, int len) throws IOException;
/**
* Returns the current byte position of the stream. The next read
* will take place starting at this offset.
*
* @return a long containing the position of the stream.
*
* @exception IOException if an I/O error occurs.
*/
long getStreamPosition() throws IOException;
/**
* Returns the current bit offset, as an integer between 0 and 7,
* inclusive. The bit offset is updated implicitly by calls to
* the <code>readBits</code> method. A value of 0 indicates the
* most-significant bit, and a value of 7 indicates the least
* significant bit, of the byte being read.
*
* <p> The bit offset is set to 0 when a stream is first
* opened, and is reset to 0 by calls to <code>seek</code>,
* <code>skipBytes</code>, or any <code>read</code> or
* <code>readFully</code> method.
*
* @return an <code>int</code> containing the bit offset between
* 0 and 7, inclusive.
*
* @exception IOException if an I/O error occurs.
*
* @see #setBitOffset
*/
int getBitOffset() throws IOException;
/**
* Sets the bit offset to an integer between 0 and 7, inclusive.
* The byte offset within the stream, as returned by
* <code>getStreamPosition</code>, is left unchanged.
* A value of 0 indicates the
* most-significant bit, and a value of 7 indicates the least
* significant bit, of the byte being read.
*
* @param bitOffset the desired offset, as an <code>int</code>
* between 0 and 7, inclusive.
*
* @exception IllegalArgumentException if <code>bitOffset</code>
* is not between 0 and 7, inclusive.
* @exception IOException if an I/O error occurs.
*
* @see #getBitOffset
*/
void setBitOffset(int bitOffset) throws IOException;
/**
* Reads a single bit from the stream and returns it as an
* <code>int</code> with the value <code>0</code> or
* <code>1</code>. The bit offset is advanced by one and reduced
* modulo 8.
*
* @return an <code>int</code> containing the value <code>0</code>
* or <code>1</code>.
*
* @exception EOFException if the stream reaches the end before
* reading all the bits.
* @exception IOException if an I/O error occurs.
*/
int readBit() throws IOException;
/**
* Reads a bitstring from the stream and returns it as a
* <code>long</code>, with the first bit read becoming the most
* significant bit of the output. The read starts within the byte
* indicated by <code>getStreamPosition</code>, at the bit given
* by <code>getBitOffset</code>. The bit offset is advanced by
* <code>numBits</code> and reduced modulo 8.
*
* <p> The byte order of the stream has no effect on this
* method. The return value of this method is constructed as
* though the bits were read one at a time, and shifted into
* the right side of the return value, as shown by the following
* pseudo-code:
*
* <pre>
* long accum = 0L;
* for (int i = 0; i < numBits; i++) {
* accum <<= 1; // Shift left one bit to make room
* accum |= readBit();
* }
* </pre>
*
* Note that the result of <code>readBits(32)</code> may thus not
* be equal to that of <code>readInt()</code> if a reverse network
* byte order is being used (i.e., <code>getByteOrder() ==
* false</code>).
*
* <p> If the end of the stream is encountered before all the bits
* have been read, an <code>EOFException</code> is thrown.
*
* @param numBits the number of bits to read, as an <code>int</code>
* between 0 and 64, inclusive.
* @return the bitstring, as a <code>long</code> with the last bit
* read stored in the least significant bit.
*
* @exception IllegalArgumentException if <code>numBits</code>
* is not between 0 and 64, inclusive.
* @exception EOFException if the stream reaches the end before
* reading all the bits.
* @exception IOException if an I/O error occurs.
*/
long readBits(int numBits) throws IOException;
/**
* Returns the total length of the stream, if known. Otherwise,
* <code>-1</code> is returned.
*
* @return a <code>long</code> containing the length of the
* stream, if known, or else <code>-1</code>.
*
* @exception IOException if an I/O error occurs.
*/
long length() throws IOException;
/**
* Moves the stream position forward by a given number of bytes. It
* is possible that this method will only be able to skip forward
* by a smaller number of bytes than requested, for example if the
* end of the stream is reached. In all cases, the actual number
* of bytes skipped is returned. The bit offset is set to zero
* prior to advancing the position.
*
* @param n an <code>int</code> containing the number of bytes to
* be skipped.
*
* @return an <code>int</code> representing the number of bytes skipped.
*
* @exception IOException if an I/O error occurs.
*/
int skipBytes(int n) throws IOException;
/**
* Moves the stream position forward by a given number of bytes.
* This method is identical to <code>skipBytes(int)</code> except
* that it allows for a larger skip distance.
*
* @param n a <code>long</code> containing the number of bytes to
* be skipped.
*
* @return a <code>long</code> representing the number of bytes
* skipped.
*
* @exception IOException if an I/O error occurs.
*/
long skipBytes(long n) throws IOException;
/**
* Sets the current stream position to the desired location. The
* next read will occur at this location. The bit offset is set
* to 0.
*
* <p> An <code>IndexOutOfBoundsException</code> will be thrown if
* <code>pos</code> is smaller than the flushed position (as
* returned by <code>getflushedPosition</code>).
*
* <p> It is legal to seek past the end of the file; an
* <code>EOFException</code> will be thrown only if a read is
* performed.
*
* @param pos a <code>long</code> containing the desired file
* pointer position.
*
* @exception IndexOutOfBoundsException if <code>pos</code> is smaller
* than the flushed position.
* @exception IOException if any other I/O error occurs.
*/
void seek(long pos) throws IOException;
/**
* Marks a position in the stream to be returned to by a
* subsequent call to <code>reset</code>. Unlike a standard
* <code>InputStream</code>, all <code>ImageInputStream</code>s
* support marking. Additionally, calls to <code>mark</code> and
* <code>reset</code> may be nested arbitrarily.
*
* <p> Unlike the <code>mark</code> methods declared by the
* <code>Reader</code> and <code>InputStream</code> interfaces, no
* <code>readLimit</code> parameter is used. An arbitrary amount
* of data may be read following the call to <code>mark</code>.
*
* <p> The bit position used by the <code>readBits</code> method
* is saved and restored by each pair of calls to
* <code>mark</code> and <code>reset</code>.
*
* <p> Note that it is valid for an <code>ImageReader</code> to call
* <code>flushBefore</code> as part of a read operation.
* Therefore, if an application calls <code>mark</code> prior to
* passing that stream to an <code>ImageReader</code>, the application
* should not assume that the marked position will remain valid after
* the read operation has completed.
*/
void mark();
/**
* Returns the stream pointer to its previous position, including
* the bit offset, at the time of the most recent unmatched call
* to <code>mark</code>.
*
* <p> Calls to <code>reset</code> without a corresponding call
* to <code>mark</code> have no effect.
*
* <p> An <code>IOException</code> will be thrown if the previous
* marked position lies in the discarded portion of the stream.
*
* @exception IOException if an I/O error occurs.
*/
void reset() throws IOException;
/**
* Discards the initial portion of the stream prior to the
* indicated postion. Attempting to seek to an offset within the
* flushed portion of the stream will result in an
* <code>IndexOutOfBoundsException</code>.
*
* <p> Calling <code>flushBefore</code> may allow classes
* implementing this interface to free up resources such as memory
* or disk space that are being used to store data from the
* stream.
*
* @param pos a <code>long</code> containing the length of the
* stream prefix that may be flushed.
*
* @exception IndexOutOfBoundsException if <code>pos</code> lies
* in the flushed portion of the stream or past the current stream
* position.
* @exception IOException if an I/O error occurs.
*/
void flushBefore(long pos) throws IOException;
/**
* Discards the initial position of the stream prior to the current
* stream position. Equivalent to
* <code>flushBefore(getStreamPosition())</code>.
*
* @exception IOException if an I/O error occurs.
*/
void flush() throws IOException;
/**
* Returns the earliest position in the stream to which seeking
* may be performed. The returned value will be the maximum of
* all values passed into previous calls to
* <code>flushBefore</code>.
*
* @return the earliest legal position for seeking, as a
* <code>long</code>.
*/
long getFlushedPosition();
/**
* Returns <code>true</code> if this <code>ImageInputStream</code>
* caches data itself in order to allow seeking backwards.
* Applications may consult this in order to decide how frequently,
* or whether, to flush in order to conserve cache resources.
*
* @return <code>true</code> if this <code>ImageInputStream</code>
* caches data.
*
* @see #isCachedMemory
* @see #isCachedFile
*/
boolean isCached();
/**
* Returns <code>true</code> if this <code>ImageInputStream</code>
* caches data itself in order to allow seeking backwards, and
* the cache is kept in main memory. Applications may consult
* this in order to decide how frequently, or whether, to flush
* in order to conserve cache resources.
*
* @return <code>true</code> if this <code>ImageInputStream</code>
* caches data in main memory.
*
* @see #isCached
* @see #isCachedFile
*/
boolean isCachedMemory();
/**
* Returns <code>true</code> if this <code>ImageInputStream</code>
* caches data itself in order to allow seeking backwards, and
* the cache is kept in a temporary file. Applications may consult
* this in order to decide how frequently, or whether, to flush
* in order to conserve cache resources.
*
* @return <code>true</code> if this <code>ImageInputStream</code>
* caches data in a temporary file.
*
* @see #isCached
* @see #isCachedMemory
*/
boolean isCachedFile();
/**
* Closes the stream. Attempts to access a stream that has been
* closed may result in <code>IOException</code>s or incorrect
* behavior. Calling this method may allow classes implementing
* this interface to release resources associated with the stream
* such as memory, disk space, or file descriptors.
*
* @exception IOException if an I/O error occurs.
*/
void close() throws IOException;
}