Official Go implementation of the Ethereum protocol
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go-ethereum/eth/tracers/native/tracer.go

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// Copyright 2021 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 native is a collection of tracers written in go.
//
// In order to add a native tracer and have it compiled into the binary, a new
// file needs to be added to this folder, containing an implementation of the
// `eth.tracers.Tracer` interface.
//
// Aside from implementing the tracer, it also needs to register itself, using the
// `register` method -- and this needs to be done in the package initialization.
//
// Example:
//
// func init() {
// register("noopTracerNative", newNoopTracer)
// }
package native
import (
"encoding/json"
"errors"
"github.com/ethereum/go-ethereum/eth/tracers"
)
// init registers itself this packages as a lookup for tracers.
func init() {
tracers.RegisterLookup(false, lookup)
}
// ctorFn is the constructor signature of a native tracer.
type ctorFn = func(*tracers.Context, json.RawMessage) (tracers.Tracer, error)
/*
ctors is a map of package-local tracer constructors.
We cannot be certain about the order of init-functions within a package,
The go spec (https://golang.org/ref/spec#Package_initialization) says
> To ensure reproducible initialization behavior, build systems
> are encouraged to present multiple files belonging to the same
> package in lexical file name order to a compiler.
Hence, we cannot make the map in init, but must make it upon first use.
*/
var ctors map[string]ctorFn
// register is used by native tracers to register their presence.
func register(name string, ctor ctorFn) {
if ctors == nil {
ctors = make(map[string]ctorFn)
}
ctors[name] = ctor
}
// lookup returns a tracer, if one can be matched to the given name.
func lookup(name string, ctx *tracers.Context, cfg json.RawMessage) (tracers.Tracer, error) {
if ctors == nil {
ctors = make(map[string]ctorFn)
}
if ctor, ok := ctors[name]; ok {
return ctor(ctx, cfg)
}
return nil, errors.New("no tracer found")
}