github.com/cryptogateway/go-paymex@v0.0.0-20210204174735-96277fb1e602/trie/stacktrie.go (about)

     1  // Copyright 2020 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package trie
    18  
    19  import (
    20  	"errors"
    21  	"fmt"
    22  	"sync"
    23  
    24  	"github.com/cryptogateway/go-paymex/common"
    25  	"github.com/cryptogateway/go-paymex/ethdb"
    26  	"github.com/cryptogateway/go-paymex/log"
    27  	"github.com/cryptogateway/go-paymex/rlp"
    28  )
    29  
    30  var ErrCommitDisabled = errors.New("no database for committing")
    31  
    32  var stPool = sync.Pool{
    33  	New: func() interface{} {
    34  		return NewStackTrie(nil)
    35  	},
    36  }
    37  
    38  func stackTrieFromPool(db ethdb.KeyValueStore) *StackTrie {
    39  	st := stPool.Get().(*StackTrie)
    40  	st.db = db
    41  	return st
    42  }
    43  
    44  func returnToPool(st *StackTrie) {
    45  	st.Reset()
    46  	stPool.Put(st)
    47  }
    48  
    49  // StackTrie is a trie implementation that expects keys to be inserted
    50  // in order. Once it determines that a subtree will no longer be inserted
    51  // into, it will hash it and free up the memory it uses.
    52  type StackTrie struct {
    53  	nodeType  uint8          // node type (as in branch, ext, leaf)
    54  	val       []byte         // value contained by this node if it's a leaf
    55  	key       []byte         // key chunk covered by this (full|ext) node
    56  	keyOffset int            // offset of the key chunk inside a full key
    57  	children  [16]*StackTrie // list of children (for fullnodes and exts)
    58  
    59  	db ethdb.KeyValueStore // Pointer to the commit db, can be nil
    60  }
    61  
    62  // NewStackTrie allocates and initializes an empty trie.
    63  func NewStackTrie(db ethdb.KeyValueStore) *StackTrie {
    64  	return &StackTrie{
    65  		nodeType: emptyNode,
    66  		db:       db,
    67  	}
    68  }
    69  
    70  func newLeaf(ko int, key, val []byte, db ethdb.KeyValueStore) *StackTrie {
    71  	st := stackTrieFromPool(db)
    72  	st.nodeType = leafNode
    73  	st.keyOffset = ko
    74  	st.key = append(st.key, key[ko:]...)
    75  	st.val = val
    76  	return st
    77  }
    78  
    79  func newExt(ko int, key []byte, child *StackTrie, db ethdb.KeyValueStore) *StackTrie {
    80  	st := stackTrieFromPool(db)
    81  	st.nodeType = extNode
    82  	st.keyOffset = ko
    83  	st.key = append(st.key, key[ko:]...)
    84  	st.children[0] = child
    85  	return st
    86  }
    87  
    88  // List all values that StackTrie#nodeType can hold
    89  const (
    90  	emptyNode = iota
    91  	branchNode
    92  	extNode
    93  	leafNode
    94  	hashedNode
    95  )
    96  
    97  // TryUpdate inserts a (key, value) pair into the stack trie
    98  func (st *StackTrie) TryUpdate(key, value []byte) error {
    99  	k := keybytesToHex(key)
   100  	if len(value) == 0 {
   101  		panic("deletion not supported")
   102  	}
   103  	st.insert(k[:len(k)-1], value)
   104  	return nil
   105  }
   106  
   107  func (st *StackTrie) Update(key, value []byte) {
   108  	if err := st.TryUpdate(key, value); err != nil {
   109  		log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
   110  	}
   111  }
   112  
   113  func (st *StackTrie) Reset() {
   114  	st.db = nil
   115  	st.key = st.key[:0]
   116  	st.val = nil
   117  	for i := range st.children {
   118  		st.children[i] = nil
   119  	}
   120  	st.nodeType = emptyNode
   121  	st.keyOffset = 0
   122  }
   123  
   124  // Helper function that, given a full key, determines the index
   125  // at which the chunk pointed by st.keyOffset is different from
   126  // the same chunk in the full key.
   127  func (st *StackTrie) getDiffIndex(key []byte) int {
   128  	diffindex := 0
   129  	for ; diffindex < len(st.key) && st.key[diffindex] == key[st.keyOffset+diffindex]; diffindex++ {
   130  	}
   131  	return diffindex
   132  }
   133  
   134  // Helper function to that inserts a (key, value) pair into
   135  // the trie.
   136  func (st *StackTrie) insert(key, value []byte) {
   137  	switch st.nodeType {
   138  	case branchNode: /* Branch */
   139  		idx := int(key[st.keyOffset])
   140  		// Unresolve elder siblings
   141  		for i := idx - 1; i >= 0; i-- {
   142  			if st.children[i] != nil {
   143  				if st.children[i].nodeType != hashedNode {
   144  					st.children[i].hash()
   145  				}
   146  				break
   147  			}
   148  		}
   149  		// Add new child
   150  		if st.children[idx] == nil {
   151  			st.children[idx] = stackTrieFromPool(st.db)
   152  			st.children[idx].keyOffset = st.keyOffset + 1
   153  		}
   154  		st.children[idx].insert(key, value)
   155  	case extNode: /* Ext */
   156  		// Compare both key chunks and see where they differ
   157  		diffidx := st.getDiffIndex(key)
   158  
   159  		// Check if chunks are identical. If so, recurse into
   160  		// the child node. Otherwise, the key has to be split
   161  		// into 1) an optional common prefix, 2) the fullnode
   162  		// representing the two differing path, and 3) a leaf
   163  		// for each of the differentiated subtrees.
   164  		if diffidx == len(st.key) {
   165  			// Ext key and key segment are identical, recurse into
   166  			// the child node.
   167  			st.children[0].insert(key, value)
   168  			return
   169  		}
   170  		// Save the original part. Depending if the break is
   171  		// at the extension's last byte or not, create an
   172  		// intermediate extension or use the extension's child
   173  		// node directly.
   174  		var n *StackTrie
   175  		if diffidx < len(st.key)-1 {
   176  			n = newExt(diffidx+1, st.key, st.children[0], st.db)
   177  		} else {
   178  			// Break on the last byte, no need to insert
   179  			// an extension node: reuse the current node
   180  			n = st.children[0]
   181  		}
   182  		// Convert to hash
   183  		n.hash()
   184  		var p *StackTrie
   185  		if diffidx == 0 {
   186  			// the break is on the first byte, so
   187  			// the current node is converted into
   188  			// a branch node.
   189  			st.children[0] = nil
   190  			p = st
   191  			st.nodeType = branchNode
   192  		} else {
   193  			// the common prefix is at least one byte
   194  			// long, insert a new intermediate branch
   195  			// node.
   196  			st.children[0] = stackTrieFromPool(st.db)
   197  			st.children[0].nodeType = branchNode
   198  			st.children[0].keyOffset = st.keyOffset + diffidx
   199  			p = st.children[0]
   200  		}
   201  		// Create a leaf for the inserted part
   202  		o := newLeaf(st.keyOffset+diffidx+1, key, value, st.db)
   203  
   204  		// Insert both child leaves where they belong:
   205  		origIdx := st.key[diffidx]
   206  		newIdx := key[diffidx+st.keyOffset]
   207  		p.children[origIdx] = n
   208  		p.children[newIdx] = o
   209  		st.key = st.key[:diffidx]
   210  
   211  	case leafNode: /* Leaf */
   212  		// Compare both key chunks and see where they differ
   213  		diffidx := st.getDiffIndex(key)
   214  
   215  		// Overwriting a key isn't supported, which means that
   216  		// the current leaf is expected to be split into 1) an
   217  		// optional extension for the common prefix of these 2
   218  		// keys, 2) a fullnode selecting the path on which the
   219  		// keys differ, and 3) one leaf for the differentiated
   220  		// component of each key.
   221  		if diffidx >= len(st.key) {
   222  			panic("Trying to insert into existing key")
   223  		}
   224  
   225  		// Check if the split occurs at the first nibble of the
   226  		// chunk. In that case, no prefix extnode is necessary.
   227  		// Otherwise, create that
   228  		var p *StackTrie
   229  		if diffidx == 0 {
   230  			// Convert current leaf into a branch
   231  			st.nodeType = branchNode
   232  			p = st
   233  			st.children[0] = nil
   234  		} else {
   235  			// Convert current node into an ext,
   236  			// and insert a child branch node.
   237  			st.nodeType = extNode
   238  			st.children[0] = NewStackTrie(st.db)
   239  			st.children[0].nodeType = branchNode
   240  			st.children[0].keyOffset = st.keyOffset + diffidx
   241  			p = st.children[0]
   242  		}
   243  
   244  		// Create the two child leaves: the one containing the
   245  		// original value and the one containing the new value
   246  		// The child leave will be hashed directly in order to
   247  		// free up some memory.
   248  		origIdx := st.key[diffidx]
   249  		p.children[origIdx] = newLeaf(diffidx+1, st.key, st.val, st.db)
   250  		p.children[origIdx].hash()
   251  
   252  		newIdx := key[diffidx+st.keyOffset]
   253  		p.children[newIdx] = newLeaf(p.keyOffset+1, key, value, st.db)
   254  
   255  		// Finally, cut off the key part that has been passed
   256  		// over to the children.
   257  		st.key = st.key[:diffidx]
   258  		st.val = nil
   259  	case emptyNode: /* Empty */
   260  		st.nodeType = leafNode
   261  		st.key = key[st.keyOffset:]
   262  		st.val = value
   263  	case hashedNode:
   264  		panic("trying to insert into hash")
   265  	default:
   266  		panic("invalid type")
   267  	}
   268  }
   269  
   270  // hash() hashes the node 'st' and converts it into 'hashedNode', if possible.
   271  // Possible outcomes:
   272  // 1. The rlp-encoded value was >= 32 bytes:
   273  //  - Then the 32-byte `hash` will be accessible in `st.val`.
   274  //  - And the 'st.type' will be 'hashedNode'
   275  // 2. The rlp-encoded value was < 32 bytes
   276  //  - Then the <32 byte rlp-encoded value will be accessible in 'st.val'.
   277  //  - And the 'st.type' will be 'hashedNode' AGAIN
   278  //
   279  // This method will also:
   280  // set 'st.type' to hashedNode
   281  // clear 'st.key'
   282  func (st *StackTrie) hash() {
   283  	/* Shortcut if node is already hashed */
   284  	if st.nodeType == hashedNode {
   285  		return
   286  	}
   287  	// The 'hasher' is taken from a pool, but we don't actually
   288  	// claim an instance until all children are done with their hashing,
   289  	// and we actually need one
   290  	var h *hasher
   291  
   292  	switch st.nodeType {
   293  	case branchNode:
   294  		var nodes [17]node
   295  		for i, child := range st.children {
   296  			if child == nil {
   297  				nodes[i] = nilValueNode
   298  				continue
   299  			}
   300  			child.hash()
   301  			if len(child.val) < 32 {
   302  				nodes[i] = rawNode(child.val)
   303  			} else {
   304  				nodes[i] = hashNode(child.val)
   305  			}
   306  			st.children[i] = nil // Reclaim mem from subtree
   307  			returnToPool(child)
   308  		}
   309  		nodes[16] = nilValueNode
   310  		h = newHasher(false)
   311  		defer returnHasherToPool(h)
   312  		h.tmp.Reset()
   313  		if err := rlp.Encode(&h.tmp, nodes); err != nil {
   314  			panic(err)
   315  		}
   316  	case extNode:
   317  		st.children[0].hash()
   318  		h = newHasher(false)
   319  		defer returnHasherToPool(h)
   320  		h.tmp.Reset()
   321  		var valuenode node
   322  		if len(st.children[0].val) < 32 {
   323  			valuenode = rawNode(st.children[0].val)
   324  		} else {
   325  			valuenode = hashNode(st.children[0].val)
   326  		}
   327  		n := struct {
   328  			Key []byte
   329  			Val node
   330  		}{
   331  			Key: hexToCompact(st.key),
   332  			Val: valuenode,
   333  		}
   334  		if err := rlp.Encode(&h.tmp, n); err != nil {
   335  			panic(err)
   336  		}
   337  		returnToPool(st.children[0])
   338  		st.children[0] = nil // Reclaim mem from subtree
   339  	case leafNode:
   340  		h = newHasher(false)
   341  		defer returnHasherToPool(h)
   342  		h.tmp.Reset()
   343  		st.key = append(st.key, byte(16))
   344  		sz := hexToCompactInPlace(st.key)
   345  		n := [][]byte{st.key[:sz], st.val}
   346  		if err := rlp.Encode(&h.tmp, n); err != nil {
   347  			panic(err)
   348  		}
   349  	case emptyNode:
   350  		st.val = st.val[:0]
   351  		st.val = append(st.val, emptyRoot[:]...)
   352  		st.key = st.key[:0]
   353  		st.nodeType = hashedNode
   354  		return
   355  	default:
   356  		panic("Invalid node type")
   357  	}
   358  	st.key = st.key[:0]
   359  	st.nodeType = hashedNode
   360  	if len(h.tmp) < 32 {
   361  		st.val = st.val[:0]
   362  		st.val = append(st.val, h.tmp...)
   363  		return
   364  	}
   365  	// Going to write the hash to the 'val'. Need to ensure it's properly sized first
   366  	// Typically, 'branchNode's will have no 'val', and require this allocation
   367  	if required := 32 - len(st.val); required > 0 {
   368  		buf := make([]byte, required)
   369  		st.val = append(st.val, buf...)
   370  	}
   371  	st.val = st.val[:32]
   372  	h.sha.Reset()
   373  	h.sha.Write(h.tmp)
   374  	h.sha.Read(st.val)
   375  	if st.db != nil {
   376  		// TODO! Is it safe to Put the slice here?
   377  		// Do all db implementations copy the value provided?
   378  		st.db.Put(st.val, h.tmp)
   379  	}
   380  }
   381  
   382  // Hash returns the hash of the current node
   383  func (st *StackTrie) Hash() (h common.Hash) {
   384  	st.hash()
   385  	if len(st.val) != 32 {
   386  		// If the node's RLP isn't 32 bytes long, the node will not
   387  		// be hashed, and instead contain the  rlp-encoding of the
   388  		// node. For the top level node, we need to force the hashing.
   389  		ret := make([]byte, 32)
   390  		h := newHasher(false)
   391  		defer returnHasherToPool(h)
   392  		h.sha.Reset()
   393  		h.sha.Write(st.val)
   394  		h.sha.Read(ret)
   395  		return common.BytesToHash(ret)
   396  	}
   397  	return common.BytesToHash(st.val)
   398  }
   399  
   400  // Commit will firstly hash the entrie trie if it's still not hashed
   401  // and then commit all nodes to the associated database. Actually most
   402  // of the trie nodes MAY have been committed already. The main purpose
   403  // here is to commit the root node.
   404  //
   405  // The associated database is expected, otherwise the whole commit
   406  // functionality should be disabled.
   407  func (st *StackTrie) Commit() (common.Hash, error) {
   408  	if st.db == nil {
   409  		return common.Hash{}, ErrCommitDisabled
   410  	}
   411  	st.hash()
   412  	if len(st.val) != 32 {
   413  		// If the node's RLP isn't 32 bytes long, the node will not
   414  		// be hashed (and committed), and instead contain the  rlp-encoding of the
   415  		// node. For the top level node, we need to force the hashing+commit.
   416  		ret := make([]byte, 32)
   417  		h := newHasher(false)
   418  		defer returnHasherToPool(h)
   419  		h.sha.Reset()
   420  		h.sha.Write(st.val)
   421  		h.sha.Read(ret)
   422  		st.db.Put(ret, st.val)
   423  		return common.BytesToHash(ret), nil
   424  	}
   425  	return common.BytesToHash(st.val), nil
   426  }