path: root/swarm/bmt/bmt_test.go

// 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 bmt

import (
    "bytes"
    "encoding/binary"
    "fmt"
    "math/rand"
    "sync"
    "sync/atomic"
    "testing"
    "time"

    "github.com/dexon-foundation/dexon/swarm/testutil"
    "golang.org/x/crypto/sha3"
)

// the actual data length generated (could be longer than max datalength of the BMT)
const BufferSize = 4128

const (
    // segmentCount is the maximum number of segments of the underlying chunk
    // Should be equal to max-chunk-data-size / hash-size
    // Currently set to 128 == 4096 (default chunk size) / 32 (sha3.keccak256 size)
    segmentCount = 128
)

var counts = []int{1, 2, 3, 4, 5, 8, 9, 15, 16, 17, 32, 37, 42, 53, 63, 64, 65, 111, 127, 128}

// calculates the Keccak256 SHA3 hash of the data
func sha3hash(data ...[]byte) []byte {
    h := sha3.NewLegacyKeccak256()
    return doSum(h, nil, data...)
}

// TestRefHasher tests that the RefHasher computes the expected BMT hash for
// some small data lengths
func TestRefHasher(t *testing.T) {
    // the test struct is used to specify the expected BMT hash for
    // segment counts between from and to and lengths from 1 to datalength
    type test struct {
        from     int
        to       int
        expected func([]byte) []byte
    }

    var tests []*test
    // all lengths in [0,64] should be:
    //
    //   sha3hash(data)
    //
    tests = append(tests, &test{
        from: 1,
        to:   2,
        expected: func(d []byte) []byte {
            data := make([]byte, 64)
            copy(data, d)
            return sha3hash(data)
        },
    })

    // all lengths in [3,4] should be:
    //
    //   sha3hash(
    //     sha3hash(data[:64])
    //     sha3hash(data[64:])
    //   )
    //
    tests = append(tests, &test{
        from: 3,
        to:   4,
        expected: func(d []byte) []byte {
            data := make([]byte, 128)
            copy(data, d)
            return sha3hash(sha3hash(data[:64]), sha3hash(data[64:]))
        },
    })

    // all segmentCounts in [5,8] should be:
    //
    //   sha3hash(
    //     sha3hash(
    //       sha3hash(data[:64])
    //       sha3hash(data[64:128])
    //     )
    //     sha3hash(
    //       sha3hash(data[128:192])
    //       sha3hash(data[192:])
    //     )
    //   )
    //
    tests = append(tests, &test{
        from: 5,
        to:   8,
        expected: func(d []byte) []byte {
            data := make([]byte, 256)
            copy(data, d)
            return sha3hash(sha3hash(sha3hash(data[:64]), sha3hash(data[64:128])), sha3hash(sha3hash(data[128:192]), sha3hash(data[192:])))
        },
    })

    // run the tests
    for i, x := range tests {
        for segmentCount := x.from; segmentCount <= x.to; segmentCount++ {
            for length := 1; length <= segmentCount*32; length++ {
                t.Run(fmt.Sprintf("%d_segments_%d_bytes", segmentCount, length), func(t *testing.T) {
                    data := testutil.RandomBytes(i, length)
                    expected := x.expected(data)
                    actual := NewRefHasher(sha3.NewLegacyKeccak256, segmentCount).Hash(data)
                    if !bytes.Equal(actual, expected) {
                        t.Fatalf("expected %x, got %x", expected, actual)
                    }
                })
            }
        }
    }
}

// tests if hasher responds with correct hash comparing the reference implementation return value
func TestHasherEmptyData(t *testing.T) {
    hasher := sha3.NewLegacyKeccak256
    var data []byte
    for _, count := range counts {
        t.Run(fmt.Sprintf("%d_segments", count), func(t *testing.T) {
            pool := NewTreePool(hasher, count, PoolSize)
            defer pool.Drain(0)
            bmt := New(pool)
            rbmt := NewRefHasher(hasher, count)
            refHash := rbmt.Hash(data)
            expHash := syncHash(bmt, nil, data)
            if !bytes.Equal(expHash, refHash) {
                t.Fatalf("hash mismatch with reference. expected %x, got %x", refHash, expHash)
            }
        })
    }
}

// tests sequential write with entire max size written in one go
func TestSyncHasherCorrectness(t *testing.T) {
    data := testutil.RandomBytes(1, BufferSize)
    hasher := sha3.NewLegacyKeccak256
    size := hasher().Size()

    var err error
    for _, count := range counts {
        t.Run(fmt.Sprintf("segments_%v", count), func(t *testing.T) {
            max := count * size
            var incr int
            capacity := 1
            pool := NewTreePool(hasher, count, capacity)
            defer pool.Drain(0)
            for n := 0; n <= max; n += incr {
                incr = 1 + rand.Intn(5)
                bmt := New(pool)
                err = testHasherCorrectness(bmt, hasher, data, n, count)
                if err != nil {
                    t.Fatal(err)
                }
            }
        })
    }
}

// tests order-neutral concurrent writes with entire max size written in one go
func TestAsyncCorrectness(t *testing.T) {
    data := testutil.RandomBytes(1, BufferSize)
    hasher := sha3.NewLegacyKeccak256
    size := hasher().Size()
    whs := []whenHash{first, last, random}

    for _, double := range []bool{false, true} {
        for _, wh := range whs {
            for _, count := range counts {
                t.Run(fmt.Sprintf("double_%v_hash_when_%v_segments_%v", double, wh, count), func(t *testing.T) {
                    max := count * size
                    var incr int
                    capacity := 1
                    pool := NewTreePool(hasher, count, capacity)
                    defer pool.Drain(0)
                    for n := 1; n <= max; n += incr {
                        incr = 1 + rand.Intn(5)
                        bmt := New(pool)
                        d := data[:n]
                        rbmt := NewRefHasher(hasher, count)
                        exp := rbmt.Hash(d)
                        got := syncHash(bmt, nil, d)
                        if !bytes.Equal(got, exp) {
                            t.Fatalf("wrong sync hash for datalength %v: expected %x (ref), got %x", n, exp, got)
                        }
                        sw := bmt.NewAsyncWriter(double)
                        got = asyncHashRandom(sw, nil, d, wh)
                        if !bytes.Equal(got, exp) {
                            t.Fatalf("wrong async hash for datalength %v: expected %x, got %x", n, exp, got)
                        }
                    }
                })
            }
        }
    }
}

// Tests that the BMT hasher can be synchronously reused with poolsizes 1 and PoolSize
func TestHasherReuse(t *testing.T) {
    t.Run(fmt.Sprintf("poolsize_%d", 1), func(t *testing.T) {
        testHasherReuse(1, t)
    })
    t.Run(fmt.Sprintf("poolsize_%d", PoolSize), func(t *testing.T) {
        testHasherReuse(PoolSize, t)
    })
}

// tests if bmt reuse is not corrupting result
func testHasherReuse(poolsize int, t *testing.T) {
    hasher := sha3.NewLegacyKeccak256
    pool := NewTreePool(hasher, segmentCount, poolsize)
    defer pool.Drain(0)
    bmt := New(pool)

    for i := 0; i < 100; i++ {
        data := testutil.RandomBytes(1, BufferSize)
        n := rand.Intn(bmt.Size())
        err := testHasherCorrectness(bmt, hasher, data, n, segmentCount)
        if err != nil {
            t.Fatal(err)
        }
    }
}

// Tests if pool can be cleanly reused even in concurrent use by several hasher
func TestBMTConcurrentUse(t *testing.T) {
    hasher := sha3.NewLegacyKeccak256
    pool := NewTreePool(hasher, segmentCount, PoolSize)
    defer pool.Drain(0)
    cycles := 100
    errc := make(chan error)

    for i := 0; i < cycles; i++ {
        go func() {
            bmt := New(pool)
            data := testutil.RandomBytes(1, BufferSize)
            n := rand.Intn(bmt.Size())
            errc <- testHasherCorrectness(bmt, hasher, data, n, 128)
        }()
    }
LOOP:
    for {
        select {
        case <-time.NewTimer(5 * time.Second).C:
            t.Fatal("timed out")
        case err := <-errc:
            if err != nil {
                t.Fatal(err)
            }
            cycles--
            if cycles == 0 {
                break LOOP
            }
        }
    }
}

// Tests BMT Hasher io.Writer interface is working correctly
// even multiple short random write buffers
func TestBMTWriterBuffers(t *testing.T) {
    hasher := sha3.NewLegacyKeccak256

    for _, count := range counts {
        t.Run(fmt.Sprintf("%d_segments", count), func(t *testing.T) {
            errc := make(chan error)
            pool := NewTreePool(hasher, count, PoolSize)
            defer pool.Drain(0)
            n := count * 32
            bmt := New(pool)
            data := testutil.RandomBytes(1, n)
            rbmt := NewRefHasher(hasher, count)
            refHash := rbmt.Hash(data)
            expHash := syncHash(bmt, nil, data)
            if !bytes.Equal(expHash, refHash) {
                t.Fatalf("hash mismatch with reference. expected %x, got %x", refHash, expHash)
            }
            attempts := 10
            f := func() error {
                bmt := New(pool)
                bmt.Reset()
                var buflen int
                for offset := 0; offset < n; offset += buflen {
                    buflen = rand.Intn(n-offset) + 1
                    read, err := bmt.Write(data[offset : offset+buflen])
                    if err != nil {
                        return err
                    }
                    if read != buflen {
                        return fmt.Errorf("incorrect read. expected %v bytes, got %v", buflen, read)
                    }
                }
                hash := bmt.Sum(nil)
                if !bytes.Equal(hash, expHash) {
                    return fmt.Errorf("hash mismatch. expected %x, got %x", hash, expHash)
                }
                return nil
            }

            for j := 0; j < attempts; j++ {
                go func() {
                    errc <- f()
                }()
            }
            timeout := time.NewTimer(2 * time.Second)
            for {
                select {
                case err := <-errc:
                    if err != nil {
                        t.Fatal(err)
                    }
                    attempts--
                    if attempts == 0 {
                        return
                    }
                case <-timeout.C:
                    t.Fatalf("timeout")
                }
            }
        })
    }
}

// helper function that compares reference and optimised implementations on
// correctness
func testHasherCorrectness(bmt *Hasher, hasher BaseHasherFunc, d []byte, n, count int) (err error) {
    span := make([]byte, 8)
    if len(d) < n {
        n = len(d)
    }
    binary.BigEndian.PutUint64(span, uint64(n))
    data := d[:n]
    rbmt := NewRefHasher(hasher, count)
    exp := sha3hash(span, rbmt.Hash(data))
    got := syncHash(bmt, span, data)
    if !bytes.Equal(got, exp) {
        return fmt.Errorf("wrong hash: expected %x, got %x", exp, got)
    }
    return err
}

//
func BenchmarkBMT(t *testing.B) {
    for size := 4096; size >= 128; size /= 2 {
        t.Run(fmt.Sprintf("%v_size_%v", "SHA3", size), func(t *testing.B) {
            benchmarkSHA3(t, size)
        })
        t.Run(fmt.Sprintf("%v_size_%v", "Baseline", size), func(t *testing.B) {
            benchmarkBMTBaseline(t, size)
        })
        t.Run(fmt.Sprintf("%v_size_%v", "REF", size), func(t *testing.B) {
            benchmarkRefHasher(t, size)
        })
        t.Run(fmt.Sprintf("%v_size_%v", "BMT", size), func(t *testing.B) {
            benchmarkBMT(t, size)
        })
    }
}

type whenHash = int

const (
    first whenHash = iota
    last
    random
)

func BenchmarkBMTAsync(t *testing.B) {
    whs := []whenHash{first, last, random}
    for size := 4096; size >= 128; size /= 2 {
        for _, wh := range whs {
            for _, double := range []bool{false, true} {
                t.Run(fmt.Sprintf("double_%v_hash_when_%v_size_%v", double, wh, size), func(t *testing.B) {
                    benchmarkBMTAsync(t, size, wh, double)
                })
            }
        }
    }
}

func BenchmarkPool(t *testing.B) {
    caps := []int{1, PoolSize}
    for size := 4096; size >= 128; size /= 2 {
        for _, c := range caps {
            t.Run(fmt.Sprintf("poolsize_%v_size_%v", c, size), func(t *testing.B) {
                benchmarkPool(t, c, size)
            })
        }
    }
}

// benchmarks simple sha3 hash on chunks
func benchmarkSHA3(t *testing.B, n int) {
    data := testutil.RandomBytes(1, n)
    hasher := sha3.NewLegacyKeccak256
    h := hasher()

    t.ReportAllocs()
    t.ResetTimer()
    for i := 0; i < t.N; i++ {
        doSum(h, nil, data)
    }
}

// benchmarks the minimum hashing time for a balanced (for simplicity) BMT
// by doing count/segmentsize parallel hashings of 2*segmentsize bytes
// doing it on n PoolSize each reusing the base hasher
// the premise is that this is the minimum computation needed for a BMT
// therefore this serves as a theoretical optimum for concurrent implementations
func benchmarkBMTBaseline(t *testing.B, n int) {
    hasher := sha3.NewLegacyKeccak256
    hashSize := hasher().Size()
    data := testutil.RandomBytes(1, hashSize)

    t.ReportAllocs()
    t.ResetTimer()
    for i := 0; i < t.N; i++ {
        count := int32((n-1)/hashSize + 1)
        wg := sync.WaitGroup{}
        wg.Add(PoolSize)
        var i int32
        for j := 0; j < PoolSize; j++ {
            go func() {
                defer wg.Done()
                h := hasher()
                for atomic.AddInt32(&i, 1) < count {
                    doSum(h, nil, data)
                }
            }()
        }
        wg.Wait()
    }
}

// benchmarks BMT Hasher
func benchmarkBMT(t *testing.B, n int) {
    data := testutil.RandomBytes(1, n)
    hasher := sha3.NewLegacyKeccak256
    pool := NewTreePool(hasher, segmentCount, PoolSize)
    bmt := New(pool)

    t.ReportAllocs()
    t.ResetTimer()
    for i := 0; i < t.N; i++ {
        syncHash(bmt, nil, data)
    }
}

// benchmarks BMT hasher with asynchronous concurrent segment/section writes
func benchmarkBMTAsync(t *testing.B, n int, wh whenHash, double bool) {
    data := testutil.RandomBytes(1, n)
    hasher := sha3.NewLegacyKeccak256
    pool := NewTreePool(hasher, segmentCount, PoolSize)
    bmt := New(pool).NewAsyncWriter(double)
    idxs, segments := splitAndShuffle(bmt.SectionSize(), data)
    rand.Shuffle(len(idxs), func(i int, j int) {
        idxs[i], idxs[j] = idxs[j], idxs[i]
    })

    t.ReportAllocs()
    t.ResetTimer()
    for i := 0; i < t.N; i++ {
        asyncHash(bmt, nil, n, wh, idxs, segments)
    }
}

// benchmarks 100 concurrent bmt hashes with pool capacity
func benchmarkPool(t *testing.B, poolsize, n int) {
    data := testutil.RandomBytes(1, n)
    hasher := sha3.NewLegacyKeccak256
    pool := NewTreePool(hasher, segmentCount, poolsize)
    cycles := 100

    t.ReportAllocs()
    t.ResetTimer()
    wg := sync.WaitGroup{}
    for i := 0; i < t.N; i++ {
        wg.Add(cycles)
        for j := 0; j < cycles; j++ {
            go func() {
                defer wg.Done()
                bmt := New(pool)
                syncHash(bmt, nil, data)
            }()
        }
        wg.Wait()
    }
}

// benchmarks the reference hasher
func benchmarkRefHasher(t *testing.B, n int) {
    data := testutil.RandomBytes(1, n)
    hasher := sha3.NewLegacyKeccak256
    rbmt := NewRefHasher(hasher, 128)

    t.ReportAllocs()
    t.ResetTimer()
    for i := 0; i < t.N; i++ {
        rbmt.Hash(data)
    }
}

// Hash hashes the data and the span using the bmt hasher
func syncHash(h *Hasher, span, data []byte) []byte {
    h.ResetWithLength(span)
    h.Write(data)
    return h.Sum(nil)
}

func splitAndShuffle(secsize int, data []byte) (idxs []int, segments [][]byte) {
    l := len(data)
    n := l / secsize
    if l%secsize > 0 {
        n++
    }
    for i := 0; i < n; i++ {
        idxs = append(idxs, i)
        end := (i + 1) * secsize
        if end > l {
            end = l
        }
        section := data[i*secsize : end]
        segments = append(segments, section)
    }
    rand.Shuffle(n, func(i int, j int) {
        idxs[i], idxs[j] = idxs[j], idxs[i]
    })
    return idxs, segments
}

// splits the input data performs a random shuffle to mock async section writes
func asyncHashRandom(bmt SectionWriter, span []byte, data []byte, wh whenHash) (s []byte) {
    idxs, segments := splitAndShuffle(bmt.SectionSize(), data)
    return asyncHash(bmt, span, len(data), wh, idxs, segments)
}

// mock for async section writes for BMT SectionWriter
// requires a permutation (a random shuffle) of list of all indexes of segments
// and writes them in order to the appropriate section
// the Sum function is called according to the wh parameter (first, last, random [relative to segment writes])
func asyncHash(bmt SectionWriter, span []byte, l int, wh whenHash, idxs []int, segments [][]byte) (s []byte) {
    bmt.Reset()
    if l == 0 {
        return bmt.Sum(nil, l, span)
    }
    c := make(chan []byte, 1)
    hashf := func() {
        c <- bmt.Sum(nil, l, span)
    }
    maxsize := len(idxs)
    var r int
    if wh == random {
        r = rand.Intn(maxsize)
    }
    for i, idx := range idxs {
        bmt.Write(idx, segments[idx])
        if (wh == first || wh == random) && i == r {
            go hashf()
        }
    }
    if wh == last {
        return bmt.Sum(nil, l, span)
    }
    return <-c
}