compress/flate: move idempotent close logic to compressor

The compressor methods already have logic for handling a sticky error.
Merge the logic from CL 136475 into that.

This slightly changes the error message to be more sensible
in the situation where it's returned by Flush.

Updates #27741

Change-Id: Ie34cf3164d0fa6bd0811175ca467dbbcb3be1395
Reviewed-on: https://go-review.googlesource.com/c/go/+/403514
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

diff --git a/src/compress/flate/deflate.go b/src/compress/flate/deflate.go
index ccf03d74eb211baccefd4699fce917cc6ed622ab..4ca20b87ba57872e2aa78d04e14b57e88263c79e 100644 (file)
--- a/src/compress/flate/deflate.go
+++ b/src/compress/flate/deflate.go
@@ -640,6 +640,9 @@ func (d *compressor) reset(w io.Writer) {
 }
 
 func (d *compressor) close() error {
+       if d.err == errWriterClosed {
+               return nil
+       }
        if d.err != nil {
                return d.err
        }
@@ -652,7 +655,11 @@ func (d *compressor) close() error {
                return d.w.err
        }
        d.w.flush()
-       return d.w.err
+       if d.w.err != nil {
+               return d.w.err
+       }
+       d.err = errWriterClosed
+       return nil
 }
 
 // NewWriter returns a new Writer compressing data at the given level.
@@ -700,27 +707,19 @@ func (w *dictWriter) Write(b []byte) (n int, err error) {
        return w.w.Write(b)
 }
 
-var errWriteAfterClose = errors.New("compress/flate: write after close")
+var errWriterClosed = errors.New("flate: closed writer")
 
 // A Writer takes data written to it and writes the compressed
 // form of that data to an underlying writer (see NewWriter).
 type Writer struct {
        d    compressor
        dict []byte
-       err  error
 }
 
 // Write writes data to w, which will eventually write the
 // compressed form of data to its underlying writer.
 func (w *Writer) Write(data []byte) (n int, err error) {
-       if w.err != nil {
-               return 0, w.err
-       }
-       n, err = w.d.write(data)
-       if err != nil {
-               w.err = err
-       }
-       return n, err
+       return w.d.write(data)
 }
 
 // Flush flushes any pending data to the underlying writer.
@@ -735,37 +734,18 @@ func (w *Writer) Write(data []byte) (n int, err error) {
 func (w *Writer) Flush() error {
        // For more about flushing:
        // https://www.bolet.org/~pornin/deflate-flush.html
-       if w.err != nil {
-               return w.err
-       }
-       if err := w.d.syncFlush(); err != nil {
-               w.err = err
-               return err
-       }
-       return nil
+       return w.d.syncFlush()
 }
 
 // Close flushes and closes the writer.
 func (w *Writer) Close() error {
-       if w.err == errWriteAfterClose {
-               return nil
-       }
-       if w.err != nil {
-               return w.err
-       }
-       if err := w.d.close(); err != nil {
-               w.err = err
-               return err
-       }
-       w.err = errWriteAfterClose
-       return nil
+       return w.d.close()
 }
 
 // Reset discards the writer's state and makes it equivalent to
 // the result of NewWriter or NewWriterDict called with dst
 // and w's level and dictionary.
 func (w *Writer) Reset(dst io.Writer) {
-       w.err = nil
        if dw, ok := w.d.w.writer.(*dictWriter); ok {
                // w was created with NewWriterDict
                dw.w = dst

diff --git a/src/compress/flate/deflate_test.go b/src/compress/flate/deflate_test.go
index 8c9ee72feb47e0f06e92a715c0e0ac62a4c2e48a..6d2043091aff1d43fc48db172068a072c50666d3 100644 (file)
--- a/src/compress/flate/deflate_test.go
+++ b/src/compress/flate/deflate_test.go
@@ -143,7 +143,7 @@ func TestWriterClose(t *testing.T) {
        afterClose := b.Len()
 
        if c, err := zw.Write([]byte("Test")); err == nil || c != 0 {
-               t.Fatalf("Write to closed writer: %s, %d", err, c)
+               t.Fatalf("Write to closed writer: %v, %d", err, c)
        }
 
        if err := zw.Flush(); err == nil {
@@ -794,7 +794,7 @@ func TestWriterPersistentCloseError(t *testing.T) {
 
        flushErr = zw.Flush()
        _, writeErr = zw.Write([]byte("Test"))
-       checkErrors([]error{flushErr, writeErr}, errWriteAfterClose, t)
+       checkErrors([]error{flushErr, writeErr}, errWriterClosed, t)
 }
 
 func checkErrors(got []error, want error, t *testing.T) {