Interface ImageInputStream
- All Superinterfaces:
-
AutoCloseable
,Closeable
,DataInput
- All Known Subinterfaces:
ImageOutputStream
- All Known Implementing Classes:
-
FileCacheImageInputStream
,FileCacheImageOutputStream
,FileImageInputStream
,FileImageOutputStream
,ImageInputStreamImpl
,ImageOutputStreamImpl
,MemoryCacheImageInputStream
,MemoryCacheImageOutputStream
public interface ImageInputStream extends DataInput, Closeable
A seekable input stream interface for use by ImageReader
s. Various input sources, such as InputStream
s and File
s, as well as future fast I/O sources may be "wrapped" by a suitable implementation of this interface for use by the Image I/O API.
- See Also:
-
ImageInputStreamImpl
,FileImageInputStream
,FileCacheImageInputStream
,MemoryCacheImageInputStream
Method Summary
Modifier and Type | Method | Description |
---|---|---|
void | close() | Closes the stream. |
void | flush() | Discards the initial position of the stream prior to the current stream position. |
void | flushBefore(long pos) | Discards the initial portion of the stream prior to the indicated position. |
int | getBitOffset() | Returns the current bit offset, as an integer between 0 and 7, inclusive. |
ByteOrder | getByteOrder() | Returns the byte order with which data values will be read from this stream as an instance of the |
long | getFlushedPosition() | Returns the earliest position in the stream to which seeking may be performed. |
long | getStreamPosition() | Returns the current byte position of the stream. |
boolean | isCached() | Returns |
boolean | isCachedFile() | Returns |
boolean | isCachedMemory() | Returns |
long | length() | Returns the total length of the stream, if known. |
void | mark() | Marks a position in the stream to be returned to by a subsequent call to |
int | read() | Reads a single byte from the stream and returns it as an integer between 0 and 255. |
int | read(byte[] b) | Reads up to |
int | read(byte[] b,
int off,
int len) | Reads up to |
int | readBit() | Reads a single bit from the stream and returns it as an |
long | readBits(int numBits) | Reads a bitstring from the stream and returns it as a |
boolean | readBoolean() | Reads a byte from the stream and returns a |
byte | readByte() | Reads a byte from the stream and returns it as a |
void | readBytes(IIOByteBuffer buf,
int len) | Reads up to |
char | readChar() | Equivalent to |
double | readDouble() | Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a |
float | readFloat() | Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a |
void | readFully(byte[] b) | Reads |
void | readFully(byte[] b,
int off,
int len) | Reads |
void | readFully(char[] c,
int off,
int len) | Reads |
void | readFully(double[] d,
int off,
int len) | Reads |
void | readFully(float[] f,
int off,
int len) | Reads |
void | readFully(int[] i,
int off,
int len) | Reads |
void | readFully(long[] l,
int off,
int len) | Reads |
void | readFully(short[] s,
int off,
int len) | Reads |
int | readInt() | Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an |
String | readLine() | Reads the next line of text from the input stream. |
long | readLong() | Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a |
short | readShort() | Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a |
int | readUnsignedByte() | Reads a byte from the stream, and (conceptually) converts it to an int, masks it with |
long | readUnsignedInt() | Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the result to a long, masks it with |
int | readUnsignedShort() | Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an |
String | readUTF() | Reads in a string that has been encoded using a modified UTF-8 format. |
void | reset() | Returns the stream pointer to its previous position, including the bit offset, at the time of the most recent unmatched call to |
void | seek(long pos) | Sets the current stream position to the desired location. |
void | setBitOffset(int bitOffset) | Sets the bit offset to an integer between 0 and 7, inclusive. |
void | setByteOrder(ByteOrder byteOrder) | Sets the desired byte order for future reads of data values from this stream. |
int | skipBytes(int n) | Moves the stream position forward by a given number of bytes. |
long | skipBytes(long n) | Moves the stream position forward by a given number of bytes. |
Method Detail
setByteOrder
void setByteOrder(ByteOrder byteOrder)
Sets the desired byte order for future reads of data values from this stream. For example, the sequence of bytes '0x01 0x02 0x03 0x04' if read as a 4-byte integer would have the value '0x01020304' using network byte order and the value '0x04030201' under the reverse byte order.
The enumeration class java.nio.ByteOrder
is used to specify the byte order. A value of ByteOrder.BIG_ENDIAN
specifies so-called big-endian or network byte order, in which the high-order byte comes first. Motorola and Sparc processors store data in this format, while Intel processors store data in the reverse ByteOrder.LITTLE_ENDIAN
order.
The byte order has no effect on the results returned from the readBits
method (or the value written by ImageOutputStream.writeBits
).
- Parameters:
-
byteOrder
- one ofByteOrder.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 the java.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
- 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
- ifb
isnull
. -
IOException
- if an I/O error occurs.
read
int read(byte[] b, int off, int len) throws IOException
Reads up to len
bytes from the stream, and stores them into b
starting at index off
. The number of bytes read is returned. If no bytes can be read because the end of the stream has been reached, -1
is returned.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
b
- an array of bytes to be written to. -
off
- the starting position withinb
to write to. -
len
- the maximum number ofbyte
s to read. - Returns:
- the number of bytes actually read, or
-1
to indicate EOF. - Throws:
-
NullPointerException
- ifb
isnull
. -
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thanb.length
. -
IOException
- if an I/O error occurs.
readBytes
void readBytes(IIOByteBuffer buf, int len) throws IOException
Reads up to len
bytes from the stream, and modifies the supplied IIOByteBuffer
to indicate the byte array, offset, and length where the data may be found. The caller should not attempt to modify the data found in the IIOByteBuffer
.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
buf
- an IIOByteBuffer object to be modified. -
len
- the maximum number ofbyte
s to read. - Throws:
-
IndexOutOfBoundsException
- iflen
is negative. -
NullPointerException
- ifbuf
isnull
. -
IOException
- if an I/O error occurs.
readBoolean
boolean readBoolean() throws IOException
Reads a byte from the stream and returns a boolean
value of true
if it is nonzero, false
if it is zero.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readBoolean
in interfaceDataInput
- Returns:
- a boolean value from the stream.
- Throws:
-
EOFException
- if the end of the stream is reached. -
IOException
- if an I/O error occurs.
readByte
byte readByte() throws IOException
Reads a byte from the stream and returns it as a byte
value. Byte values between 0x00
and 0x7f
represent integer values between 0
and 127
. Values between 0x80
and 0xff
represent negative values from -128
to /1
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readByte
in interfaceDataInput
- Returns:
- a signed byte value from the stream.
- Throws:
-
EOFException
- if the end of the stream is reached. -
IOException
- if an I/O error occurs.
readUnsignedByte
int readUnsignedByte() throws IOException
Reads a byte from the stream, and (conceptually) converts it to an int, masks it with 0xff
in order to strip off any sign-extension bits, and returns it as a byte
value.
Thus, byte values between 0x00
and 0x7f
are simply returned as integer values between 0
and 127
. Values between 0x80
and 0xff
, which normally represent negative byte
values, will be mapped into positive integers between 128
and 255
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readUnsignedByte
in interfaceDataInput
- Returns:
- an unsigned byte value from the stream.
- Throws:
-
EOFException
- if the end of the stream is reached. -
IOException
- if an I/O error occurs.
readShort
short readShort() throws IOException
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a short
value.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readShort
in interfaceDataInput
- Returns:
- a signed short value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readUnsignedShort
int readUnsignedShort() throws IOException
Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an int
, masks it with 0xffff
in order to strip off any sign-extension buts, and returns the result as an unsigned int
value.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readUnsignedShort
in interfaceDataInput
- Returns:
- an unsigned short value from the stream, as an int.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readChar
char readChar() throws IOException
Equivalent to readUnsignedShort
, except that the result is returned using the char
datatype.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readChar
in interfaceDataInput
- Returns:
- an unsigned char value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
readUnsignedShort()
readInt
int readInt() throws IOException
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an int
.
The bit offset within the stream is ignored and treated as though it were zero.
- Specified by:
-
readInt
in interfaceDataInput
- Returns:
- a signed int value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readUnsignedInt
long readUnsignedInt() throws IOException
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the result to a long, masks it with 0xffffffffL
in order to strip off any sign-extension bits, and returns the result as an unsigned long
value.
The bit offset within the stream is reset to zero before the read occurs.
- Returns:
- an unsigned int value from the stream, as a long.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readLong
long readLong() throws IOException
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a long
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readLong
in interfaceDataInput
- Returns:
- a signed long value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readFloat
float readFloat() throws IOException
Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a float
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readFloat
in interfaceDataInput
- Returns:
- a float value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readDouble
double readDouble() throws IOException
Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a double
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readDouble
in interfaceDataInput
- Returns:
- a double value from the stream.
- Throws:
-
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs. - See Also:
getByteOrder()
readLine
String readLine() throws IOException
Reads the next line of text from the input stream. It reads successive bytes, converting each byte separately into a character, until it encounters a line terminator or end of file; the characters read are then returned as a String
. Note that because this method processes bytes, it does not support input of the full Unicode character set.
If end of file is encountered before even one byte can be read, then null
is returned. Otherwise, each byte that is read is converted to type char
by zero-extension. If the character '\n'
is encountered, it is discarded and reading ceases. If the character '\r'
is encountered, it is discarded and, if the following byte converts to the character '\n'
, then that is discarded also; reading then ceases. If end of file is encountered before either of the characters '\n'
and '\r'
is encountered, reading ceases. Once reading has ceased, a String
is returned that contains all the characters read and not discarded, taken in order. Note that every character in this string will have a value less than \u0100
, that is, (char)256
.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readLine
in interfaceDataInput
- Returns:
- a String containing a line of text from the stream.
- Throws:
-
IOException
- if an I/O error occurs.
readUTF
String readUTF() throws IOException
Reads in a string that has been encoded using a modified UTF-8 format. The general contract of readUTF
is that it reads a representation of a Unicode character string encoded in modified UTF-8 format; this string of characters is then returned as a String
.
First, two bytes are read and used to construct an unsigned 16-bit integer in the manner of the readUnsignedShort
method, using network byte order (regardless of the current byte order setting). This integer value is called the UTF length and specifies the number of additional bytes to be read. These bytes are then converted to characters by considering them in groups. The length of each group is computed from the value of the first byte of the group. The byte following a group, if any, is the first byte of the next group.
If the first byte of a group matches the bit pattern 0xxxxxxx
(where x
means "may be 0
or 1
"), then the group consists of just that byte. The byte is zero-extended to form a character.
If the first byte of a group matches the bit pattern 110xxxxx
, then the group consists of that byte a
and a second byte b
. If there is no byte b
(because byte a
was the last of the bytes to be read), or if byte b
does not match the bit pattern 10xxxxxx
, then a UTFDataFormatException
is thrown. Otherwise, the group is converted to the character:
(char)(((a& 0x1F) << 6) | (b & 0x3F))If the first byte of a group matches the bit pattern
1110xxxx
, then the group consists of that byte a
and two more bytes b
and c
. If there is no byte c
(because byte a
was one of the last two of the bytes to be read), or either byte b
or byte c
does not match the bit pattern 10xxxxxx
, then a UTFDataFormatException
is thrown. Otherwise, the group is converted to the character: (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))If the first byte of a group matches the pattern
1111xxxx
or the pattern 10xxxxxx
, then a UTFDataFormatException
is thrown. If end of file is encountered at any time during this entire process, then a java.io.EOFException
is thrown.
After every group has been converted to a character by this process, the characters are gathered, in the same order in which their corresponding groups were read from the input stream, to form a String
, which is returned.
The current byte order setting is ignored.
The bit offset within the stream is reset to zero before the read occurs.
Note: This method should not be used in the implementation of image formats that use standard UTF-8, because the modified UTF-8 used here is incompatible with standard UTF-8.
- Specified by:
-
readUTF
in interfaceDataInput
- Returns:
- a String read from the stream.
- Throws:
-
EOFException
- if this stream reaches the end before reading all the bytes. -
UTFDataFormatException
- if the bytes do not represent a valid modified UTF-8 encoding of a string. -
IOException
- if an I/O error occurs.
readFully
void readFully(byte[] b, int off, int len) throws IOException
Reads len
bytes from the stream, and stores them into b
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readFully
in interfaceDataInput
- Parameters:
-
b
- an array of bytes to be written to. -
off
- the starting position withinb
to write to. -
len
- the maximum number ofbyte
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thanb.length
. -
NullPointerException
- ifb
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(byte[] b) throws IOException
Reads b.length
bytes from the stream, and stores them into b
starting at index 0
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Specified by:
-
readFully
in interfaceDataInput
- Parameters:
-
b
- an array ofbyte
s. - Throws:
-
NullPointerException
- ifb
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(short[] s, int off, int len) throws IOException
Reads len
shorts (signed 16-bit integers) from the stream according to the current byte order, and stores them into s
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
s
- an array of shorts to be written to. -
off
- the starting position withins
to write to. -
len
- the maximum number ofshort
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thans.length
. -
NullPointerException
- ifs
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(char[] c, int off, int len) throws IOException
Reads len
chars (unsigned 16-bit integers) from the stream according to the current byte order, and stores them into c
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
c
- an array of chars to be written to. -
off
- the starting position withinc
to write to. -
len
- the maximum number ofchar
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thanc.length
. -
NullPointerException
- ifc
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(int[] i, int off, int len) throws IOException
Reads len
ints (signed 32-bit integers) from the stream according to the current byte order, and stores them into i
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
i
- an array of ints to be written to. -
off
- the starting position withini
to write to. -
len
- the maximum number ofint
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thani.length
. -
NullPointerException
- ifi
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(long[] l, int off, int len) throws IOException
Reads len
longs (signed 64-bit integers) from the stream according to the current byte order, and stores them into l
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
l
- an array of longs to be written to. -
off
- the starting position withinl
to write to. -
len
- the maximum number oflong
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thanl.length
. -
NullPointerException
- ifl
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(float[] f, int off, int len) throws IOException
Reads len
floats (32-bit IEEE single-precision floats) from the stream according to the current byte order, and stores them into f
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
f
- an array of floats to be written to. -
off
- the starting position withinf
to write to. -
len
- the maximum number offloat
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thanf.length
. -
NullPointerException
- iff
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
readFully
void readFully(double[] d, int off, int len) throws IOException
Reads len
doubles (64-bit IEEE double-precision floats) from the stream according to the current byte order, and stores them into d
starting at index off
. If the end of the stream is reached, a java.io.EOFException
will be thrown.
The bit offset within the stream is reset to zero before the read occurs.
- Parameters:
-
d
- an array of doubles to be written to. -
off
- the starting position withind
to write to. -
len
- the maximum number ofdouble
s to read. - Throws:
-
IndexOutOfBoundsException
- ifoff
is negative,len
is negative, oroff + len
is greater thand.length
. -
NullPointerException
- ifd
isnull
. -
EOFException
- if the stream reaches the end before reading all the bytes. -
IOException
- if an I/O error occurs.
getStreamPosition
long getStreamPosition() throws IOException
Returns the current byte position of the stream. The next read will take place starting at this offset.
- Returns:
- a long containing the position of the stream.
- Throws:
-
IOException
- if an I/O error occurs.
getBitOffset
int getBitOffset() throws IOException
Returns the current bit offset, as an integer between 0 and 7, inclusive. The bit offset is updated implicitly by calls to the readBits
method. A value of 0 indicates the most-significant bit, and a value of 7 indicates the least significant bit, of the byte being read.
The bit offset is set to 0 when a stream is first opened, and is reset to 0 by calls to seek
, skipBytes
, or any read
or readFully
method.
- Returns:
- an
int
containing the bit offset between 0 and 7, inclusive. - Throws:
-
IOException
- if an I/O error occurs. - See Also:
setBitOffset(int)
setBitOffset
void setBitOffset(int bitOffset) throws IOException
Sets the bit offset to an integer between 0 and 7, inclusive. The byte offset within the stream, as returned by getStreamPosition
, is left unchanged. A value of 0 indicates the most-significant bit, and a value of 7 indicates the least significant bit, of the byte being read.
- Parameters:
-
bitOffset
- the desired offset, as anint
between 0 and 7, inclusive. - Throws:
-
IllegalArgumentException
- ifbitOffset
is not between 0 and 7, inclusive. -
IOException
- if an I/O error occurs. - See Also:
getBitOffset()
readBit
int readBit() throws IOException
Reads a single bit from the stream and returns it as an int
with the value 0
or 1
. The bit offset is advanced by one and reduced modulo 8.
- Returns:
- an
int
containing the value0
or1
. - Throws:
-
EOFException
- if the stream reaches the end before reading all the bits. -
IOException
- if an I/O error occurs.
readBits
long readBits(int numBits) throws IOException
Reads a bitstring from the stream and returns it as a long
, with the first bit read becoming the most significant bit of the output. The read starts within the byte indicated by getStreamPosition
, at the bit given by getBitOffset
. The bit offset is advanced by numBits
and reduced modulo 8.
The byte order of the stream has no effect on this method. The return value of this method is constructed as though the bits were read one at a time, and shifted into the right side of the return value, as shown by the following pseudo-code:
long accum = 0L; for (int i = 0; i < numBits; i++) { accum <<= 1; // Shift left one bit to make room accum |= readBit(); }Note that the result of
readBits(32)
may thus not be equal to that of readInt()
if a reverse network byte order is being used (i.e., getByteOrder() == false
). If the end of the stream is encountered before all the bits have been read, a java.io.EOFException
is thrown.
- Parameters:
-
numBits
- the number of bits to read, as anint
between 0 and 64, inclusive. - Returns:
- the bitstring, as a
long
with the last bit read stored in the least significant bit. - Throws:
-
IllegalArgumentException
- ifnumBits
is not between 0 and 64, inclusive. -
EOFException
- if the stream reaches the end before reading all the bits. -
IOException
- if an I/O error occurs.
length
long length() throws IOException
Returns the total length of the stream, if known. Otherwise, -1
is returned.
- Returns:
- a
long
containing the length of the stream, if known, or else-1
. - Throws:
-
IOException
- if an I/O error occurs.
skipBytes
int skipBytes(int n) throws IOException
Moves the stream position forward by a given number of bytes. It is possible that this method will only be able to skip forward by a smaller number of bytes than requested, for example if the end of the stream is reached. In all cases, the actual number of bytes skipped is returned. The bit offset is set to zero prior to advancing the position.
- Specified by:
-
skipBytes
in interfaceDataInput
- Parameters:
-
n
- anint
containing the number of bytes to be skipped. - Returns:
- an
int
representing the number of bytes skipped. - Throws:
-
IOException
- if an I/O error occurs.
skipBytes
long skipBytes(long n) throws IOException
Moves the stream position forward by a given number of bytes. This method is identical to skipBytes(int)
except that it allows for a larger skip distance.
- Parameters:
-
n
- along
containing the number of bytes to be skipped. - Returns:
- a
long
representing the number of bytes skipped. - Throws:
-
IOException
- if an I/O error occurs.
seek
void seek(long pos) throws IOException
Sets the current stream position to the desired location. The next read will occur at this location. The bit offset is set to 0.
An IndexOutOfBoundsException
will be thrown if pos
is smaller than the flushed position (as returned by getflushedPosition
).
It is legal to seek past the end of the file; a java.io.EOFException
will be thrown only if a read is performed.
- Parameters:
-
pos
- along
containing the desired file pointer position. - Throws:
-
IndexOutOfBoundsException
- ifpos
is smaller than the flushed position. -
IOException
- if any other I/O error occurs.
mark
void mark()
Marks a position in the stream to be returned to by a subsequent call to reset
. Unlike a standard InputStream
, all ImageInputStream
s support marking. Additionally, calls to mark
and reset
may be nested arbitrarily.
Unlike the mark
methods declared by the Reader
and InputStream
interfaces, no readLimit
parameter is used. An arbitrary amount of data may be read following the call to mark
.
The bit position used by the readBits
method is saved and restored by each pair of calls to mark
and reset
.
Note that it is valid for an ImageReader
to call flushBefore
as part of a read operation. Therefore, if an application calls mark
prior to passing that stream to an ImageReader
, the application should not assume that the marked position will remain valid after the read operation has completed.
reset
void reset() throws IOException
Returns the stream pointer to its previous position, including the bit offset, at the time of the most recent unmatched call to mark
.
Calls to reset
without a corresponding call to mark
have no effect.
An IOException
will be thrown if the previous marked position lies in the discarded portion of the stream.
- Throws:
-
IOException
- if an I/O error occurs.
flushBefore
void flushBefore(long pos) throws IOException
Discards the initial portion of the stream prior to the indicated position. Attempting to seek to an offset within the flushed portion of the stream will result in an IndexOutOfBoundsException
.
Calling flushBefore
may allow classes implementing this interface to free up resources such as memory or disk space that are being used to store data from the stream.
- Parameters:
-
pos
- along
containing the length of the stream prefix that may be flushed. - Throws:
-
IndexOutOfBoundsException
- ifpos
lies in the flushed portion of the stream or past the current stream position. -
IOException
- if an I/O error occurs.
flush
void flush() throws IOException
Discards the initial position of the stream prior to the current stream position. Equivalent to flushBefore(getStreamPosition())
.
- Throws:
-
IOException
- if an I/O error occurs.
getFlushedPosition
long getFlushedPosition()
Returns the earliest position in the stream to which seeking may be performed. The returned value will be the maximum of all values passed into previous calls to flushBefore
.
- Returns:
- the earliest legal position for seeking, as a
long
.
isCached
boolean isCached()
Returns true
if this ImageInputStream
caches data itself in order to allow seeking backwards. Applications may consult this in order to decide how frequently, or whether, to flush in order to conserve cache resources.
- Returns:
-
true
if thisImageInputStream
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 thisImageInputStream
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 thisImageInputStream
caches data in a temporary file. - See Also:
-
isCached()
,isCachedMemory()
close
void close() throws IOException
Closes the stream. Attempts to access a stream that has been closed may result in IOException
s or incorrect behavior. Calling this method may allow classes implementing this interface to release resources associated with the stream such as memory, disk space, or file descriptors.
- Specified by:
-
close
in interfaceAutoCloseable
- Specified by:
-
close
in interfaceCloseable
- Throws:
-
IOException
- if an I/O error occurs.