github.com/ethereum/go-ethereum@v1.16.1/trie/trie_reader.go (about)

     1  // Copyright 2022 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  	"github.com/ethereum/go-ethereum/common"
    21  	"github.com/ethereum/go-ethereum/core/types"
    22  	"github.com/ethereum/go-ethereum/triedb/database"
    23  )
    24  
    25  // trieReader is a wrapper of the underlying node reader. It's not safe
    26  // for concurrent usage.
    27  type trieReader struct {
    28  	owner  common.Hash
    29  	reader database.NodeReader
    30  	banned map[string]struct{} // Marker to prevent node from being accessed, for tests
    31  }
    32  
    33  // newTrieReader initializes the trie reader with the given node reader.
    34  func newTrieReader(stateRoot, owner common.Hash, db database.NodeDatabase) (*trieReader, error) {
    35  	if stateRoot == (common.Hash{}) || stateRoot == types.EmptyRootHash {
    36  		return &trieReader{owner: owner}, nil
    37  	}
    38  	reader, err := db.NodeReader(stateRoot)
    39  	if err != nil {
    40  		return nil, &MissingNodeError{Owner: owner, NodeHash: stateRoot, err: err}
    41  	}
    42  	return &trieReader{owner: owner, reader: reader}, nil
    43  }
    44  
    45  // newEmptyReader initializes the pure in-memory reader. All read operations
    46  // should be forbidden and returns the MissingNodeError.
    47  func newEmptyReader() *trieReader {
    48  	return &trieReader{}
    49  }
    50  
    51  // node retrieves the rlp-encoded trie node with the provided trie node
    52  // information. An MissingNodeError will be returned in case the node is
    53  // not found or any error is encountered.
    54  //
    55  // Don't modify the returned byte slice since it's not deep-copied and
    56  // still be referenced by database.
    57  func (r *trieReader) node(path []byte, hash common.Hash) ([]byte, error) {
    58  	// Perform the logics in tests for preventing trie node access.
    59  	if r.banned != nil {
    60  		if _, ok := r.banned[string(path)]; ok {
    61  			return nil, &MissingNodeError{Owner: r.owner, NodeHash: hash, Path: path}
    62  		}
    63  	}
    64  	if r.reader == nil {
    65  		return nil, &MissingNodeError{Owner: r.owner, NodeHash: hash, Path: path}
    66  	}
    67  	blob, err := r.reader.Node(r.owner, path, hash)
    68  	if err != nil || len(blob) == 0 {
    69  		return nil, &MissingNodeError{Owner: r.owner, NodeHash: hash, Path: path, err: err}
    70  	}
    71  	return blob, nil
    72  }