/
delta.go
495 lines (443 loc) · 10.8 KB
/
delta.go
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package rsync
import (
"bytes"
"errors"
"fmt"
"io"
//"log"
"github.com/smtc/rollsum"
)
type delta struct {
sig *Signature
pos int
weakSum uint32
blockLen uint32
outer io.Writer
ms matchStat
mss []matchStat
debug bool
}
// dst.sig与src比较后,是否匹配的结果输出
type matchStat struct {
match int // 0: 未知状态,仅第一次出现,不能出现在最终结果中;1:匹配;-1:不匹配
pos int64 // 如果match为true,pos为dst文件的match位置,否则,pos为src中不匹配的起点位置
// 当生成delta文件时,从src中读取该位置的数据,写入delta文件中
length int64 // 如果match为true,length代表dst文件与src文件匹配的长度;否则,length代表src文件中
// 没有匹配到的位置的总长度
}
const (
// RS_OP_LITERAL_Nx与librsync中的定义不同
// RS_OP_LITERAL_Nx = librsync RS_OP_LITERAL_Nx - 0x40
// 这样,使用高位字节来存储数据压缩方式
RS_OP_LITERAL_N1 uint8 = 0x01
RS_OP_LITERAL_N2 uint8 = 0x02
RS_OP_LITERAL_N4 uint8 = 0x03
RS_OP_LITERAL_N8 uint8 = 0x04
// 压缩方式
RS_COMPRESS_NONE uint8 = 0x00
RS_COMPRESS_BZIP2 uint8 = 0x10
RS_COMPRESS_GZIP uint8 = 0x20
RS_COMPRESS_LZW uint8 = 0x30
RS_COMPRESS_FLATE uint8 = 0x40
RS_OP_COPY_N1_N1 uint8 = 0x45
RS_OP_COPY_N1_N2 uint8 = 0x46
RS_OP_COPY_N1_N4 uint8 = 0x47
RS_OP_COPY_N1_N8 uint8 = 0x48
RS_OP_COPY_N2_N1 uint8 = 0x49
RS_OP_COPY_N2_N2 uint8 = 0x4a
RS_OP_COPY_N2_N4 uint8 = 0x4b
RS_OP_COPY_N2_N8 uint8 = 0x4c
RS_OP_COPY_N4_N1 uint8 = 0x4d
RS_OP_COPY_N4_N2 uint8 = 0x4e
RS_OP_COPY_N4_N4 uint8 = 0x4f
RS_OP_COPY_N4_N8 uint8 = 0x50
RS_OP_COPY_N8_N1 uint8 = 0x51
RS_OP_COPY_N8_N2 uint8 = 0x52
RS_OP_COPY_N8_N4 uint8 = 0x53
RS_OP_COPY_N8_N8 uint8 = 0x54
)
// generate delta
// param:
// dstSig: reader of dst signature file
// src: reader of src file
// srcLen: src file content length
// result: detla file writer
func GenDelta(dstSig io.Reader,
src io.ReadSeeker,
srcLen int64,
result io.Writer,
args ...bool) (err error) {
var (
df delta
)
if len(args) > 0 {
df.debug = args[0]
}
// load signature file
if df.sig, err = LoadSign(dstSig, df.debug); err != nil {
err = errors.New("Load Signature failed: " + err.Error())
return
}
df.blockLen = df.sig.block_len
df.outer = result
if err = df.genDelta(src, srcLen); err != nil {
err = errors.New("generate Delta failed: " + err.Error())
return
}
// 打印调试信息
if df.debug {
df.dump()
}
if err = df.flush(src); err != nil {
err = errors.New("write Delta failed: " + err.Error())
}
return
}
func (d *delta) genDelta(src io.ReadSeeker, srcLen int64) (err error) {
var (
c byte
p []byte
rs rollsum.Rollsum
rb *rotateBuffer
srcPos int64
matchAt int64
blockLen int
)
if d.debug {
d.dumpSign()
}
blockLen = int(d.sig.block_len)
rb = NewRotateBuffer(srcLen, d.sig.block_len, src)
p, srcPos, err = rb.rollFirst()
if err == nil {
// 计算初始weaksum
rs.Init()
rs.Update(p)
for err == nil {
// srcPos是当前读取src文件的绝对位置,matchAt对应于dstSig和dst文件的位置
matchAt = d.findMatch(p, srcPos, rs.Digest())
if matchAt < 0 {
p, c, srcPos, err = rb.rollByte()
if err != nil {
break
}
rs.Rotate(c, p[blockLen-1])
} else {
p, srcPos, err = rb.rollBlock()
rs.Init()
if err != nil {
break
}
rs.Update(p)
}
}
} else if err == noBytesLeft {
// reader没有内容
if d.debug {
fmt.Println("reader has no content:", srcLen)
}
err = nil
return
}
if err != noBytesLeft && err != notEnoughBytes {
// 出错
return
}
if d.debug {
fmt.Printf("rotate buffer left no more than a block: block=%d start=%d end=%d absHead=%d absTail=%d eof=%v\n",
blockLen, rb.start, rb.end, rb.absHead, rb.absTail, rb.eof)
}
if p, c, srcPos, err = rb.rollLeft(); err == nil {
rs.Init()
rs.Update(p)
for err == nil {
matchAt = d.findMatch(p, srcPos, rs.Digest())
if matchAt >= 0 {
// 剩余的内容已经匹配到,不需要继续处理
break
} else {
p, c, srcPos, err = rb.rollLeft()
if err != nil {
break
}
rs.Rollout(c)
}
}
} else {
if d.debug {
fmt.Println(string(p), c, srcPos, err)
}
}
if err == noBytesLeft || err == nil {
if d.debug {
fmt.Println("last match stat:", d.ms.match, d.ms.pos, d.ms.length)
}
d.mss = append(d.mss, d.ms)
err = nil
}
return
}
// delta文件的header。
// 格式:
// delta magic
func (d *delta) writeHeader() (err error) {
_, err = d.outer.Write(htonl(DeltaMagic))
return
}
// matchAt is basic file position
func (d *delta) findMatch(p []byte, pos int64, sum uint32) (matchAt int64) {
matchAt = -1
if blocks, ok := d.sig.block_sigs[sum]; ok {
ssum := strongSum(p, d.sig.strong_sum_len)
// 二分查找
matchAt = blockSlice(blocks).search(ssum, pos, d.blockLen)
}
if matchAt < 0 {
if d.ms.match == 1 {
// 上个匹配状态为匹配,重设ms
d.mss = append(d.mss, d.ms)
if d.debug {
fmt.Printf(" delta match: pos=%d len=%d\n", d.ms.pos, d.ms.length)
}
d.ms.match = -1
d.ms.pos = pos
d.ms.length = 1
} else {
// 上个匹配状态为不匹配,增加不匹配的长度
if d.ms.match == 0 {
d.ms.match = -1
}
d.ms.length++
}
} else {
// 找到匹配
if d.ms.match == -1 {
// 上个状态为不匹配, 重设ms
d.mss = append(d.mss, d.ms)
if d.debug {
fmt.Printf(" delta miss: pos=%d len=%d\n", d.ms.pos, d.ms.length)
}
d.ms.match = 1
d.ms.pos = matchAt
d.ms.length = int64(len(p))
} else {
// 上个状态为初始状态或匹配状态
if d.ms.match == 0 {
d.ms.match = 1
d.ms.pos = matchAt
d.ms.length = int64(len(p))
} else {
// 2015-08-09
// 检查与上一个匹配是否能够合并
if d.ms.pos+d.ms.length == matchAt {
d.ms.length += int64(len(p))
} else {
d.mss = append(d.mss, d.ms)
if d.debug {
fmt.Printf(" delta match (not merged!!!): pos=%d len=%d\n",
d.ms.pos, d.ms.length)
}
d.ms.match = 1
d.ms.pos = matchAt
d.ms.length = int64(len(p))
}
}
}
}
return
}
func (d *delta) dumpSign() {
var s string
sig := d.sig
s = fmt.Sprintf("dump Signature:\n src length: %d blocks: %d tlen: %d block len: %d sum len: %d magic: 0x%x\n",
sig.flength, sig.count, sig.flength, sig.block_len, sig.strong_sum_len, sig.magic)
for _, block_sigs := range sig.block_sigs {
//s += fmt.Sprintf(" block sum: 0x%x:\n", sum)
for _, block_sig := range block_sigs {
s += fmt.Sprintf(" block index: %d block weak sum: 0x%x strong sum: %x\n", block_sig.i, block_sig.wsum, block_sig.ssum)
}
}
fmt.Println(s)
}
// 比较两个MatchStats是否相同
func (d1 *delta) equalMatchStats(d2 *delta) bool {
if len(d1.mss) != len(d2.mss) {
return false
}
for i := 0; i < len(d1.mss); i++ {
m1 := d1.mss[i]
m2 := d2.mss[i]
if m1.length != m2.length || m1.match != m2.match || m1.pos != m2.pos {
return false
}
}
return true
}
// 打印到终端,调试用
func (d *delta) dump() {
buf := &bytes.Buffer{}
d.dumpMatchStats(buf)
fmt.Println(string(buf.Bytes()))
}
// 打印matchstats
func (d *delta) dumpMatchStats(wr io.Writer) {
pos := int64(0)
wr.Write([]byte(fmt.Sprintf("\nDelta info: blockLen=%d matchBlock=%d\n",
d.blockLen, len(d.mss))))
for i, ms := range d.mss {
switch ms.match {
case 1:
wr.Write([]byte(fmt.Sprintf("Match Block(%d): start at %d %d, length: %d\n", i, pos, ms.pos, ms.length)))
pos += ms.length
case -1:
wr.Write([]byte(fmt.Sprintf("Miss Block(%d): start at %d %d, length: %d\n", i, pos, ms.pos, ms.length)))
pos += ms.length
default:
panic("ms.match should only be 1 or -1.")
}
}
}
// 生成delta文件
// 1 delta文件头
// 2 将matchStat写入delta文件
//
func (d *delta) flush(src io.ReadSeeker) (err error) {
err = d.writeHeader()
if err != nil {
return
}
for _, ms := range d.mss {
switch ms.match {
case 1:
if err = d.flushMatch(ms); err != nil {
panic(fmt.Sprintf("flushMatch failed: %s matchStat: %v", err.Error(), ms))
return
}
case -1:
if err = d.flushMiss(ms, src); err != nil {
panic(fmt.Sprintf("flushMiss failed: %s: matchStat: %v", err.Error(), ms))
return
}
default:
panic("ms.match should only be 1 or -1.")
}
}
// todo: delta文件结尾
return nil
}
func int64Length(i uint64) uint8 {
if i&uint64(0xffffffff00000000) != 0 {
return 8
} else if i&uint64(0xffffffffffff0000) != 0 {
return 4
} else if i&uint64(0xffffffffffffff00) != 0 {
return 2
}
return 1
}
func intLength(i uint32) uint8 {
if i&uint32(0xffff0000) != 0 {
return 4
} else if i&uint32(0xffffff00) != 0 {
return 2
}
return 1
}
// cmd: 1字节
// pos: 变长,1,2,4,8字节,根据cmd决定
// length: 变长:1,2,4,8字节,根据cmd决定
func (d *delta) flushMatch(ms matchStat) (err error) {
var (
cmd uint8
buf []byte
)
whereBytes := int64Length(uint64(ms.pos))
lenBytes := int64Length(uint64(ms.length))
switch whereBytes {
case 8:
cmd = RS_OP_COPY_N8_N1
case 4:
cmd = RS_OP_COPY_N4_N1
case 2:
cmd = RS_OP_COPY_N2_N1
case 1:
cmd = RS_OP_COPY_N1_N1
}
switch lenBytes {
case 8:
cmd += 3
case 4:
cmd += 2
case 2:
cmd += 1
case 1:
}
buf = append(buf, byte(cmd))
buf = append(buf, vhtonll(uint64(ms.pos), int8(whereBytes))...)
buf = append(buf, vhtonll(uint64(ms.length), int8(lenBytes))...)
_, err = d.outer.Write(buf)
if d.debug {
fmt.Printf(" flush Match [where=%d len=%d], buf length: %d\n",
ms.pos, ms.length, len(buf))
}
return
}
// cmd: 1字节
// length: 变长:1,2,4,8字节,根据cmd决定
// 内容区: 变长,长度=length
// 2015-08-10: todo: 数据压缩
func (d *delta) flushMiss(ms matchStat, src io.ReadSeeker) (err error) {
var (
//n int
ml int64 // miss length
cmd uint8
hdr []byte
buf []byte
tmp []byte
)
bytes := int64Length(uint64(ms.length))
switch bytes {
case 8:
cmd = RS_OP_LITERAL_N8
case 4:
cmd = RS_OP_LITERAL_N4
case 2:
cmd = RS_OP_LITERAL_N2
case 1:
cmd = RS_OP_LITERAL_N1
}
// 写入miss block头部
hdr = append(hdr, byte(cmd))
hdr = append(hdr, vhtonll(uint64(ms.length), int8(bytes))...)
if _, err = d.outer.Write(hdr); err != nil {
return
}
if _, err = src.Seek(ms.pos, 0); err != nil {
err = errors.New("Seek failed: " + err.Error())
return
}
ml = ms.length
buf = make([]byte, 4096)
for err == nil && ml > 0 {
if ml >= 4096 {
tmp = buf[0:4096]
ml -= 4096
} else {
tmp = buf[0:ml]
ml = 0
}
// 不应该出现错误
_, err = src.Read(tmp)
if err != nil {
panic(fmt.Sprintf("pipe: read failed: expect %d, error: %s", len(tmp), err.Error()))
}
if _, err = d.outer.Write(tmp); err != nil {
return
}
}
if d.debug {
fmt.Printf(" flush miss [where=%d len=%d], hdr len: %d miss len: %d\n",
ms.pos, ms.length, len(hdr), ms.length)
}
return
}