eth/tracers: package restructuring (#23857)

* eth/tracers: restructure tracer package

* core/vm/runtime: load js tracers

* eth/tracers: mv bigint js code to own file

* eth/tracers: add method docs for native tracers

* eth/tracers: minor doc fix

* core,eth: cancel evm on nativecalltracer stop

* core/vm: fix failing test

Co-authored-by: Sina Mahmoodi <itz.s1na@gmail.com>

eth/tracers/native/tracer.go

@@ -0,0 +1,79 @@
+// 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:
+
+```golang
+func init() {
+	register("noopTracerNative", newNoopTracer)
+}
+```
+*/
+package native
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/eth/tracers"
+)
+
+// init registers itself this packages as a lookup for tracers.
+func init() {
+	tracers.RegisterLookup(false, lookup)
+}
+
+/*
+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]func() tracers.Tracer
+
+// register is used by native tracers to register their presence.
+func register(name string, ctor func() tracers.Tracer) {
+	if ctors == nil {
+		ctors = make(map[string]func() tracers.Tracer)
+	}
+	ctors[name] = ctor
+}
+
+// lookup returns a tracer, if one can be matched to the given name.
+func lookup(name string, ctx *tracers.Context) (tracers.Tracer, error) {
+	if ctors == nil {
+		ctors = make(map[string]func() tracers.Tracer)
+	}
+	if ctor, ok := ctors[name]; ok {
+		return ctor(), nil
+	}
+	return nil, errors.New("no tracer found")
+}