func Symlink(linkname string, filename string, consumer *state.Consumer) error {
consumer.Debugf("ln -s %s %s", linkname, filename)
err := os.RemoveAll(filename)
if err != nil {
return errors.Wrap(err, 1)
}
dirname := filepath.Dir(filename)
err = os.MkdirAll(dirname, LuckyMode)
if err != nil {
return errors.Wrap(err, 1)
}
err = os.Symlink(linkname, filename)
if err != nil {
return errors.Wrap(err, 1)
}
return nil
}
// Faster Suffix Sorting, see: http://www.larsson.dogma.net/ssrev-tr.pdf
// Output `I` is a sorted suffix array.
// TODO: implement parallel sorting as a faster alternative for high-RAM environments
// see http://www.zbh.uni-hamburg.de/pubs/pdf/FutAluKur2001.pdf
func qsufsort(obuf []byte, ctx *DiffContext, consumer *state.Consumer) []int32 {
parallel := ctx.SuffixSortConcurrency != 0
numWorkers := ctx.SuffixSortConcurrency
if numWorkers < 1 {
numWorkers += runtime.NumCPU()
}
var buckets [256]int32
var i, h int32
var obuflen = int32(len(obuf))
I := make([]int32, obuflen+1)
V := make([]int32, obuflen+1)
for _, c := range obuf {
buckets[c]++
}
for i = 1; i < 256; i++ {
buckets[i] += buckets[i-1]
}
copy(buckets[1:], buckets[:])
buckets[0] = 0
for i, c := range obuf {
buckets[c]++
I[buckets[c]] = int32(i)
}
I[0] = obuflen
for i, c := range obuf {
V[i] = buckets[c]
}
V[obuflen] = 0
for i = 1; i < 256; i++ {
if buckets[i] == buckets[i-1]+1 {
I[buckets[i]] = -1
}
}
I[0] = -1
const progressInterval = 64 * 1024
var V2 []int32
var marks []mark
if parallel {
consumer.Debugf("parallel suffix sorting (%d workers)", numWorkers)
V2 = append([]int32{}, V...)
marks = make([]mark, 0)
} else {
consumer.Debugf("single-core suffix sorting")
}
// we buffer the tasks channel so that we can queue workloads (and
// combine sorted groups) faster than workers can handle them: this helps throughput.
// picking a value too small would lower core utilization.
// picking a value too large would add overhead, negating the benefits.
taskBufferSize := numWorkers * 4
done := make(chan bool)
var copyStart time.Time
var copyDuration time.Duration
for h = 1; I[0] != -(obuflen + 1); h += h {
// in practice, h < 32, so this is a calculated waste of memory
tasks := make(chan sortTask, taskBufferSize)
if parallel {
// in parallel mode, fan-out sorting tasks to a few workers
for i := 0; i < numWorkers; i++ {
go func() {
for task := range tasks {
// see split's definition for why V and V2 are necessary
split(I, V, V2, task.start, task.length, task.h)
}
done <- true
}()
}
// keep track of combined groups we found while scanning I
marks = marks[:0]
}
consumer.ProgressLabel(fmt.Sprintf("Suffix sorting (%d-order)", h))
// used to combine adjacent sorted groups into a single, bigger sorted group
// eventually we'll be left with a single sorted group of size len(obuf)+1
var n int32
// total number of suffixes sorted at the end of this pass
var nTotal int32
// last index at which we emitted progress info
var lastI int32
for i = 0; i < obuflen+1; {
if i-lastI > progressInterval {
// calling Progress on every iteration woudl slow down diff significantly
progress := float64(i) / float64(obuflen)
consumer.Progress(progress)
lastI = i
}
if I[i] < 0 {
// found a combined-sorted group
// n accumulates adjacent combined-sorted groups
n -= I[i]
// count towards total number of suffixes sorted
nTotal -= I[i]
// skip over it, since it's already sorted
i -= I[i]
} else {
if n != 0 {
// before we encountered this group, we had "-n" sorted suffixes
// (potentially from different groups), merge them into a single group
if parallel {
// if working in parallel, only mark after tasks are done, otherwise
// it messes with indices the quicksort is relying on
marks = append(marks, mark{index: i - n, value: -n})
} else {
// if working sequentially, we can mark them immediately.
I[i-n] = -n
}
}
// retrieve size of group to sort (g - f + 1), where g is the group number
// and f is the index of the start of the group (i, here)
n = V[I[i]] + 1 - i
// only hand out sorts to other cores if:
// - we're doing a parallel suffix sort,
// - the array to sort is big enough
// otherwise, the overhead cancels the performance gains.
// this means not all cores will always be maxed out
// (especially in later passes), but we'll still complete sooner
if parallel && n > 128 {
tasks <- sortTask{
start: i,
length: n,
h: h,
}
} else {
if parallel {
// other groups might be sorted in parallel, still need to use V and V2
split(I, V, V2, i, n, h)
} else {
// no need for V2 in sequential mode, only one core ever reads/write to V
split(I, V, V, i, n, h)
}
}
// advance over entire group
i += n
// reset "combined sorted group" length accumulator
n = 0
}
}
if parallel {
// this will break out of the "for-range" of the workers when
// the channel's buffer is empty
close(tasks)
for i := 0; i < numWorkers; i++ {
// workers cannot err, only panic, we're just looking for completion here
<-done
}
// we can now safely mark groups as sorted
for _, mark := range marks {
// consumer.Debugf("Setting I[%d] to %d", I[i-n], -n)
I[mark.index] = mark.value
}
}
if n != 0 {
// eventually, this will write I[0] = -(len(obuf) + 1), when
// all suffixes are sorted. until then, it'll catch the last combined
// sorted group
I[i-n] = -n
}
// consumer.Debugf("%d/%d was already done (%.2f%%)", doneI, (obuflen + 1),
// 100.0*float64(doneI)/float64(obuflen+1))
if parallel {
if ctx.MeasureParallelOverhead {
copyStart = time.Now()
copy(V, V2)
copyDuration += time.Since(copyStart)
} else {
copy(V, V2)
}
}
}
if parallel && ctx.MeasureParallelOverhead {
consumer.Debugf("Parallel copy overhead: %s", copyDuration)
}
// at this point, V[i] contains the group number of the ith suffix:
// all groups are now of size 1, so V[i] is the final position of the
// suffix in the list of indices of sorted suffixes. Commit it to I,
// our result.
for i = 0; i < obuflen+1; i++ {
I[V[i]] = i
}
return I
}
// Do computes the difference between old and new, according to the bsdiff
// algorithm, and writes the result to patch.
func (ctx *DiffContext) Do(old, new io.Reader, writeMessage WriteMessageFunc, consumer *state.Consumer) error {
var memstats *runtime.MemStats
if ctx.MeasureMem {
memstats = &runtime.MemStats{}
runtime.ReadMemStats(memstats)
consumer.Debugf("Allocated bytes at start of bsdiff: %s (%s total)", humanize.IBytes(uint64(memstats.Alloc)), humanize.IBytes(uint64(memstats.TotalAlloc)))
}
if ctx.db == nil {
ctx.db = make([]byte, MaxMessageSize)
}
if ctx.eb == nil {
ctx.eb = make([]byte, MaxMessageSize)
}
obuf, err := ioutil.ReadAll(old)
if err != nil {
return err
}
if int64(len(obuf)) > MaxFileSize {
return fmt.Errorf("bsdiff: old file too large (%s > %s)", humanize.IBytes(uint64(len(obuf))), humanize.IBytes(uint64(MaxFileSize)))
}
obuflen := int32(len(obuf))
nbuf, err := ioutil.ReadAll(new)
if err != nil {
return err
}
if int64(len(nbuf)) > MaxFileSize {
// TODO: provide a different (int64) codepath for >=2GB files
return fmt.Errorf("bsdiff: new file too large (%s > %s)", humanize.IBytes(uint64(len(nbuf))), humanize.IBytes(uint64(MaxFileSize)))
}
nbuflen := int32(len(nbuf))
if ctx.MeasureMem {
runtime.ReadMemStats(memstats)
consumer.Debugf("Allocated bytes after ReadAll: %s (%s total)", humanize.IBytes(uint64(memstats.Alloc)), humanize.IBytes(uint64(memstats.TotalAlloc)))
}
var lenf int32
startTime := time.Now()
I := qsufsort(obuf, ctx, consumer)
duration := time.Since(startTime)
consumer.Debugf("Suffix sorting done in %s", duration)
if ctx.MeasureMem {
runtime.ReadMemStats(memstats)
consumer.Debugf("Allocated bytes after qsufsort: %s (%s total)", humanize.IBytes(uint64(memstats.Alloc)), humanize.IBytes(uint64(memstats.TotalAlloc)))
}
// FIXME: the streaming format allows us to allocate less than that
db := make([]byte, len(nbuf))
eb := make([]byte, len(nbuf))
bsdc := &Control{}
consumer.ProgressLabel("Scanning...")
// Compute the differences, writing ctrl as we go
var scan, pos, length int32
var lastscan, lastpos, lastoffset int32
for scan < nbuflen {
var oldscore int32
scan += length
progress := float64(scan) / float64(nbuflen)
consumer.Progress(progress)
for scsc := scan; scan < nbuflen; scan++ {
pos, length = search(I, obuf, nbuf[scan:], 0, obuflen)
for ; scsc < scan+length; scsc++ {
if scsc+lastoffset < obuflen &&
obuf[scsc+lastoffset] == nbuf[scsc] {
oldscore++
}
}
if (length == oldscore && length != 0) || length > oldscore+8 {
break
}
if scan+lastoffset < obuflen && obuf[scan+lastoffset] == nbuf[scan] {
oldscore--
}
}
if length != oldscore || scan == nbuflen {
var s, Sf int32
lenf = 0
for i := int32(0); lastscan+i < scan && lastpos+i < obuflen; {
if obuf[lastpos+i] == nbuf[lastscan+i] {
s++
}
i++
if s*2-i > Sf*2-lenf {
Sf = s
lenf = i
}
}
lenb := int32(0)
if scan < nbuflen {
var s, Sb int32
for i := int32(1); (scan >= lastscan+i) && (pos >= i); i++ {
if obuf[pos-i] == nbuf[scan-i] {
s++
}
if s*2-i > Sb*2-lenb {
Sb = s
lenb = i
}
}
}
if lastscan+lenf > scan-lenb {
overlap := (lastscan + lenf) - (scan - lenb)
s := int32(0)
Ss := int32(0)
lens := int32(0)
for i := int32(0); i < overlap; i++ {
if nbuf[lastscan+lenf-overlap+i] == obuf[lastpos+lenf-overlap+i] {
s++
}
if nbuf[scan-lenb+i] == obuf[pos-lenb+i] {
s--
}
if s > Ss {
Ss = s
lens = i + 1
}
}
lenf += lens - overlap
lenb -= lens
}
for i := int32(0); i < lenf; i++ {
db[i] = nbuf[lastscan+i] - obuf[lastpos+i]
}
for i := int32(0); i < (scan-lenb)-(lastscan+lenf); i++ {
eb[i] = nbuf[lastscan+lenf+i]
}
bsdc.Add = db[:lenf]
bsdc.Copy = eb[:(scan-lenb)-(lastscan+lenf)]
bsdc.Seek = int64((pos - lenb) - (lastpos + lenf))
err := writeMessage(bsdc)
if err != nil {
return err
}
lastscan = scan - lenb
lastpos = pos - lenb
lastoffset = pos - scan
}
}
if ctx.MeasureMem {
runtime.ReadMemStats(memstats)
consumer.Debugf("Allocated bytes after scan: %s (%s total)", humanize.IBytes(uint64(memstats.Alloc)), humanize.IBytes(uint64(memstats.TotalAlloc)))
}
bsdc.Reset()
bsdc.Eof = true
err = writeMessage(bsdc)
if err != nil {
return err
}
return nil
}