java.lang.Object | |
↳ | javax.imageio.stream.ImageInputStreamImpl |
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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.
Fields | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
bitOffset | The current bit offset within the stream. | ||||||||||
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. |
||||||||||
flushedPos | The position prior to which data may be discarded. | ||||||||||
streamPos | The current read position within the stream. |
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Constructs an
ImageInputStreamImpl . |
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Closes the stream.
| |||||||||||
Discards the initial position of the stream prior to the current
stream position.
| |||||||||||
Discards the initial portion of the stream prior to the
indicated postion.
| |||||||||||
Returns the current bit offset, as an integer between 0 and 7,
inclusive.
| |||||||||||
Returns the byte order with which data values will be read from
this stream as an instance of the
java.nio.ByteOrder enumeration. | |||||||||||
Returns the earliest position in the stream to which seeking
may be performed.
| |||||||||||
Returns the current byte position of the stream.
| |||||||||||
Default implementation returns false.
| |||||||||||
Default implementation returns false.
| |||||||||||
Default implementation returns false.
| |||||||||||
Returns
-1L to indicate that the stream has unknown
length. | |||||||||||
Pushes the current stream position onto a stack of marked
positions.
| |||||||||||
Reads up to
len bytes from the stream, and stores
them into b starting at index off . | |||||||||||
A convenience method that calls
read(b, 0, b.length) . | |||||||||||
Reads a single byte from the stream and returns it as an
int between 0 and 255. | |||||||||||
Reads a single bit from the stream and returns it as an
int with the value 0 or
1 . | |||||||||||
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. | |||||||||||
Reads a byte from the stream and returns a
boolean
value of true if it is nonzero, false
if it is zero. | |||||||||||
Reads a byte from the stream and returns it as a
byte value. | |||||||||||
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. | |||||||||||
Equivalent to
readUnsignedShort , except that the
result is returned using the char datatype. | |||||||||||
Reads 8 bytes from the stream, and (conceptually) concatenates
them according to the current byte order and returns the result
as a
double . | |||||||||||
Reads 4 bytes from the stream, and (conceptually) concatenates
them according to the current byte order and returns the result
as a
float . | |||||||||||
Reads
b.length bytes from the stream, and stores them
into b starting at index 0 . | |||||||||||
Reads
len bytes from the stream, and stores them
into b starting at index off . | |||||||||||
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 . | |||||||||||
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 . | |||||||||||
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 . | |||||||||||
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 . | |||||||||||
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 . | |||||||||||
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 . | |||||||||||
Reads 4 bytes from the stream, and (conceptually) concatenates
them according to the current byte order and returns the result
as an
int . | |||||||||||
Reads the next line of text from the input stream.
| |||||||||||
Reads 8 bytes from the stream, and (conceptually) concatenates
them according to the current byte order and returns the result
as a
long . | |||||||||||
Reads two bytes from the stream, and (conceptually)
concatenates them according to the current byte order, and
returns the result as a
short value. | |||||||||||
Reads in a string that has been encoded using a
modified
UTF-8
format.
| |||||||||||
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. | |||||||||||
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. | |||||||||||
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. | |||||||||||
Resets the current stream byte and bit positions from the stack
of marked positions.
| |||||||||||
Sets the current stream position to the desired location.
| |||||||||||
Sets the bit offset to an integer between 0 and 7, inclusive.
| |||||||||||
Sets the desired byte order for future reads of data values
from this stream.
| |||||||||||
Advances the current stream position by calling
seek(getStreamPosition() + n) . | |||||||||||
Advances the current stream position by calling
seek(getStreamPosition() + n) . |
Protected Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Throws an
IOException if the stream has been closed. | |||||||||||
Finalizes this object prior to garbage collection.
|
[Expand]
Inherited Methods | |||||||||||
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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.
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
.
The position prior to which data may be discarded. Seeking
to a smaller position is not allowed. flushedPos
will always be >= 0.
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.
Constructs an ImageInputStreamImpl
.
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.
IOException |
---|
Discards the initial position of the stream prior to the current
stream position. Equivalent to
flushBefore(getStreamPosition())
.
IOException |
---|
Discards the initial portion of the stream prior to the
indicated postion. Attempting to seek to an offset within the
flushed portion of the stream will result in an
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.
pos | a long containing the length of the
stream prefix that may be flushed. |
---|
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.
int
containing the bit offset between
0 and 7, inclusive.IOException |
---|
Returns the byte order with which data values will be read from
this stream as an instance of the
java.nio.ByteOrder
enumeration.
ByteOrder.BIG_ENDIAN
or
ByteOrder.LITTLE_ENDIAN
, indicating which byte
order is being used.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
.
long
.
Returns the current byte position of the stream. The next read will take place starting at this offset.
IOException |
---|
Default implementation returns false. Subclasses should override this if they cache data.
true
if this ImageInputStream
caches data.Default implementation returns false. Subclasses should override this if they cache data in a temporary file.
true
if this ImageInputStream
caches data in a temporary file.Default implementation returns false. Subclasses should override this if they cache data in main memory.
true
if this ImageInputStream
caches data in main memory.Returns -1L
to indicate that the stream has unknown
length. Subclasses must override this method to provide actual
length information.
Pushes the current stream position onto a stack of marked positions.
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.
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. |
A convenience method that calls read(b, 0, b.length)
.
The bit offset within the stream is reset to zero before the read occurs.
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. |
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.
-1
if EOF is reached.IOException | if the stream has been closed. |
---|
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.
int
containing the value 0
or 1
.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, an EOFException
is thrown.
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.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.
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.
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.
buf | an IIOByteBuffer object to be modified. |
---|---|
len | the maximum number of byte s to read. |
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.
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.
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.
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.
b | an array of byte s. |
---|
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.
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. |
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, an
EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
c | an array of chars to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of char s to read. |
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, an
EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
i | an array of ints to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of int s to read. |
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.
f | an array of floats to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of float s to read. |
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, an
EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
s | an array of shorts to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of short s to read. |
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.
d | an array of doubles to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of double s to read. |
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, an
EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
l | an array of longs to be written to. |
---|---|
off | the starting position withinb to write to. |
len | the maximum number of long s to read. |
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
IOException | if an I/O error occurs. |
---|
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
EOFException
will be thrown only if a read is
performed.
pos | a long containing the desired file
pointer position. |
---|
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.
bitOffset | the desired offset, as an int
between 0 and 7, inclusive. |
---|
IOException |
---|
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
).
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. |
---|
Advances the current stream position by calling
seek(getStreamPosition() + n)
.
The bit offset is reset to zero.
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.
|
---|
Advances the current stream position by calling
seek(getStreamPosition() + n)
.
The bit offset is reset to zero.
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.
|
---|
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. |
---|
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.
Throwable | if an error occurs during superclass finalization. |
---|