plugeth/trie/hasher.go

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// Copyright 2016 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 trie
import (
"sync"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/rlp"
"golang.org/x/crypto/sha3"
)
// hasher is a type used for the trie Hash operation. A hasher has some
// internal preallocated temp space
type hasher struct {
sha crypto.KeccakState
tmp []byte
encbuf rlp.EncoderBuffer
parallel bool // Whether to use parallel threads when hashing
}
// hasherPool holds pureHashers
var hasherPool = sync.Pool{
New: func() interface{} {
return &hasher{
tmp: make([]byte, 0, 550), // cap is as large as a full fullNode.
sha: sha3.NewLegacyKeccak256().(crypto.KeccakState),
encbuf: rlp.NewEncoderBuffer(nil),
}
},
}
func newHasher(parallel bool) *hasher {
h := hasherPool.Get().(*hasher)
h.parallel = parallel
return h
}
func returnHasherToPool(h *hasher) {
hasherPool.Put(h)
}
// hash collapses a node down into a hash node, also returning a copy of the
// original node initialized with the computed hash to replace the original one.
func (h *hasher) hash(n node, force bool) (hashed node, cached node) {
// Return the cached hash if it's available
if hash, _ := n.cache(); hash != nil {
return hash, n
}
// Trie not processed yet, walk the children
switch n := n.(type) {
case *shortNode:
collapsed, cached := h.hashShortNodeChildren(n)
hashed := h.shortnodeToHash(collapsed, force)
// We need to retain the possibly _not_ hashed node, in case it was too
// small to be hashed
if hn, ok := hashed.(hashNode); ok {
cached.flags.hash = hn
} else {
cached.flags.hash = nil
}
return hashed, cached
case *fullNode:
collapsed, cached := h.hashFullNodeChildren(n)
hashed = h.fullnodeToHash(collapsed, force)
if hn, ok := hashed.(hashNode); ok {
cached.flags.hash = hn
} else {
cached.flags.hash = nil
}
return hashed, cached
default:
// Value and hash nodes don't have children, so they're left as were
return n, n
}
}
// hashShortNodeChildren collapses the short node. The returned collapsed node
// holds a live reference to the Key, and must not be modified.
func (h *hasher) hashShortNodeChildren(n *shortNode) (collapsed, cached *shortNode) {
// Hash the short node's child, caching the newly hashed subtree
collapsed, cached = n.copy(), n.copy()
// Previously, we did copy this one. We don't seem to need to actually
// do that, since we don't overwrite/reuse keys
// cached.Key = common.CopyBytes(n.Key)
collapsed.Key = hexToCompact(n.Key)
// Unless the child is a valuenode or hashnode, hash it
switch n.Val.(type) {
case *fullNode, *shortNode:
collapsed.Val, cached.Val = h.hash(n.Val, false)
}
return collapsed, cached
}
func (h *hasher) hashFullNodeChildren(n *fullNode) (collapsed *fullNode, cached *fullNode) {
// Hash the full node's children, caching the newly hashed subtrees
cached = n.copy()
collapsed = n.copy()
if h.parallel {
var wg sync.WaitGroup
wg.Add(16)
for i := 0; i < 16; i++ {
go func(i int) {
hasher := newHasher(false)
if child := n.Children[i]; child != nil {
collapsed.Children[i], cached.Children[i] = hasher.hash(child, false)
} else {
collapsed.Children[i] = nilValueNode
}
returnHasherToPool(hasher)
wg.Done()
}(i)
}
wg.Wait()
} else {
for i := 0; i < 16; i++ {
if child := n.Children[i]; child != nil {
collapsed.Children[i], cached.Children[i] = h.hash(child, false)
} else {
collapsed.Children[i] = nilValueNode
}
}
}
return collapsed, cached
}
// shortnodeToHash creates a hashNode from a shortNode. The supplied shortnode
// should have hex-type Key, which will be converted (without modification)
// into compact form for RLP encoding.
// If the rlp data is smaller than 32 bytes, `nil` is returned.
func (h *hasher) shortnodeToHash(n *shortNode, force bool) node {
n.encode(h.encbuf)
enc := h.encodedBytes()
if len(enc) < 32 && !force {
return n // Nodes smaller than 32 bytes are stored inside their parent
}
return h.hashData(enc)
}
// fullnodeToHash is used to create a hashNode from a fullNode, (which
// may contain nil values)
func (h *hasher) fullnodeToHash(n *fullNode, force bool) node {
n.encode(h.encbuf)
enc := h.encodedBytes()
if len(enc) < 32 && !force {
return n // Nodes smaller than 32 bytes are stored inside their parent
}
return h.hashData(enc)
}
// encodedBytes returns the result of the last encoding operation on h.encbuf.
// This also resets the encoder buffer.
//
// All node encoding must be done like this:
//
// node.encode(h.encbuf)
// enc := h.encodedBytes()
//
// This convention exists because node.encode can only be inlined/escape-analyzed when
// called on a concrete receiver type.
func (h *hasher) encodedBytes() []byte {
h.tmp = h.encbuf.AppendToBytes(h.tmp[:0])
h.encbuf.Reset(nil)
return h.tmp
}
// hashData hashes the provided data
func (h *hasher) hashData(data []byte) hashNode {
n := make(hashNode, 32)
h.sha.Reset()
h.sha.Write(data)
h.sha.Read(n)
return n
}
// proofHash is used to construct trie proofs, and returns the 'collapsed'
// node (for later RLP encoding) as well as the hashed node -- unless the
// node is smaller than 32 bytes, in which case it will be returned as is.
// This method does not do anything on value- or hash-nodes.
func (h *hasher) proofHash(original node) (collapsed, hashed node) {
switch n := original.(type) {
case *shortNode:
sn, _ := h.hashShortNodeChildren(n)
return sn, h.shortnodeToHash(sn, false)
case *fullNode:
fn, _ := h.hashFullNodeChildren(n)
return fn, h.fullnodeToHash(fn, false)
default:
// Value and hash nodes don't have children, so they're left as were
return n, n
}
}