github.com/ethw3/go-ethereuma@v0.0.0-20221013053120-c14602a4c23c/eth/tracers/native/tracer.go (about)

     1  // Copyright 2021 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  /*
    18  Package native is a collection of tracers written in go.
    19  
    20  In order to add a native tracer and have it compiled into the binary, a new
    21  file needs to be added to this folder, containing an implementation of the
    22  `eth.tracers.Tracer` interface.
    23  
    24  Aside from implementing the tracer, it also needs to register itself, using the
    25  `register` method -- and this needs to be done in the package initialization.
    26  
    27  Example:
    28  
    29  ```golang
    30  func init() {
    31  	register("noopTracerNative", newNoopTracer)
    32  }
    33  ```
    34  */
    35  package native
    36  
    37  import (
    38  	"encoding/json"
    39  	"errors"
    40  
    41  	"github.com/ethw3/go-ethereuma/eth/tracers"
    42  )
    43  
    44  // init registers itself this packages as a lookup for tracers.
    45  func init() {
    46  	tracers.RegisterLookup(false, lookup)
    47  }
    48  
    49  // ctorFn is the constructor signature of a native tracer.
    50  type ctorFn = func(*tracers.Context, json.RawMessage) (tracers.Tracer, error)
    51  
    52  /*
    53  ctors is a map of package-local tracer constructors.
    54  
    55  We cannot be certain about the order of init-functions within a package,
    56  The go spec (https://golang.org/ref/spec#Package_initialization) says
    57  
    58  > To ensure reproducible initialization behavior, build systems
    59  > are encouraged to present multiple files belonging to the same
    60  > package in lexical file name order to a compiler.
    61  
    62  Hence, we cannot make the map in init, but must make it upon first use.
    63  */
    64  var ctors map[string]ctorFn
    65  
    66  // register is used by native tracers to register their presence.
    67  func register(name string, ctor ctorFn) {
    68  	if ctors == nil {
    69  		ctors = make(map[string]ctorFn)
    70  	}
    71  	ctors[name] = ctor
    72  }
    73  
    74  // lookup returns a tracer, if one can be matched to the given name.
    75  func lookup(name string, ctx *tracers.Context, cfg json.RawMessage) (tracers.Tracer, error) {
    76  	if ctors == nil {
    77  		ctors = make(map[string]ctorFn)
    78  	}
    79  	if ctor, ok := ctors[name]; ok {
    80  		return ctor(ctx, cfg)
    81  	}
    82  	return nil, errors.New("no tracer found")
    83  }