Java tutorial
/* * Copyright (c) 1999, 2018, 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.Closeable; import java.io.DataInput; import java.io.IOException; import java.nio.ByteOrder; /** * A seekable input stream interface for use by * {@code ImageReader}s. Various input sources, such as * {@code InputStream}s and {@code File}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, Closeable { /** * 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} is * used to specify the byte order. A value of * {@code ByteOrder.BIG_ENDIAN} 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} order. * * <p> The byte order has no effect on the results returned from * the {@code readBits} method (or the value written by * {@code ImageOutputStream.writeBits}). * * @param byteOrder one of {@code ByteOrder.BIG_ENDIAN} or * {@code java.nio.ByteOrder.LITTLE_ENDIAN}, 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} enumeration. * * @return one of {@code ByteOrder.BIG_ENDIAN} or * {@code ByteOrder.LITTLE_ENDIAN}, 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} bytes from the stream, and * stores them into {@code b} 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} * to indicate EOF. * * @exception NullPointerException if {@code b} is * {@code null}. * * @exception IOException if an I/O error occurs. */ int read(byte[] b) throws IOException; /** * Reads up to {@code len} bytes from the stream, and stores * them into {@code b} starting at index {@code off}. * The number of bytes read is returned. If no bytes can be read * because the end of the stream has been reached, {@code -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. * @param off the starting position within {@code b} to write to. * @param len the maximum number of {@code byte}s to read. * * @return the number of bytes actually read, or {@code -1} * to indicate EOF. * * @exception NullPointerException if {@code b} is * {@code null}. * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code b.length}. * @exception IOException if an I/O error occurs. */ int read(byte[] b, int off, int len) throws IOException; /** * Reads up to {@code len} bytes from the stream, and * modifies the supplied {@code IIOByteBuffer} 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}. * * <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}s to read. * * @exception IndexOutOfBoundsException if {@code len} is * negative. * @exception NullPointerException if {@code buf} is * {@code null}. * * @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} * value of {@code true} if it is nonzero, {@code false} * 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 java.io.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} value. Byte values between {@code 0x00} * and {@code 0x7f} represent integer values between * {@code 0} and {@code 127}. Values between * {@code 0x80} and {@code 0xff} represent negative * values from {@code -128} to {@code /1}. * * <p> The bit offset within the stream is reset to zero before * the read occurs. * * @return a signed byte value from the stream. * * @exception java.io.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} in order to strip off * any sign-extension bits, and returns it as a {@code byte} * value. * * <p> Thus, byte values between {@code 0x00} and * {@code 0x7f} are simply returned as integer values between * {@code 0} and {@code 127}. Values between * {@code 0x80} and {@code 0xff}, which normally * represent negative {@code byte} values, will be mapped into * positive integers between {@code 128} and * {@code 255}. * * <p> The bit offset within the stream is reset to zero before * the read occurs. * * @return an unsigned byte value from the stream. * * @exception java.io.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} 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 java.io.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}, masks it with * {@code 0xffff} in order to strip off any sign-extension * buts, and returns the result as an unsigned {@code int} * 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 java.io.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}, except that the * result is returned using the {@code char} 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 java.io.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}. * * <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 java.io.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} in order to * strip off any sign-extension bits, and returns the result as an * unsigned {@code long} 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 java.io.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}. * * <p> The bit offset within the stream is reset to zero before * the read occurs. * * @return a signed long value from the stream. * * @exception java.io.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}. * * <p> The bit offset within the stream is reset to zero before * the read occurs. * * @return a float value from the stream. * * @exception java.io.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}. * * <p> The bit offset within the stream is reset to zero before * the read occurs. * * @return a double value from the stream. * * @exception java.io.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}. 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} is returned. Otherwise, each byte * that is read is converted to type {@code char} by * zero-extension. If the character {@code '\n'} is * encountered, it is discarded and reading ceases. If the * character {@code '\r'} is encountered, it is discarded * and, if the following byte converts  to the character * {@code '\n'}, then that is discarded also; reading then * ceases. If end of file is encountered before either of the * characters {@code '\n'} and {@code '\r'} is * encountered, reading ceases. Once reading has ceased, a * {@code 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 * <code>\u0100</code>, that is, {@code (char)256}. * * <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.base/java/io/DataInput.html#modified-utf-8"> * modified UTF-8</a> * format. The general contract of {@code readUTF} 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}. * * <p> First, two bytes are read and used to construct an unsigned * 16-bit integer in the manner of the * {@code readUnsignedShort} 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} (where {@code x} means "may be * {@code 0} or {@code 1}"), 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}, then the group consists of that byte * {@code a} and a second byte {@code b}. If there is no * byte {@code b} (because byte {@code a} was the last * of the bytes to be read), or if byte {@code b} does not * match the bit pattern {@code 10xxxxxx}, then a * {@code UTFDataFormatException} is thrown. Otherwise, the * group is converted to the character: * * <pre><code> * (char)(((a& 0x1F) << 6) | (b & 0x3F)) * </code></pre> * * If the first byte of a group matches the bit pattern * {@code 1110xxxx}, then the group consists of that byte * {@code a} and two more bytes {@code b} and * {@code c}. If there is no byte {@code c} (because * byte {@code a} was one of the last two of the bytes to be * read), or either byte {@code b} or byte {@code c} * does not match the bit pattern {@code 10xxxxxx}, then a * {@code UTFDataFormatException} is thrown. Otherwise, the * group is converted to the character: * * <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} or the pattern {@code 10xxxxxx}, * then a {@code UTFDataFormatException} is thrown. * * <p> If end of file is encountered at any time during this * entire process, then a {@code java.io.EOFException} 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}, 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 java.io.EOFException if this stream reaches the end * before reading all the bytes. * @exception java.io.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} bytes from the stream, and stores them * into {@code b} starting at index {@code off}. * If the end of the stream is reached, a {@code java.io.EOFException} * 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} to write to. * @param len the maximum number of {@code byte}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code b.length}. * @exception NullPointerException if {@code b} is * {@code null}. * @exception java.io.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} bytes from the stream, and stores them * into {@code b} starting at index {@code 0}. * If the end of the stream is reached, a {@code java.io.EOFException} * 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}s. * * @exception NullPointerException if {@code b} is * {@code null}. * @exception java.io.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} shorts (signed 16-bit integers) from the * stream according to the current byte order, and * stores them into {@code s} starting at index * {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code s} to write to. * @param len the maximum number of {@code short}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code s.length}. * @exception NullPointerException if {@code s} is * {@code null}. * @exception java.io.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} chars (unsigned 16-bit integers) from the * stream according to the current byte order, and * stores them into {@code c} starting at index * {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code c} to write to. * @param len the maximum number of {@code char}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code c.length}. * @exception NullPointerException if {@code c} is * {@code null}. * @exception java.io.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} ints (signed 32-bit integers) from the * stream according to the current byte order, and * stores them into {@code i} starting at index * {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code i} to write to. * @param len the maximum number of {@code int}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code i.length}. * @exception NullPointerException if {@code i} is * {@code null}. * @exception java.io.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} longs (signed 64-bit integers) from the * stream according to the current byte order, and * stores them into {@code l} starting at index * {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code l} to write to. * @param len the maximum number of {@code long}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code l.length}. * @exception NullPointerException if {@code l} is * {@code null}. * @exception java.io.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} floats (32-bit IEEE single-precision * floats) from the stream according to the current byte order, * and stores them into {@code f} starting at * index {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code f} to write to. * @param len the maximum number of {@code float}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code f.length}. * @exception NullPointerException if {@code f} is * {@code null}. * @exception java.io.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} doubles (64-bit IEEE double-precision * floats) from the stream according to the current byte order, * and stores them into {@code d} starting at * index {@code off}. If the end of the stream is reached, * a {@code java.io.EOFException} 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 within {@code d} to write to. * @param len the maximum number of {@code double}s to read. * * @exception IndexOutOfBoundsException if {@code off} is * negative, {@code len} is negative, or {@code off + len} * is greater than {@code d.length}. * @exception NullPointerException if {@code d} is * {@code null}. * @exception java.io.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} 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 skipBytes}, or any {@code read} or * {@code readFully} method. * * @return an {@code int} 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}, 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} * between 0 and 7, inclusive. * * @exception IllegalArgumentException if {@code bitOffset} * 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} with the value {@code 0} or * {@code 1}. The bit offset is advanced by one and reduced * modulo 8. * * @return an {@code int} containing the value {@code 0} * or {@code 1}. * * @exception java.io.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}, with the first bit read becoming the most * significant bit of the output. The read starts within the byte * indicated by {@code getStreamPosition}, at the bit given * by {@code getBitOffset}. The bit offset is advanced by * {@code numBits} 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>{@code * 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)} may thus not * be equal to that of {@code readInt()} if a reverse network * byte order is being used (i.e., {@code getByteOrder() == false}). * * <p> If the end of the stream is encountered before all the bits * have been read, a {@code java.io.EOFException} is thrown. * * @param numBits the number of bits to read, as an {@code int} * between 0 and 64, inclusive. * @return the bitstring, as a {@code long} with the last bit * read stored in the least significant bit. * * @exception IllegalArgumentException if {@code numBits} * is not between 0 and 64, inclusive. * @exception java.io.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} is returned. * * @return a {@code long} containing the length of the * stream, if known, or else {@code -1}. * * @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} containing the number of bytes to * be skipped. * * @return an {@code int} 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)} except * that it allows for a larger skip distance. * * @param n a {@code long} containing the number of bytes to * be skipped. * * @return a {@code long} 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} will be thrown if * {@code pos} is smaller than the flushed position (as * returned by {@code getflushedPosition}). * * <p> It is legal to seek past the end of the file; * a {@code java.io.EOFException} will be thrown only if a read is * performed. * * @param pos a {@code long} containing the desired file * pointer position. * * @exception IndexOutOfBoundsException if {@code pos} 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}. Unlike a standard * {@code InputStream}, all {@code ImageInputStream}s * support marking. Additionally, calls to {@code mark} and * {@code reset} may be nested arbitrarily. * * <p> Unlike the {@code mark} methods declared by the * {@code Reader} and {@code InputStream} interfaces, no * {@code readLimit} parameter is used. An arbitrary amount * of data may be read following the call to {@code mark}. * * <p> The bit position used by the {@code readBits} method * is saved and restored by each pair of calls to * {@code mark} and {@code reset}. * * <p> Note that it is valid for an {@code ImageReader} to call * {@code flushBefore} as part of a read operation. * Therefore, if an application calls {@code mark} prior to * passing that stream to an {@code ImageReader}, 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}. * * <p> Calls to {@code reset} without a corresponding call * to {@code mark} have no effect. * * <p> An {@code IOException} 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 position. Attempting to seek to an offset within the * flushed portion of the stream will result in an * {@code IndexOutOfBoundsException}. * * <p> Calling {@code flushBefore} 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} containing the length of the * stream prefix that may be flushed. * * @exception IndexOutOfBoundsException if {@code pos} 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())}. * * @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}. * * @return the earliest legal position for seeking, as a * {@code long}. */ long getFlushedPosition(); /** * Returns {@code true} if this {@code ImageInputStream} * 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} if this {@code ImageInputStream} * caches data. * * @see #isCachedMemory * @see #isCachedFile */ boolean isCached(); /** * Returns {@code true} if this {@code ImageInputStream} * 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} if this {@code ImageInputStream} * caches data in main memory. * * @see #isCached * @see #isCachedFile */ boolean isCachedMemory(); /** * Returns {@code true} if this {@code ImageInputStream} * 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} if this {@code ImageInputStream} * 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}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; }