Package org.eclipse.jgit.internal.storage.pack

Class DeltaEncoder

java.lang.Object

org.eclipse.jgit.internal.storage.pack.DeltaEncoder

public class DeltaEncoder
extends java.lang.Object

Encodes an instruction stream for BinaryDelta.

Field Summary

Fields

Modifier and Type	Field	Description
private byte[]	buf
private int	limit
private static int	MAX_COPY_CMD_SIZE	Maximum number of bytes used by a copy instruction.
private static int	MAX_INSERT_DATA_SIZE	Maximum length that an insert command can encode at once.
private static int	MAX_V2_COPY	Maximum number of bytes to be copied in pack v2 format.
private java.io.OutputStream	out
private int	size

Constructor Summary

Constructors

Constructor	Description
DeltaEncoder(java.io.OutputStream out, long baseSize, long resultSize)	Create an encoder with no upper bound on the instruction stream size.
DeltaEncoder(java.io.OutputStream out, long baseSize, long resultSize, int limit)	Create an encoder with an upper limit on the instruction size.

Method Summary

Modifier and Type	Method	Description
boolean	copy(long offset, int cnt)	Create a copy instruction to copy from the base object.
private int	encodeCopy(int p, long offset, int cnt)
int	getSize()	Get current size of the delta stream, in bytes.
boolean	insert(byte[] text)	Insert a literal binary sequence.
boolean	insert(byte[] text, int off, int cnt)	Insert a literal binary sequence.
boolean	insert(java.lang.String text)	Insert a literal string of text, in UTF-8 encoding.
private void	writeVarint(long sz)

Methods inherited from class java.lang.Object

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

Field Detail

MAX_V2_COPY

private static final int MAX_V2_COPY

Maximum number of bytes to be copied in pack v2 format.

Historical limitations have this at 64k, even though current delta decoders recognize larger copy instructions.

See Also:

Constant Field Values

MAX_COPY_CMD_SIZE

private static final int MAX_COPY_CMD_SIZE

Maximum number of bytes used by a copy instruction.

See Also:

Constant Field Values

MAX_INSERT_DATA_SIZE

private static final int MAX_INSERT_DATA_SIZE

Maximum length that an insert command can encode at once.

See Also:

Constant Field Values

out

private final java.io.OutputStream out

buf

private final byte[] buf

limit

private final int limit

size

private int size

Constructor Detail

DeltaEncoder

public DeltaEncoder(java.io.OutputStream out,
                    long baseSize,
                    long resultSize)
             throws java.io.IOException

Create an encoder with no upper bound on the instruction stream size.

Parameters:

out - buffer to store the instructions written.

baseSize - size of the base object, in bytes.

resultSize - size of the resulting object, after applying this instruction stream to the base object, in bytes.

Throws:

java.io.IOException - the output buffer cannot store the instruction stream's header with the size fields.

DeltaEncoder

public DeltaEncoder(java.io.OutputStream out,
                    long baseSize,
                    long resultSize,
                    int limit)
             throws java.io.IOException

Create an encoder with an upper limit on the instruction size.

Parameters:

out - buffer to store the instructions written.

baseSize - size of the base object, in bytes.

resultSize - size of the resulting object, after applying this instruction stream to the base object, in bytes.

limit - maximum number of bytes to write to the out buffer declaring the stream is over limit and should be discarded. May be 0 to specify an infinite limit.

Throws:

java.io.IOException - the output buffer cannot store the instruction stream's header with the size fields.

Method Detail

writeVarint

private void writeVarint(long sz)
                  throws java.io.IOException

Throws:

java.io.IOException

getSize

public int getSize()

Get current size of the delta stream, in bytes.

Returns:

current size of the delta stream, in bytes.

insert

public boolean insert(java.lang.String text)
               throws java.io.IOException

Insert a literal string of text, in UTF-8 encoding.

Parameters:

text - the string to insert.

Returns:

true if the insert fits within the limit; false if the insert would cause the instruction stream to exceed the limit.

Throws:

java.io.IOException - the instruction buffer can't store the instructions.

insert

public boolean insert(byte[] text)
               throws java.io.IOException

Insert a literal binary sequence.

Parameters:

text - the binary to insert.

Returns:

true if the insert fits within the limit; false if the insert would cause the instruction stream to exceed the limit.

Throws:

java.io.IOException - the instruction buffer can't store the instructions.

insert

public boolean insert(byte[] text,
                      int off,
                      int cnt)
               throws java.io.IOException

Insert a literal binary sequence.

Parameters:

text - the binary to insert.

off - offset within text to start copying from.

cnt - number of bytes to insert.

Returns:

true if the insert fits within the limit; false if the insert would cause the instruction stream to exceed the limit.

Throws:

java.io.IOException - the instruction buffer can't store the instructions.

copy

public boolean copy(long offset,
                    int cnt)
             throws java.io.IOException

Create a copy instruction to copy from the base object.

Parameters:

offset - position in the base object to copy from. This is absolute, from the beginning of the base.

cnt - number of bytes to copy.

Returns:

true if the copy fits within the limit; false if the copy would cause the instruction stream to exceed the limit.

Throws:

java.io.IOException - the instruction buffer cannot store the instructions.

encodeCopy

private int encodeCopy(int p,
                       long offset,
                       int cnt)