archive/tar: centralize errors in common.go

Move all sentinel errors to common.go since some of them are
returned by both the reader and writer and remove errInvalidHeader
since it not used.

Also, consistently use the "tar: " prefix for errors.

Change-Id: I0afb185bbf3db80dfd9595321603924454a4c2f9
Reviewed-on: https://go-review.googlesource.com/55650Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/archive/tar/common.go

@@ -25,6 +25,13 @@ import (
 // architectures. If a large value is encountered when decoding, the result
 // stored in Header will be the truncated version.
 
+var (
+	ErrHeader          = errors.New("tar: invalid tar header")
+	ErrWriteTooLong    = errors.New("tar: write too long")
+	ErrFieldTooLong    = errors.New("tar: header field too long")
+	ErrWriteAfterClose = errors.New("tar: write after close")
+)
+
 // Header type flags.
 const (
 	TypeReg           = '0'    // regular file
@@ -331,9 +338,9 @@ func FileInfoHeader(fi os.FileInfo, link string) (*Header, error) {
 	case fm&os.ModeNamedPipe != 0:
 		h.Typeflag = TypeFifo
 	case fm&os.ModeSocket != 0:
-		return nil, fmt.Errorf("archive/tar: sockets not supported")
+		return nil, fmt.Errorf("tar: sockets not supported")
 	default:
-		return nil, fmt.Errorf("archive/tar: unknown file mode %v", fm)
+		return nil, fmt.Errorf("tar: unknown file mode %v", fm)
 	}
 	if fm&os.ModeSetuid != 0 {
 		h.Mode |= c_ISUID

src/archive/tar/reader.go

@@ -9,7 +9,6 @@ package tar
 
 import (
 	"bytes"
-	"errors"
 	"io"
 	"io/ioutil"
 	"math"
@@ -18,10 +17,6 @@ import (
 	"time"
 )
 
-var (
-	ErrHeader = errors.New("archive/tar: invalid tar header")
-)
-
 // A Reader provides sequential access to the contents of a tar archive.
 // A tar archive consists of a sequence of files.
 // The Next method advances to the next file in the archive (including the first),

src/archive/tar/writer.go

@@ -9,7 +9,6 @@ package tar
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
 	"path"
@@ -18,13 +17,6 @@ import (
 	"time"
 )
 
-var (
-	ErrWriteTooLong    = errors.New("archive/tar: write too long")
-	ErrFieldTooLong    = errors.New("archive/tar: header field too long")
-	ErrWriteAfterClose = errors.New("archive/tar: write after close")
-	errInvalidHeader   = errors.New("archive/tar: header field too long or contains invalid values")
-)
-
 // A Writer provides sequential writing of a tar archive in POSIX.1 format.
 // A tar archive consists of a sequence of files.
 // Call WriteHeader to begin a new file, and then call Write to supply that file's data,
@@ -49,7 +41,7 @@ func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
 // will implicitly flush out the file's padding.
 func (tw *Writer) Flush() error {
 	if tw.nb > 0 {
-		tw.err = fmt.Errorf("archive/tar: missed writing %d bytes", tw.nb)
+		tw.err = fmt.Errorf("tar: missed writing %d bytes", tw.nb)
 		return tw.err
 	}
 	if _, tw.err = tw.w.Write(zeroBlock[:tw.pad]); tw.err != nil {