ImageInputStream (Java 2 Platform SE 5.0) (original) (raw)

javax.imageio.stream

Interface ImageInputStream

All Superinterfaces:

DataInput

All Known Subinterfaces:

ImageOutputStream

All Known Implementing Classes:

FileCacheImageInputStream, FileCacheImageOutputStream, FileImageInputStream, FileImageOutputStream, ImageInputStreamImpl, ImageOutputStreamImpl, MemoryCacheImageInputStream, MemoryCacheImageOutputStream

public interface ImageInputStream

extends DataInput

A seekable input stream interface for use byImageReaders. Various input sources, such asInputStreams and Files, 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

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 ofByteOrder.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 reverseByteOrder.LITTLE_ENDIAN order.

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

Parameters:

byteOrder - one of ByteOrder.BIG_ENDIAN orjava.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 thejava.nio.ByteOrder enumeration.

Returns:

one of ByteOrder.BIG_ENDIAN orByteOrder.LITTLE_ENDIAN, indicating which byte order is being used.

See Also:

ByteOrder, setByteOrder(java.nio.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](../../../java/io/IOException.html "class in java.io") - 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](../../../java/lang/NullPointerException.html "class in java.lang") - if b isnull.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 bytes to read.

Returns:

the number of bytes actually read, or -1 to indicate EOF.

Throws:

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if b isnull.

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than b.length.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 theIIOByteBuffer.

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 bytes to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if len is negative.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if buf isnull.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readBoolean%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a boolean value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the end of the stream is reached.

[IOException](../../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

readByte

byte readByte() throws IOException

Reads a byte from the stream and returns it as abyte value. Byte values between 0x00 and 0x7f represent integer values between0 and 127. Values between0x80 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](../../../java/io/DataInput.html#readByte%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a signed byte value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the end of the stream is reached.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 and0x7f are simply returned as integer values between0 and 127. Values between0x80 and 0xff, which normally represent negative bytevalues, will be mapped into positive integers between 128 and255.

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

Specified by:

[readUnsignedByte](../../../java/io/DataInput.html#readUnsignedByte%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

an unsigned byte value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the end of the stream is reached.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readShort%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a signed short value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 with0xffff 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](../../../java/io/DataInput.html#readUnsignedShort%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

an unsigned short value from the stream, as an int.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readChar%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

an unsigned char value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readInt%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a signed int value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readLong%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a signed long value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readFloat%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a float value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#readDouble%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a double value from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 aString. 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, aString 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](../../../java/io/DataInput.html#readLine%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a String containing a line of text from the stream.

Throws:

[IOException](../../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

readUTF

String readUTF() throws IOException

Reads in a string that has been encoded using amodified 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 thereadUnsignedShort 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 pattern0xxxxxxx (where x means "may be0 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 pattern110xxxxx, then the group consists of that bytea 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 aUTFDataFormatException 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 pattern1110xxxx, then the group consists of that bytea and two more bytes b andc. 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 aUTFDataFormatException 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 pattern1111xxxx or the pattern 10xxxxxx, then a UTFDataFormatException is thrown.

If end of file is encountered at any time during this entire process, then an 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](../../../java/io/DataInput.html#readUTF%28%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Returns:

a String read from the stream.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if this stream reaches the end before reading all the bytes.

[UTFDataFormatException](../../../java/io/UTFDataFormatException.html "class in java.io") - if the bytes do not represent a valid modified UTF-8 encoding of a string.

[IOException](../../../java/io/IOException.html "class in java.io") - 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, an EOFException will be thrown.

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

Specified by:

[readFully](../../../java/io/DataInput.html#readFully%28byte[], int, int%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Parameters:

b - an array of bytes to be written to.

off - the starting position within b to write to.

len - the maximum number of bytes to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than b.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if b isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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, an EOFException will be thrown.

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

Specified by:

[readFully](../../../java/io/DataInput.html#readFully%28byte[]%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Parameters:

b - an array of bytes.

Throws:

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if b isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 indexoff. If the end of the stream is reached, anEOFException 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 withinb to write to.

len - the maximum number of shorts to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than s.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if s isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 indexoff. If the end of the stream is reached, anEOFException 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 withinb to write to.

len - the maximum number of chars to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than c.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if c isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 indexoff. If the end of the stream is reached, anEOFException 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 withinb to write to.

len - the maximum number of ints to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than i.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if i isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 indexoff. If the end of the stream is reached, anEOFException 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 withinb to write to.

len - the maximum number of longs to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than l.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if l isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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, an 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 withinb to write to.

len - the maximum number of floats to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than f.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if f isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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, an 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 withinb to write to.

len - the maximum number of doubles to read.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if off is negative, len is negative, or off + len is greater than d.length.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if d isnull.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bytes.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/IOException.html "class in java.io") - 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 bygetStreamPosition, 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](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if bitOffset is not between 0 and 7, inclusive.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 anint with the value 0 or1. The bit offset is advanced by one and reduced modulo 8.

Returns:

an int containing the value 0 or 1.

Throws:

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bits.

[IOException](../../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

readBits

long readBits(int numBits) throws IOException

Reads a bitstring from the stream and returns it as along, 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 bynumBits 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, an 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](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if numBits is not between 0 and 64, inclusive.

[EOFException](../../../java/io/EOFException.html "class in java.io") - if the stream reaches the end before reading all the bits.

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/DataInput.html#skipBytes%28int%29) in interface [DataInput](../../../java/io/DataInput.html "interface in java.io")

Parameters:

n - an int containing the number of bytes to be skipped.

Returns:

an int representing the number of bytes skipped.

Throws:

[IOException](../../../java/io/IOException.html "class in java.io") - 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](../../../java/io/IOException.html "class in java.io") - 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 ifpos is smaller than the flushed position (as returned by getflushedPosition).

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

Parameters:

pos - a long containing the desired file pointer position.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if pos is smaller than the flushed position.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 standardInputStream, all ImageInputStreams support marking. Additionally, calls to mark andreset may be nested arbitrarily.

Unlike the mark methods declared by theReader InputStream interfaces, noreadLimit 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 tomark and reset.

reset

void reset() throws IOException

Returns the file 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](../../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

flushBefore

void flushBefore(long pos) 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 anIndexOutOfBoundsException.

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 file prefix that may be flushed.

Throws:

[IndexOutOfBoundsException](../../../java/lang/IndexOutOfBoundsException.html "class in java.lang") - if pos lies in the flushed portion of the stream or past the current stream position.

[IOException](../../../java/io/IOException.html "class in java.io") - 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 toflushBefore(getStreamPosition()).

Throws:

[IOException](../../../java/io/IOException.html "class in java.io") - 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 toflushBefore.

Returns:

the earliest legal position for seeking, as along.

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 IOExceptions 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.

Throws:

[IOException](../../../java/io/IOException.html "class in java.io") - if an I/O error occurs.

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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