package packfile

import (
	

	
	
)
See https://github.com/jelmer/dulwich/blob/master/dulwich/pack.py and https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js for more info

Standard chunk size used to generate fingerprints
	s = 16
https://github.com/git/git/blob/f7466e94375b3be27f229c78873f0acf8301c0a5/diff-delta.c#L428 Max size of a copy operation (64KB)
	maxCopySize = 64 * 1024
)
GetDelta returns an EncodedObject of type OFSDeltaObject. Base and Target object, will be loaded into memory to be able to create the delta object. To generate target again, you will need the obtained object and "base" one. Error will be returned if base or target object cannot be read.
func (,  plumbing.EncodedObject) (plumbing.EncodedObject, error) {
	return getDelta(new(deltaIndex), , )
}

func ( *deltaIndex, ,  plumbing.EncodedObject) ( plumbing.EncodedObject,  error) {
	,  := .Reader()
	if  != nil {
		return nil, 
	}

	defer ioutil.CheckClose(, &)

	,  := .Reader()
	if  != nil {
		return nil, 
	}

	defer ioutil.CheckClose(, &)

	 := bufPool.Get().(*bytes.Buffer)
	defer bufPool.Put()
	.Reset()

	_,  = .ReadFrom()
	if  != nil {
		return nil, 
	}

	 := bufPool.Get().(*bytes.Buffer)
	defer bufPool.Put()
	.Reset()

	_,  = .ReadFrom()
	if  != nil {
		return nil, 
	}

	 := diffDelta(, .Bytes(), .Bytes())
	 := &plumbing.MemoryObject{}
	_,  = .Write()
	if  != nil {
		return nil, 
	}

	.SetSize(int64(len()))
	.SetType(plumbing.OFSDeltaObject)

	return , nil
}
DiffDelta returns the delta that transforms src into tgt.
func (,  []byte) []byte {
	return diffDelta(new(deltaIndex), , )
}

func ( *deltaIndex,  []byte,  []byte) []byte {
	 := bufPool.Get().(*bytes.Buffer)
	defer bufPool.Put()
	.Reset()
	.Write(deltaEncodeSize(len()))
	.Write(deltaEncodeSize(len()))

	if len(.entries) == 0 {
		.init()
	}

	 := bufPool.Get().(*bytes.Buffer)
	defer bufPool.Put()
	.Reset()
	for  := 0;  < len(); ++ {
		,  := .findMatch(, , )

couldn't find a match, just write the current byte and continue
			.WriteByte([])
src is less than blksz, copy the rest of the target to avoid calls to findMatch
			for ;  < len(); ++ {
				.WriteByte([])
			}
remaining target is less than blksz, copy what's left of it and avoid calls to findMatch
			for  := ;  < +; ++ {
				.WriteByte([])
			}
			 +=  - 1
		} else {
			encodeInsertOperation(, )

			 := 
			 := 
			for  > 0 {
				if  < maxCopySize {
					.Write(encodeCopyOperation(, ))
					break
				}

				.Write(encodeCopyOperation(, maxCopySize))
				 -= maxCopySize
				 += maxCopySize
			}

			 +=  - 1
		}
	}

	encodeInsertOperation(, )
buf.Bytes() is only valid until the next modifying operation on the buffer. Copy it.
	return append([]byte{}, .Bytes()...)
}

func (,  *bytes.Buffer) {
	if .Len() == 0 {
		return
	}

	 := .Bytes()
	 := .Len()
	 := 0
	for {
		if  <= 127 {
			break
		}
		.WriteByte(byte(127))
		.Write([ : +127])
		 -= 127
		 += 127
	}
	.WriteByte(byte())
	.Write([ : +])

	.Reset()
}

func ( int) []byte {
	var  []byte
	 :=  & 0x7f
	 >>= 7
	for {
		if  == 0 {
			break
		}

		 = append(, byte(|0x80))
		 =  & 0x7f
		 >>= 7
	}
	 = append(, byte())

	return 
}

func (,  int) []byte {
	 := 0x80
	var  []byte

	var  uint
	for  = 0;  < 4; ++ {
		 := 0xff << ( * 8)
		if & != 0 {
			 = append(, byte(&>>(*8)))
			 |= 0x01 << 
		}
	}

	for  = 0;  < 3; ++ {
		 := 0xff << ( * 8)
		if & != 0 {
			 = append(, byte(&>>(*8)))
			 |= 0x10 << 
		}
	}

	return append([]byte{byte()}, ...)