com.jcraft.jsch

Class Buffer

java.lang.Object

com.jcraft.jsch.Buffer

public class Buffer
extends Object

Usually not to be used by applications. A chunk of bytes together with methods to access them. This implements the low-level protocol elements used by the different layers of the SSH protocol.

The Buffer maintains a current index (from where on the put methods write, updating it on the way) and an offset. The offset is used by the get methods to read (and they update the offset, too). If a buffer is used for both reading and writing, the index should normally be bigger than the offset. Initially both are 0.

See Also:

RFC 4251, section 5. Data Type Representations Used in the SSH Protocols

Constructor Summary

Constructors

Constructor and Description
Buffer() Creates a buffer with a default size of 20 KB.
Buffer(byte[] buffer) Creates a buffer using the given array as backing store.
Buffer(int size) creates a Buffer with given size.

Method Summary

Modifier and Type	Method and Description
int	getByte() reads a (unsigned) byte from the buffer.
void	getByte(byte[] foo) reads some byte from the buffer.
int	getByte(int len) ignores len bytes in the buffer.
int	getInt() reads a signed 32-bit number from the buffer.
int	getLength() calculates the length of this buffer, which is the difference between index and offset.
long	getLong() reads a 64-bit number from the buffer.
byte[]	getMPInt() reads a multiple-precision (signed) integer.
byte[]	getMPIntBits() reads a multiple precision signed integer as unsigned (i.e. the highest-order bit is guaranteed to be 0).
int	getOffSet() returns the current offset.
byte[]	getString() reads a string.
long	getUInt() reads an unsigned 32-bit number from the buffer.
void	putByte(byte foo) puts one byte into the buffer.
void	putByte(byte[] foo) puts all bytes in the given byte array in the buffer.
void	putByte(byte[] foo, int begin, int length) puts a subsequence of the given byte array in the buffer.
void	putInt(int val) Puts a 32-bit number as 4 bytes into the buffer.
void	putLong(long val) Puts a 64-bit number as 8 bytes into the buffer.
void	putMPInt(byte[] foo) Puts a byte[] as an unsigned multiple precision integer (mpint).
void	putString(byte[] foo) puts a byte sequence formatted as a SSH string into the buffer.
void	putString(byte[] foo, int begin, int length) puts a byte sequence formatted as a SSH string into the buffer.
void	reset() resets index and offset.
void	setOffSet(int s) changes the current offset.
void	shift() Shifts the contents between offset and index back to the start of the buffer, and then sets these two values accordingly.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Buffer

public Buffer(int size)

creates a Buffer with given size.

Buffer

public Buffer(byte[] buffer)

Creates a buffer using the given array as backing store.

Buffer

public Buffer()

Creates a buffer with a default size of 20 KB.

Method Detail

putByte

public void putByte(byte foo)

puts one byte into the buffer.

putByte

public void putByte(byte[] foo)

puts all bytes in the given byte array in the buffer. (This should have been named putBytes, really.)

putByte

public void putByte(byte[] foo,
                    int begin,
                    int length)

puts a subsequence of the given byte array in the buffer. (This should have been named putBytes, really.)

putString

public void putString(byte[] foo)

puts a byte sequence formatted as a SSH string into the buffer.

See Also:

putString(byte[], int, int)

putString

public void putString(byte[] foo,
                      int begin,
                      int length)

puts a byte sequence formatted as a SSH string into the buffer. A SSH string consists of first a (big-endian) 32-bit number indicating the length of the string (number of bytes), then the bytes themselves.

Parameters:

foo - the array from which we take the data.

begin - the start of the data in the array.

length - how many bytes to put.

putInt

public void putInt(int val)

Puts a 32-bit number as 4 bytes into the buffer.

putLong

public void putLong(long val)

Puts a 64-bit number as 8 bytes into the buffer.

putMPInt

public void putMPInt(byte[] foo)

Puts a byte[] as an unsigned multiple precision integer (mpint). This consists of first the number of bytes as a 32-bit integer, then the bytes of the number themselves.

getLength

public int getLength()

calculates the length of this buffer, which is the difference between index and offset.

getOffSet

public int getOffSet()

returns the current offset.

setOffSet

public void setOffSet(int s)

changes the current offset. This is normally only used to start parsing a packet at a (known) later position, when creating a buffer from existing data.

Parameters:

s - the new offset.

getLong

public long getLong()

reads a 64-bit number from the buffer.

See Also:

putLong(long)

getInt

public int getInt()

reads a signed 32-bit number from the buffer.

getUInt

public long getUInt()

reads an unsigned 32-bit number from the buffer.

getByte

public int getByte()

reads a (unsigned) byte from the buffer.

getByte

public void getByte(byte[] foo)

reads some byte from the buffer.

Parameters:

foo - the array to put the bytes to. This array will be filled, i.e. we read foo.length bytes from the buffer.

getByte

public int getByte(int len)

ignores len bytes in the buffer. This simply sets the offset forward by len bytes.

This is now only used in getString(int[],int[]), and could maybe be non-public. Or at least be named something else. skip would be a nice name, but this is already used for the same method for {@code index}.

Returns:

the old offset.

getMPInt

public byte[] getMPInt()

reads a multiple-precision (signed) integer.

See Also:

putMPInt(byte[])

getMPIntBits

public byte[] getMPIntBits()

reads a multiple precision signed integer as unsigned (i.e. the highest-order bit is guaranteed to be 0).

getString

public byte[] getString()

reads a string.

Returns:

a new byte[] with the contents of the string.

See Also:

putString(byte[])

reset

public void reset()

resets index and offset.

shift

public void shift()

Shifts the contents between offset and index back to the start of the buffer, and then sets these two values accordingly.