public abstract class ImageInputStreamImpl extends Object implements ImageInputStream
An abstract class implementing the ImageInputStream interface. This class is designed to reduce the number of methods that must be implemented by subclasses.
In particular, this class handles most or all of the details of byte order interpretation, buffering, mark/reset, discarding, closing, and disposing.
protected ByteOrder byteOrder
The byte order of the stream as an instance of the enumeration class java.nio.ByteOrder, where ByteOrder.BIG_ENDIAN indicates network byte order and ByteOrder.LITTLE_ENDIAN indicates the reverse order. By default, the value is ByteOrder.BIG_ENDIAN.
protected long streamPos
The current read position within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the read position.
protected int bitOffset
The current bit offset within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the bit offset.
protected long flushedPos
The position prior to which data may be discarded. Seeking to a smaller position is not allowed. flushedPos will always be >= 0.
public ImageInputStreamImpl()
Constructs an ImageInputStreamImpl.
protected final void checkClosed()
throws IOException Throws an IOException if the stream has been closed. Subclasses may call this method from any of their methods that require the stream not to be closed.
IOException - if the stream is closed.public void setByteOrder(ByteOrder byteOrder)
Description copied from interface: ImageInputStream
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).
setByteOrder in interface ImageInputStream
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.ByteOrder, ImageInputStream.getByteOrder(), ImageInputStream.readBits(int)
public ByteOrder getByteOrder()
Description copied from interface: ImageInputStream
Returns the byte order with which data values will be read from this stream as an instance of the java.nio.ByteOrder enumeration.
getByteOrder in interface ImageInputStream
ByteOrder.BIG_ENDIAN or ByteOrder.LITTLE_ENDIAN, indicating which byte order is being used.ByteOrder, ImageInputStream.setByteOrder(java.nio.ByteOrder)
public abstract int read()
throws IOException Reads a single byte from the stream and returns it as an int between 0 and 255. If EOF is reached, -1 is returned.
Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.
The bit offset within the stream must be reset to zero before the read occurs.
read in interface ImageInputStream
-1 if EOF is reached.IOException - if the stream has been closed.public int read(byte[] b)
throws IOException A convenience method that calls read(b, 0, b.length).
The bit offset within the stream is reset to zero before the read occurs.
read in interface ImageInputStream
b - an array of bytes to be written to.-1 to indicate EOF.NullPointerException - if b is null.IOException - if an I/O error occurs.public abstract 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. If no bytes can be read because the end of the stream has been reached, -1 is returned.
The bit offset within the stream must be reset to zero before the read occurs.
Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.
read in interface ImageInputStream
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.-1 to indicate EOF.IndexOutOfBoundsException - if off is negative, len is negative, or off +
len is greater than b.length.NullPointerException - if b is null.IOException - if an I/O error occurs.public void readBytes(IIOByteBuffer buf,
int len)
throws IOException Description copied from interface: ImageInputStream
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.
readBytes in interface ImageInputStream
buf - an IIOByteBuffer object to be modified.len - the maximum number of bytes to read.IOException - if an I/O error occurs.public boolean readBoolean()
throws IOException Description copied from interface: ImageInputStream
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.
readBoolean in interface DataInput
readBoolean in interface ImageInputStream
EOFException - if the end of the stream is reached.IOException - if an I/O error occurs.public byte readByte()
throws IOException Description copied from interface: ImageInputStream
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.
readByte in interface DataInput
readByte in interface ImageInputStream
EOFException - if the end of the stream is reached.IOException - if an I/O error occurs.public int readUnsignedByte()
throws IOException Description copied from interface: ImageInputStream
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 bytevalues, will be mapped into positive integers between 128 and 255.
The bit offset within the stream is reset to zero before the read occurs.
readUnsignedByte in interface DataInput
readUnsignedByte in interface ImageInputStream
EOFException - if the end of the stream is reached.IOException - if an I/O error occurs.public short readShort()
throws IOException Description copied from interface: ImageInputStream
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.
readShort in interface DataInput
readShort in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public int readUnsignedShort()
throws IOException Description copied from interface: ImageInputStream
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.
readUnsignedShort in interface DataInput
readUnsignedShort in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public char readChar()
throws IOException Description copied from interface: ImageInputStream
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.
readChar in interface DataInput
readChar in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.readUnsignedShort()public int readInt()
throws IOException Description copied from interface: ImageInputStream
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.
readInt in interface DataInput
readInt in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public long readUnsignedInt()
throws IOException Description copied from interface: ImageInputStream
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.
readUnsignedInt in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public long readLong()
throws IOException Description copied from interface: ImageInputStream
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.
readLong in interface DataInput
readLong in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public float readFloat()
throws IOException Description copied from interface: ImageInputStream
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.
readFloat in interface DataInput
readFloat in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public double readDouble()
throws IOException Description copied from interface: ImageInputStream
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.
readDouble in interface DataInput
readDouble in interface ImageInputStream
EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.ImageInputStream.getByteOrder()public String readLine()
throws IOException Description copied from interface: ImageInputStream
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.
readLine in interface DataInput
readLine in interface ImageInputStream
IOException - if an I/O error occurs.public String readUTF()
throws IOException Description copied from interface: ImageInputStream
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 an 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.
readUTF in interface DataInput
readUTF in interface ImageInputStream
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.public void readFully(byte[] b,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
Reads len bytes from the stream, and stores them into b starting at index off. If the end of the stream is reached, an java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface DataInput
readFully in interface ImageInputStream
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.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(byte[] b)
throws IOException Description copied from interface: ImageInputStream
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 java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface DataInput
readFully in interface ImageInputStream
b - an array of bytes.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(short[] s,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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, an java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
s - an array of shorts to be written to.off - the starting position within s to write to.len - the maximum number of shorts to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(char[] c,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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, an java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
c - an array of chars to be written to.off - the starting position within c to write to.len - the maximum number of chars to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(int[] i,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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, an java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
i - an array of ints to be written to.off - the starting position within i to write to.len - the maximum number of ints to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(long[] l,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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, an java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
l - an array of longs to be written to.off - the starting position within l to write to.len - the maximum number of longs to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(float[] f,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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 java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
f - an array of floats to be written to.off - the starting position within f to write to.len - the maximum number of floats to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public void readFully(double[] d,
int off,
int len)
throws IOException Description copied from interface: ImageInputStream
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 java.io.EOFException will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
readFully in interface ImageInputStream
d - an array of doubles to be written to.off - the starting position within d to write to.len - the maximum number of doubles to read.EOFException - if the stream reaches the end before reading all the bytes.IOException - if an I/O error occurs.public long getStreamPosition()
throws IOException Description copied from interface: ImageInputStream
Returns the current byte position of the stream. The next read will take place starting at this offset.
getStreamPosition in interface ImageInputStream
IOException - if an I/O error occurs.public int getBitOffset()
throws IOException Description copied from interface: ImageInputStream
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.
getBitOffset in interface ImageInputStream
int containing the bit offset between 0 and 7, inclusive.IOException - if an I/O error occurs.ImageInputStream.setBitOffset(int)public void setBitOffset(int bitOffset)
throws IOException Description copied from interface: ImageInputStream
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.
setBitOffset in interface ImageInputStream
bitOffset - the desired offset, as an int between 0 and 7, inclusive.IOException - if an I/O error occurs.ImageInputStream.getBitOffset()public int readBit()
throws IOException Description copied from interface: ImageInputStream
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.
readBit in interface ImageInputStream
int containing the value 0 or 1.EOFException - if the stream reaches the end before reading all the bits.IOException - if an I/O error occurs.public long readBits(int numBits)
throws IOException Description copied from interface: ImageInputStream
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, an java.io.EOFException is thrown.
readBits in interface ImageInputStream
numBits - the number of bits to read, as an int between 0 and 64, inclusive.long with the last bit read stored in the least significant bit.EOFException - if the stream reaches the end before reading all the bits.IOException - if an I/O error occurs.public long length()
Returns -1L to indicate that the stream has unknown length. Subclasses must override this method to provide actual length information.
length in interface ImageInputStream
public int skipBytes(int n)
throws IOException Advances the current stream position by calling seek(getStreamPosition() + n).
The bit offset is reset to zero.
skipBytes in interface DataInput
skipBytes in interface ImageInputStream
n - the number of bytes to seek forward.int representing the number of bytes skipped.IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.public long skipBytes(long n)
throws IOException Advances the current stream position by calling seek(getStreamPosition() + n).
The bit offset is reset to zero.
skipBytes in interface ImageInputStream
n - the number of bytes to seek forward.long representing the number of bytes skipped.IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.public void seek(long pos)
throws IOException Description copied from interface: ImageInputStream
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; an java.io.EOFException will be thrown only if a read is performed.
seek in interface ImageInputStream
pos - a long containing the desired file pointer position.IOException - if any other I/O error occurs.public void mark()
Pushes the current stream position onto a stack of marked positions.
mark in interface ImageInputStream
public void reset()
throws IOException Resets the current stream byte and bit positions from the stack of marked positions.
An IOException will be thrown if the previous marked position lies in the discarded portion of the stream.
reset in interface ImageInputStream
IOException - if an I/O error occurs.public void flushBefore(long pos)
throws IOException Description copied from interface: ImageInputStream
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.
flushBefore in interface ImageInputStream
pos - a long containing the length of the stream prefix that may be flushed.IOException - if an I/O error occurs.public void flush()
throws IOException Description copied from interface: ImageInputStream
Discards the initial position of the stream prior to the current stream position. Equivalent to flushBefore(getStreamPosition()).
flush in interface ImageInputStream
IOException - if an I/O error occurs.public long getFlushedPosition()
Description copied from interface: ImageInputStream
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.
getFlushedPosition in interface ImageInputStream
long.public boolean isCached()
Default implementation returns false. Subclasses should override this if they cache data.
isCached in interface ImageInputStream
true if this ImageInputStream caches data.ImageInputStream.isCachedMemory(), ImageInputStream.isCachedFile()
public boolean isCachedMemory()
Default implementation returns false. Subclasses should override this if they cache data in main memory.
isCachedMemory in interface ImageInputStream
true if this ImageInputStream caches data in main memory.ImageInputStream.isCached(), ImageInputStream.isCachedFile()
public boolean isCachedFile()
Default implementation returns false. Subclasses should override this if they cache data in a temporary file.
isCachedFile in interface ImageInputStream
true if this ImageInputStream caches data in a temporary file.ImageInputStream.isCached(), ImageInputStream.isCachedMemory()
public void close()
throws IOException Description copied from interface: ImageInputStream
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.
close in interface Closeable
close in interface AutoCloseable
close in interface ImageInputStream
IOException - if an I/O error occurs.protected void finalize()
throws Throwable Finalizes this object prior to garbage collection. The close method is called to close any open input source. This method should not be called from application code.
finalize in class Object
Throwable - if an error occurs during superclass finalization.WeakReference, PhantomReference
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