java.io.InputStream
java.io.ObjectInputStream.BlockDataInputStream
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java.lang.Object
Input stream with two modes: in default mode, inputs data written in the same format as DataOutputStream; in "block data" mode, inputs data bracketed by block data markers (see object serialization specification for details). Buffering depends on block data mode: when in default mode, no data is buffered in advance; when in block data mode, all data for the current data block is read in at once (and buffered).
| Field Summary | |
private boolean |
blkmode
block data mode |
private byte[] |
buf
buffer for reading general/block data |
private char[] |
cbuf
char buffer for fast string reads |
private static int |
CHAR_BUF_SIZE
(tunable) length of char buffer (for reading strings) |
private DataInputStream |
din
loopback stream (for data reads that span data blocks) |
private int |
end
end offset of valid data in buf, or -1 if no more block data |
private byte[] |
hbuf
buffer for reading block data headers |
private static int |
HEADER_BLOCKED
readBlockHeader() return value indicating header read may block |
private ObjectInputStream.PeekInputStream |
in
underlying stream (wrapped in peekable filter stream) |
private static int |
MAX_BLOCK_SIZE
maximum data block length |
private static int |
MAX_HEADER_SIZE
maximum data block header length |
private int |
pos
current offset into buf |
private int |
unread
number of bytes in current block yet to be read from stream |
| Fields inherited from class java.io.InputStream |
|
| Constructor Summary | |
(package private) |
ObjectInputStream.BlockDataInputStream(InputStream in)
Creates new BlockDataInputStream on top of given underlying stream. |
| Method Summary | |
int |
available()
Returns the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream. |
void |
close()
Closes this input stream and releases any system resources associated with the stream. |
(package private) int |
currentBlockRemaining()
If in block data mode, returns the number of unconsumed bytes remaining in the current data block. |
(package private) boolean |
getBlockDataMode()
Returns true if the stream is currently in block data mode, false otherwise. |
(package private) int |
peek()
Peeks at (but does not consume) and returns the next byte value in the stream, or -1 if the end of the stream/block data (if in block data mode) has been reached. |
(package private) byte |
peekByte()
Peeks at (but does not consume) and returns the next byte value in the stream, or throws EOFException if end of stream/block data has been reached. |
int |
read()
Reads the next byte of data from the input stream. |
int |
read(byte[] b,
int off,
int len)
Reads up to len bytes of data from the input stream into
an array of bytes. |
(package private) int |
read(byte[] b,
int off,
int len,
boolean copy)
Attempts to read len bytes into byte array b at offset off. |
private int |
readBlockHeader(boolean canBlock)
Attempts to read in the next block data header (if any). |
boolean |
readBoolean()
Reads one input byte and returns true if that byte is nonzero,
false if that byte is zero.
|
(package private) void |
readBooleans(boolean[] v,
int off,
int len)
|
byte |
readByte()
Reads and returns one input byte. |
char |
readChar()
Reads an input char and returns the char value.
|
(package private) void |
readChars(char[] v,
int off,
int len)
|
double |
readDouble()
Reads eight input bytes and returns a double value. |
(package private) void |
readDoubles(double[] v,
int off,
int len)
|
float |
readFloat()
Reads four input bytes and returns a float value. |
(package private) void |
readFloats(float[] v,
int off,
int len)
|
void |
readFully(byte[] b)
Reads some bytes from an input stream and stores them into the buffer array b. |
void |
readFully(byte[] b,
int off,
int len)
Reads len
bytes from
an input stream.
|
void |
readFully(byte[] b,
int off,
int len,
boolean copy)
|
int |
readInt()
Reads four input bytes and returns an int value. |
(package private) void |
readInts(int[] v,
int off,
int len)
|
String |
readLine()
Reads the next line of text from the input stream. |
long |
readLong()
Reads eight input bytes and returns a long value. |
(package private) void |
readLongs(long[] v,
int off,
int len)
|
(package private) String |
readLongUTF()
Reads in string written in "long" UTF format. |
short |
readShort()
Reads two input bytes and returns a short value. |
(package private) void |
readShorts(short[] v,
int off,
int len)
|
int |
readUnsignedByte()
Reads one input byte, zero-extends it to type int, and returns
the result, which is therefore in the range
0
through 255.
|
int |
readUnsignedShort()
Reads two input bytes and returns an int value in the range 0
through 65535. |
String |
readUTF()
Reads in a string that has been encoded using a modified UTF-8 format. |
private String |
readUTFBody(long utflen)
Reads in the "body" (i.e., the UTF representation minus the 2-byte or 8-byte length header) of a UTF encoding, which occupies the next utflen bytes. |
private int |
readUTFChar(StringBuffer sbuf,
long utflen)
Reads in single UTF-encoded character one byte at a time, appends the character to sbuf, and returns the number of bytes consumed. |
private long |
readUTFSpan(StringBuffer sbuf,
long utflen)
Reads span of UTF-encoded characters out of internal buffer (starting at offset pos and ending at or before offset end), consuming no more than utflen bytes. |
private void |
refill()
Refills internal buffer buf with block data. |
(package private) boolean |
setBlockDataMode(boolean newmode)
Sets block data mode to the given mode (true == on, false == off) and returns the previous mode value. |
long |
skip(long len)
Skips over and discards n bytes of data from this input
stream. |
(package private) void |
skipBlockData()
If in block data mode, skips to the end of the current group of data blocks (but does not unset block data mode). |
int |
skipBytes(int n)
Makes an attempt to skip over n bytes
of data from the input
stream, discarding the skipped bytes. |
| Methods inherited from class java.io.InputStream |
mark, markSupported, read, reset |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
private static final int MAX_BLOCK_SIZE
private static final int MAX_HEADER_SIZE
private static final int CHAR_BUF_SIZE
private static final int HEADER_BLOCKED
private final byte[] buf
private final byte[] hbuf
private final char[] cbuf
private boolean blkmode
private int pos
private int end
private int unread
private final ObjectInputStream.PeekInputStream in
private final DataInputStream din
| Constructor Detail |
ObjectInputStream.BlockDataInputStream(InputStream in)
| Method Detail |
boolean setBlockDataMode(boolean newmode)
throws IOException
IOExceptionboolean getBlockDataMode()
void skipBlockData()
throws IOException
IOException
private int readBlockHeader(boolean canBlock)
throws IOException
IOException
private void refill()
throws IOException
IOExceptionint currentBlockRemaining()
int peek() throws IOException
IOException
byte peekByte()
throws IOException
IOException
public int read()
throws IOException
InputStreamint in the range 0 to
255. If no byte is available because the end of the stream
has been reached, the value -1 is returned. This method
blocks until input data is available, the end of the stream is detected,
or an exception is thrown.
A subclass must provide an implementation of this method.
read in class InputStream-1 if the end of the
stream is reached.
IOException - if an I/O error occurs.
public int read(byte[] b,
int off,
int len)
throws IOException
InputStreamlen bytes of data from the input stream into
an array of bytes. An attempt is made to read as many as
len bytes, but a smaller number may be read, possibly
zero. The number of bytes actually read is returned as an integer.
This method blocks until input data is available, end of file is detected, or an exception is thrown.
If b is null, a
NullPointerException is thrown.
If off is negative, or len is negative, or
off+len is greater than the length of the array
b, then an IndexOutOfBoundsException is
thrown.
If len is zero, then no bytes are read and
0 is returned; otherwise, there is an attempt to read at
least one byte. If no byte is available because the stream is at end of
file, the value -1 is returned; otherwise, at least one
byte is read and stored into b.
The first byte read is stored into element b[off], the
next one into b[off+1], and so on. The number of bytes read
is, at most, equal to len. Let k be the number of
bytes actually read; these bytes will be stored in elements
b[off] through b[off+k-1],
leaving elements b[off+k] through
b[off+len-1] unaffected.
In every case, elements b[0] through
b[off] and elements b[off+len] through
b[b.length-1] are unaffected.
If the first byte cannot be read for any reason other than end of
file, then an IOException is thrown. In particular, an
IOException is thrown if the input stream has been closed.
The read(b, off, len) method
for class InputStream simply calls the method
read() repeatedly. If the first such call results in an
IOException, that exception is returned from the call to
the read(b, off, len) method. If
any subsequent call to read() results in a
IOException, the exception is caught and treated as if it
were end of file; the bytes read up to that point are stored into
b and the number of bytes read before the exception
occurred is returned. Subclasses are encouraged to provide a more
efficient implementation of this method.
read in class InputStreamb - the buffer into which the data is read.off - the start offset in array b
at which the data is written.len - the maximum number of bytes to read.
-1 if there is no more data because the end of
the stream has been reached.
IOException - if an I/O error occurs.InputStream.read()
public long skip(long len)
throws IOException
InputStreamn bytes of data from this input
stream. The skip method may, for a variety of reasons, end
up skipping over some smaller number of bytes, possibly 0.
This may result from any of a number of conditions; reaching end of file
before n bytes have been skipped is only one possibility.
The actual number of bytes skipped is returned. If n is
negative, no bytes are skipped.
The skip method of InputStream creates a
byte array and then repeatedly reads into it until n bytes
have been read or the end of the stream has been reached. Subclasses are
encouraged to provide a more efficient implementation of this method.
skip in class InputStreamlen - the number of bytes to be skipped.
IOException - if an I/O error occurs.
public int available()
throws IOException
InputStream The available method for class InputStream
always returns 0.
This method should be overridden by subclasses.
available in class InputStreamIOException - if an I/O error occurs.
public void close()
throws IOException
InputStream The close method of InputStream does
nothing.
close in class InputStreamIOException - if an I/O error occurs.
int read(byte[] b,
int off,
int len,
boolean copy)
throws IOException
IOException
public void readFully(byte[] b)
throws IOException
DataInputb. The number of bytes
read is equal
to the length of b.
This method blocks until one of the following conditions occurs:
b.length
bytes of input data are available, in which
case a normal return is made.
EOFException
is thrown.
IOException other
than EOFException is thrown.
If b is null,
a NullPointerException is thrown.
If b.length is zero, then
no bytes are read. Otherwise, the first
byte read is stored into element b[0],
the next one into b[1], and
so on.
If an exception is thrown from
this method, then it may be that some but
not all bytes of b have been
updated with data from the input stream.
readFully in interface DataInputb - the buffer into which the data is read.
IOException - if an I/O error occurs.
public void readFully(byte[] b,
int off,
int len)
throws IOException
DataInputlen
bytes from
an input stream.
This method blocks until one of the following conditions occurs:
len bytes
of input data are available, in which case
a normal return is made.
EOFException
is thrown.
IOException other
than EOFException is thrown.
If b is null,
a NullPointerException is thrown.
If off is negative, or len
is negative, or off+len is
greater than the length of the array b,
then an IndexOutOfBoundsException
is thrown.
If len is zero,
then no bytes are read. Otherwise, the first
byte read is stored into element b[off],
the next one into b[off+1],
and so on. The number of bytes read is,
at most, equal to len.
readFully in interface DataInputb - the buffer into which the data is read.off - an int specifying the offset into the data.len - an int specifying the number of bytes to read.
IOException - if an I/O error occurs.
public void readFully(byte[] b,
int off,
int len,
boolean copy)
throws IOException
IOException
public int skipBytes(int n)
throws IOException
DataInputn bytes
of data from the input
stream, discarding the skipped bytes. However,
it may skip
over some smaller number of
bytes, possibly zero. This may result from
any of a
number of conditions; reaching
end of file before n bytes
have been skipped is
only one possibility.
This method never throws an EOFException.
The actual
number of bytes skipped is returned.
skipBytes in interface DataInputn - the number of bytes to be skipped.
IOException - if an I/O error occurs.
public boolean readBoolean()
throws IOException
DataInputtrue if that byte is nonzero,
false if that byte is zero.
This method is suitable for reading
the byte written by the writeBoolean
method of interface DataOutput.
readBoolean in interface DataInputboolean value read.
IOException - if an I/O error occurs.
public byte readByte()
throws IOException
DataInput-128 through 127,
inclusive.
This method is suitable for
reading the byte written by the writeByte
method of interface DataOutput.
readByte in interface DataInputIOException - if an I/O error occurs.
public int readUnsignedByte()
throws IOException
DataInputint, and returns
the result, which is therefore in the range
0
through 255.
This method is suitable for reading
the byte written by the writeByte
method of interface DataOutput
if the argument to writeByte
was intended to be a value in the range
0 through 255.
readUnsignedByte in interface DataInputIOException - if an I/O error occurs.
public char readChar()
throws IOException
DataInputchar and returns the char value.
A Unicode char is made up of two bytes.
Let a
be the first byte read and b
be the second byte. The value
returned is:
(char)((a << 8) | (b & 0xff))
writeChar method of interface
DataOutput.
readChar in interface DataInputchar read.
IOException - if an I/O error occurs.
public short readShort()
throws IOException
DataInputshort value. Let a
be the first byte read and b
be the second byte. The value
returned
is:
(short)((a << 8) * | (b & 0xff))
writeShort method of
interface DataOutput.
readShort in interface DataInputIOException - if an I/O error occurs.
public int readUnsignedShort()
throws IOException
DataInputint value in the range 0
through 65535. Let a
be the first byte read and
b
be the second byte. The value returned is:
(((a & 0xff) << 8) | (b & 0xff))
writeShort method
of interface DataOutput if
the argument to writeShort
was intended to be a value in the range
0 through 65535.
readUnsignedShort in interface DataInputIOException - if an I/O error occurs.
public int readInt()
throws IOException
DataInputint value. Let a
be the first byte read, b be
the second byte, c be the third
byte,
and d be the fourth
byte. The value returned is:
(((a & 0xff) << 24) | ((b & 0xff) << 16) |
((c & 0xff) << 8) | (d & 0xff))
This method is suitable
for reading bytes written by the writeInt
method of interface DataOutput.
readInt in interface DataInputint value read.
IOException - if an I/O error occurs.
public float readFloat()
throws IOException
DataInputfloat value. It does this
by first constructing an int
value in exactly the manner
of the readInt
method, then converting this int
value to a float in
exactly the manner of the method Float.intBitsToFloat.
This method is suitable for reading
bytes written by the writeFloat
method of interface DataOutput.
readFloat in interface DataInputfloat value read.
IOException - if an I/O error occurs.
public long readLong()
throws IOException
DataInputlong value. Let a
be the first byte read, b be
the second byte, c be the third
byte, d
be the fourth byte,
e be the fifth byte, f
be the sixth byte, g be the
seventh byte,
and h be the
eighth byte. The value returned is:
(((long)(a & 0xff) << 56) |
((long)(b & 0xff) << 48) |
((long)(c & 0xff) << 40) |
((long)(d & 0xff) << 32) |
((long)(e & 0xff) << 24) |
((long)(f & 0xff) << 16) |
((long)(g & 0xff) << 8) |
((long)(h & 0xff)))
This method is suitable
for reading bytes written by the writeLong
method of interface DataOutput.
readLong in interface DataInputlong value read.
IOException - if an I/O error occurs.
public double readDouble()
throws IOException
DataInputdouble value. It does this
by first constructing a long
value in exactly the manner
of the readlong
method, then converting this long
value to a double in exactly
the manner of the method Double.longBitsToDouble.
This method is suitable for reading
bytes written by the writeDouble
method of interface DataOutput.
readDouble in interface DataInputdouble value read.
IOException - if an I/O error occurs.
public String readUTF()
throws IOException
DataInputreadUTF
is that it reads a representation of a Unicode
character string encoded in Java 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
exactly the manner of the readUnsignedShort
method . 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))
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))
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 writeUTF
method of interface DataOutput
may be used to write data that is suitable
for reading by this method.
readUTF in interface DataInputIOException - if an I/O error occurs.
public String readLine()
throws IOException
DataInputString. 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.
readLine in interface DataInputnull if the end of file is
encountered before a byte can be read.
IOException - if an I/O error occurs.
void readBooleans(boolean[] v,
int off,
int len)
throws IOException
IOException
void readChars(char[] v,
int off,
int len)
throws IOException
IOException
void readShorts(short[] v,
int off,
int len)
throws IOException
IOException
void readInts(int[] v,
int off,
int len)
throws IOException
IOException
void readFloats(float[] v,
int off,
int len)
throws IOException
IOException
void readLongs(long[] v,
int off,
int len)
throws IOException
IOException
void readDoubles(double[] v,
int off,
int len)
throws IOException
IOException
String readLongUTF()
throws IOException
IOException
private String readUTFBody(long utflen)
throws IOException
IOException
private long readUTFSpan(StringBuffer sbuf,
long utflen)
throws IOException
IOException
private int readUTFChar(StringBuffer sbuf,
long utflen)
throws IOException
IOException
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