Merge pull request 'move hooks' (#397) from devstigneev/micro:move_hooks_v3 into v3

Reviewed-on: #397

README.md

@@ -1,5 +1,5 @@
 # Micro
-![Coverage](https://img.shields.io/badge/Coverage-44.6%25-yellow)
+![Coverage](https://img.shields.io/badge/Coverage-44.7%25-yellow)
 [![License](https://img.shields.io/:license-apache-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 [![Doc](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/go.unistack.org/micro/v3?tab=overview)
 [![Status](https://git.unistack.org/unistack-org/micro/actions/workflows/job_tests.yml/badge.svg?branch=v3)](https://git.unistack.org/unistack-org/micro/actions?query=workflow%3Abuild+branch%3Av3+event%3Apush)
@@ -9,20 +9,20 @@ Micro is a standard library for microservices.
 
 ## Overview
 
-Micro provides the core requirements for distributed systems development including RPC and Event driven communication. 
+Micro provides the core requirements for distributed systems development including SYNC and ASYNC communication. 
 
 ## Features
 
-Micro abstracts away the details of distributed systems. Here are the main features.
+Micro abstracts away the details of distributed systems. Main features:
 
 - **Dynamic Config** - Load and hot reload dynamic config from anywhere. The config interface provides a way to load application 
-level config from any source such as env vars, cmdline, file, consul, vault... You can merge the sources and even define fallbacks.
+level config from any source such as env vars, cmdline, file, consul, vault, etc... You can merge the sources and even define fallbacks.
 
 - **Data Storage** - A simple data store interface to read, write and delete records. It includes support for memory, file and 
 s3. State and persistence becomes a core requirement beyond prototyping and Micro looks to build that into the framework.
 
 - **Service Discovery** - Automatic service registration and name resolution. Service discovery is at the core of micro service 
-development. When service A needs to speak to service B it needs the location of that service.
+development.
 
 - **Message Encoding** - Dynamic message encoding based on content-type. The client and server will use codecs along with content-type 
 to seamlessly encode and decode Go types for you. Any variety of messages could be encoded and sent from different clients. The client 

SECURITY.md

@@ -1,15 +0,0 @@
-# Security Policy
-
-## Supported Versions
-
-Use this section to tell people about which versions of your project are
-currently being supported with security updates.
-
-| Version | Supported          |
-| ------- | ------------------ |
-| 3.7.x   | :white_check_mark: |
-| < 3.7.0 | :x:                |
-
-## Reporting a Vulnerability
-
-If you find any issue, please create github issue in this repo

hooks/metadata/metadata.go

@@ -0,0 +1,76 @@
+package metadata
+
+import (
+	"context"
+
+	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v3/server"
+)
+
+var DefaultMetadataKeys = []string{"x-request-id"}
+
+type hook struct {
+	keys []string
+}
+
+func NewHook(keys ...string) *hook {
+	return &hook{keys: keys}
+}
+
+func metadataCopy(ctx context.Context, keys []string) context.Context {
+	if keys == nil {
+		return ctx
+	}
+	if imd, iok := metadata.FromIncomingContext(ctx); iok && imd != nil {
+		omd, ook := metadata.FromOutgoingContext(ctx)
+		if !ook || omd == nil {
+			omd = metadata.New(len(keys))
+		}
+		for _, k := range keys {
+			if v, ok := imd.Get(k); ok && v != "" {
+				omd.Set(k, v)
+			}
+		}
+		if !ook {
+			ctx = metadata.NewOutgoingContext(ctx, omd)
+		}
+	}
+	return ctx
+}
+
+func (w *hook) ClientCall(next client.FuncCall) client.FuncCall {
+	return func(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error {
+		return next(metadataCopy(ctx, w.keys), req, rsp, opts...)
+	}
+}
+
+func (w *hook) ClientStream(next client.FuncStream) client.FuncStream {
+	return func(ctx context.Context, req client.Request, opts ...client.CallOption) (client.Stream, error) {
+		return next(metadataCopy(ctx, w.keys), req, opts...)
+	}
+}
+
+func (w *hook) ClientPublish(next client.FuncPublish) client.FuncPublish {
+	return func(ctx context.Context, msg client.Message, opts ...client.PublishOption) error {
+		return next(metadataCopy(ctx, w.keys), msg, opts...)
+	}
+}
+
+func (w *hook) ClientBatchPublish(next client.FuncBatchPublish) client.FuncBatchPublish {
+	return func(ctx context.Context, msgs []client.Message, opts ...client.PublishOption) error {
+		return next(metadataCopy(ctx, w.keys), msgs, opts...)
+	}
+}
+
+func (w *hook) ServerHandler(next server.FuncHandler) server.FuncHandler {
+	return func(ctx context.Context, req server.Request, rsp interface{}) error {
+		return next(metadataCopy(ctx, w.keys), req, rsp)
+	}
+}
+
+func (w *hook) ServerSubscriber(next server.FuncSubHandler) server.FuncSubHandler {
+	return func(ctx context.Context, msg server.Message) error {
+		return next(metadataCopy(ctx, w.keys), msg)
+	}
+}

hooks/recovery/recovery.go

@@ -0,0 +1,94 @@
+package recovery
+
+import (
+	"context"
+	"fmt"
+
+	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v3/server"
+)
+
+func NewOptions(opts ...Option) Options {
+	options := Options{
+		ServerHandlerFn:    DefaultServerHandlerFn,
+		ServerSubscriberFn: DefaultServerSubscriberFn,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+	return options
+}
+
+type Options struct {
+	ServerHandlerFn    func(context.Context, server.Request, interface{}, error) error
+	ServerSubscriberFn func(context.Context, server.Message, error) error
+}
+
+type Option func(*Options)
+
+func ServerHandlerFunc(fn func(context.Context, server.Request, interface{}, error) error) Option {
+	return func(o *Options) {
+		o.ServerHandlerFn = fn
+	}
+}
+
+func ServerSubscriberFunc(fn func(context.Context, server.Message, error) error) Option {
+	return func(o *Options) {
+		o.ServerSubscriberFn = fn
+	}
+}
+
+var (
+	DefaultServerHandlerFn = func(ctx context.Context, req server.Request, rsp interface{}, err error) error {
+		return errors.BadRequest("", "%v", err)
+	}
+	DefaultServerSubscriberFn = func(ctx context.Context, req server.Message, err error) error {
+		return errors.BadRequest("", "%v", err)
+	}
+)
+
+var Hook = NewHook()
+
+type hook struct {
+	opts Options
+}
+
+func NewHook(opts ...Option) *hook {
+	return &hook{opts: NewOptions(opts...)}
+}
+
+func (w *hook) ServerHandler(next server.FuncHandler) server.FuncHandler {
+	return func(ctx context.Context, req server.Request, rsp interface{}) (err error) {
+		defer func() {
+			r := recover()
+			switch verr := r.(type) {
+			case nil:
+				return
+			case error:
+				err = w.opts.ServerHandlerFn(ctx, req, rsp, verr)
+			default:
+				err = w.opts.ServerHandlerFn(ctx, req, rsp, fmt.Errorf("%v", r))
+			}
+		}()
+		err = next(ctx, req, rsp)
+		return err
+	}
+}
+
+func (w *hook) ServerSubscriber(next server.FuncSubHandler) server.FuncSubHandler {
+	return func(ctx context.Context, msg server.Message) (err error) {
+		defer func() {
+			r := recover()
+			switch verr := r.(type) {
+			case nil:
+				return
+			case error:
+				err = w.opts.ServerSubscriberFn(ctx, msg, verr)
+			default:
+				err = w.opts.ServerSubscriberFn(ctx, msg, fmt.Errorf("%v", r))
+			}
+		}()
+		err = next(ctx, msg)
+		return err
+	}
+}

hooks/requestid/requestid.go

@@ -0,0 +1,139 @@
+package requestid
+
+import (
+	"context"
+	"net/textproto"
+	
+	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v3/metadata"
+	"go.unistack.org/micro/v3/server"
+	"go.unistack.org/micro/v3/util/id"
+)
+
+type XRequestIDKey struct{}
+
+// DefaultMetadataKey contains metadata key
+var DefaultMetadataKey = textproto.CanonicalMIMEHeaderKey("x-request-id")
+
+// DefaultMetadataFunc wil be used if user not provide own func to fill metadata
+var DefaultMetadataFunc = func(ctx context.Context) (context.Context, error) {
+	var xid string
+
+	cid, cok := ctx.Value(XRequestIDKey{}).(string)
+	if cok && cid != "" {
+		xid = cid
+	}
+
+	imd, iok := metadata.FromIncomingContext(ctx)
+	if !iok || imd == nil {
+		imd = metadata.New(1)
+		ctx = metadata.NewIncomingContext(ctx, imd)
+	}
+
+	omd, ook := metadata.FromOutgoingContext(ctx)
+	if !ook || omd == nil {
+		omd = metadata.New(1)
+		ctx = metadata.NewOutgoingContext(ctx, omd)
+	}
+
+	if xid == "" {
+		var id string
+		if id, iok = imd.Get(DefaultMetadataKey); iok && id != "" {
+			xid = id
+		}
+		if id, ook = omd.Get(DefaultMetadataKey); ook && id != "" {
+			xid = id
+		}
+	}
+
+	if xid == "" {
+		var err error
+		xid, err = id.New()
+		if err != nil {
+			return ctx, err
+		}
+	}
+
+	if !cok {
+		ctx = context.WithValue(ctx, XRequestIDKey{}, xid)
+	}
+
+	if !iok {
+		imd.Set(DefaultMetadataKey, xid)
+	}
+
+	if !ook {
+		omd.Set(DefaultMetadataKey, xid)
+	}
+
+	return ctx, nil
+}
+
+type hook struct{}
+
+func NewHook() *hook {
+	return &hook{}
+}
+
+func (w *hook) ServerSubscriber(next server.FuncSubHandler) server.FuncSubHandler {
+	return func(ctx context.Context, msg server.Message) error {
+		var err error
+		if xid, ok := msg.Header()[DefaultMetadataKey]; ok {
+			ctx = context.WithValue(ctx, XRequestIDKey{}, xid)
+		}
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return err
+		}
+		return next(ctx, msg)
+	}
+}
+
+func (w *hook) ServerHandler(next server.FuncHandler) server.FuncHandler {
+	return func(ctx context.Context, req server.Request, rsp interface{}) error {
+		var err error
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return err
+		}
+		return next(ctx, req, rsp)
+	}
+}
+
+func (w *hook) ClientBatchPublish(next client.FuncBatchPublish) client.FuncBatchPublish {
+	return func(ctx context.Context, msgs []client.Message, opts ...client.PublishOption) error {
+		var err error
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return err
+		}
+		return next(ctx, msgs, opts...)
+	}
+}
+
+func (w *hook) ClientPublish(next client.FuncPublish) client.FuncPublish {
+	return func(ctx context.Context, msg client.Message, opts ...client.PublishOption) error {
+		var err error
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return err
+		}
+		return next(ctx, msg, opts...)
+	}
+}
+
+func (w *hook) ClientCall(next client.FuncCall) client.FuncCall {
+	return func(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error {
+		var err error
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return err
+		}
+		return next(ctx, req, rsp, opts...)
+	}
+}
+
+func (w *hook) ClientStream(next client.FuncStream) client.FuncStream {
+	return func(ctx context.Context, req client.Request, opts ...client.CallOption) (client.Stream, error) {
+		var err error
+		if ctx, err = DefaultMetadataFunc(ctx); err != nil {
+			return nil, err
+		}
+		return next(ctx, req, opts...)
+	}
+}

hooks/requestid/requestid_test.go

@@ -0,0 +1,33 @@
+package requestid
+
+import (
+	"context"
+	"testing"
+
+	"go.unistack.org/micro/v3/metadata"
+)
+
+func TestDefaultMetadataFunc(t *testing.T) {
+	ctx := context.TODO()
+
+	nctx, err := DefaultMetadataFunc(ctx)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	imd, ok := metadata.FromIncomingContext(nctx)
+	if !ok {
+		t.Fatalf("md missing in incoming context")
+	}
+	omd, ok := metadata.FromOutgoingContext(nctx)
+	if !ok {
+		t.Fatalf("md missing in outgoing context")
+	}
+
+	_, iok := imd.Get(DefaultMetadataKey)
+	_, ook := omd.Get(DefaultMetadataKey)
+
+	if !iok || !ook {
+		t.Fatalf("missing metadata key value")
+	}
+}

hooks/validator/validator.go

@@ -0,0 +1,194 @@
+package validator
+
+import (
+	"context"
+
+	"go.unistack.org/micro/v3/client"
+	"go.unistack.org/micro/v3/errors"
+	"go.unistack.org/micro/v3/server"
+)
+
+var (
+	DefaultClientErrorFunc = func(req client.Request, rsp interface{}, err error) error {
+		if rsp != nil {
+			return errors.BadGateway(req.Service(), "%v", err)
+		}
+		return errors.BadRequest(req.Service(), "%v", err)
+	}
+
+	DefaultServerErrorFunc = func(req server.Request, rsp interface{}, err error) error {
+		if rsp != nil {
+			return errors.BadGateway(req.Service(), "%v", err)
+		}
+		return errors.BadRequest(req.Service(), "%v", err)
+	}
+
+	DefaultPublishErrorFunc = func(msg client.Message, err error) error {
+		return errors.BadRequest(msg.Topic(), "%v", err)
+	}
+
+	DefaultSubscribeErrorFunc = func(msg server.Message, err error) error {
+		return errors.BadRequest(msg.Topic(), "%v", err)
+	}
+)
+
+type (
+	ClientErrorFunc    func(client.Request, interface{}, error) error
+	ServerErrorFunc    func(server.Request, interface{}, error) error
+	PublishErrorFunc   func(client.Message, error) error
+	SubscribeErrorFunc func(server.Message, error) error
+)
+
+// Options struct holds wrapper options
+type Options struct {
+	ClientErrorFn          ClientErrorFunc
+	ServerErrorFn          ServerErrorFunc
+	PublishErrorFn         PublishErrorFunc
+	SubscribeErrorFn       SubscribeErrorFunc
+	ClientValidateResponse bool
+	ServerValidateResponse bool
+}
+
+// Option func signature
+type Option func(*Options)
+
+func ClientValidateResponse(b bool) Option {
+	return func(o *Options) {
+		o.ClientValidateResponse = b
+	}
+}
+
+func ServerValidateResponse(b bool) Option {
+	return func(o *Options) {
+		o.ClientValidateResponse = b
+	}
+}
+
+func ClientReqErrorFn(fn ClientErrorFunc) Option {
+	return func(o *Options) {
+		o.ClientErrorFn = fn
+	}
+}
+
+func ServerErrorFn(fn ServerErrorFunc) Option {
+	return func(o *Options) {
+		o.ServerErrorFn = fn
+	}
+}
+
+func PublishErrorFn(fn PublishErrorFunc) Option {
+	return func(o *Options) {
+		o.PublishErrorFn = fn
+	}
+}
+
+func SubscribeErrorFn(fn SubscribeErrorFunc) Option {
+	return func(o *Options) {
+		o.SubscribeErrorFn = fn
+	}
+}
+
+func NewOptions(opts ...Option) Options {
+	options := Options{
+		ClientErrorFn:    DefaultClientErrorFunc,
+		ServerErrorFn:    DefaultServerErrorFunc,
+		PublishErrorFn:   DefaultPublishErrorFunc,
+		SubscribeErrorFn: DefaultSubscribeErrorFunc,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+	return options
+}
+
+func NewHook(opts ...Option) *hook {
+	return &hook{opts: NewOptions(opts...)}
+}
+
+type validator interface {
+	Validate() error
+}
+
+type hook struct {
+	opts Options
+}
+
+func (w *hook) ClientCall(next client.FuncCall) client.FuncCall {
+	return func(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error {
+		if v, ok := req.Body().(validator); ok {
+			if err := v.Validate(); err != nil {
+				return w.opts.ClientErrorFn(req, nil, err)
+			}
+		}
+		err := next(ctx, req, rsp, opts...)
+		if v, ok := rsp.(validator); ok && w.opts.ClientValidateResponse {
+			if verr := v.Validate(); verr != nil {
+				return w.opts.ClientErrorFn(req, rsp, verr)
+			}
+		}
+		return err
+	}
+}
+
+func (w *hook) ClientStream(next client.FuncStream) client.FuncStream {
+	return func(ctx context.Context, req client.Request, opts ...client.CallOption) (client.Stream, error) {
+		if v, ok := req.Body().(validator); ok {
+			if err := v.Validate(); err != nil {
+				return nil, w.opts.ClientErrorFn(req, nil, err)
+			}
+		}
+		return next(ctx, req, opts...)
+	}
+}
+
+func (w *hook) ClientPublish(next client.FuncPublish) client.FuncPublish {
+	return func(ctx context.Context, msg client.Message, opts ...client.PublishOption) error {
+		if v, ok := msg.Payload().(validator); ok {
+			if err := v.Validate(); err != nil {
+				return w.opts.PublishErrorFn(msg, err)
+			}
+		}
+		return next(ctx, msg, opts...)
+	}
+}
+
+func (w *hook) ClientBatchPublish(next client.FuncBatchPublish) client.FuncBatchPublish {
+	return func(ctx context.Context, msgs []client.Message, opts ...client.PublishOption) error {
+		for _, msg := range msgs {
+			if v, ok := msg.Payload().(validator); ok {
+				if err := v.Validate(); err != nil {
+					return w.opts.PublishErrorFn(msg, err)
+				}
+			}
+		}
+		return next(ctx, msgs, opts...)
+	}
+}
+
+func (w *hook) ServerHandler(next server.FuncHandler) server.FuncHandler {
+	return func(ctx context.Context, req server.Request, rsp interface{}) error {
+		if v, ok := req.Body().(validator); ok {
+			if err := v.Validate(); err != nil {
+				return w.opts.ServerErrorFn(req, nil, err)
+			}
+		}
+		err := next(ctx, req, rsp)
+		if v, ok := rsp.(validator); ok && w.opts.ServerValidateResponse {
+			if verr := v.Validate(); verr != nil {
+				return w.opts.ServerErrorFn(req, rsp, verr)
+			}
+		}
+		return err
+	}
+}
+
+func (w *hook) ServerSubscriber(next server.FuncSubHandler) server.FuncSubHandler {
+	return func(ctx context.Context, msg server.Message) error {
+		if v, ok := msg.Body().(validator); ok {
+			if err := v.Validate(); err != nil {
+				return w.opts.SubscribeErrorFn(msg, err)
+			}
+		}
+		return next(ctx, msg)
+	}
+}

logger/options.go

@@ -99,6 +99,7 @@ func WithAddFields(fields ...interface{}) Option {
 					iv, iok := o.Fields[i].(string)
 					jv, jok := fields[j].(string)
 					if iok && jok && iv == jv {
+						o.Fields[i+1] = fields[j+1]
 						fields = slices.Delete(fields, j, j+2)
 					}
 				}

logger/slog/slog.go

@@ -278,7 +278,7 @@ func (s *slogLogger) printLog(ctx context.Context, lvl logger.Level, msg string,
 		}
 	}
 
-	if (s.opts.AddStacktrace || lvl == logger.FatalLevel) || (s.opts.AddStacktrace && lvl == logger.ErrorLevel) {
+	if s.opts.AddStacktrace && (lvl == logger.FatalLevel || lvl == logger.ErrorLevel) {
 		stackInfo := make([]byte, 1024*1024)
 		if stackSize := runtime.Stack(stackInfo, false); stackSize > 0 {
 			traceLines := reTrace.Split(string(stackInfo[:stackSize]), -1)

logger/slog/slog_test.go

@@ -21,7 +21,7 @@ import (
 func TestStacktrace(t *testing.T) {
 	ctx := context.TODO()
 	buf := bytes.NewBuffer(nil)
-	l := NewLogger(logger.WithLevel(logger.ErrorLevel), logger.WithOutput(buf),
+	l := NewLogger(logger.WithLevel(logger.DebugLevel), logger.WithOutput(buf),
 		WithHandlerFunc(slog.NewTextHandler),
 		logger.WithAddStacktrace(true),
 	)
@@ -124,7 +124,7 @@ func TestWithDedupKeysWithAddFields(t *testing.T) {
 
 	l.Info(ctx, "msg3")
 
-	if !bytes.Contains(buf.Bytes(), []byte(`msg=msg3 key1=val1 key2=val2`)) {
+	if !bytes.Contains(buf.Bytes(), []byte(`msg=msg3 key1=val4 key2=val3`)) {
 		t.Fatalf("logger error not works, buf contains: %s", buf.Bytes())
 	}
 }

tracer/memory/memory.go

@@ -89,6 +89,10 @@ func (s *Span) Tracer() tracer.Tracer {
 	return s.tracer
 }
 
+func (s *Span) IsRecording() bool {
+	return true
+}
+
 type Event struct {
 	name   string
 	labels []interface{}

tracer/noop.go

@@ -120,6 +120,10 @@ func (s *noopSpan) SetStatus(st SpanStatus, msg string) {
 	s.statusMsg = msg
 }
 
+func (s *noopSpan) IsRecording() bool {
+	return false
+}
+
 // NewTracer returns new memory tracer
 func NewTracer(opts ...Option) Tracer {
 	return &noopTracer{

tracer/tracer.go

@@ -78,4 +78,6 @@ type Span interface {
 	TraceID() string
 	// SpanID returns span id
 	SpanID() string
+	// IsRecording returns the recording state of the Span.
+	IsRecording() bool
 }

util/buffer/seeker_buffer.go

@@ -0,0 +1,78 @@
+package buffer
+
+import "io"
+
+var _ interface {
+	io.ReadCloser
+	io.ReadSeeker
+} = (*SeekerBuffer)(nil)
+
+// Buffer is a ReadWriteCloser that supports seeking. It's intended to
+// replicate the functionality of bytes.Buffer that I use in my projects.
+//
+// Note that the seeking is limited to the read marker; all writes are
+// append-only.
+type SeekerBuffer struct {
+	data []byte
+	pos  int64
+}
+
+func NewSeekerBuffer(data []byte) *SeekerBuffer {
+	return &SeekerBuffer{
+		data: data,
+	}
+}
+
+func (b *SeekerBuffer) Read(p []byte) (int, error) {
+	if b.pos >= int64(len(b.data)) {
+		return 0, io.EOF
+	}
+
+	n := copy(p, b.data[b.pos:])
+	b.pos += int64(n)
+	return n, nil
+}
+
+func (b *SeekerBuffer) Write(p []byte) (int, error) {
+	b.data = append(b.data, p...)
+	return len(p), nil
+}
+
+// Seek sets the read pointer to pos.
+func (b *SeekerBuffer) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case io.SeekStart:
+		b.pos = offset
+	case io.SeekEnd:
+		b.pos = int64(len(b.data)) + offset
+	case io.SeekCurrent:
+		b.pos += offset
+	}
+
+	return b.pos, nil
+}
+
+// Rewind resets the read pointer to 0.
+func (b *SeekerBuffer) Rewind() error {
+	if _, err := b.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Close clears all the data out of the buffer and sets the read position to 0.
+func (b *SeekerBuffer) Close() error {
+	b.data = nil
+	b.pos = 0
+	return nil
+}
+
+// Len returns the length of data remaining to be read.
+func (b *SeekerBuffer) Len() int {
+	return len(b.data[b.pos:])
+}
+
+// Bytes returns the underlying bytes from the current position.
+func (b *SeekerBuffer) Bytes() []byte {
+	return b.data[b.pos:]
+}

util/buffer/seeker_buffer_test.go

@@ -0,0 +1,55 @@
+package buffer
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func noErrorT(t *testing.T, err error) {
+	if nil != err {
+		t.Fatalf("%s", err)
+	}
+}
+
+func boolT(t *testing.T, cond bool, s ...string) {
+	if !cond {
+		what := strings.Join(s, ", ")
+		if len(what) > 0 {
+			what = ": " + what
+		}
+		t.Fatalf("assert.Bool failed%s", what)
+	}
+}
+
+func TestSeeking(t *testing.T) {
+	partA := []byte("hello, ")
+	partB := []byte("world!")
+
+	buf := NewSeekerBuffer(partA)
+
+	boolT(t, buf.Len() == len(partA), fmt.Sprintf("on init: have length %d, want length %d", buf.Len(), len(partA)))
+
+	b := make([]byte, 32)
+
+	n, err := buf.Read(b)
+	noErrorT(t, err)
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after reading 1: have length %d, want length 0", buf.Len()))
+	boolT(t, n == len(partA), fmt.Sprintf("after reading 2: have length %d, want length %d", n, len(partA)))
+
+	n, err = buf.Write(partB)
+	noErrorT(t, err)
+	boolT(t, n == len(partB), fmt.Sprintf("after writing: have length %d, want length %d", n, len(partB)))
+
+	n, err = buf.Read(b)
+	noErrorT(t, err)
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after rereading 1: have length %d, want length 0", buf.Len()))
+	boolT(t, n == len(partB), fmt.Sprintf("after rereading 2: have length %d, want length %d", n, len(partB)))
+
+	partsLen := len(partA) + len(partB)
+	_ = buf.Rewind()
+	boolT(t, buf.Len() == partsLen, fmt.Sprintf("after rewinding: have length %d, want length %d", buf.Len(), partsLen))
+
+	buf.Close()
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after closing, have length %d, want length 0", buf.Len()))
+}