//ref:
//http://www.ieyebrain.com:8080/pts/src/rsync/
type Rollsum struct {
a, b uint16
Xk byte
count int
}
func New(count int) *Rollsum {
return &Rollsum{
a:0,
b:0,
count: count}
}
func (r *Rollsum) Init(a uint16, b uint16, xk uint8) {
r.a = a
r.b = b
r.Xk = xk
}
func (r *Rollsum) InitByBuf(buf []byte) {
r.a,r.b = calc_weaksum(buf)
r.Xk = buf[0]
}
func (r *Rollsum) Update(Xk_1 byte, Xl_one byte) {
var a,b int
a , b = int(r.a),int(r.b)
a = a - int(r.Xk) + int(Xl_one)
b = a + b - r.count * int(r.Xk)
r.Xk = Xk_1
r.a = uint16(a)
r.b = uint16(b)
}
func (r *Rollsum) GetValues() (uint16,uint16) {
return r.a,r.b
}
type Weaksum struct {
a,b uint16
}
func calc_weaksum(buf []byte) (uint16, uint16) {
var a,b,c int;
i := 0
len := len(buf)
a,b = 0,0
for len > 0 {
c = int(buf[i])
a = a + c
b = b + (len * c)
len--
i++
}
//return Weaksum{a:uint16(a),b:uint16(b)}
return uint16(a), uint16(b)
}
func calc_strongsum(buf []byte) ([]byte) {
ctx := md4.New()
ctx.Write(buf)
return ctx.Sum(nil)
}
package rsync
type Rollsum struct {
a, b uint16
Xk byte
count int
}
func New(count int) *Rollsum {
return &Rollsum{
a:0,
b:0,
count: count}
}
func (r *Rollsum) Init(a uint16, b uint16, xk uint8) {
r.a = a
r.b = b
r.Xk = xk
}
func (r *Rollsum) InitByBuf(buf []byte) {
r.a,r.b = calc_weaksum(buf)
r.Xk = buf[0]
}
func (r *Rollsum) Update(Xk_1 byte, Xl_one byte) {
var a,b int
a , b = int(r.a),int(r.b)
a = a - int(r.Xk) + int(Xl_one)
b = a + b - r.count * int(r.Xk)
r.Xk = Xk_1
r.a = uint16(a)
r.b = uint16(b)
}
func (r *Rollsum) GetValues() (uint16,uint16) {
return r.a,r.b
}
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