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// Copyright 2019 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/>.
//go:generate go-bindata -nometadata -o 4byte.go -pkg fourbyte 4byte.json
//go:generate gofmt -s -w 4byte.go
// Package fourbyte contains the 4byte database.
package fourbyte
import (
"encoding/hex"
"encoding/json"
"fmt"
"io/ioutil"
"os"
)
// Database is a 4byte database with the possibility of maintaining an immutable
// set (embedded) into the process and a mutable set (loaded and written to file).
type Database struct {
embedded map[string]string
custom map[string]string
customPath string
}
// newEmpty exists for testing purposes.
func newEmpty() *Database {
return &Database{
embedded: make(map[string]string),
custom: make(map[string]string),
}
}
// New loads the standard signature database embedded in the package.
func New() (*Database, error) {
return NewWithFile("")
}
// NewFromFile loads signature database from file, and errors if the file is not
// valid JSON. The constructor does no other validation of contents. This method
// does not load the embedded 4byte database.
//
// The provided path will be used to write new values into if they are submitted
// via the API.
func NewFromFile(path string) (*Database, error) {
raw, err := os.Open(path)
if err != nil {
return nil, err
}
defer raw.Close()
db := newEmpty()
if err := json.NewDecoder(raw).Decode(&db.embedded); err != nil {
return nil, err
}
return db, nil
}
// NewWithFile loads both the standard signature database (embedded resource
// file) as well as a custom database. The latter will be used to write new
// values into if they are submitted via the API.
func NewWithFile(path string) (*Database, error) {
db := &Database{make(map[string]string), make(map[string]string), path}
db.customPath = path
blob, err := Asset("4byte.json")
if err != nil {
return nil, err
}
if err := json.Unmarshal(blob, &db.embedded); err != nil {
return nil, err
}
// Custom file may not exist. Will be created during save, if needed.
if _, err := os.Stat(path); err == nil {
if blob, err = ioutil.ReadFile(path); err != nil {
return nil, err
}
if err := json.Unmarshal(blob, &db.custom); err != nil {
return nil, err
}
}
return db, nil
}
// Size returns the number of 4byte entries in the embedded and custom datasets.
func (db *Database) Size() (int, int) {
return len(db.embedded), len(db.custom)
}
// Selector checks the given 4byte ID against the known ABI methods.
//
// This method does not validate the match, it's assumed the caller will do.
func (db *Database) Selector(id []byte) (string, error) {
if len(id) < 4 {
return "", fmt.Errorf("expected 4-byte id, got %d", len(id))
}
sig := hex.EncodeToString(id[:4])
if selector, exists := db.embedded[sig]; exists {
return selector, nil
}
if selector, exists := db.custom[sig]; exists {
return selector, nil
}
return "", fmt.Errorf("signature %v not found", sig)
}
// AddSelector inserts a new 4byte entry into the database. If custom database
// saving is enabled, the new dataset is also persisted to disk.
//
// Node, this method does _not_ validate the correctness of the data. It assumes
// the caller has already done so.
func (db *Database) AddSelector(selector string, data []byte) error {
// If the selector is already known, skip duplicating it
if len(data) < 4 {
return nil
}
if _, err := db.Selector(data[:4]); err == nil {
return nil
}
// Inject the custom selector into the database and persist if needed
db.custom[hex.EncodeToString(data[:4])] = selector
if db.customPath == "" {
return nil
}
blob, err := json.Marshal(db.custom)
if err != nil {
return err
}
return ioutil.WriteFile(db.customPath, blob, 0600)
}
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