Merge branch 'master' into dev-docs

Reviewed-on: #2

README.md

@@ -0,0 +1,2 @@
+# MultiReader
+Single writer with multiple readers. Designed for small number of concurrent readers.

multiread_test.go

@@ -2,6 +2,7 @@ package multireader
 
 import (
 	"bytes"
+	"io"
 	"math/rand"
 	"sync"
 	"testing"
@@ -46,9 +47,10 @@ func TestReadWrite(t *testing.T) {
 
 	writeFunc := func(t *testing.T, m *MultiReader, data []byte, wg *sync.WaitGroup) {
 		var (
-			n  int
-			dl int
-			r  int
+			n        int
+			dl       int
+			r        int
+			loopFlag bool
 		)
 		defer wg.Done()
 
@@ -60,13 +62,21 @@ func TestReadWrite(t *testing.T) {
 				r, _ = m.Write(data[n : n+512+dl])
 			}
 			n += r
+			if rand.Intn(5) == 0 {
+				loopFlag = false
+				for !loopFlag {
+					if rand.Intn(100) == 0 {
+						loopFlag = true
+					}
+				}
+			}
 		}
 		_ = m.Close()
 	}
 	wg.Add(1)
 	go writeFunc(t, m, src, wg)
 
-	readFunc := func(t *testing.T, r *Reader, data []byte, wg *sync.WaitGroup) {
+	readFunc := func(t *testing.T, r *Reader, data []byte, wg *sync.WaitGroup, split bool) {
 		var (
 			offset int
 			n      int
@@ -77,10 +87,30 @@ func TestReadWrite(t *testing.T) {
 		offset = 0
 		for {
 			if offset+1024 < len(data) {
-				n, err = r.Read(data[offset : offset+1024])
-				if err != nil {
-					t.Logf("reader got error: %v", err)
-					break
+				if split {
+					_, err = r.WaitAvailable()
+					if err != nil {
+						t.Logf("reader got error on WaitAvailable: %v", err)
+						break
+					}
+					n, err = r.ReadAhead(data[offset : offset+1024])
+					if err != nil {
+						t.Logf("reader got error on ReadAhead: %v", err)
+						break
+					}
+
+					n -= 5
+					_, err = r.Seek(int64(n), io.SeekCurrent)
+					if err != nil {
+						t.Logf("reader got error on Seek: %v", err)
+						break
+					}
+				} else {
+					n, err = r.Read(data[offset : offset+1024])
+					if err != nil {
+						t.Logf("reader got error: %v", err)
+						break
+					}
 				}
 			} else {
 				n, err = r.Read(data[offset:])
@@ -95,11 +125,11 @@ func TestReadWrite(t *testing.T) {
 	}
 
 	wg.Add(1)
-	go readFunc(t, r1, dst1, wg)
+	go readFunc(t, r1, dst1, wg, false)
 	wg.Add(1)
-	go readFunc(t, r2, dst2, wg)
+	go readFunc(t, r2, dst2, wg, false)
 	wg.Add(1)
-	go readFunc(t, r3, dst3, wg)
+	go readFunc(t, r3, dst3, wg, true)
 
 	wg.Wait()
 	if !bytes.Equal(src, dst1) {
@@ -112,3 +142,87 @@ func TestReadWrite(t *testing.T) {
 		t.Error("src and dst3 mismatch")
 	}
 }
+
+func TestReaderClose(t *testing.T) {
+	var (
+		m                    *MultiReader
+		r1                   *Reader
+		r2                   *Reader
+		r3                   *Reader
+		src, dst, dst1, dst3 []byte
+		err                  error
+		found                bool
+		ctr                  int
+	)
+
+	src = make([]byte, 16)
+	dst = make([]byte, 32)
+	dst1 = dst[:16]
+	dst3 = dst[16:]
+	m = NewMultiReader(0)
+	r1 = m.NewReader()
+	r2 = m.NewReader()
+	r3 = m.NewReader()
+
+	_, _ = rand.Read(src)
+	_, err = m.Write(src)
+	if err != nil {
+		t.Fatalf("error setting up data: %v", err)
+	}
+
+	found = false
+	for ctr = range m.pos {
+		if m.pos[ctr].id == r2.id {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("unexpected behavior, r2 should exist in reader position list")
+	}
+
+	_ = r2.Close()
+	_, err = r2.Read(dst)
+	if err == nil && err != ErrReaderClosed {
+		t.Error("unexpected behavior, r2 should be closed")
+	}
+
+	found = false
+	for ctr = range m.pos {
+		if m.pos[ctr].id == r2.id {
+			found = true
+			break
+		}
+	}
+	if found {
+		t.Error("unexpected behavior, r2 should be removed from reader position list")
+	}
+
+	_, err = r1.Read(dst1)
+	if err != nil {
+		t.Errorf("failing to read from r1")
+	}
+	if !bytes.Equal(dst1, src) {
+		t.Error("invalid result reading from r1")
+	}
+
+	_ = m.Close()
+	_, err = r3.Read(dst3)
+	if err != nil {
+		t.Errorf("unexpected behavior, cannot read form r3: %v", err)
+	}
+	if !bytes.Equal(src, dst3) {
+		t.Error("invalid result reading from r3")
+	}
+
+	_, err = r3.WaitAvailable()
+	if err == nil {
+		t.Error("unexpected behavior; WaitAvailable when readpos == lastWritePos should fail")
+	}
+
+	_, err = r3.ReadAhead(dst3)
+	if err == nil {
+		t.Error("unexpected behavior; ReadAhead when readpos == lastWritePos should fail")
+	}
+
+}

multireader.go

@@ -1,3 +1,4 @@
+//Package multireader provides capability for single writer to multiple reader
 package multireader
 
 import (
@@ -33,6 +34,7 @@ type Reader struct {
 	closed      bool
 }
 
+//MultiReader initialize new MultiReader object. The object also implements WriteCloser.
 func NewMultiReader(len int) *MultiReader {
 	if len < 0 {
 		len = 0
@@ -51,6 +53,7 @@ func NewMultiReader(len int) *MultiReader {
 	}
 }
 
+// Write implements Writer interface. The function will not return error. Error return only satisfy the interface.
 func (m *MultiReader) Write(data []byte) (int, error) {
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
@@ -91,6 +94,32 @@ func (m *MultiReader) shift() {
 	}
 }
 
+func (m *MultiReader) removeReader(id int) {
+	var (
+		pin int
+		nb  []*Reader
+	)
+	for idx := range m.pos {
+		if m.pos[idx].id == id {
+			pin = idx
+			break
+		}
+	}
+
+	nb = make([]*Reader, len(m.pos)-1)
+	if pin == 0 {
+		copy(nb, m.pos[1:])
+	} else if pin == len(m.pos)-1 {
+		copy(nb, m.pos[:len(m.pos)-1])
+	} else {
+		copy(nb, m.pos[:pin])
+		copy(nb[pin:], m.pos[pin+1:])
+	}
+
+	m.pos = nb
+}
+
+// Close will not return error. The error return only satisfy the interface signature.
 func (m *MultiReader) Close() error {
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
@@ -98,6 +127,7 @@ func (m *MultiReader) Close() error {
 	return nil
 }
 
+// NewReader initialize new Reader object. The object implements ReadCloser and Seeker interface.
 func (m *MultiReader) NewReader() *Reader {
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
@@ -116,6 +146,8 @@ func (m *MultiReader) NewReader() *Reader {
 	return reader
 }
 
+// Read implements Reader interface. If the reader reached the same position with the writer. It will wait.
+// Calling Read() is the same with calling WaitAvailable(), ReadAhead(), and Seek()
 func (r *Reader) Read(data []byte) (int, error) {
 	r.mtx.Lock()
 	defer r.mtx.Unlock()
@@ -126,15 +158,9 @@ func (r *Reader) Read(data []byte) (int, error) {
 		err error
 	)
 
-	if r.closed {
-		return 0, ErrReaderClosed
-	}
-
-	for r.readPos >= r.multiReader.lastWritePos {
-		if r.multiReader.closed {
-			return 0, ErrMultiReaderClosed
-		}
-		r.cond.Wait()
+	_, err = r.waitAvailable()
+	if err != nil {
+		return 0, err
 	}
 
 	n, err = r.readAhead(data)
@@ -155,6 +181,8 @@ func (r *Reader) seek(offset int, whence int) (int, error) {
 		r.readPos = offset
 	case io.SeekEnd:
 		r.readPos = r.multiReader.lastWritePos - offset
+	default:
+		return 0, ErrUnsupportedWhence
 	}
 
 	r.multiReader.sortLastPos()
@@ -163,6 +191,8 @@ func (r *Reader) seek(offset int, whence int) (int, error) {
 	return r.readPos, nil
 }
 
+// Seek implements Seeker interface. The underlying function will move the reader position.
+// It only returns error when the whence parameter is not in io.SeekStart, io.SeekCurrent, io.SeekEnd
 func (r *Reader) Seek(offset int64, whence int) (int64, error) {
 	n, err := r.seek(int(offset), whence)
 	return int64(n), err
@@ -182,15 +212,44 @@ func (r *Reader) readAhead(data []byte) (int, error) {
 	return len(data), nil
 }
 
+// ReadAhead reads buffer ahead of current position without moving the reader position.
 func (r *Reader) ReadAhead(data []byte) (int, error) {
 	r.mtx.Lock()
 	defer r.mtx.Unlock()
 	return r.readAhead(data)
 }
 
+func (r *Reader) waitAvailable() (int, error) {
+	if r.closed {
+		return 0, ErrReaderClosed
+	}
+
+	for r.readPos >= r.multiReader.lastWritePos {
+		if r.closed {
+			return 0, ErrReaderClosed
+		}
+		if r.multiReader.closed {
+			return 0, ErrMultiReaderClosed
+		}
+		r.cond.Wait()
+	}
+
+	return r.multiReader.lastWritePos - r.readPos, nil
+}
+
+// WaitAvailable will only wait when Reader position reached Writer position.
+func (r *Reader) WaitAvailable() (int, error) {
+	r.mtx.Lock()
+	defer r.mtx.Unlock()
+	return r.waitAvailable()
+}
+
+// Close implements ReadCloser interface. It will not return error.
 func (r *Reader) Close() error {
 	r.mtx.Lock()
 	defer r.mtx.Unlock()
 	r.closed = true
+
+	r.multiReader.removeReader(r.id)
 	return nil
 }