swarm/storage: pyramid chunker re-write (#14382)

11 files changed, 1007 insertions, 235 deletions

diff --git a/swarm/network/depo.go b/swarm/network/depo.go
index e76bfa66c..8695bf5d9 100644
--- a/swarm/network/depo.go
+++ b/swarm/network/depo.go
@@ -29,12 +29,12 @@ import (
 // Handler for storage/retrieval related protocol requests
 // implements the StorageHandler interface used by the bzz protocol
 type Depo struct {
-	hashfunc   storage.Hasher
+	hashfunc   storage.SwarmHasher
 	localStore storage.ChunkStore
 	netStore   storage.ChunkStore
 }
 
-func NewDepo(hash storage.Hasher, localStore, remoteStore storage.ChunkStore) *Depo {
+func NewDepo(hash storage.SwarmHasher, localStore, remoteStore storage.ChunkStore) *Depo {
 	return &Depo{
 		hashfunc:   hash,
 		localStore: localStore,
diff --git a/swarm/storage/chunker.go b/swarm/storage/chunker.go
index ca85e4333..0454828b9 100644
--- a/swarm/storage/chunker.go
+++ b/swarm/storage/chunker.go
@@ -20,9 +20,9 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
-	"hash"
 	"io"
 	"sync"
+	"time"
 )
 
 /*
@@ -50,14 +50,6 @@ data_{i} := size(subtree_{i}) || key_{j} || key_{j+1} .... || key_{j+n-1}
  The underlying hash function is configurable
 */
 
-const (
-	defaultHash = "SHA3"
-	// defaultHash = "BMTSHA3" // http://golang.org/pkg/hash/#Hash
-	// defaultHash           = "SHA256" // http://golang.org/pkg/hash/#Hash
-	defaultBranches int64 = 128
-	// hashSize     int64 = hasherfunc.New().Size() // hasher knows about its own length in bytes
-	// chunksize    int64 = branches * hashSize     // chunk is defined as this
-)
 
 /*
 Tree chunker is a concrete implementation of data chunking.
@@ -67,25 +59,19 @@ If all is well it is possible to implement this by simply composing readers so t
 The hashing itself does use extra copies and allocation though, since it does need it.
 */
 
-type ChunkerParams struct {
-	Branches int64
-	Hash     string
-}
-
-func NewChunkerParams() *ChunkerParams {
-	return &ChunkerParams{
-		Branches: defaultBranches,
-		Hash:     defaultHash,
-	}
-}
+var (
+	errAppendOppNotSuported = errors.New("Append operation not supported")
+	errOperationTimedOut = errors.New("operation timed out")
+)
 
 type TreeChunker struct {
 	branches int64
-	hashFunc Hasher
+	hashFunc SwarmHasher
 	// calculated
 	hashSize    int64 // self.hashFunc.New().Size()
 	chunkSize   int64 // hashSize* branches
-	workerCount int
+	workerCount int64 // the number of worker routines used
+	workerLock	sync.RWMutex // lock for the worker count
 }
 
 func NewTreeChunker(params *ChunkerParams) (self *TreeChunker) {
@@ -94,7 +80,8 @@ func NewTreeChunker(params *ChunkerParams) (self *TreeChunker) {
 	self.branches = params.Branches
 	self.hashSize = int64(self.hashFunc().Size())
 	self.chunkSize = self.hashSize * self.branches
-	self.workerCount = 1
+	self.workerCount = 0
+
 	return
 }
 
@@ -114,13 +101,31 @@ type hashJob struct {
 	parentWg *sync.WaitGroup
 }
 
-func (self *TreeChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, swg, wwg *sync.WaitGroup) (Key, error) {
+func (self *TreeChunker) incrementWorkerCount() {
+	self.workerLock.Lock()
+	defer self.workerLock.Unlock()
+	self.workerCount += 1
+}
+
+func (self *TreeChunker) getWorkerCount() int64 {
+	self.workerLock.RLock()
+	defer self.workerLock.RUnlock()
+	return self.workerCount
+}
 
+func (self *TreeChunker) decrementWorkerCount() {
+	self.workerLock.Lock()
+	defer self.workerLock.Unlock()
+	self.workerCount -= 1
+}
+
+func (self *TreeChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, swg, wwg *sync.WaitGroup) (Key, error) {
 	if self.chunkSize <= 0 {
 		panic("chunker must be initialised")
 	}
 
-	jobC := make(chan *hashJob, 2*processors)
+
+	jobC := make(chan *hashJob, 2*ChunkProcessors)
 	wg := &sync.WaitGroup{}
 	errC := make(chan error)
 	quitC := make(chan bool)
@@ -129,6 +134,8 @@ func (self *TreeChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, s
 	if wwg != nil {
 		wwg.Add(1)
 	}
+
+	self.incrementWorkerCount()
 	go self.hashWorker(jobC, chunkC, errC, quitC, swg, wwg)
 
 	depth := 0
@@ -157,10 +164,15 @@ func (self *TreeChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, s
 		close(errC)
 	}()
 
-	//TODO: add a timeout
-	if err := <-errC; err != nil {
-		close(quitC)
-		return nil, err
+
+	defer close(quitC)
+	select {
+	case err := <-errC:
+		if err != nil {
+			return nil, err
+		}
+	case <-time.NewTimer(splitTimeout).C:
+		return nil,errOperationTimedOut
 	}
 
 	return key, nil
@@ -168,6 +180,8 @@ func (self *TreeChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, s
 
 func (self *TreeChunker) split(depth int, treeSize int64, key Key, data io.Reader, size int64, jobC chan *hashJob, chunkC chan *Chunk, errC chan error, quitC chan bool, parentWg, swg, wwg *sync.WaitGroup) {
 
+	//
+
 	for depth > 0 && size < treeSize {
 		treeSize /= self.branches
 		depth--
@@ -223,12 +237,15 @@ func (self *TreeChunker) split(depth int, treeSize int64, key Key, data io.Reade
 	// parentWg.Add(1)
 	// go func() {
 	childrenWg.Wait()
-	if len(jobC) > self.workerCount && self.workerCount < processors {
+
+	worker := self.getWorkerCount()
+	if int64(len(jobC)) > worker && worker < ChunkProcessors {
 		if wwg != nil {
 			wwg.Add(1)
 		}
-		self.workerCount++
+		self.incrementWorkerCount()
 		go self.hashWorker(jobC, chunkC, errC, quitC, swg, wwg)
+
 	}
 	select {
 	case jobC <- &hashJob{key, chunk, size, parentWg}:
@@ -237,6 +254,8 @@ func (self *TreeChunker) split(depth int, treeSize int64, key Key, data io.Reade
 }
 
 func (self *TreeChunker) hashWorker(jobC chan *hashJob, chunkC chan *Chunk, errC chan error, quitC chan bool, swg, wwg *sync.WaitGroup) {
+	defer self.decrementWorkerCount()
+
 	hasher := self.hashFunc()
 	if wwg != nil {
 		defer wwg.Done()
@@ -249,7 +268,6 @@ func (self *TreeChunker) hashWorker(jobC chan *hashJob, chunkC chan *Chunk, errC
 				return
 			}
 			// now we got the hashes in the chunk, then hash the chunks
-			hasher.Reset()
 			self.hashChunk(hasher, job, chunkC, swg)
 		case <-quitC:
 			return
@@ -260,9 +278,11 @@ func (self *TreeChunker) hashWorker(jobC chan *hashJob, chunkC chan *Chunk, errC
 // The treeChunkers own Hash hashes together
 // - the size (of the subtree encoded in the Chunk)
 // - the Chunk, ie. the contents read from the input reader
-func (self *TreeChunker) hashChunk(hasher hash.Hash, job *hashJob, chunkC chan *Chunk, swg *sync.WaitGroup) {
-	hasher.Write(job.chunk)
+func (self *TreeChunker) hashChunk(hasher SwarmHash, job *hashJob, chunkC chan *Chunk, swg *sync.WaitGroup) {
+	hasher.ResetWithLength(job.chunk[:8]) // 8 bytes of length
+	hasher.Write(job.chunk[8:])           // minus 8 []byte length
 	h := hasher.Sum(nil)
+
 	newChunk := &Chunk{
 		Key:   h,
 		SData: job.chunk,
@@ -285,6 +305,10 @@ func (self *TreeChunker) hashChunk(hasher hash.Hash, job *hashJob, chunkC chan *
 	}
 }
 
+func (self *TreeChunker) Append(key Key, data io.Reader, chunkC chan *Chunk, swg, wwg *sync.WaitGroup) (Key, error) {
+	return nil, errAppendOppNotSuported
+}
+
 // LazyChunkReader implements LazySectionReader
 type LazyChunkReader struct {
 	key       Key         // root key
@@ -298,7 +322,6 @@ type LazyChunkReader struct {
 
 // implements the Joiner interface
 func (self *TreeChunker) Join(key Key, chunkC chan *Chunk) LazySectionReader {
-
 	return &LazyChunkReader{
 		key:       key,
 		chunkC:    chunkC,
diff --git a/swarm/storage/chunker_test.go b/swarm/storage/chunker_test.go
index 426074e59..b41d7dd33 100644
--- a/swarm/storage/chunker_test.go
+++ b/swarm/storage/chunker_test.go
@@ -20,12 +20,14 @@ import (
 	"bytes"
 	"crypto/rand"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
-	"runtime"
 	"sync"
 	"testing"
 	"time"
+
+	"github.com/ethereum/go-ethereum/crypto/sha3"
 )
 
 /*
@@ -43,7 +45,7 @@ type chunkerTester struct {
 	t      test
 }
 
-func (self *chunkerTester) Split(chunker Splitter, data io.Reader, size int64, chunkC chan *Chunk, swg *sync.WaitGroup, expectedError error) (key Key) {
+func (self *chunkerTester) Split(chunker Splitter, data io.Reader, size int64, chunkC chan *Chunk, swg *sync.WaitGroup, expectedError error) (key Key, err error) {
 	// reset
 	self.chunks = make(map[string]*Chunk)
 
@@ -54,13 +56,13 @@ func (self *chunkerTester) Split(chunker Splitter, data io.Reader, size int64, c
 	quitC := make(chan bool)
 	timeout := time.After(600 * time.Second)
 	if chunkC != nil {
-		go func() {
+		go func() error {
 			for {
 				select {
 				case <-timeout:
-					self.t.Fatalf("Join timeout error")
+					return errors.New(("Split timeout error"))
 				case <-quitC:
-					return
+					return nil
 				case chunk := <-chunkC:
 					// self.chunks = append(self.chunks, chunk)
 					self.chunks[chunk.Key.String()] = chunk
@@ -68,22 +70,69 @@ func (self *chunkerTester) Split(chunker Splitter, data io.Reader, size int64, c
 						chunk.wg.Done()
 					}
 				}
+
 			}
 		}()
 	}
-	key, err := chunker.Split(data, size, chunkC, swg, nil)
+
+	key, err = chunker.Split(data, size, chunkC, swg, nil)
 	if err != nil && expectedError == nil {
-		self.t.Fatalf("Split error: %v", err)
-	} else if expectedError != nil && (err == nil || err.Error() != expectedError.Error()) {
-		self.t.Fatalf("Not receiving the correct error! Expected %v, received %v", expectedError, err)
+		err = errors.New(fmt.Sprintf("Split error: %v", err))
 	}
+
 	if chunkC != nil {
 		if swg != nil {
 			swg.Wait()
 		}
 		close(quitC)
 	}
-	return
+	return key, err
+}
+
+func (self *chunkerTester) Append(chunker Splitter, rootKey Key, data io.Reader, chunkC chan *Chunk, swg *sync.WaitGroup, expectedError error) (key Key, err error) {
+	quitC := make(chan bool)
+	timeout := time.After(60 * time.Second)
+	if chunkC != nil {
+		go func() error {
+			for {
+				select {
+				case <-timeout:
+					return errors.New(("Append timeout error"))
+				case <-quitC:
+					return nil
+				case chunk := <-chunkC:
+					if chunk != nil {
+						stored, success := self.chunks[chunk.Key.String()]
+						if !success {
+							// Requesting data
+							self.chunks[chunk.Key.String()] = chunk
+							if chunk.wg != nil {
+								chunk.wg.Done()
+							}
+						} else {
+							// getting data
+							chunk.SData = stored.SData
+							chunk.Size = int64(binary.LittleEndian.Uint64(chunk.SData[0:8]))
+							close(chunk.C)
+						}
+					}
+				}
+			}
+		}()
+	}
+
+	key, err = chunker.Append(rootKey, data, chunkC, swg, nil)
+	if err != nil && expectedError == nil {
+		err = errors.New(fmt.Sprintf("Append error: %v", err))
+	}
+
+	if chunkC != nil {
+		if swg != nil {
+			swg.Wait()
+		}
+		close(quitC)
+	}
+	return key, err
 }
 
 func (self *chunkerTester) Join(chunker Chunker, key Key, c int, chunkC chan *Chunk, quitC chan bool) LazySectionReader {
@@ -93,22 +142,20 @@ func (self *chunkerTester) Join(chunker Chunker, key Key, c int, chunkC chan *Ch
 
 	timeout := time.After(600 * time.Second)
 	i := 0
-	go func() {
+	go func() error {
 		for {
 			select {
 			case <-timeout:
-				self.t.Fatalf("Join timeout error")
-
+				return errors.New(("Join timeout error"))
 			case chunk, ok := <-chunkC:
 				if !ok {
 					close(quitC)
-					return
+					return nil
 				}
 				// this just mocks the behaviour of a chunk store retrieval
 				stored, success := self.chunks[chunk.Key.String()]
 				if !success {
-					self.t.Fatalf("not found")
-					return
+					return errors.New(("Not found"))
 				}
 				chunk.SData = stored.SData
 				chunk.Size = int64(binary.LittleEndian.Uint64(chunk.SData[0:8]))
@@ -136,11 +183,15 @@ func testRandomBrokenData(splitter Splitter, n int, tester *chunkerTester) {
 	chunkC := make(chan *Chunk, 1000)
 	swg := &sync.WaitGroup{}
 
-	key := tester.Split(splitter, brokendata, int64(n), chunkC, swg, fmt.Errorf("Broken reader"))
+	expectedError := fmt.Errorf("Broken reader")
+	key, err := tester.Split(splitter, brokendata, int64(n), chunkC, swg, expectedError)
+	if err == nil || err.Error() != expectedError.Error() {
+		tester.t.Fatalf("Not receiving the correct error! Expected %v, received %v", expectedError, err)
+	}
 	tester.t.Logf(" Key = %v\n", key)
 }
 
-func testRandomData(splitter Splitter, n int, tester *chunkerTester) {
+func testRandomData(splitter Splitter, n int, tester *chunkerTester) Key {
 	if tester.inputs == nil {
 		tester.inputs = make(map[uint64][]byte)
 	}
@@ -156,7 +207,10 @@ func testRandomData(splitter Splitter, n int, tester *chunkerTester) {
 	chunkC := make(chan *Chunk, 1000)
 	swg := &sync.WaitGroup{}
 
-	key := tester.Split(splitter, data, int64(n), chunkC, swg, nil)
+	key, err := tester.Split(splitter, data, int64(n), chunkC, swg, nil)
+	if err != nil {
+		tester.t.Fatalf(err.Error())
+	}
 	tester.t.Logf(" Key = %v\n", key)
 
 	chunkC = make(chan *Chunk, 1000)
@@ -176,29 +230,145 @@ func testRandomData(splitter Splitter, n int, tester *chunkerTester) {
 	}
 	close(chunkC)
 	<-quitC
+
+	return key
+}
+
+func testRandomDataAppend(splitter Splitter, n, m int, tester *chunkerTester) {
+	if tester.inputs == nil {
+		tester.inputs = make(map[uint64][]byte)
+	}
+	input, found := tester.inputs[uint64(n)]
+	var data io.Reader
+	if !found {
+		data, input = testDataReaderAndSlice(n)
+		tester.inputs[uint64(n)] = input
+	} else {
+		data = io.LimitReader(bytes.NewReader(input), int64(n))
+	}
+
+	chunkC := make(chan *Chunk, 1000)
+	swg := &sync.WaitGroup{}
+
+	key, err := tester.Split(splitter, data, int64(n), chunkC, swg, nil)
+	if err != nil {
+		tester.t.Fatalf(err.Error())
+	}
+	tester.t.Logf(" Key = %v\n", key)
+
+	//create a append data stream
+	appendInput, found := tester.inputs[uint64(m)]
+	var appendData io.Reader
+	if !found {
+		appendData, appendInput = testDataReaderAndSlice(m)
+		tester.inputs[uint64(m)] = appendInput
+	} else {
+		appendData = io.LimitReader(bytes.NewReader(appendInput), int64(m))
+	}
+
+	chunkC = make(chan *Chunk, 1000)
+	swg = &sync.WaitGroup{}
+
+	newKey, err := tester.Append(splitter, key, appendData, chunkC, swg, nil)
+	if err != nil {
+		tester.t.Fatalf(err.Error())
+	}
+	tester.t.Logf(" NewKey = %v\n", newKey)
+
+	chunkC = make(chan *Chunk, 1000)
+	quitC := make(chan bool)
+
+	chunker := NewTreeChunker(NewChunkerParams())
+	reader := tester.Join(chunker, newKey, 0, chunkC, quitC)
+	newOutput := make([]byte, n+m)
+	r, err := reader.Read(newOutput)
+	if r != (n + m) {
+		tester.t.Fatalf("read error  read: %v  n = %v  err = %v\n", r, n, err)
+	}
+
+	newInput := append(input, appendInput...)
+	if !bytes.Equal(newOutput, newInput) {
+		tester.t.Fatalf("input and output mismatch\n IN: %v\nOUT: %v\n", newInput, newOutput)
+	}
+
+	close(chunkC)
+}
+
+func TestSha3ForCorrectness(t *testing.T) {
+	tester := &chunkerTester{t: t}
+
+	size := 4096
+	input := make([]byte, size+8)
+	binary.LittleEndian.PutUint64(input[:8], uint64(size))
+
+	io.LimitReader(bytes.NewReader(input[8:]), int64(size))
+
+	rawSha3 := sha3.NewKeccak256()
+	rawSha3.Reset()
+	rawSha3.Write(input)
+	rawSha3Output := rawSha3.Sum(nil)
+
+	sha3FromMakeFunc := MakeHashFunc(SHA3Hash)()
+	sha3FromMakeFunc.ResetWithLength(input[:8])
+	sha3FromMakeFunc.Write(input[8:])
+	sha3FromMakeFuncOutput := sha3FromMakeFunc.Sum(nil)
+
+	if len(rawSha3Output) != len(sha3FromMakeFuncOutput) {
+		tester.t.Fatalf("Original SHA3 and abstracted Sha3 has different length %v:%v\n", len(rawSha3Output), len(sha3FromMakeFuncOutput))
+	}
+
+	if !bytes.Equal(rawSha3Output, sha3FromMakeFuncOutput) {
+		tester.t.Fatalf("Original SHA3 and abstracted Sha3 mismatch %v:%v\n", rawSha3Output, sha3FromMakeFuncOutput)
+	}
+
+}
+
+func TestDataAppend(t *testing.T) {
+	sizes := []int{1, 1, 1, 4095, 4096, 4097, 1, 1, 1, 123456, 2345678, 2345678}
+	appendSizes := []int{4095, 4096, 4097, 1, 1, 1, 8191, 8192, 8193, 9000, 3000, 5000}
+
+	tester := &chunkerTester{t: t}
+	chunker := NewPyramidChunker(NewChunkerParams())
+	for i, s := range sizes {
+		testRandomDataAppend(chunker, s, appendSizes[i], tester)
+
+	}
 }
 
 func TestRandomData(t *testing.T) {
-	// sizes := []int{123456}
-	sizes := []int{1, 60, 83, 179, 253, 1024, 4095, 4096, 4097, 8191, 8192, 8193, 123456, 2345678}
+	sizes := []int{1, 60, 83, 179, 253, 1024, 4095, 4096, 4097, 8191, 8192, 8193, 12287, 12288, 12289, 123456, 2345678}
 	tester := &chunkerTester{t: t}
+
 	chunker := NewTreeChunker(NewChunkerParams())
+	pyramid := NewPyramidChunker(NewChunkerParams())
 	for _, s := range sizes {
-		testRandomData(chunker, s, tester)
+		treeChunkerKey := testRandomData(chunker, s, tester)
+		pyramidChunkerKey := testRandomData(pyramid, s, tester)
+		if treeChunkerKey.String() != pyramidChunkerKey.String() {
+			tester.t.Fatalf("tree chunker and pyramid chunker key mismatch for size %v\n TC: %v\n PC: %v\n", s, treeChunkerKey.String(), pyramidChunkerKey.String())
+		}
 	}
-	pyramid := NewPyramidChunker(NewChunkerParams())
+
+	cp := NewChunkerParams()
+	cp.Hash = BMTHash
+	chunker = NewTreeChunker(cp)
+	pyramid = NewPyramidChunker(cp)
 	for _, s := range sizes {
-		testRandomData(pyramid, s, tester)
+		treeChunkerKey := testRandomData(chunker, s, tester)
+		pyramidChunkerKey := testRandomData(pyramid, s, tester)
+		if treeChunkerKey.String() != pyramidChunkerKey.String() {
+			tester.t.Fatalf("tree chunker BMT and pyramid chunker BMT key mismatch for size %v \n TC: %v\n PC: %v\n", s, treeChunkerKey.String(), pyramidChunkerKey.String())
+		}
 	}
+
 }
 
 func TestRandomBrokenData(t *testing.T) {
-	sizes := []int{1, 60, 83, 179, 253, 1024, 4095, 4096, 4097, 8191, 8192, 8193, 123456, 2345678}
+	sizes := []int{1, 60, 83, 179, 253, 1024, 4095, 4096, 4097, 8191, 8192, 8193, 12287, 12288, 12289, 123456, 2345678}
 	tester := &chunkerTester{t: t}
 	chunker := NewTreeChunker(NewChunkerParams())
 	for _, s := range sizes {
 		testRandomBrokenData(chunker, s, tester)
-		t.Logf("done size: %v", s)
 	}
 }
 
@@ -220,45 +390,100 @@ func benchmarkJoin(n int, t *testing.B) {
 		chunkC := make(chan *Chunk, 1000)
 		swg := &sync.WaitGroup{}
 
-		key := tester.Split(chunker, data, int64(n), chunkC, swg, nil)
-		// t.StartTimer()
+		key, err := tester.Split(chunker, data, int64(n), chunkC, swg, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
 		chunkC = make(chan *Chunk, 1000)
 		quitC := make(chan bool)
 		reader := tester.Join(chunker, key, i, chunkC, quitC)
 		benchReadAll(reader)
 		close(chunkC)
 		<-quitC
-		// t.StopTimer()
 	}
-	stats := new(runtime.MemStats)
-	runtime.ReadMemStats(stats)
-	fmt.Println(stats.Sys)
 }
 
-func benchmarkSplitTree(n int, t *testing.B) {
+func benchmarkSplitTreeSHA3(n int, t *testing.B) {
 	t.ReportAllocs()
 	for i := 0; i < t.N; i++ {
 		chunker := NewTreeChunker(NewChunkerParams())
 		tester := &chunkerTester{t: t}
 		data := testDataReader(n)
-		tester.Split(chunker, data, int64(n), nil, nil, nil)
+		_, err := tester.Split(chunker, data, int64(n), nil, nil, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
 	}
-	stats := new(runtime.MemStats)
-	runtime.ReadMemStats(stats)
-	fmt.Println(stats.Sys)
 }
 
-func benchmarkSplitPyramid(n int, t *testing.B) {
+func benchmarkSplitTreeBMT(n int, t *testing.B) {
+	t.ReportAllocs()
+	for i := 0; i < t.N; i++ {
+		cp := NewChunkerParams()
+		cp.Hash = BMTHash
+		chunker := NewTreeChunker(cp)
+		tester := &chunkerTester{t: t}
+		data := testDataReader(n)
+		_, err := tester.Split(chunker, data, int64(n), nil, nil, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
+	}
+}
+
+func benchmarkSplitPyramidSHA3(n int, t *testing.B) {
 	t.ReportAllocs()
 	for i := 0; i < t.N; i++ {
 		splitter := NewPyramidChunker(NewChunkerParams())
 		tester := &chunkerTester{t: t}
 		data := testDataReader(n)
-		tester.Split(splitter, data, int64(n), nil, nil, nil)
+		_, err := tester.Split(splitter, data, int64(n), nil, nil, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
+	}
+}
+
+func benchmarkSplitPyramidBMT(n int, t *testing.B) {
+	t.ReportAllocs()
+	for i := 0; i < t.N; i++ {
+		cp := NewChunkerParams()
+		cp.Hash = BMTHash
+		splitter := NewPyramidChunker(cp)
+		tester := &chunkerTester{t: t}
+		data := testDataReader(n)
+		_, err := tester.Split(splitter, data, int64(n), nil, nil, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
+	}
+}
+
+func benchmarkAppendPyramid(n, m int, t *testing.B) {
+	t.ReportAllocs()
+	for i := 0; i < t.N; i++ {
+		chunker := NewPyramidChunker(NewChunkerParams())
+		tester := &chunkerTester{t: t}
+		data := testDataReader(n)
+		data1 := testDataReader(m)
+
+		chunkC := make(chan *Chunk, 1000)
+		swg := &sync.WaitGroup{}
+		key, err := tester.Split(chunker, data, int64(n), chunkC, swg, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
+
+		chunkC = make(chan *Chunk, 1000)
+		swg = &sync.WaitGroup{}
+
+		_, err = tester.Append(chunker, key, data1, chunkC, swg, nil)
+		if err != nil {
+			tester.t.Fatalf(err.Error())
+		}
+
+		close(chunkC)
 	}
-	stats := new(runtime.MemStats)
-	runtime.ReadMemStats(stats)
-	fmt.Println(stats.Sys)
 }
 
 func BenchmarkJoin_2(t *testing.B) { benchmarkJoin(100, t) }
@@ -269,26 +494,59 @@ func BenchmarkJoin_6(t *testing.B) { benchmarkJoin(1000000, t) }
 func BenchmarkJoin_7(t *testing.B) { benchmarkJoin(10000000, t) }
 func BenchmarkJoin_8(t *testing.B) { benchmarkJoin(100000000, t) }
 
-func BenchmarkSplitTree_2(t *testing.B)  { benchmarkSplitTree(100, t) }
-func BenchmarkSplitTree_2h(t *testing.B) { benchmarkSplitTree(500, t) }
-func BenchmarkSplitTree_3(t *testing.B)  { benchmarkSplitTree(1000, t) }
-func BenchmarkSplitTree_3h(t *testing.B) { benchmarkSplitTree(5000, t) }
-func BenchmarkSplitTree_4(t *testing.B)  { benchmarkSplitTree(10000, t) }
-func BenchmarkSplitTree_4h(t *testing.B) { benchmarkSplitTree(50000, t) }
-func BenchmarkSplitTree_5(t *testing.B)  { benchmarkSplitTree(100000, t) }
-func BenchmarkSplitTree_6(t *testing.B)  { benchmarkSplitTree(1000000, t) }
-func BenchmarkSplitTree_7(t *testing.B)  { benchmarkSplitTree(10000000, t) }
-func BenchmarkSplitTree_8(t *testing.B)  { benchmarkSplitTree(100000000, t) }
-
-func BenchmarkSplitPyramid_2(t *testing.B)  { benchmarkSplitPyramid(100, t) }
-func BenchmarkSplitPyramid_2h(t *testing.B) { benchmarkSplitPyramid(500, t) }
-func BenchmarkSplitPyramid_3(t *testing.B)  { benchmarkSplitPyramid(1000, t) }
-func BenchmarkSplitPyramid_3h(t *testing.B) { benchmarkSplitPyramid(5000, t) }
-func BenchmarkSplitPyramid_4(t *testing.B)  { benchmarkSplitPyramid(10000, t) }
-func BenchmarkSplitPyramid_4h(t *testing.B) { benchmarkSplitPyramid(50000, t) }
-func BenchmarkSplitPyramid_5(t *testing.B)  { benchmarkSplitPyramid(100000, t) }
-func BenchmarkSplitPyramid_6(t *testing.B)  { benchmarkSplitPyramid(1000000, t) }
-func BenchmarkSplitPyramid_7(t *testing.B)  { benchmarkSplitPyramid(10000000, t) }
-func BenchmarkSplitPyramid_8(t *testing.B)  { benchmarkSplitPyramid(100000000, t) }
-
-// godep go test -bench ./swarm/storage -cpuprofile cpu.out -memprofile mem.out
+func BenchmarkSplitTreeSHA3_2(t *testing.B)  { benchmarkSplitTreeSHA3(100, t) }
+func BenchmarkSplitTreeSHA3_2h(t *testing.B) { benchmarkSplitTreeSHA3(500, t) }
+func BenchmarkSplitTreeSHA3_3(t *testing.B)  { benchmarkSplitTreeSHA3(1000, t) }
+func BenchmarkSplitTreeSHA3_3h(t *testing.B) { benchmarkSplitTreeSHA3(5000, t) }
+func BenchmarkSplitTreeSHA3_4(t *testing.B)  { benchmarkSplitTreeSHA3(10000, t) }
+func BenchmarkSplitTreeSHA3_4h(t *testing.B) { benchmarkSplitTreeSHA3(50000, t) }
+func BenchmarkSplitTreeSHA3_5(t *testing.B)  { benchmarkSplitTreeSHA3(100000, t) }
+func BenchmarkSplitTreeSHA3_6(t *testing.B)  { benchmarkSplitTreeSHA3(1000000, t) }
+func BenchmarkSplitTreeSHA3_7(t *testing.B)  { benchmarkSplitTreeSHA3(10000000, t) }
+func BenchmarkSplitTreeSHA3_8(t *testing.B)  { benchmarkSplitTreeSHA3(100000000, t) }
+
+func BenchmarkSplitTreeBMT_2(t *testing.B)  { benchmarkSplitTreeBMT(100, t) }
+func BenchmarkSplitTreeBMT_2h(t *testing.B) { benchmarkSplitTreeBMT(500, t) }
+func BenchmarkSplitTreeBMT_3(t *testing.B)  { benchmarkSplitTreeBMT(1000, t) }
+func BenchmarkSplitTreeBMT_3h(t *testing.B) { benchmarkSplitTreeBMT(5000, t) }
+func BenchmarkSplitTreeBMT_4(t *testing.B)  { benchmarkSplitTreeBMT(10000, t) }
+func BenchmarkSplitTreeBMT_4h(t *testing.B) { benchmarkSplitTreeBMT(50000, t) }
+func BenchmarkSplitTreeBMT_5(t *testing.B)  { benchmarkSplitTreeBMT(100000, t) }
+func BenchmarkSplitTreeBMT_6(t *testing.B)  { benchmarkSplitTreeBMT(1000000, t) }
+func BenchmarkSplitTreeBMT_7(t *testing.B)  { benchmarkSplitTreeBMT(10000000, t) }
+func BenchmarkSplitTreeBMT_8(t *testing.B)  { benchmarkSplitTreeBMT(100000000, t) }
+
+func BenchmarkSplitPyramidSHA3_2(t *testing.B)  { benchmarkSplitPyramidSHA3(100, t) }
+func BenchmarkSplitPyramidSHA3_2h(t *testing.B) { benchmarkSplitPyramidSHA3(500, t) }
+func BenchmarkSplitPyramidSHA3_3(t *testing.B)  { benchmarkSplitPyramidSHA3(1000, t) }
+func BenchmarkSplitPyramidSHA3_3h(t *testing.B) { benchmarkSplitPyramidSHA3(5000, t) }
+func BenchmarkSplitPyramidSHA3_4(t *testing.B)  { benchmarkSplitPyramidSHA3(10000, t) }
+func BenchmarkSplitPyramidSHA3_4h(t *testing.B) { benchmarkSplitPyramidSHA3(50000, t) }
+func BenchmarkSplitPyramidSHA3_5(t *testing.B)  { benchmarkSplitPyramidSHA3(100000, t) }
+func BenchmarkSplitPyramidSHA3_6(t *testing.B)  { benchmarkSplitPyramidSHA3(1000000, t) }
+func BenchmarkSplitPyramidSHA3_7(t *testing.B)  { benchmarkSplitPyramidSHA3(10000000, t) }
+func BenchmarkSplitPyramidSHA3_8(t *testing.B)  { benchmarkSplitPyramidSHA3(100000000, t) }
+
+func BenchmarkSplitPyramidBMT_2(t *testing.B)  { benchmarkSplitPyramidBMT(100, t) }
+func BenchmarkSplitPyramidBMT_2h(t *testing.B) { benchmarkSplitPyramidBMT(500, t) }
+func BenchmarkSplitPyramidBMT_3(t *testing.B)  { benchmarkSplitPyramidBMT(1000, t) }
+func BenchmarkSplitPyramidBMT_3h(t *testing.B) { benchmarkSplitPyramidBMT(5000, t) }
+func BenchmarkSplitPyramidBMT_4(t *testing.B)  { benchmarkSplitPyramidBMT(10000, t) }
+func BenchmarkSplitPyramidBMT_4h(t *testing.B) { benchmarkSplitPyramidBMT(50000, t) }
+func BenchmarkSplitPyramidBMT_5(t *testing.B)  { benchmarkSplitPyramidBMT(100000, t) }
+func BenchmarkSplitPyramidBMT_6(t *testing.B)  { benchmarkSplitPyramidBMT(1000000, t) }
+func BenchmarkSplitPyramidBMT_7(t *testing.B)  { benchmarkSplitPyramidBMT(10000000, t) }
+func BenchmarkSplitPyramidBMT_8(t *testing.B)  { benchmarkSplitPyramidBMT(100000000, t) }
+
+func BenchmarkAppendPyramid_2(t *testing.B)  { benchmarkAppendPyramid(100, 1000, t) }
+func BenchmarkAppendPyramid_2h(t *testing.B) { benchmarkAppendPyramid(500, 1000, t) }
+func BenchmarkAppendPyramid_3(t *testing.B)  { benchmarkAppendPyramid(1000, 1000, t) }
+func BenchmarkAppendPyramid_4(t *testing.B)  { benchmarkAppendPyramid(10000, 1000, t) }
+func BenchmarkAppendPyramid_4h(t *testing.B) { benchmarkAppendPyramid(50000, 1000, t) }
+func BenchmarkAppendPyramid_5(t *testing.B)  { benchmarkAppendPyramid(1000000, 1000, t) }
+func BenchmarkAppendPyramid_6(t *testing.B)  { benchmarkAppendPyramid(1000000, 1000, t) }
+func BenchmarkAppendPyramid_7(t *testing.B)  { benchmarkAppendPyramid(10000000, 1000, t) }
+func BenchmarkAppendPyramid_8(t *testing.B)  { benchmarkAppendPyramid(100000000, 1000, t) }
+
+// go test -timeout 20m -cpu 4 -bench=./swarm/storage -run no
+// If you dont add the timeout argument above .. the benchmark will timeout and dump
diff --git a/swarm/storage/common_test.go b/swarm/storage/common_test.go
index 44d1dd1f7..cd4c2ef13 100644
--- a/swarm/storage/common_test.go
+++ b/swarm/storage/common_test.go
@@ -76,7 +76,7 @@ func testStore(m ChunkStore, l int64, branches int64, t *testing.T) {
 	}()
 	chunker := NewTreeChunker(&ChunkerParams{
 		Branches: branches,
-		Hash:     defaultHash,
+		Hash:     SHA3Hash,
 	})
 	swg := &sync.WaitGroup{}
 	key, _ := chunker.Split(rand.Reader, l, chunkC, swg, nil)
diff --git a/swarm/storage/dbstore.go b/swarm/storage/dbstore.go
index cbeddb8cb..46a5c16cc 100644
--- a/swarm/storage/dbstore.go
+++ b/swarm/storage/dbstore.go
@@ -72,12 +72,12 @@ type DbStore struct {
 	gcPos, gcStartPos []byte
 	gcArray           []*gcItem
 
-	hashfunc Hasher
+	hashfunc SwarmHasher
 
 	lock sync.Mutex
 }
 
-func NewDbStore(path string, hash Hasher, capacity uint64, radius int) (s *DbStore, err error) {
+func NewDbStore(path string, hash SwarmHasher, capacity uint64, radius int) (s *DbStore, err error) {
 	s = new(DbStore)
 
 	s.hashfunc = hash
diff --git a/swarm/storage/dbstore_test.go b/swarm/storage/dbstore_test.go
index ddce7ccfe..dd165b576 100644
--- a/swarm/storage/dbstore_test.go
+++ b/swarm/storage/dbstore_test.go
@@ -29,7 +29,7 @@ func initDbStore(t *testing.T) *DbStore {
 	if err != nil {
 		t.Fatal(err)
 	}
-	m, err := NewDbStore(dir, MakeHashFunc(defaultHash), defaultDbCapacity, defaultRadius)
+	m, err := NewDbStore(dir, MakeHashFunc(SHA3Hash), defaultDbCapacity, defaultRadius)
 	if err != nil {
 		t.Fatal("can't create store:", err)
 	}
diff --git a/swarm/storage/localstore.go b/swarm/storage/localstore.go
index 58f59d0a2..b442e6cc5 100644
--- a/swarm/storage/localstore.go
+++ b/swarm/storage/localstore.go
@@ -28,7 +28,7 @@ type LocalStore struct {
 }
 
 // This constructor uses MemStore and DbStore as components
-func NewLocalStore(hash Hasher, params *StoreParams) (*LocalStore, error) {
+func NewLocalStore(hash SwarmHasher, params *StoreParams) (*LocalStore, error) {
 	dbStore, err := NewDbStore(params.ChunkDbPath, hash, params.DbCapacity, params.Radius)
 	if err != nil {
 		return nil, err
diff --git a/swarm/storage/netstore.go b/swarm/storage/netstore.go
index 746dd85f6..7b0612edc 100644
--- a/swarm/storage/netstore.go
+++ b/swarm/storage/netstore.go
@@ -36,7 +36,7 @@ NetStore falls back to a backend (CloudStorage interface)
 implemented by bzz/network/forwarder. forwarder or IPFS or IPΞS
 */
 type NetStore struct {
-	hashfunc   Hasher
+	hashfunc   SwarmHasher
 	localStore *LocalStore
 	cloud      CloudStore
 }
@@ -69,7 +69,7 @@ func NewStoreParams(path string) (self *StoreParams) {
 // netstore contructor, takes path argument that is used to initialise dbStore,
 // the persistent (disk) storage component of LocalStore
 // the second argument is the hive, the connection/logistics manager for the node
-func NewNetStore(hash Hasher, lstore *LocalStore, cloud CloudStore, params *StoreParams) *NetStore {
+func NewNetStore(hash SwarmHasher, lstore *LocalStore, cloud CloudStore, params *StoreParams) *NetStore {
 	return &NetStore{
 		hashfunc:   hash,
 		localStore: lstore,
diff --git a/swarm/storage/pyramid.go b/swarm/storage/pyramid.go
index 74e00a497..e3be2a987 100644
--- a/swarm/storage/pyramid.go
+++ b/swarm/storage/pyramid.go
@@ -18,53 +18,112 @@ package storage
 
 import (
 	"encoding/binary"
-	"fmt"
+	"errors"
 	"io"
-	"math"
-	"strings"
 	"sync"
+	"time"
+)
+
+/*
+   The main idea of a pyramid chunker is to process the input data without knowing the entire size apriori.
+   For this to be achieved, the chunker tree is built from the ground up until the data is exhausted.
+   This opens up new aveneus such as easy append and other sort of modifications to the tree therby avoiding
+   duplication of data chunks.
+
+
+   Below is an example of a two level chunks tree. The leaf chunks are called data chunks and all the above
+   chunks are called tree chunks. The tree chunk above data chunks is level 0 and so on until it reaches
+   the root tree chunk.
+
+
+
+                                            T10                                        <- Tree chunk lvl1
+                                            |
+                  __________________________|_____________________________
+                 /                  |                   |                \
+                /                   |                   \                 \
+            __T00__             ___T01__           ___T02__           ___T03__         <- Tree chunks lvl 0
+           / /     \           / /      \         / /      \         / /      \
+          / /       \         / /        \       / /       \        / /        \
+         D1 D2 ... D128	     D1 D2 ... D128     D1 D2 ... D128     D1 D2 ... D128      <-  Data Chunks
+
+
+    The split function continuously read the data and creates data chunks and send them to storage.
+    When certain no of data chunks are created (defaultBranches), a signal is sent to create a tree
+    entry. When the level 0 tree entries reaches certain threshold (defaultBranches), another signal
+    is sent to a tree entry one level up.. and so on... until only the data is exhausted AND only one
+    tree entry is present in certain level. The key of tree entry is given out as the rootKey of the file.
+
+*/
+
+var (
+	errLoadingTreeRootChunk = errors.New("LoadTree Error: Could not load root chunk")
+	errLoadingTreeChunk     = errors.New("LoadTree Error: Could not load chunk")
+)
 
-	"github.com/ethereum/go-ethereum/common"
+const (
+	ChunkProcessors       = 8
+	DefaultBranches int64 = 128
+	splitTimeout          = time.Minute * 5
 )
 
 const (
-	processors = 8
+	DataChunk = 0
+	TreeChunk = 1
 )
 
-type Tree struct {
-	Chunks int64
-	Levels []map[int64]*Node
-	Lock   sync.RWMutex
+type ChunkerParams struct {
+	Branches int64
+	Hash     string
+}
+
+func NewChunkerParams() *ChunkerParams {
+	return &ChunkerParams{
+		Branches: DefaultBranches,
+		Hash:     SHA3Hash,
+	}
 }
 
-type Node struct {
-	Pending  int64
-	Size     uint64
-	Children []common.Hash
-	Last     bool
+// Entry to create a tree node
+type TreeEntry struct {
+	level         int
+	branchCount   int64
+	subtreeSize   uint64
+	chunk         []byte
+	key           []byte
+	index         int  // used in append to indicate the index of existing tree entry
+	updatePending bool // indicates if the entry is loaded from existing tree
 }
 
-func (self *Node) String() string {
-	var children []string
-	for _, node := range self.Children {
-		children = append(children, node.Hex())
+func NewTreeEntry(pyramid *PyramidChunker) *TreeEntry {
+	return &TreeEntry{
+		level:         0,
+		branchCount:   0,
+		subtreeSize:   0,
+		chunk:         make([]byte, pyramid.chunkSize+8),
+		key:           make([]byte, pyramid.hashSize),
+		index:         0,
+		updatePending: false,
 	}
-	return fmt.Sprintf("pending: %v, size: %v, last :%v, children: %v", self.Pending, self.Size, self.Last, strings.Join(children, ", "))
 }
 
-type Task struct {
-	Index int64 // Index of the chunk being processed
-	Size  uint64
-	Data  []byte // Binary blob of the chunk
-	Last  bool
+// Used by the hash processor to create a data/tree chunk and send to storage
+type chunkJob struct {
+	key       Key
+	chunk     []byte
+	size      int64
+	parentWg  *sync.WaitGroup
+	chunkType int // used to identify the tree related chunks for debugging
+	chunkLvl  int // leaf-1 is level 0 and goes upwards until it reaches root
 }
 
 type PyramidChunker struct {
-	hashFunc    Hasher
+	hashFunc    SwarmHasher
 	chunkSize   int64
 	hashSize    int64
 	branches    int64
-	workerCount int
+	workerCount int64
+	workerLock	sync.RWMutex
 }
 
 func NewPyramidChunker(params *ChunkerParams) (self *PyramidChunker) {
@@ -73,128 +132,506 @@ func NewPyramidChunker(params *ChunkerParams) (self *PyramidChunker) {
 	self.branches = params.Branches
 	self.hashSize = int64(self.hashFunc().Size())
 	self.chunkSize = self.hashSize * self.branches
-	self.workerCount = 1
+	self.workerCount = 0
 	return
 }
 
-func (self *PyramidChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, swg, wwg *sync.WaitGroup) (Key, error) {
+func (self *PyramidChunker) Join(key Key, chunkC chan *Chunk) LazySectionReader {
+	return &LazyChunkReader{
+		key:       key,
+		chunkC:    chunkC,
+		chunkSize: self.chunkSize,
+		branches:  self.branches,
+		hashSize:  self.hashSize,
+	}
+}
 
-	chunks := (size + self.chunkSize - 1) / self.chunkSize
-	depth := int(math.Ceil(math.Log(float64(chunks))/math.Log(float64(self.branches)))) + 1
+func (self *PyramidChunker) incrementWorkerCount() {
+	self.workerLock.Lock()
+	defer self.workerLock.Unlock()
+	self.workerCount += 1
+}
 
-	results := Tree{
-		Chunks: chunks,
-		Levels: make([]map[int64]*Node, depth),
+func (self *PyramidChunker) getWorkerCount() int64 {
+	self.workerLock.Lock()
+	defer self.workerLock.Unlock()
+	return self.workerCount
+}
+
+func (self *PyramidChunker) decrementWorkerCount() {
+	self.workerLock.Lock()
+	defer self.workerLock.Unlock()
+	self.workerCount -= 1
+}
+
+func (self *PyramidChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, storageWG, processorWG *sync.WaitGroup) (Key, error) {
+	jobC := make(chan *chunkJob, 2*ChunkProcessors)
+	wg := &sync.WaitGroup{}
+	errC := make(chan error)
+	quitC := make(chan bool)
+	rootKey := make([]byte, self.hashSize)
+	chunkLevel := make([][]*TreeEntry, self.branches)
+
+	wg.Add(1)
+	go self.prepareChunks(false, chunkLevel, data, rootKey, quitC, wg, jobC, processorWG, chunkC, errC, storageWG)
+
+	// closes internal error channel if all subprocesses in the workgroup finished
+	go func() {
+
+		// waiting for all chunks to finish
+		wg.Wait()
+
+		// if storage waitgroup is non-nil, we wait for storage to finish too
+		if storageWG != nil {
+			storageWG.Wait()
+		}
+		//We close errC here because this is passed down to 8 parallel routines underneath.
+		// if a error happens in one of them.. that particular routine raises error...
+		// once they all complete successfully, the control comes back and we can safely close this here.
+		close(errC)
+	}()
+
+	defer close(quitC)
+
+	select {
+	case err := <-errC:
+		if err != nil {
+			return nil, err
+		}
+	case <-time.NewTimer(splitTimeout).C:
 	}
-	for i := 0; i < depth; i++ {
-		results.Levels[i] = make(map[int64]*Node)
+	return rootKey, nil
+
+}
+
+func (self *PyramidChunker) Append(key Key, data io.Reader, chunkC chan *Chunk, storageWG, processorWG *sync.WaitGroup) (Key, error) {
+	quitC := make(chan bool)
+	rootKey := make([]byte, self.hashSize)
+	chunkLevel := make([][]*TreeEntry, self.branches)
+
+	// Load the right most unfinished tree chunks in every level
+	self.loadTree(chunkLevel, key, chunkC, quitC)
+
+	jobC := make(chan *chunkJob, 2*ChunkProcessors)
+	wg := &sync.WaitGroup{}
+	errC := make(chan error)
+
+	wg.Add(1)
+	go self.prepareChunks(true, chunkLevel, data, rootKey, quitC, wg, jobC, processorWG, chunkC, errC, storageWG)
+
+	// closes internal error channel if all subprocesses in the workgroup finished
+	go func() {
+
+		// waiting for all chunks to finish
+		wg.Wait()
+
+		// if storage waitgroup is non-nil, we wait for storage to finish too
+		if storageWG != nil {
+			storageWG.Wait()
+		}
+		close(errC)
+	}()
+
+	defer close(quitC)
+
+	select {
+	case err := <-errC:
+		if err != nil {
+			return nil, err
+		}
+	case <-time.NewTimer(splitTimeout).C:
 	}
-	// Create a pool of workers to crunch through the file
-	tasks := make(chan *Task, 2*processors)
-	pend := new(sync.WaitGroup)
-	abortC := make(chan bool)
-	for i := 0; i < processors; i++ {
-		pend.Add(1)
-		go self.processor(pend, swg, tasks, chunkC, &results)
+	return rootKey, nil
+
+}
+
+func (self *PyramidChunker) processor(id int64, jobC chan *chunkJob, chunkC chan *Chunk, errC chan error, quitC chan bool, swg, wwg *sync.WaitGroup) {
+	defer self.decrementWorkerCount()
+
+	hasher := self.hashFunc()
+	if wwg != nil {
+		defer wwg.Done()
 	}
-	// Feed the chunks into the task pool
-	read := 0
-	for index := 0; ; index++ {
-		buffer := make([]byte, self.chunkSize+8)
-		n, err := data.Read(buffer[8:])
-		read += n
-		last := int64(read) == size || err == io.ErrUnexpectedEOF || err == io.EOF
-		if err != nil && !last {
-			close(abortC)
-			break
-		}
-		binary.LittleEndian.PutUint64(buffer[:8], uint64(n))
-		pend.Add(1)
+	for {
 		select {
-		case tasks <- &Task{Index: int64(index), Size: uint64(n), Data: buffer[:n+8], Last: last}:
-		case <-abortC:
-			return nil, err
+
+		case job, ok := <-jobC:
+			if !ok {
+				return
+			}
+			self.processChunk(id, hasher, job, chunkC, swg)
+		case <-quitC:
+			return
 		}
-		if last {
-			break
+	}
+}
+
+func (self *PyramidChunker) processChunk(id int64, hasher SwarmHash, job *chunkJob, chunkC chan *Chunk, swg *sync.WaitGroup) {
+	hasher.ResetWithLength(job.chunk[:8]) // 8 bytes of length
+	hasher.Write(job.chunk[8:])           // minus 8 []byte length
+	h := hasher.Sum(nil)
+
+	newChunk := &Chunk{
+		Key:   h,
+		SData: job.chunk,
+		Size:  job.size,
+		wg:    swg,
+	}
+
+	// report hash of this chunk one level up (keys corresponds to the proper subslice of the parent chunk)
+	copy(job.key, h)
+
+	// send off new chunk to storage
+	if chunkC != nil {
+		if swg != nil {
+			swg.Add(1)
 		}
 	}
-	// Wait for the workers and return
-	close(tasks)
-	pend.Wait()
+	job.parentWg.Done()
 
-	key := results.Levels[0][0].Children[0][:]
-	return key, nil
+	if chunkC != nil {
+		chunkC <- newChunk
+	}
 }
 
-func (self *PyramidChunker) processor(pend, swg *sync.WaitGroup, tasks chan *Task, chunkC chan *Chunk, results *Tree) {
-	defer pend.Done()
+func (self *PyramidChunker) loadTree(chunkLevel [][]*TreeEntry, key Key, chunkC chan *Chunk, quitC chan bool) error {
+	// Get the root chunk to get the total size
+	chunk := retrieve(key, chunkC, quitC)
+	if chunk == nil {
+		return errLoadingTreeRootChunk
+	}
 
-	// Start processing leaf chunks ad infinitum
-	hasher := self.hashFunc()
-	for task := range tasks {
-		depth, pow := len(results.Levels)-1, self.branches
-		size := task.Size
-		data := task.Data
-		var node *Node
-		for depth >= 0 {
-			// New chunk received, reset the hasher and start processing
-			hasher.Reset()
-			if node == nil { // Leaf node, hash the data chunk
-				hasher.Write(task.Data)
-			} else { // Internal node, hash the children
-				size = node.Size
-				data = make([]byte, hasher.Size()*len(node.Children)+8)
-				binary.LittleEndian.PutUint64(data[:8], size)
-
-				hasher.Write(data[:8])
-				for i, hash := range node.Children {
-					copy(data[i*hasher.Size()+8:], hash[:])
-					hasher.Write(hash[:])
+	//if data size is less than a chunk... add a parent with update as pending
+	if chunk.Size <= self.chunkSize {
+		newEntry := &TreeEntry{
+			level:         0,
+			branchCount:   1,
+			subtreeSize:   uint64(chunk.Size),
+			chunk:         make([]byte, self.chunkSize+8),
+			key:           make([]byte, self.hashSize),
+			index:         0,
+			updatePending: true,
+		}
+		copy(newEntry.chunk[8:], chunk.Key)
+		chunkLevel[0] = append(chunkLevel[0], newEntry)
+		return nil
+	}
+
+	var treeSize int64
+	var depth int
+	treeSize = self.chunkSize
+	for ; treeSize < chunk.Size; treeSize *= self.branches {
+		depth++
+	}
+
+	// Add the root chunk entry
+	branchCount := int64(len(chunk.SData)-8) / self.hashSize
+	newEntry := &TreeEntry{
+		level:         int(depth - 1),
+		branchCount:   branchCount,
+		subtreeSize:   uint64(chunk.Size),
+		chunk:         chunk.SData,
+		key:           key,
+		index:         0,
+		updatePending: true,
+	}
+	chunkLevel[depth-1] = append(chunkLevel[depth-1], newEntry)
+
+	// Add the rest of the tree
+	for lvl := (depth - 1); lvl >= 1; lvl-- {
+
+		//TODO(jmozah): instead of loading finished branches and then trim in the end,
+		//avoid loading them in the first place
+		for _, ent := range chunkLevel[lvl] {
+			branchCount = int64(len(ent.chunk)-8) / self.hashSize
+			for i := int64(0); i < branchCount; i++ {
+				key := ent.chunk[8+(i*self.hashSize) : 8+((i+1)*self.hashSize)]
+				newChunk := retrieve(key, chunkC, quitC)
+				if newChunk == nil {
+					return errLoadingTreeChunk
 				}
-			}
-			hash := hasher.Sum(nil)
-			last := task.Last || (node != nil) && node.Last
-			// Insert the subresult into the memoization tree
-			results.Lock.Lock()
-			if node = results.Levels[depth][task.Index/pow]; node == nil {
-				// Figure out the pending tasks
-				pending := self.branches
-				if task.Index/pow == results.Chunks/pow {
-					pending = (results.Chunks + pow/self.branches - 1) / (pow / self.branches) % self.branches
+				bewBranchCount := int64(len(newChunk.SData)-8) / self.hashSize
+				newEntry := &TreeEntry{
+					level:         int(lvl - 1),
+					branchCount:   bewBranchCount,
+					subtreeSize:   uint64(newChunk.Size),
+					chunk:         newChunk.SData,
+					key:           key,
+					index:         0,
+					updatePending: true,
 				}
-				node = &Node{pending, 0, make([]common.Hash, pending), last}
-				results.Levels[depth][task.Index/pow] = node
+				chunkLevel[lvl-1] = append(chunkLevel[lvl-1], newEntry)
+
 			}
-			node.Pending--
-			i := task.Index / (pow / self.branches) % self.branches
-			if last {
-				node.Last = true
+
+			// We need to get only the right most unfinished branch.. so trim all finished branches
+			if int64(len(chunkLevel[lvl-1])) >= self.branches {
+				chunkLevel[lvl-1] = nil
 			}
-			copy(node.Children[i][:], hash)
-			node.Size += size
-			left := node.Pending
-			if chunkC != nil {
-				if swg != nil {
-					swg.Add(1)
-				}
+		}
+	}
+
+	return nil
+}
+
+func (self *PyramidChunker) prepareChunks(isAppend bool, chunkLevel [][]*TreeEntry, data io.Reader, rootKey []byte, quitC chan bool, wg *sync.WaitGroup, jobC chan *chunkJob, processorWG *sync.WaitGroup, chunkC chan *Chunk, errC chan error, storageWG *sync.WaitGroup) {
+	defer wg.Done()
+
+	chunkWG := &sync.WaitGroup{}
+	totalDataSize := 0
 
-				chunkC <- &Chunk{Key: hash, SData: data, wg: swg}
-				// TODO: consider selecting on self.quitC to avoid blocking forever on shutdown
+	// processorWG keeps track of workers spawned for hashing chunks
+	if processorWG != nil {
+		processorWG.Add(1)
+	}
+
+	self.incrementWorkerCount()
+	go self.processor(self.workerCount, jobC, chunkC, errC, quitC, storageWG, processorWG)
+
+	parent := NewTreeEntry(self)
+	var unFinishedChunk *Chunk
+
+	if isAppend == true && len(chunkLevel[0]) != 0 {
+
+		lastIndex := len(chunkLevel[0]) - 1
+		ent := chunkLevel[0][lastIndex]
+
+		if ent.branchCount < self.branches {
+			parent = &TreeEntry{
+				level:         0,
+				branchCount:   ent.branchCount,
+				subtreeSize:   ent.subtreeSize,
+				chunk:         ent.chunk,
+				key:           ent.key,
+				index:         lastIndex,
+				updatePending: true,
 			}
-			if depth+1 < len(results.Levels) {
-				delete(results.Levels[depth+1], task.Index/(pow/self.branches))
+
+			lastBranch := parent.branchCount - 1
+			lastKey := parent.chunk[8+lastBranch*self.hashSize : 8+(lastBranch+1)*self.hashSize]
+
+			unFinishedChunk = retrieve(lastKey, chunkC, quitC)
+			if unFinishedChunk.Size < self.chunkSize {
+
+				parent.subtreeSize = parent.subtreeSize - uint64(unFinishedChunk.Size)
+				parent.branchCount = parent.branchCount - 1
+			} else {
+				unFinishedChunk = nil
 			}
+		}
+	}
 
-			results.Lock.Unlock()
-			// If there's more work to be done, leave for others
-			if left > 0 {
+	for index := 0; ; index++ {
+
+		var n int
+		var err error
+		chunkData := make([]byte, self.chunkSize+8)
+		if unFinishedChunk != nil {
+			copy(chunkData, unFinishedChunk.SData)
+			n, err = data.Read(chunkData[8+unFinishedChunk.Size:])
+			n += int(unFinishedChunk.Size)
+			unFinishedChunk = nil
+		} else {
+			n, err = data.Read(chunkData[8:])
+		}
+
+		totalDataSize += n
+		if err != nil {
+			if err == io.EOF || err == io.ErrUnexpectedEOF {
+				if parent.branchCount == 1 {
+					// Data is exactly one chunk.. pick the last chunk key as root
+					chunkWG.Wait()
+					lastChunksKey := parent.chunk[8 : 8+self.hashSize]
+					copy(rootKey, lastChunksKey)
+					break
+				}
+			} else {
+				close(quitC)
 				break
 			}
-			// We're the last ones in this batch, merge the children together
-			depth--
-			pow *= self.branches
 		}
-		pend.Done()
+
+		// Data ended in chunk boundry.. just signal to start bulding tree
+		if n == 0 {
+			self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, true, rootKey)
+			break
+		} else {
+
+			pkey := self.enqueueDataChunk(chunkData, uint64(n), parent, chunkWG, jobC, quitC)
+
+			// update tree related parent data structures
+			parent.subtreeSize += uint64(n)
+			parent.branchCount++
+
+			// Data got exhausted... signal to send any parent tree related chunks
+			if int64(n) < self.chunkSize {
+
+				// only one data chunk .. so dont add any parent chunk
+				if parent.branchCount <= 1 {
+					chunkWG.Wait()
+					copy(rootKey, pkey)
+					break
+				}
+
+				self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, true, rootKey)
+				break
+			}
+
+			if parent.branchCount == self.branches {
+				self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, false, rootKey)
+				parent = NewTreeEntry(self)
+			}
+
+		}
+
+		workers := self.getWorkerCount()
+		if int64(len(jobC)) > workers && workers < ChunkProcessors {
+			if processorWG != nil {
+				processorWG.Add(1)
+			}
+			self.incrementWorkerCount()
+			go self.processor(self.workerCount, jobC, chunkC, errC, quitC, storageWG, processorWG)
+		}
+
+	}
+
+}
+
+func (self *PyramidChunker) buildTree(isAppend bool, chunkLevel [][]*TreeEntry, ent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool, last bool, rootKey []byte) {
+	chunkWG.Wait()
+	self.enqueueTreeChunk(chunkLevel, ent, chunkWG, jobC, quitC, last)
+
+	compress := false
+	endLvl := self.branches
+	for lvl := int64(0); lvl < self.branches; lvl++ {
+		lvlCount := int64(len(chunkLevel[lvl]))
+		if lvlCount >= self.branches {
+			endLvl = lvl + 1
+			compress = true
+			break
+		}
+	}
+
+	if compress == false && last == false {
+		return
+	}
+
+	// Wait for all the keys to be processed before compressing the tree
+	chunkWG.Wait()
+
+	for lvl := int64(ent.level); lvl < endLvl; lvl++ {
+
+		lvlCount := int64(len(chunkLevel[lvl]))
+		if lvlCount == 1 && last == true {
+			copy(rootKey, chunkLevel[lvl][0].key)
+			return
+		}
+
+		for startCount := int64(0); startCount < lvlCount; startCount += self.branches {
+
+			endCount := startCount + self.branches
+			if endCount > lvlCount {
+				endCount = lvlCount
+			}
+
+			var nextLvlCount int64
+			var tempEntry *TreeEntry
+			if len(chunkLevel[lvl+1]) > 0 {
+				nextLvlCount = int64(len(chunkLevel[lvl+1]) - 1)
+				tempEntry = chunkLevel[lvl+1][nextLvlCount]
+			}
+			if isAppend == true && tempEntry != nil && tempEntry.updatePending == true {
+				updateEntry := &TreeEntry{
+					level:         int(lvl + 1),
+					branchCount:   0,
+					subtreeSize:   0,
+					chunk:         make([]byte, self.chunkSize+8),
+					key:           make([]byte, self.hashSize),
+					index:         int(nextLvlCount),
+					updatePending: true,
+				}
+				for index := int64(0); index < lvlCount; index++ {
+					updateEntry.branchCount++
+					updateEntry.subtreeSize += chunkLevel[lvl][index].subtreeSize
+					copy(updateEntry.chunk[8+(index*self.hashSize):8+((index+1)*self.hashSize)], chunkLevel[lvl][index].key[:self.hashSize])
+				}
+
+				self.enqueueTreeChunk(chunkLevel, updateEntry, chunkWG, jobC, quitC, last)
+
+			} else {
+
+				noOfBranches := endCount - startCount
+				newEntry := &TreeEntry{
+					level:         int(lvl + 1),
+					branchCount:   noOfBranches,
+					subtreeSize:   0,
+					chunk:         make([]byte, (noOfBranches*self.hashSize)+8),
+					key:           make([]byte, self.hashSize),
+					index:         int(nextLvlCount),
+					updatePending: false,
+				}
+
+				index := int64(0)
+				for i := startCount; i < endCount; i++ {
+					entry := chunkLevel[lvl][i]
+					newEntry.subtreeSize += entry.subtreeSize
+					copy(newEntry.chunk[8+(index*self.hashSize):8+((index+1)*self.hashSize)], entry.key[:self.hashSize])
+					index++
+				}
+
+				self.enqueueTreeChunk(chunkLevel, newEntry, chunkWG, jobC, quitC, last)
+
+			}
+
+		}
+
+		if isAppend == false {
+			chunkWG.Wait()
+			if compress == true {
+				chunkLevel[lvl] = nil
+			}
+		}
 	}
+
 }
+
+func (self *PyramidChunker) enqueueTreeChunk(chunkLevel [][]*TreeEntry, ent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool, last bool) {
+	if ent != nil {
+
+		// wait for data chunks to get over before processing the tree chunk
+		if last == true {
+			chunkWG.Wait()
+		}
+
+		binary.LittleEndian.PutUint64(ent.chunk[:8], ent.subtreeSize)
+		ent.key = make([]byte, self.hashSize)
+		chunkWG.Add(1)
+		select {
+		case jobC <- &chunkJob{ent.key, ent.chunk[:ent.branchCount*self.hashSize+8], int64(ent.subtreeSize), chunkWG, TreeChunk, 0}:
+		case <-quitC:
+		}
+
+		// Update or append based on weather it is a new entry or being reused
+		if ent.updatePending == true {
+			chunkWG.Wait()
+			chunkLevel[ent.level][ent.index] = ent
+		} else {
+			chunkLevel[ent.level] = append(chunkLevel[ent.level], ent)
+		}
+
+	}
+}
+
+func (self *PyramidChunker) enqueueDataChunk(chunkData []byte, size uint64, parent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool) Key {
+	binary.LittleEndian.PutUint64(chunkData[:8], size)
+	pkey := parent.chunk[8+parent.branchCount*self.hashSize : 8+(parent.branchCount+1)*self.hashSize]
+
+	chunkWG.Add(1)
+	select {
+	case jobC <- &chunkJob{pkey, chunkData[:size+8], int64(size), chunkWG, DataChunk, -1}:
+	case <-quitC:
+	}
+
+	return pkey
+
+}
\ No newline at end of file
diff --git a/swarm/storage/swarmhasher.go b/swarm/storage/swarmhasher.go
new file mode 100644
index 000000000..38b86373c
--- /dev/null
+++ b/swarm/storage/swarmhasher.go
@@ -0,0 +1,40 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package storage
+
+import (
+	"hash"
+)
+
+const (
+	BMTHash  = "BMT"
+	SHA3Hash = "SHA3" // http://golang.org/pkg/hash/#Hash
+)
+
+type SwarmHash interface {
+	hash.Hash
+	ResetWithLength([]byte)
+}
+
+type HashWithLength struct {
+	hash.Hash
+}
+
+func (self *HashWithLength) ResetWithLength(length []byte) {
+	self.Reset()
+	self.Write(length)
+}
diff --git a/swarm/storage/types.go b/swarm/storage/types.go
index a9de23c93..d35f1f929 100644
--- a/swarm/storage/types.go
+++ b/swarm/storage/types.go
@@ -24,12 +24,13 @@ import (
 	"io"
 	"sync"
 
-	// "github.com/ethereum/go-ethereum/bmt"
+	"github.com/ethereum/go-ethereum/bmt"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
 )
 
 type Hasher func() hash.Hash
+type SwarmHasher func() SwarmHash
 
 // Peer is the recorded as Source on the chunk
 // should probably not be here? but network should wrap chunk object
@@ -78,12 +79,18 @@ func IsZeroKey(key Key) bool {
 
 var ZeroKey = Key(common.Hash{}.Bytes())
 
-func MakeHashFunc(hash string) Hasher {
+func MakeHashFunc(hash string) SwarmHasher {
 	switch hash {
 	case "SHA256":
-		return crypto.SHA256.New
+		return func() SwarmHash { return &HashWithLength{crypto.SHA256.New()} }
 	case "SHA3":
-		return sha3.NewKeccak256
+		return func() SwarmHash { return &HashWithLength{sha3.NewKeccak256()} }
+	case "BMT":
+		return func() SwarmHash {
+			hasher := sha3.NewKeccak256
+			pool := bmt.NewTreePool(hasher, bmt.DefaultSegmentCount, bmt.DefaultPoolSize)
+			return bmt.New(pool)
+		}
 	}
 	return nil
 }
@@ -192,6 +199,13 @@ type Splitter interface {
 	   A closed error signals process completion at which point the key can be considered final if there were no errors.
 	*/
 	Split(io.Reader, int64, chan *Chunk, *sync.WaitGroup, *sync.WaitGroup) (Key, error)
+
+	/* This is the first step in making files mutable (not chunks)..
+	   Append allows adding more data chunks to the end of the already existsing file.
+	   The key for the root chunk is supplied to load the respective tree.
+	   Rest of the parameters behave like Split.
+	*/
+	Append(Key, io.Reader, chan *Chunk, *sync.WaitGroup, *sync.WaitGroup) (Key, error)
 }
 
 type Joiner interface {