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Diffstat (limited to 'vendor/github.com/ethereum/ethash/ethash.go')
| -rw-r--r-- | vendor/github.com/ethereum/ethash/ethash.go | 441 |
1 files changed, 441 insertions, 0 deletions
diff --git a/vendor/github.com/ethereum/ethash/ethash.go b/vendor/github.com/ethereum/ethash/ethash.go new file mode 100644 index 000000000..2a31aaf2d --- /dev/null +++ b/vendor/github.com/ethereum/ethash/ethash.go @@ -0,0 +1,441 @@ +// Copyright 2015 The go-ethereum Authors +// Copyright 2015 Lefteris Karapetsas <lefteris@refu.co> +// Copyright 2015 Matthew Wampler-Doty <matthew.wampler.doty@gmail.com> +// 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 ethash + +/* +#include "src/libethash/internal.h" + +int ethashGoCallback_cgo(unsigned); +*/ +import "C" + +import ( + "errors" + "fmt" + "io/ioutil" + "math/big" + "math/rand" + "os" + "os/user" + "path/filepath" + "runtime" + "sync" + "sync/atomic" + "time" + "unsafe" + + "github.com/ethereum/go-ethereum/common" + "github.com/ethereum/go-ethereum/crypto" + "github.com/ethereum/go-ethereum/logger" + "github.com/ethereum/go-ethereum/logger/glog" + "github.com/ethereum/go-ethereum/pow" +) + +var ( + maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0)) + sharedLight = new(Light) +) + +const ( + epochLength uint64 = 30000 + cacheSizeForTesting C.uint64_t = 1024 + dagSizeForTesting C.uint64_t = 1024 * 32 +) + +var DefaultDir = defaultDir() + +func defaultDir() string { + home := os.Getenv("HOME") + if user, err := user.Current(); err == nil { + home = user.HomeDir + } + if runtime.GOOS == "windows" { + return filepath.Join(home, "AppData", "Ethash") + } + return filepath.Join(home, ".ethash") +} + +// cache wraps an ethash_light_t with some metadata +// and automatic memory management. +type cache struct { + epoch uint64 + used time.Time + test bool + + gen sync.Once // ensures cache is only generated once. + ptr *C.struct_ethash_light +} + +// generate creates the actual cache. it can be called from multiple +// goroutines. the first call will generate the cache, subsequent +// calls wait until it is generated. +func (cache *cache) generate() { + cache.gen.Do(func() { + started := time.Now() + seedHash := makeSeedHash(cache.epoch) + glog.V(logger.Debug).Infof("Generating cache for epoch %d (%x)", cache.epoch, seedHash) + size := C.ethash_get_cachesize(C.uint64_t(cache.epoch * epochLength)) + if cache.test { + size = cacheSizeForTesting + } + cache.ptr = C.ethash_light_new_internal(size, (*C.ethash_h256_t)(unsafe.Pointer(&seedHash[0]))) + runtime.SetFinalizer(cache, freeCache) + glog.V(logger.Debug).Infof("Done generating cache for epoch %d, it took %v", cache.epoch, time.Since(started)) + }) +} + +func freeCache(cache *cache) { + C.ethash_light_delete(cache.ptr) + cache.ptr = nil +} + +func (cache *cache) compute(dagSize uint64, hash common.Hash, nonce uint64) (ok bool, mixDigest, result common.Hash) { + ret := C.ethash_light_compute_internal(cache.ptr, C.uint64_t(dagSize), hashToH256(hash), C.uint64_t(nonce)) + // Make sure cache is live until after the C call. + // This is important because a GC might happen and execute + // the finalizer before the call completes. + _ = cache + return bool(ret.success), h256ToHash(ret.mix_hash), h256ToHash(ret.result) +} + +// Light implements the Verify half of the proof of work. It uses a few small +// in-memory caches to verify the nonces found by Full. +type Light struct { + test bool // If set, use a smaller cache size + + mu sync.Mutex // Protects the per-epoch map of verification caches + caches map[uint64]*cache // Currently maintained verification caches + future *cache // Pre-generated cache for the estimated future DAG + + NumCaches int // Maximum number of caches to keep before eviction (only init, don't modify) +} + +// Verify checks whether the block's nonce is valid. +func (l *Light) Verify(block pow.Block) bool { + // TODO: do ethash_quick_verify before getCache in order + // to prevent DOS attacks. + blockNum := block.NumberU64() + if blockNum >= epochLength*2048 { + glog.V(logger.Debug).Infof("block number %d too high, limit is %d", epochLength*2048) + return false + } + + difficulty := block.Difficulty() + /* Cannot happen if block header diff is validated prior to PoW, but can + happen if PoW is checked first due to parallel PoW checking. + We could check the minimum valid difficulty but for SoC we avoid (duplicating) + Ethereum protocol consensus rules here which are not in scope of Ethash + */ + if difficulty.Cmp(common.Big0) == 0 { + glog.V(logger.Debug).Infof("invalid block difficulty") + return false + } + + cache := l.getCache(blockNum) + dagSize := C.ethash_get_datasize(C.uint64_t(blockNum)) + if l.test { + dagSize = dagSizeForTesting + } + // Recompute the hash using the cache. + ok, mixDigest, result := cache.compute(uint64(dagSize), block.HashNoNonce(), block.Nonce()) + if !ok { + return false + } + + // avoid mixdigest malleability as it's not included in a block's "hashNononce" + if block.MixDigest() != mixDigest { + return false + } + + // The actual check. + target := new(big.Int).Div(maxUint256, difficulty) + return result.Big().Cmp(target) <= 0 +} + +func h256ToHash(in C.ethash_h256_t) common.Hash { + return *(*common.Hash)(unsafe.Pointer(&in.b)) +} + +func hashToH256(in common.Hash) C.ethash_h256_t { + return C.ethash_h256_t{b: *(*[32]C.uint8_t)(unsafe.Pointer(&in[0]))} +} + +func (l *Light) getCache(blockNum uint64) *cache { + var c *cache + epoch := blockNum / epochLength + + // If we have a PoW for that epoch, use that + l.mu.Lock() + if l.caches == nil { + l.caches = make(map[uint64]*cache) + } + if l.NumCaches == 0 { + l.NumCaches = 3 + } + c = l.caches[epoch] + if c == nil { + // No cached DAG, evict the oldest if the cache limit was reached + if len(l.caches) >= l.NumCaches { + var evict *cache + for _, cache := range l.caches { + if evict == nil || evict.used.After(cache.used) { + evict = cache + } + } + glog.V(logger.Debug).Infof("Evicting DAG for epoch %d in favour of epoch %d", evict.epoch, epoch) + delete(l.caches, evict.epoch) + } + // If we have the new DAG pre-generated, use that, otherwise create a new one + if l.future != nil && l.future.epoch == epoch { + glog.V(logger.Debug).Infof("Using pre-generated DAG for epoch %d", epoch) + c, l.future = l.future, nil + } else { + glog.V(logger.Debug).Infof("No pre-generated DAG available, creating new for epoch %d", epoch) + c = &cache{epoch: epoch, test: l.test} + } + l.caches[epoch] = c + + // If we just used up the future cache, or need a refresh, regenerate + if l.future == nil || l.future.epoch <= epoch { + glog.V(logger.Debug).Infof("Pre-generating DAG for epoch %d", epoch+1) + l.future = &cache{epoch: epoch + 1, test: l.test} + go l.future.generate() + } + } + c.used = time.Now() + l.mu.Unlock() + + // Wait for generation finish and return the cache + c.generate() + return c +} + +// dag wraps an ethash_full_t with some metadata +// and automatic memory management. +type dag struct { + epoch uint64 + test bool + dir string + + gen sync.Once // ensures DAG is only generated once. + ptr *C.struct_ethash_full +} + +// generate creates the actual DAG. it can be called from multiple +// goroutines. the first call will generate the DAG, subsequent +// calls wait until it is generated. +func (d *dag) generate() { + d.gen.Do(func() { + var ( + started = time.Now() + seedHash = makeSeedHash(d.epoch) + blockNum = C.uint64_t(d.epoch * epochLength) + cacheSize = C.ethash_get_cachesize(blockNum) + dagSize = C.ethash_get_datasize(blockNum) + ) + if d.test { + cacheSize = cacheSizeForTesting + dagSize = dagSizeForTesting + } + if d.dir == "" { + d.dir = DefaultDir + } + glog.V(logger.Info).Infof("Generating DAG for epoch %d (size %d) (%x)", d.epoch, dagSize, seedHash) + // Generate a temporary cache. + // TODO: this could share the cache with Light + cache := C.ethash_light_new_internal(cacheSize, (*C.ethash_h256_t)(unsafe.Pointer(&seedHash[0]))) + defer C.ethash_light_delete(cache) + // Generate the actual DAG. + d.ptr = C.ethash_full_new_internal( + C.CString(d.dir), + hashToH256(seedHash), + dagSize, + cache, + (C.ethash_callback_t)(unsafe.Pointer(C.ethashGoCallback_cgo)), + ) + if d.ptr == nil { + panic("ethash_full_new IO or memory error") + } + runtime.SetFinalizer(d, freeDAG) + glog.V(logger.Info).Infof("Done generating DAG for epoch %d, it took %v", d.epoch, time.Since(started)) + }) +} + +func freeDAG(d *dag) { + C.ethash_full_delete(d.ptr) + d.ptr = nil +} + +func (d *dag) Ptr() unsafe.Pointer { + return unsafe.Pointer(d.ptr.data) +} + +//export ethashGoCallback +func ethashGoCallback(percent C.unsigned) C.int { + glog.V(logger.Info).Infof("Generating DAG: %d%%", percent) + return 0 +} + +// MakeDAG pre-generates a DAG file for the given block number in the +// given directory. If dir is the empty string, the default directory +// is used. +func MakeDAG(blockNum uint64, dir string) error { + d := &dag{epoch: blockNum / epochLength, dir: dir} + if blockNum >= epochLength*2048 { + return fmt.Errorf("block number too high, limit is %d", epochLength*2048) + } + d.generate() + if d.ptr == nil { + return errors.New("failed") + } + return nil +} + +// Full implements the Search half of the proof of work. +type Full struct { + Dir string // use this to specify a non-default DAG directory + + test bool // if set use a smaller DAG size + turbo bool + hashRate int32 + + mu sync.Mutex // protects dag + current *dag // current full DAG +} + +func (pow *Full) getDAG(blockNum uint64) (d *dag) { + epoch := blockNum / epochLength + pow.mu.Lock() + if pow.current != nil && pow.current.epoch == epoch { + d = pow.current + } else { + d = &dag{epoch: epoch, test: pow.test, dir: pow.Dir} + pow.current = d + } + pow.mu.Unlock() + // wait for it to finish generating. + d.generate() + return d +} + +func (pow *Full) Search(block pow.Block, stop <-chan struct{}, index int) (nonce uint64, mixDigest []byte) { + dag := pow.getDAG(block.NumberU64()) + + r := rand.New(rand.NewSource(time.Now().UnixNano())) + diff := block.Difficulty() + + i := int64(0) + starti := i + start := time.Now().UnixNano() + previousHashrate := int32(0) + + nonce = uint64(r.Int63()) + hash := hashToH256(block.HashNoNonce()) + target := new(big.Int).Div(maxUint256, diff) + for { + select { + case <-stop: + atomic.AddInt32(&pow.hashRate, -previousHashrate) + return 0, nil + default: + i++ + + // we don't have to update hash rate on every nonce, so update after + // first nonce check and then after 2^X nonces + if i == 2 || ((i % (1 << 16)) == 0) { + elapsed := time.Now().UnixNano() - start + hashes := (float64(1e9) / float64(elapsed)) * float64(i-starti) + hashrateDiff := int32(hashes) - previousHashrate + previousHashrate = int32(hashes) + atomic.AddInt32(&pow.hashRate, hashrateDiff) + } + + ret := C.ethash_full_compute(dag.ptr, hash, C.uint64_t(nonce)) + result := h256ToHash(ret.result).Big() + + // TODO: disagrees with the spec https://github.com/ethereum/wiki/wiki/Ethash#mining + if ret.success && result.Cmp(target) <= 0 { + mixDigest = C.GoBytes(unsafe.Pointer(&ret.mix_hash), C.int(32)) + atomic.AddInt32(&pow.hashRate, -previousHashrate) + return nonce, mixDigest + } + nonce += 1 + } + + if !pow.turbo { + time.Sleep(20 * time.Microsecond) + } + } +} + +func (pow *Full) GetHashrate() int64 { + return int64(atomic.LoadInt32(&pow.hashRate)) +} + +func (pow *Full) Turbo(on bool) { + // TODO: this needs to use an atomic operation. + pow.turbo = on +} + +// Ethash combines block verification with Light and +// nonce searching with Full into a single proof of work. +type Ethash struct { + *Light + *Full +} + +// New creates an instance of the proof of work. +func New() *Ethash { + return &Ethash{new(Light), &Full{turbo: true}} +} + +// NewShared creates an instance of the proof of work., where a single instance +// of the Light cache is shared across all instances created with NewShared. +func NewShared() *Ethash { + return &Ethash{sharedLight, &Full{turbo: true}} +} + +// NewForTesting creates a proof of work for use in unit tests. +// It uses a smaller DAG and cache size to keep test times low. +// DAG files are stored in a temporary directory. +// +// Nonces found by a testing instance are not verifiable with a +// regular-size cache. +func NewForTesting() (*Ethash, error) { + dir, err := ioutil.TempDir("", "ethash-test") + if err != nil { + return nil, err + } + return &Ethash{&Light{test: true}, &Full{Dir: dir, test: true}}, nil +} + +func GetSeedHash(blockNum uint64) ([]byte, error) { + if blockNum >= epochLength*2048 { + return nil, fmt.Errorf("block number too high, limit is %d", epochLength*2048) + } + sh := makeSeedHash(blockNum / epochLength) + return sh[:], nil +} + +func makeSeedHash(epoch uint64) (sh common.Hash) { + for ; epoch > 0; epoch-- { + sh = crypto.Sha3Hash(sh[:]) + } + return sh +} |