Rewrited buffer to make enable repeating read & added tests (#11)

* Added test for slow data source

* Added

* Fixed slow reader test

* Fixed slowReader.Read

* Removed outdated comments from readBuffer

async_test.go

@@ -0,0 +1,62 @@
+package json
+
+import (
+	"encoding/json"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"io"
+	"testing"
+	"time"
+)
+
+var _ io.Reader = &slowReader{}
+
+type slowReader struct {
+	src   []byte
+	index int
+	len   int
+	pause time.Duration
+}
+
+func newSlowReader(src []byte, pause time.Duration) *slowReader {
+	return &slowReader{
+		src:   src,
+		len:   1,
+		pause: pause,
+	}
+}
+
+func (s *slowReader) Work() {
+	for i := s.len; i <= len(s.src); i++ {
+		time.Sleep(s.pause)
+		s.len = i
+	}
+}
+
+func (s *slowReader) Read(p []byte) (int, error) {
+	n := len(p)
+	readerLen := s.len
+	if s.index == len(s.src) {
+		return 0, io.EOF
+	}
+	if s.index+n <= readerLen {
+		copy(p, s.src[s.index:s.index+n])
+		s.index += n
+		return n, nil
+	}
+	length := readerLen - s.index
+	copy(p, s.src[s.index:readerLen])
+	s.index = readerLen
+	return length, nil
+}
+
+func TestUnmarshal_SlowReader(t *testing.T) {
+	initBig()
+	data := newSlowReader(jsonBig, time.Microsecond)
+	res := new(map[string]interface{})
+	expected := new(map[string]interface{})
+	require.NoError(t, json.Unmarshal(jsonBig, expected))
+	go data.Work()
+	require.NoError(t, Unmarshal(data, res))
+	assert.Equal(t, expected, res)
+}

internal/readbuffer/readbuffer.go

@@ -1,8 +1,14 @@
 package readbuffer
 
-import "io"
+import (
+	"io"
+	"time"
+)
 
-const readBufSize = 1 << 10
+const (
+	readBufSize = 1 << 10
+	readTimeout = 100 * time.Millisecond
+)
 
 type ReadBuffer struct {
 	buf   []byte
@@ -24,21 +30,24 @@ func (r *ReadBuffer) Get(n int) ([]byte, error) {
 		r.index += n
 		return res, nil
 	}
-	got := make([]byte, r.len-r.index)
-	copy(got, r.buf[r.index:r.len])
+	res := make([]byte, r.len-r.index)
+	copy(res, r.buf[r.index:r.len])
 	r.index = r.len
-	n -= len(got)
-	if err := r.load(); err != nil {
-		return got, err
-	}
-	if r.len-r.index >= n {
-		res := append(got, r.buf[r.index:r.index+n]...)
-		r.index += n
-		return res, nil
+	n -= len(res)
+	var err error
+	for err = r.load(); err == nil; err = r.load() {
+		if r.len-r.index >= n {
+			res = append(res, r.buf[r.index:r.index+n]...)
+			r.index += n
+			return res, nil
+		}
+
+		res = append(res, r.buf[r.index:r.len]...)
+		n -= r.len - r.index
+		r.index = r.len
+		time.Sleep(readTimeout)
 	}
-	res := append(got, r.buf[r.index:r.len]...)
-	r.index = r.len
-	return res, nil
+	return res, err
 }
 
 func (r *ReadBuffer) load() error {