github.com/ylsGit/go-ethereum@v1.6.5/light/trie.go (about) 1 // Copyright 2015 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 light 18 19 import ( 20 "context" 21 22 "github.com/ethereum/go-ethereum/crypto" 23 "github.com/ethereum/go-ethereum/ethdb" 24 "github.com/ethereum/go-ethereum/trie" 25 ) 26 27 // LightTrie is an ODR-capable wrapper around trie.SecureTrie 28 type LightTrie struct { 29 trie *trie.SecureTrie 30 id *TrieID 31 odr OdrBackend 32 db ethdb.Database 33 } 34 35 // NewLightTrie creates a new LightTrie instance. It doesn't instantly try to 36 // access the db or network and retrieve the root node, it only initializes its 37 // encapsulated SecureTrie at the first actual operation. 38 func NewLightTrie(id *TrieID, odr OdrBackend, useFakeMap bool) *LightTrie { 39 return &LightTrie{ 40 // SecureTrie is initialized before first request 41 id: id, 42 odr: odr, 43 db: odr.Database(), 44 } 45 } 46 47 // retrieveKey retrieves a single key, returns true and stores nodes in local 48 // database if successful 49 func (t *LightTrie) retrieveKey(ctx context.Context, key []byte) bool { 50 r := &TrieRequest{Id: t.id, Key: crypto.Keccak256(key)} 51 return t.odr.Retrieve(ctx, r) == nil 52 } 53 54 // do tries and retries to execute a function until it returns with no error or 55 // an error type other than MissingNodeError 56 func (t *LightTrie) do(ctx context.Context, key []byte, fn func() error) error { 57 err := fn() 58 for err != nil { 59 if _, ok := err.(*trie.MissingNodeError); !ok { 60 return err 61 } 62 if !t.retrieveKey(ctx, key) { 63 break 64 } 65 err = fn() 66 } 67 return err 68 } 69 70 // Get returns the value for key stored in the trie. 71 // The value bytes must not be modified by the caller. 72 func (t *LightTrie) Get(ctx context.Context, key []byte) (res []byte, err error) { 73 err = t.do(ctx, key, func() (err error) { 74 if t.trie == nil { 75 t.trie, err = trie.NewSecure(t.id.Root, t.db, 0) 76 } 77 if err == nil { 78 res, err = t.trie.TryGet(key) 79 } 80 return 81 }) 82 return 83 } 84 85 // Update associates key with value in the trie. Subsequent calls to 86 // Get will return value. If value has length zero, any existing value 87 // is deleted from the trie and calls to Get will return nil. 88 // 89 // The value bytes must not be modified by the caller while they are 90 // stored in the trie. 91 func (t *LightTrie) Update(ctx context.Context, key, value []byte) (err error) { 92 err = t.do(ctx, key, func() (err error) { 93 if t.trie == nil { 94 t.trie, err = trie.NewSecure(t.id.Root, t.db, 0) 95 } 96 if err == nil { 97 err = t.trie.TryUpdate(key, value) 98 } 99 return 100 }) 101 return 102 } 103 104 // Delete removes any existing value for key from the trie. 105 func (t *LightTrie) Delete(ctx context.Context, key []byte) (err error) { 106 err = t.do(ctx, key, func() (err error) { 107 if t.trie == nil { 108 t.trie, err = trie.NewSecure(t.id.Root, t.db, 0) 109 } 110 if err == nil { 111 err = t.trie.TryDelete(key) 112 } 113 return 114 }) 115 return 116 }