eth/tracers/logger: respect logging limit (#35349)

Necessary for building fuzzers that don't take 10s of seconds for
tracing a test

eth/tracers/logger/logger.go

@@ -51,6 +51,19 @@ type Config struct {
 	Overrides *params.ChainConfig `json:"overrides,omitempty"`
 }
 
+// countingWriter wraps an io.Writer and records how many bytes have been
+// written through it.
+type countingWriter struct {
+	w io.Writer
+	n int
+}
+
+func (c *countingWriter) Write(p []byte) (int, error) {
+	n, err := c.w.Write(p)
+	c.n += n
+	return n, err
+}
+
 //go:generate go run github.com/fjl/gencodec -type StructLog -field-override structLogMarshaling -out gen_structlog.go
 
 // StructLog is emitted to the EVM each cycle and lists information about the
@@ -227,7 +240,7 @@ type StructLogger struct {
 
 	writer     io.Writer         // If set, the logger will stream instead of store logs
 	logs       []json.RawMessage // buffer of json-encoded logs
-	resultSize int
+	resultSize int               // total bytes of trace output
 
 	interrupt atomic.Bool           // Atomic flag to signal execution interruption
 	reason    atomic.Pointer[error] // Reason for the interruption, populated by Stop
@@ -237,7 +250,7 @@ type StructLogger struct {
 // NewStreamingStructLogger returns a new streaming logger.
 func NewStreamingStructLogger(cfg *Config, writer io.Writer) *StructLogger {
 	l := NewStructLogger(cfg)
-	l.writer = writer
+	l.writer = &countingWriter{w: writer}
 	return l
 }
 
@@ -334,6 +347,7 @@ func (l *StructLogger) OnOpcode(pc uint64, opcode byte, gas, cost uint64, scope
 		return
 	}
 	log.Write(l.writer)
+	l.resultSize = l.writer.(*countingWriter).n
 }
 
 // OnExit is called a call frame finishes processing.

eth/tracers/logger/logger_json.go

@@ -59,12 +59,14 @@ type jsonLogger struct {
 	cfg     *Config
 	env     *tracing.VMContext
 	hooks   *tracing.Hooks
+	written *countingWriter
 }
 
 // NewJSONLogger creates a new EVM tracer that prints execution steps as JSON objects
 // into the provided stream.
 func NewJSONLogger(cfg *Config, writer io.Writer) *tracing.Hooks {
-	l := &jsonLogger{encoder: json.NewEncoder(writer), cfg: cfg}
+	cw := &countingWriter{w: writer}
+	l := &jsonLogger{encoder: json.NewEncoder(cw), cfg: cfg, written: cw}
 	if l.cfg == nil {
 		l.cfg = &Config{}
 	}
@@ -81,7 +83,8 @@ func NewJSONLogger(cfg *Config, writer io.Writer) *tracing.Hooks {
 // NewJSONLoggerWithCallFrames creates a new EVM tracer that prints execution steps as JSON objects
 // into the provided stream. It also includes call frames in the output.
 func NewJSONLoggerWithCallFrames(cfg *Config, writer io.Writer) *tracing.Hooks {
-	l := &jsonLogger{encoder: json.NewEncoder(writer), cfg: cfg}
+	cw := &countingWriter{w: writer}
+	l := &jsonLogger{encoder: json.NewEncoder(cw), cfg: cfg, written: cw}
 	if l.cfg == nil {
 		l.cfg = &Config{}
 	}
@@ -102,6 +105,9 @@ func (l *jsonLogger) OnFault(pc uint64, op byte, gas uint64, cost uint64, scope
 }
 
 func (l *jsonLogger) OnOpcode(pc uint64, op byte, gas, cost uint64, scope tracing.OpContext, rData []byte, depth int, err error) {
+	if l.cfg.Limit != 0 && l.written.n > l.cfg.Limit {
+		return
+	}
 	memory := scope.MemoryData()
 	stack := scope.StackData()