Merge pull request 'basic functionality and docs' (#1) from dev-docs into master

Reviewed-on: #1

README.md

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

multireader.go

@@ -91,6 +91,31 @@ 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
+}
+
 func (m *MultiReader) Close() error {
 	m.mtx.Lock()
 	defer m.mtx.Unlock()
@@ -126,15 +151,9 @@ 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 +174,8 @@ 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()
@@ -188,9 +209,31 @@ func (r *Reader) ReadAhead(data []byte) (int, error) {
 	return r.readAhead(data)
 }
 
+func (r *Reader) waitAvailable() (int, error) {
+	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
+}
+
+func (r *Reader) WaitAvailable() (int, error) {
+	r.mtx.Lock()
+	defer r.mtx.Unlock()
+	return r.waitAvailable()
+}
+
 func (r *Reader) Close() error {
 	r.mtx.Lock()
 	defer r.mtx.Unlock()
 	r.closed = true
+
+	r.multiReader.removeReader(r.id)
 	return nil
 }