add exported free function to abort reading

content.go

@@ -41,7 +41,7 @@ func (w contentWriter) Write(p []byte) (int, error) {
 
 		sm, ok := <-w.r
 		if !ok {
-			return n, ErrContentAbort
+			return n, ErrAbort
 		}
 
 		ni := copy(sm.p, p)
@@ -106,7 +106,7 @@ func (c *content) close() error {
 
 		// not using errors.Is, because the writer logic may have combined the abort error with another
 		// user logic error, that needs to be reported:
-		if sm.err == ErrContentAbort {
+		if sm.err == ErrAbort {
 			continue
 		}
 

lib.go

@@ -51,9 +51,10 @@ var (
 	// ErrZeroAllocation is returned when the used pool returned a zero length byte slice.
 	ErrZeroAllocation = errors.New("zero allocation")
 
-	// ErrContentAbort is returned to the writer process in case of buffered content, when the reader
-	// experienced an error.
-	ErrContentAbort = errors.New("content pipe aborted")
+	// ErrAbort is returned to the writer process in case of buffered content, when the reader
+	// experienced an error. ErrAbort is returned to the reader process, when the resources were released
+	// using Free(), and any of the Read operations is called again.
+	ErrAbort = errors.New("read aborted")
 )
 
 // DefultPool initializes a synchronized pool that stores and returns byte slices of allocSize length. It can be
@@ -101,7 +102,7 @@ func BufferedReader(in io.Reader, o Options) Reader {
 // The provided WriterTo instances need to be safe to call in goroutines other than they were created in. The
 // writer function returns with nil error, it will be interpreted as EOF on the reader side. When the reader
 // side experiences an error, and the writer still has content to be written, the passed in io.Writer will
-// return an ErrContentAbort error.
+// return an ErrAbort error.
 func BufferedContent(c io.WriterTo, o Options) Reader {
 	if c == nil {
 		return Reader{}
@@ -209,3 +210,15 @@ func (r Reader) WriteTo(w io.Writer) (int64, error) {
 
 	return r.reader.writeTo(w)
 }
+
+// Free releases the resource held by the Reader, and puts back the underlying byte buffers into the used pool.
+//
+// It is used when a multi-step read operation is aborted. When a preceeding read operation resulted in an
+// error, it is not necessary to call Free().
+func (r Reader) Free() {
+	if r.reader == nil {
+		return
+	}
+
+	r.reader.free()
+}

lib_test.go

@@ -150,6 +150,159 @@ func TestLib(t *testing.T) {
 			}
 		})
 	})
+
+	t.Run("free", func(t *testing.T) {
+		t.Run("from blank state", func(t *testing.T) {
+			p := &fakePool{allocSize: 1 << 6}
+			r := buffer.BufferedReader(&gen{max: 1 << 12}, buffer.Options{Pool: p})
+			r.Free()
+			b := make([]byte, 1<<9)
+			n, err := r.Read(b)
+			if n != 0 || !errors.Is(err, buffer.ErrAbort) {
+				t.Fatal(n, err)
+			}
+
+			if p.alloc != 0 || p.free != 0 {
+				t.Fatal(p.alloc, p.free)
+			}
+		})
+
+		t.Run("with multiple segments", func(t *testing.T) {
+			p := &fakePool{allocSize: 1 << 6}
+			r := buffer.BufferedReader(&gen{max: 1 << 12}, buffer.Options{Pool: p})
+			b, ok, err := r.ReadBytes([]byte("123"), 1<<6+1<<5)
+			if ok || err != nil || p.alloc != 2 {
+				t.Fatal(len(b), ok, err, p.alloc)
+			}
+
+			r.Free()
+			b = make([]byte, 1<<9)
+			n, err := r.Read(b)
+			if n != 0 || !errors.Is(err, buffer.ErrAbort) {
+				t.Fatal(n, err)
+			}
+
+			if p.alloc != 2 || p.free != 2 {
+				t.Fatal(p.alloc, p.free)
+			}
+		})
+
+		t.Run("from err state", func(t *testing.T) {
+			p := &fakePool{allocSize: 1 << 6}
+			g := &gen{
+				max:      1 << 12,
+				errAfter: []int{1 << 6},
+			}
+
+			r := buffer.BufferedReader(g, buffer.Options{Pool: p})
+			b := make([]byte, 1<<9)
+			n, err := r.Read(b)
+			if n != 1<<6 || err != nil {
+				t.Fatal(n, err)
+			}
+
+			n, err = r.Read(b)
+			if n != 0 || !errors.Is(err, errTest) {
+				t.Fatal(n, err)
+			}
+
+			r.Free()
+			b = make([]byte, 1<<9)
+			n, err = r.Read(b)
+			if n != 0 || !errors.Is(err, errTest) {
+				t.Fatal(n, err)
+			}
+
+			if p.alloc != 1 || p.free != 1 {
+				t.Fatal(p.alloc, p.free)
+			}
+		})
+
+		t.Run("with content", func(t *testing.T) {
+			c := buffer.ContentFunc(func(w io.Writer) (int64, error) {
+				var n int64
+				for i := 0; i < 3; i++ {
+					ni, err := w.Write([]byte("123456789")[i*3 : i*3+3])
+					n += int64(ni)
+					if err != nil {
+						return n, err
+					}
+				}
+
+				return n, nil
+			})
+
+			p := &fakePool{allocSize: 2}
+			o := buffer.Options{Pool: p}
+			r := buffer.BufferedContent(c, o)
+			b := make([]byte, 3)
+			for i := 0; i < 2; i++ {
+				n, err := r.Read(b)
+				if n != 3 || err != nil {
+					t.Fatal(n, err)
+				}
+
+				if string(b) != "123456789"[i*3:i*3+3] {
+					t.Fatal(string(b))
+				}
+			}
+
+			r.Free()
+			n, err := r.Read(b)
+			if n != 0 || !errors.Is(err, buffer.ErrAbort) {
+				t.Fatal(n, err)
+			}
+
+			if p.alloc != 1 || p.free != 1 {
+				t.Fatal(p.alloc, p.free)
+			}
+		})
+
+		t.Run("with content error", func(t *testing.T) {
+			c := buffer.ContentFunc(func(w io.Writer) (int64, error) {
+				var n int64
+				for i := 0; i < 3; i++ {
+					ni, err := w.Write([]byte("123456789")[i*3 : i*3+3])
+					n += int64(ni)
+					if err != nil {
+						return n, err
+					}
+				}
+
+				return n, errTest
+			})
+
+			p := &fakePool{allocSize: 2}
+			o := buffer.Options{Pool: p}
+			r := buffer.BufferedContent(c, o)
+			b := make([]byte, 3)
+			for i := 0; i < 3; i++ {
+				n, err := r.Read(b)
+				if n != 3 || err != nil {
+					t.Fatal(n, err)
+				}
+
+				if string(b) != "123456789"[i*3:i*3+3] {
+					t.Fatal(string(b))
+				}
+			}
+
+			n, err := r.Read(b)
+			if n != 0 || !errors.Is(err, errTest) {
+				t.Fatal(n, err)
+			}
+
+			r.Free()
+			n, err = r.Read(b)
+			if n != 0 || !errors.Is(err, errTest) {
+				t.Fatal(n, err)
+			}
+
+			if p.alloc != 1 || p.free != 1 {
+				t.Fatal(p.alloc, p.free)
+			}
+		})
+	})
 }
 
 // -- bench

reader.go

@@ -148,11 +148,18 @@ func (r *reader) free() {
 		r.segments = r.segments[1:]
 	}
 
+	r.len = 0
+	r.options.Pool = nil
 	if c, ok := r.in.(interface{ close() error }); ok {
 		if err := c.close(); err != nil {
 			r.err = errors.Join(r.err, err)
 		}
 	}
+
+	r.in = nil
+	if r.err == nil {
+		r.err = ErrAbort
+	}
 }
 
 func (r reader) findSegmentUp(i int) (int, int) {