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public interface DataInput
Method Summary | |
boolean |
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byte |
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char |
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double |
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float |
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void |
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void |
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int |
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String |
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long |
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short |
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String |
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int |
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int |
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int |
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public boolean readBoolean() throws EOFException, IOException
This method reads a Java boolean value from an input stream. It does so by reading a single byte of data. If that byte is zero, then the value returned isfalse
. If the byte is non-zero, then the value returned istrue
. This method can read aboolean
written by an object implementing thewriteBoolean()
method in theDataOutput
interface.
- Returns:
- The
boolean
value read
- Throws:
EOFException
- If end of file is reached before reading the booleanIOException
- If any other error occurs
- See Also:
DataOutput.writeBoolean(boolean)
public byte readByte() throws EOFException, IOException
This method reads a Java byte value from an input stream. The value is in the range of -128 to 127. This method can read abyte
written by an object implementing thewriteByte()
method in theDataOutput
interface.
- Returns:
- The
byte
value read
- Throws:
EOFException
- If end of file is reached before reading the byteIOException
- If any other error occurs
- See Also:
DataOutput.writeByte(int)
public char readChar() throws EOFException, IOException
This method reads a Javachar
value from an input stream. It operates by reading two bytes from the stream and converting them to a single 16-bit Javachar
. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering. As an example, ifbyte1
andbyte2
represent the first and second byte read from the stream respectively, they will be transformed to achar
in the following manner:(char)((byte1 << 8) + byte2)
This method can read achar
written by an object implementing thewriteChar()
method in theDataOutput
interface.
- Returns:
- The
char
value read
- Throws:
EOFException
- If end of file is reached before reading the charIOException
- If any other error occurs
- See Also:
DataOutput.writeChar(int)
public double readDouble() throws EOFException, IOException
This method reads a Java double value from an input stream. It operates by first reading along
value from the stream by calling thereadLong()
method in this interface, then converts thatlong
to adouble
using thelongBitsToDouble
method in the classjava.lang.Double
. This method can read adouble
written by an object implementing thewriteDouble()
method in theDataOutput
interface.
- Returns:
- The
double
value read
- Throws:
EOFException
- If end of file is reached before reading the doubleIOException
- If any other error occurs
public float readFloat() throws EOFException, IOException
This method reads a Java float value from an input stream. It operates by first reading anint
value from the stream by calling thereadInt()
method in this interface, then converts thatint
to afloat
using theintBitsToFloat
method in the classjava.lang.Float
. This method can read afloat
written by an object implementing thewriteFloat()
method in theDataOutput
interface.
- Returns:
- The
float
value read
- Throws:
EOFException
- If end of file is reached before reading the floatIOException
- If any other error occurs
public void readFully(byte[] buf) throws EOFException, IOException
This method reads raw bytes into the passed array until the array is full. Note that this method blocks until the data is available and throws an exception if there is not enough data left in the stream to fill the buffer. Note also that zero length buffers are permitted. In this case, the method will return immediately without reading any bytes from the stream.
- Parameters:
buf
- The buffer into which to read the data
- Throws:
EOFException
- If end of file is reached before filling the bufferIOException
- If any other error occurs
public void readFully(byte[] buf, int offset, int len) throws EOFException, IOException
This method reads raw bytes into the passed arraybuf
startingoffset
bytes into the buffer. The number of bytes read will be exactlylen
. Note that this method blocks until the data is available and throws an exception if there is not enough data left in the stream to readlen
bytes. Note also that zero length buffers are permitted. In this case, the method will return immediately without reading any bytes from the stream.
- Parameters:
buf
- The buffer into which to read the dataoffset
- The offset into the buffer to start storing datalen
- The number of bytes to read into the buffer
- Throws:
EOFException
- If end of file is reached before filling the bufferIOException
- If any other error occurs
public int readInt() throws EOFException, IOException
This method reads a Javaint
value from an input stream It operates by reading four bytes from the stream and converting them to a single Javaint
. The bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering. As an example, ifbyte1
throughbyte4
represent the first four bytes read from the stream, they will be transformed to anint
in the following manner:(int)(((byte1 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) + ((byte3 & 0xFF)<< 8) + (byte4 & 0xFF)))
The value returned is in the range of -2147483648 to 2147483647. This method can read anint
written by an object implementing thewriteInt()
method in theDataOutput
interface.
- Returns:
- The
int
value read
- Throws:
EOFException
- If end of file is reached before reading the intIOException
- If any other error occurs
- See Also:
DataOutput.writeInt(int)
public String readLine() throws IOException
This method reads the next line of text data from an input stream. It operates by reading bytes and converting those bytes tochar
values by treating the byte read as the low eight bits of thechar
and using 0 as the high eight bits. Because of this, it does not support the full 16-bit Unicode character set. The reading of bytes ends when either the end of file or a line terminator is encountered. The bytes read are then returned as aString
. A line terminator is a byte sequence consisting of either\r
,\n
or\r\n
. These termination charaters are discarded and are not returned as part of the string. A line is also terminated by an end of file condition.
- Returns:
- The line read as a
String
- Throws:
IOException
- If an error occurs
public long readLong() throws EOFException, IOException
This method reads a Javalong
value from an input stream It operates by reading eight bytes from the stream and converting them to a single Javalong
. The bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering. As an example, ifbyte1
throughbyte8
represent the first eight bytes read from the stream, they will be transformed to anlong
in the following manner:(long)(((byte1 & 0xFF) << 56) + ((byte2 & 0xFF) << 48) + ((byte3 & 0xFF) << 40) + ((byte4 & 0xFF) << 32) + ((byte5 & 0xFF) << 24) + ((byte6 & 0xFF) << 16) + ((byte7 & 0xFF) << 8) + (byte8 & 0xFF)))
The value returned is in the range of -9223372036854775808 to 9223372036854775807. This method can read anlong
written by an object implementing thewriteLong()
method in theDataOutput
interface.
- Returns:
- The
long
value read
- Throws:
EOFException
- If end of file is reached before reading the longIOException
- If any other error occurs
- See Also:
DataOutput.writeLong(long)
public short readShort() throws EOFException, IOException
This method reads a signed 16-bit value into a Java in from the stream. It operates by reading two bytes from the stream and converting them to a single 16-bit Javashort
. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering. As an example, ifbyte1
andbyte2
represent the first and second byte read from the stream respectively, they will be transformed to ashort
in the following manner:(short)(((byte1 & 0xFF) << 8) + (byte2 & 0xFF))
The value returned is in the range of -32768 to 32767. This method can read ashort
written by an object implementing thewriteShort()
method in theDataOutput
interface.
- Returns:
- The
short
value read
- Throws:
EOFException
- If end of file is reached before reading the valueIOException
- If any other error occurs
- See Also:
DataOutput.writeShort(int)
public String readUTF() throws EOFException, UTFDataFormatException, IOException
This method reads aString
from an input stream that is encoded in a modified UTF-8 format. This format has a leading two byte sequence that contains the remaining number of bytes to read. This two byte sequence is read using thereadUnsignedShort()
method of this interface. After the number of remaining bytes have been determined, these bytes are read an transformed intochar
values. Thesechar
values are encoded in the stream using either a one, two, or three byte format. The particular format in use can be determined by examining the first byte read. If the first byte has a high order bit of 0, then that character consists on only one byte. This character value consists of seven bits that are at positions 0 through 6 of the byte. As an example, ifbyte1
is the byte read from the stream, it would be converted to achar
like so:(char)byte1
If the first byte has 110 as its high order bits, then the character consists of two bytes. The bits that make up the character value are in positions 0 through 4 of the first byte and bit positions 0 through 5 of the second byte. (The second byte should have 10 as its high order bits). These values are in most significant byte first (i.e., "big endian") order. As an example, ifbyte1
andbyte2
are the first two bytes read respectively, and the high order bits of them match the patterns which indicate a two byte character encoding, then they would be converted to a Javachar
like so:(char)(((byte1 & 0x1F) << 6) + (byte2 & 0x3F))
If the first byte has a 1110 as its high order bits, then the character consists of three bytes. The bits that make up the character value are in positions 0 through 3 of the first byte and bit positions 0 through 5 of the other two bytes. (The second and third bytes should have 10 as their high order bits). These values are in most significant byte first (i.e., "big endian") order. As an example, ifbyte1
,byte2
, andbyte3
are the three bytes read, and the high order bits of them match the patterns which indicate a three byte character encoding, then they would be converted to a Javachar
like so:(char)(((byte1 & 0x0F) << 12) + ((byte2 & 0x3F) + (byte3 & 0x3F))
Note that all characters are encoded in the method that requires the fewest number of bytes with the exception of the character with the value of\<llll>u0000
which is encoded as two bytes. This is a modification of the UTF standard used to prevent C language styleNUL
values from appearing in the byte stream. This method can read data that was written by an object implementing thewriteUTF()
method inDataOutput
.
- Returns:
- The
String
read
- Throws:
EOFException
- If end of file is reached before reading the StringUTFDataFormatException
- If the data is not in UTF-8 formatIOException
- If any other error occurs
- See Also:
DataOutput.writeUTF(String)
public int readUnsignedByte() throws EOFException, IOException
This method reads 8 unsigned bits into a Javaint
value from the stream. The value returned is in the range of 0 to 255. This method can read an unsigned byte written by an object implementing thewriteByte()
method in theDataOutput
interface.
- Returns:
- The unsigned bytes value read as a Java
int
.
- Throws:
EOFException
- If end of file is reached before reading the valueIOException
- If any other error occurs
- See Also:
DataOutput.writeByte(int)
public int readUnsignedShort() throws EOFException, IOException
This method reads 16 unsigned bits into a Java int value from the stream. It operates by reading two bytes from the stream and converting them to a single Javaint
. The two bytes are stored most significant byte first (i.e., "big endian") regardless of the native host byte ordering. As an example, ifbyte1
andbyte2
represent the first and second byte read from the stream respectively, they will be transformed to anint
in the following manner:(int)(((byte1 0xFF) << 8) + (byte2 & 0xFF))
The value returned is in the range of 0 to 65535. This method can read an unsigned short written by an object implementing thewriteShort()
method in theDataOutput
interface.
- Returns:
- The unsigned short value read as a Java
int
.
- Throws:
EOFException
- If end of file is reached before reading the valueIOException
- If any other error occurs
- See Also:
DataOutput.writeShort(int)
public int skipBytes(int numBytes) throws EOFException, IOException
This method skips and discards the specified number of bytes in an input stream. Note that this method may skip less than the requested number of bytes. The actual number of bytes skipped is returned. No bytes are skipped if a negative number is passed to this method.
- Parameters:
numBytes
- The number of bytes to skip
- Returns:
- The number of bytes actually skipped, which will always be
numBytes
- Throws:
EOFException
- If end of file is reached before all bytes can be skippedIOException
- If any other error occurs
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