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

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// Copyright 2017 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 tracers is a manager for transaction tracing engines.
package tracers
import (
"encoding/json"
"fmt"
"math/big"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/vm"
)
// Context contains some contextual infos for a transaction execution that is not
// available from within the EVM object.
type Context struct {
BlockHash common.Hash // Hash of the block the tx is contained within (zero if dangling tx or call)
BlockNumber *big.Int // Number of the block the tx is contained within (zero if dangling tx or call)
TxIndex int // Index of the transaction within a block (zero if dangling tx or call)
TxHash common.Hash // Hash of the transaction being traced (zero if dangling call)
}
// Tracer interface extends vm.EVMLogger and additionally
// allows collecting the tracing result.
type Tracer interface {
vm.EVMLogger
GetResult() (json.RawMessage, error)
// Stop terminates execution of the tracer at the first opportune moment.
Stop(err error)
}
type ctorFn func(*Context, json.RawMessage) (Tracer, error)
type jsCtorFn func(string, *Context, json.RawMessage) (Tracer, error)
type elem struct {
ctor ctorFn
isJS bool
}
// DefaultDirectory is the collection of tracers bundled by default.
var DefaultDirectory = directory{elems: make(map[string]elem)}
// directory provides functionality to lookup a tracer by name
// and a function to instantiate it. It falls back to a JS code evaluator
// if no tracer of the given name exists.
type directory struct {
elems map[string]elem
jsEval jsCtorFn
}
// Register registers a method as a lookup for tracers, meaning that
// users can invoke a named tracer through that lookup.
func (d *directory) Register(name string, f ctorFn, isJS bool) {
d.elems[name] = elem{ctor: f, isJS: isJS}
}
// RegisterJSEval registers a tracer that is able to parse
// dynamic user-provided JS code.
func (d *directory) RegisterJSEval(f jsCtorFn) {
d.jsEval = f
}
// New returns a new instance of a tracer, by iterating through the
// registered lookups. Name is either name of an existing tracer
// or an arbitrary JS code.
func (d *directory) New(name string, ctx *Context, cfg json.RawMessage) (Tracer, error) {
if elem, ok := d.elems[name]; ok {
return elem.ctor(ctx, cfg)
}
// Assume JS code
return d.jsEval(name, ctx, cfg)
}
// IsJS will return true if the given tracer will evaluate
// JS code. Because code evaluation has high overhead, this
// info will be used in determining fast and slow code paths.
func (d *directory) IsJS(name string) bool {
if elem, ok := d.elems[name]; ok {
return elem.isJS
}
// JS eval will execute JS code
return true
}
const (
memoryPadLimit = 1024 * 1024
)
// GetMemoryCopyPadded returns offset + size as a new slice.
// It zero-pads the slice if it extends beyond memory bounds.
func GetMemoryCopyPadded(m *vm.Memory, offset, size int64) ([]byte, error) {
if offset < 0 || size < 0 {
return nil, fmt.Errorf("offset or size must not be negative")
}
if int(offset+size) < m.Len() { // slice fully inside memory
return m.GetCopy(offset, size), nil
}
paddingNeeded := int(offset+size) - m.Len()
if paddingNeeded > memoryPadLimit {
return nil, fmt.Errorf("reached limit for padding memory slice: %d", paddingNeeded)
}
cpy := make([]byte, size)
if overlap := int64(m.Len()) - offset; overlap > 0 {
copy(cpy, m.GetPtr(offset, overlap))
}
return cpy, nil
}