# Interface ImageInputStream

All Superinterfaces:
  `AutoCloseable, Closeable, DataInput`

All Known Subinterfaces:
  `ImageOutputStream`

All Known Implementing Classes:
  `FileCacheImageInputStream, FileCacheImageOutputStream, FileImageInputStream, FileImageOutputStream, ImageInputStreamImpl, ImageOutputStreamImpl, MemoryCacheImageInputStream, MemoryCacheImageOutputStream`

public interface ImageInputStream extends DataInput, Closeable
A seekable input stream interface for use by `ImageReader`s. Various input sources, such as `InputStream`s and `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 Also:
  - `ImageInputStreamImpl`
  - `FileImageInputStream`
  - `FileCacheImageInputStream`
  - `MemoryCacheImageInputStream`

## Method Summary

Modifier and Type
Method
Description
`void`
`close()`
Closes the stream.
`void`
`flush()`
Discards the initial position of the stream prior to the current stream position.
`void`
`flushBefore(long pos)`
Discards the initial portion of the stream prior to the indicated position.
`int`
`getBitOffset()`
Returns the current bit offset, as an integer between 0 and 7, inclusive.
`ByteOrder`
`getByteOrder()`
Returns the byte order with which data values will be read from this stream as an instance of the `java.nio.ByteOrder` enumeration.
`long`
`getFlushedPosition()`
Returns the earliest position in the stream to which seeking may be performed.
`long`
`getStreamPosition()`
Returns the current byte position of the stream.
`boolean`
`isCached()`
Returns `true` if this `ImageInputStream` caches data itself in order to allow seeking backwards.
`boolean`
`isCachedFile()`
Returns `true` if this `ImageInputStream` caches data itself in order to allow seeking backwards, and the cache is kept in a temporary file.
`boolean`
`isCachedMemory()`
Returns `true` if this `ImageInputStream` caches data itself in order to allow seeking backwards, and the cache is kept in main memory.
`long`
`length()`
Returns the total length of the stream, if known.
`void`
`mark()`
Marks a position in the stream to be returned to by a subsequent call to `reset`.
`int`
`read()`
Reads a single byte from the stream and returns it as an integer between 0 and 255.
`int`
`read(byte[] b)`
Reads up to `b.length` bytes from the stream, and stores them into `b` starting at index 0.
`int`
`read(byte[] b, int off, int len)`
Reads up to `len` bytes from the stream, and stores them into `b` starting at index `off`.
`int`
`readBit()`
Reads a single bit from the stream and returns it as an `int` with the value `0` or `1`.
`long`
`readBits(int numBits)`
Reads a bitstring from the stream and returns it as a `long`, with the first bit read becoming the most significant bit of the output.
`boolean`
`readBoolean()`
Reads a byte from the stream and returns a `boolean` value of `true` if it is nonzero, `false` if it is zero.
`byte`
`readByte()`
Reads a byte from the stream and returns it as a `byte` value.
`void`
`readBytes(IIOByteBuffer buf, int len)`
Reads up to `len` bytes from the stream, and modifies the supplied `IIOByteBuffer` to indicate the byte array, offset, and length where the data may be found.
`char`
`readChar()`
Equivalent to `readUnsignedShort`, except that the result is returned using the `char` datatype.
`double`
`readDouble()`
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `double`.
`float`
`readFloat()`
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `float`.
`void`
`readFully(byte[] b)`
Reads `b.length` bytes from the stream, and stores them into `b` starting at index `0`.
`void`
`readFully(byte[] b, int off, int len)`
Reads `len` bytes from the stream, and stores them into `b` starting at index `off`.
`void`
`readFully(char[] c, int off, int len)`
Reads `len` chars (unsigned 16-bit integers) from the stream according to the current byte order, and stores them into `c` starting at index `off`.
`void`
`readFully(double[] d, int off, int len)`
Reads `len` doubles (64-bit IEEE double-precision floats) from the stream according to the current byte order, and stores them into `d` starting at index `off`.
`void`
`readFully(float[] f, int off, int len)`
Reads `len` floats (32-bit IEEE single-precision floats) from the stream according to the current byte order, and stores them into `f` starting at index `off`.
`void`
`readFully(int[] i, int off, int len)`
Reads `len` ints (signed 32-bit integers) from the stream according to the current byte order, and stores them into `i` starting at index `off`.
`void`
`readFully(long[] l, int off, int len)`
Reads `len` longs (signed 64-bit integers) from the stream according to the current byte order, and stores them into `l` starting at index `off`.
`void`
`readFully(short[] s, int off, int len)`
Reads `len` shorts (signed 16-bit integers) from the stream according to the current byte order, and stores them into `s` starting at index `off`.
`int`
`readInt()`
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an `int`.
`String`
`readLine()`
Reads the next line of text from the input stream.
`long`
`readLong()`
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `long`.
`short`
`readShort()`
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a `short` value.
`int`
`readUnsignedByte()`
Reads a byte from the stream, and (conceptually) converts it to an int, masks it with `0xff` in order to strip off any sign-extension bits, and returns it as a `byte` value.
`long`
`readUnsignedInt()`
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 `0xffffffffL` in order to strip off any sign-extension bits, and returns the result as an unsigned `long` value.
`int`
`readUnsignedShort()`
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an `int`, masks it with `0xffff` in order to strip off any sign-extension buts, and returns the result as an unsigned `int` value.
`String`
`readUTF()`
Reads in a string that has been encoded using a modified UTF-8 format.
`void`
`reset()`
Returns the stream pointer to its previous position, including the bit offset, at the time of the most recent unmatched call to `mark`.
`void`
`seek(long pos)`
Sets the current stream position to the desired location.
`void`
`setBitOffset(int bitOffset)`
Sets the bit offset to an integer between 0 and 7, inclusive.
`void`
`setByteOrder(ByteOrder byteOrder)`
Sets the desired byte order for future reads of data values from this stream.
`int`
`skipBytes(int n)`
Moves the stream position forward by a given number of bytes.
`long`
`skipBytes(long n)`
Moves the stream position forward by a given number of bytes.

## Method Details

### setByteOrder

void setByteOrder(ByteOrder byteOrder)
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.

The enumeration class `java.nio.ByteOrder` is used to specify the byte order. A value of `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 `ByteOrder.LITTLE_ENDIAN` order.

The byte order has no effect on the results returned from the `readBits` method (or the value written by `ImageOutputStream.writeBits`).

Parameters:
  `byteOrder` - one of `ByteOrder.BIG_ENDIAN` or `java.nio.ByteOrder.LITTLE_ENDIAN`, indicating whether network byte order or its reverse will be used for future reads.
See Also:
  - `ByteOrder`
  - `getByteOrder()`
  - `readBits(int)`

### getByteOrder

ByteOrder getByteOrder()
Returns the byte order with which data values will be read from this stream as an instance of the `java.nio.ByteOrder` enumeration.

Returns:
  one of `ByteOrder.BIG_ENDIAN` or `ByteOrder.LITTLE_ENDIAN`, indicating which byte order is being used.
See Also:
  - `ByteOrder`
  - `setByteOrder(ByteOrder)`

### read

int read() throws IOException
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.

The bit offset within the stream is reset to zero before the read occurs.

Returns:
  a byte value from the stream, as an int, or -1 to indicate EOF.
Throws:
  `IOException` - if an I/O error occurs.

### read

int read(byte[] b) throws IOException
Reads up to `b.length` bytes from the stream, and stores them into `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.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `b` - an array of bytes to be written to.
Returns:
  the number of bytes actually read, or `-1` to indicate EOF.
Throws:
  `NullPointerException` - if `b` is `null`.
  `IOException` - if an I/O error occurs.

### read

int read(byte[] b, int off, int len) throws IOException
Reads up to `len` bytes from the stream, and stores them into `b` starting at index `off`. 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.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `b` - an array of bytes to be written to.
  `off` - the starting position within `b` to write to.
  `len` - the maximum number of `byte`s to read.
Returns:
  the number of bytes actually read, or `-1` to indicate EOF.
Throws:
  `NullPointerException` - if `b` is `null`.
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `b.length`.
  `IOException` - if an I/O error occurs.

### readBytes

void readBytes(IIOByteBuffer buf, int len) throws IOException
Reads up to `len` bytes from the stream, and modifies the supplied `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 `IIOByteBuffer`.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `buf` - an IIOByteBuffer object to be modified.
  `len` - the maximum number of `byte`s to read.
Throws:
  `IndexOutOfBoundsException` - if `len` is negative.
  `NullPointerException` - if `buf` is `null`.
  `IOException` - if an I/O error occurs.

### readBoolean

boolean readBoolean() throws IOException
Reads a byte from the stream and returns a `boolean` value of `true` if it is nonzero, `false` if it is zero.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readBoolean` in interface `DataInput`
Returns:
  a boolean value from the stream.
Throws:
  `EOFException` - if the end of the stream is reached.
  `IOException` - if an I/O error occurs.

### readByte

byte readByte() throws IOException
Reads a byte from the stream and returns it as a `byte` value. Byte values between `0x00` and `0x7f` represent integer values between `0` and `127`. Values between `0x80` and `0xff` represent negative values from `-128` to `/1`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readByte` in interface `DataInput`
Returns:
  a signed byte value from the stream.
Throws:
  `EOFException` - if the end of the stream is reached.
  `IOException` - if an I/O error occurs.

### readUnsignedByte

int readUnsignedByte() throws IOException
Reads a byte from the stream, and (conceptually) converts it to an int, masks it with `0xff` in order to strip off any sign-extension bits, and returns it as a `byte` value.

Thus, byte values between `0x00` and `0x7f` are simply returned as integer values between `0` and `127`. Values between `0x80` and `0xff`, which normally represent negative `byte` values, will be mapped into positive integers between `128` and `255`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readUnsignedByte` in interface `DataInput`
Returns:
  an unsigned byte value from the stream.
Throws:
  `EOFException` - if the end of the stream is reached.
  `IOException` - if an I/O error occurs.

### readShort

short readShort() throws IOException
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a `short` value.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readShort` in interface `DataInput`
Returns:
  a signed short value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readUnsignedShort

int readUnsignedShort() throws IOException
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an `int`, masks it with `0xffff` in order to strip off any sign-extension buts, and returns the result as an unsigned `int` value.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readUnsignedShort` in interface `DataInput`
Returns:
  an unsigned short value from the stream, as an int.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readChar

char readChar() throws IOException
Equivalent to `readUnsignedShort`, except that the result is returned using the `char` datatype.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readChar` in interface `DataInput`
Returns:
  an unsigned char value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `readUnsignedShort()`

### readInt

int readInt() throws IOException
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an `int`.

The bit offset within the stream is ignored and treated as though it were zero.

Specified by:
  `readInt` in interface `DataInput`
Returns:
  a signed int value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readUnsignedInt

long readUnsignedInt() 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 `0xffffffffL` in order to strip off any sign-extension bits, and returns the result as an unsigned `long` value.

The bit offset within the stream is reset to zero before the read occurs.

Returns:
  an unsigned int value from the stream, as a long.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readLong

long readLong() throws IOException
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `long`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readLong` in interface `DataInput`
Returns:
  a signed long value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readFloat

float readFloat() throws IOException
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `float`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readFloat` in interface `DataInput`
Returns:
  a float value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readDouble

double readDouble() throws IOException
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `double`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readDouble` in interface `DataInput`
Returns:
  a double value from the stream.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.
See Also:
  - `getByteOrder()`

### readLine

String readLine() throws IOException
Reads the next line of text from the input stream. It reads successive bytes, converting each byte separately into a character, until it encounters a line terminator or end of file; the characters read are then returned as a `String`. Note that because this method processes bytes, it does not support input of the full Unicode character set.

If end of file is encountered before even one byte can be read, then `null` is returned. Otherwise, each byte that is read is converted to type `char` by zero-extension. If the character `'\n'` is encountered, it is discarded and reading ceases. If the character `'\r'` is encountered, it is discarded and, if the following byte converts to the character `'\n'`, then that is discarded also; reading then ceases. If end of file is encountered before either of the characters `'\n'` and `'\r'` is encountered, reading ceases. Once reading has ceased, a `String` is returned that contains all the characters read and not discarded, taken in order. Note that every character in this string will have a value less than `\u0100`, that is, `(char)256`.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readLine` in interface `DataInput`
Returns:
  a String containing a line of text from the stream.
Throws:
  `IOException` - if an I/O error occurs.

### readUTF

String readUTF() throws IOException
Reads in a string that has been encoded using a modified UTF-8 format. The general contract of `readUTF` is that it reads a representation of a Unicode character string encoded in modified UTF-8 format; this string of characters is then returned as a `String`.

First, two bytes are read and used to construct an unsigned 16-bit integer in the manner of the `readUnsignedShort` method, using network byte order (regardless of the current byte order setting). This integer value is called the UTF length and specifies the number of additional bytes to be read. These bytes are then converted to characters by considering them in groups. The length of each group is computed from the value of the first byte of the group. The byte following a group, if any, is the first byte of the next group.

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

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

    (char)(((a& 0x1F) << 6) | (b & 0x3F))

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

    (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))

If the first byte of a group matches the pattern `1111xxxx` or the pattern `10xxxxxx`, then a `UTFDataFormatException` is thrown.

If end of file is encountered at any time during this entire process, then a `java.io.EOFException` is thrown.

After every group has been converted to a character by this process, the characters are gathered, in the same order in which their corresponding groups were read from the input stream, to form a `String`, which is returned.

The current byte order setting is ignored.

The bit offset within the stream is reset to zero before the read occurs.

Note: 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.

Specified by:
  `readUTF` in interface `DataInput`
Returns:
  a String read from the stream.
Throws:
  `EOFException` - if this stream reaches the end before reading all the bytes.
  `UTFDataFormatException` - if the bytes do not represent a valid modified UTF-8 encoding of a string.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(byte[] b, int off, int len) throws IOException
Reads `len` bytes from the stream, and stores them into `b` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readFully` in interface `DataInput`
Parameters:
  `b` - an array of bytes to be written to.
  `off` - the starting position within `b` to write to.
  `len` - the maximum number of `byte`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `b.length`.
  `NullPointerException` - if `b` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(byte[] b) throws IOException
Reads `b.length` bytes from the stream, and stores them into `b` starting at index `0`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Specified by:
  `readFully` in interface `DataInput`
Parameters:
  `b` - an array of `byte`s.
Throws:
  `NullPointerException` - if `b` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(short[] s, int off, int len) throws IOException
Reads `len` shorts (signed 16-bit integers) from the stream according to the current byte order, and stores them into `s` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `s` - an array of shorts to be written to.
  `off` - the starting position within `s` to write to.
  `len` - the maximum number of `short`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `s.length`.
  `NullPointerException` - if `s` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(char[] c, int off, int len) throws IOException
Reads `len` chars (unsigned 16-bit integers) from the stream according to the current byte order, and stores them into `c` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `c` - an array of chars to be written to.
  `off` - the starting position within `c` to write to.
  `len` - the maximum number of `char`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `c.length`.
  `NullPointerException` - if `c` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(int[] i, int off, int len) throws IOException
Reads `len` ints (signed 32-bit integers) from the stream according to the current byte order, and stores them into `i` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `i` - an array of ints to be written to.
  `off` - the starting position within `i` to write to.
  `len` - the maximum number of `int`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `i.length`.
  `NullPointerException` - if `i` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(long[] l, int off, int len) throws IOException
Reads `len` longs (signed 64-bit integers) from the stream according to the current byte order, and stores them into `l` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `l` - an array of longs to be written to.
  `off` - the starting position within `l` to write to.
  `len` - the maximum number of `long`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `l.length`.
  `NullPointerException` - if `l` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(float[] f, int off, int len) throws IOException
Reads `len` floats (32-bit IEEE single-precision floats) from the stream according to the current byte order, and stores them into `f` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `f` - an array of floats to be written to.
  `off` - the starting position within `f` to write to.
  `len` - the maximum number of `float`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `f.length`.
  `NullPointerException` - if `f` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### readFully

void readFully(double[] d, int off, int len) throws IOException
Reads `len` doubles (64-bit IEEE double-precision floats) from the stream according to the current byte order, and stores them into `d` starting at index `off`. If the end of the stream is reached, a `java.io.EOFException` will be thrown.

The bit offset within the stream is reset to zero before the read occurs.

Parameters:
  `d` - an array of doubles to be written to.
  `off` - the starting position within `d` to write to.
  `len` - the maximum number of `double`s to read.
Throws:
  `IndexOutOfBoundsException` - if `off` is negative, `len` is negative, or `off + len` is greater than `d.length`.
  `NullPointerException` - if `d` is `null`.
  `EOFException` - if the stream reaches the end before reading all the bytes.
  `IOException` - if an I/O error occurs.

### getStreamPosition

long getStreamPosition() throws IOException
Returns the current byte position of the stream. The next read will take place starting at this offset.

Returns:
  a long containing the position of the stream.
Throws:
  `IOException` - if an I/O error occurs.

### getBitOffset

int getBitOffset() 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 `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.

The bit offset is set to 0 when a stream is first opened, and is reset to 0 by calls to `seek`, `skipBytes`, or any `read` or `readFully` method.

Returns:
  an `int` containing the bit offset between 0 and 7, inclusive.
Throws:
  `IOException` - if an I/O error occurs.
See Also:
  - `setBitOffset(int)`

### setBitOffset

void setBitOffset(int bitOffset) throws IOException
Sets the bit offset to an integer between 0 and 7, inclusive. The byte offset within the stream, as returned by `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.

Parameters:
  `bitOffset` - the desired offset, as an `int` between 0 and 7, inclusive.
Throws:
  `IllegalArgumentException` - if `bitOffset` is not between 0 and 7, inclusive.
  `IOException` - if an I/O error occurs.
See Also:
  - `getBitOffset()`

### readBit

int readBit() throws IOException
Reads a single bit from the stream and returns it as an `int` with the value `0` or `1`. The bit offset is advanced by one and reduced modulo 8.

Returns:
  an `int` containing the value `0` or `1`.
Throws:
  `EOFException` - if the stream reaches the end before reading all the bits.
  `IOException` - if an I/O error occurs.

### readBits

long readBits(int numBits) throws IOException
Reads a bitstring from the stream and returns it as a `long`, with the first bit read becoming the most significant bit of the output. The read starts within the byte indicated by `getStreamPosition`, at the bit given by `getBitOffset`. The bit offset is advanced by `numBits` and reduced modulo 8.

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:

    long accum = 0L;
    for (int i = 0; i < numBits; i++) {
      accum <<= 1; // Shift left one bit to make room
      accum |= readBit();
    }

Note that the result of `readBits(32)` may thus not be equal to that of `readInt()` if a reverse network byte order is being used (i.e., `getByteOrder() == false`).

If the end of the stream is encountered before all the bits have been read, a `java.io.EOFException` is thrown.

Parameters:
  `numBits` - the number of bits to read, as an `int` between 0 and 64, inclusive.
Returns:
  the bitstring, as a `long` with the last bit read stored in the least significant bit.
Throws:
  `IllegalArgumentException` - if `numBits` is not between 0 and 64, inclusive.
  `EOFException` - if the stream reaches the end before reading all the bits.
  `IOException` - if an I/O error occurs.

### length

long length() throws IOException
Returns the total length of the stream, if known. Otherwise, `-1` is returned.

Returns:
  a `long` containing the length of the stream, if known, or else `-1`.
Throws:
  `IOException` - if an I/O error occurs.

### skipBytes

int skipBytes(int n) 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.

Specified by:
  `skipBytes` in interface `DataInput`
Parameters:
  `n` - an `int` containing the number of bytes to be skipped.
Returns:
  an `int` representing the number of bytes skipped.
Throws:
  `IOException` - if an I/O error occurs.

### skipBytes

long skipBytes(long n) throws IOException
Moves the stream position forward by a given number of bytes. This method is identical to `skipBytes(int)` except that it allows for a larger skip distance.

Parameters:
  `n` - a `long` containing the number of bytes to be skipped.
Returns:
  a `long` representing the number of bytes skipped.
Throws:
  `IOException` - if an I/O error occurs.

### seek

void seek(long pos) 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.

An `IndexOutOfBoundsException` will be thrown if `pos` is smaller than the flushed position (as returned by `getflushedPosition`).

It is legal to seek past the end of the file; a `java.io.EOFException` will be thrown only if a read is performed.

Parameters:
  `pos` - a `long` containing the desired file pointer position.
Throws:
  `IndexOutOfBoundsException` - if `pos` is smaller than the flushed position.
  `IOException` - if any other I/O error occurs.

### mark

void mark()
Marks a position in the stream to be returned to by a subsequent call to `reset`. Unlike a standard `InputStream`, all `ImageInputStream`s support marking. Additionally, calls to `mark` and `reset` may be nested arbitrarily.

Unlike the `mark` methods declared by the `Reader` and `InputStream` interfaces, no `readLimit` parameter is used. An arbitrary amount of data may be read following the call to `mark`.

The bit position used by the `readBits` method is saved and restored by each pair of calls to `mark` and `reset`.

Note that it is valid for an `ImageReader` to call `flushBefore` as part of a read operation. Therefore, if an application calls `mark` prior to passing that stream to an `ImageReader`, the application should not assume that the marked position will remain valid after the read operation has completed.

### reset

void reset() throws IOException
Returns the stream pointer to its previous position, including the bit offset, at the time of the most recent unmatched call to `mark`.

Calls to `reset` without a corresponding call to `mark` have no effect.

An `IOException` will be thrown if the previous marked position lies in the discarded portion of the stream.

Throws:
  `IOException` - if an I/O error occurs.

### flushBefore

void flushBefore(long pos) 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 `IndexOutOfBoundsException`.

Calling `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.

Parameters:
  `pos` - a `long` containing the length of the stream prefix that may be flushed.
Throws:
  `IndexOutOfBoundsException` - if `pos` lies in the flushed portion of the stream or past the current stream position.
  `IOException` - if an I/O error occurs.

### flush

void flush() throws IOException
Discards the initial position of the stream prior to the current stream position. Equivalent to `flushBefore(getStreamPosition())`.

Throws:
  `IOException` - if an I/O error occurs.

### getFlushedPosition

long getFlushedPosition()
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 `flushBefore`.

Returns:
  the earliest legal position for seeking, as a `long`.

### isCached

boolean isCached()
Returns `true` if this `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.

Returns:
  `true` if this `ImageInputStream` caches data.
See Also:
  - `isCachedMemory()`
  - `isCachedFile()`

### isCachedMemory

boolean isCachedMemory()
Returns `true` if this `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.

Returns:
  `true` if this `ImageInputStream` caches data in main memory.
See Also:
  - `isCached()`
  - `isCachedFile()`

### isCachedFile

boolean isCachedFile()
Returns `true` if this `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.

Returns:
  `true` if this `ImageInputStream` caches data in a temporary file.
See Also:
  - `isCached()`
  - `isCachedMemory()`

### close

void close() throws IOException
Closes the stream. Attempts to access a stream that has been closed may result in `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.

Specified by:
  `close` in interface `AutoCloseable`
Specified by:
  `close` in interface `Closeable`
Throws:
  `IOException` - if an I/O error occurs.