move ShortWrite error into io so that other packages can use it.

R=r
DELTA=15  (7 added, 1 deleted, 7 changed)
OCL=28996
CL=28996

src/lib/bufio/bufio.go

@@ -30,11 +30,10 @@ type Error struct {
 }
 
 var (
-	PhaseError os.Error = &Error{"phase error"};
-	BufferFull os.Error = &Error{"buffer full"};
-	InternalError os.Error = &Error{"bufio internal error"};
-	BadBufSize os.Error = &Error{"bad bufio size"};
-	ShortWrite os.Error = &Error{"short write"};
+	PhaseError os.Error = &Error{"bufio: phase error"};
+	BufferFull os.Error = &Error{"bufio: buffer full"};
+	InternalError os.Error = &Error{"bufio: internal error"};
+	BadBufSize os.Error = &Error{"bufio: bad buffer size"};
 )
 
 func copySlice(dst []byte, src []byte) {
@@ -427,7 +426,7 @@ func (b *Writer) Flush() os.Error {
 		m, e := b.wr.Write(b.buf[n:b.n]);
 		n += m;
 		if m == 0 && e == nil {
-			e = ShortWrite
+			e = io.ErrShortWrite
 		}
 		if e != nil {
 			if n < b.n {

src/lib/http/server.go

@@ -177,7 +177,7 @@ func (c *Conn) Write(data []byte) (n int, err os.Error) {
 	n, err = c.buf.Write(data);
 	if err == nil && c.chunking {
 		if n != len(data) {
-			err = bufio.ShortWrite;
+			err = io.ErrShortWrite;
 		}
 		if err == nil {
 			io.WriteString(c.buf, "\r\n");

src/lib/io/io.go

@@ -13,12 +13,19 @@ import (
 	"os";
 )
 
-// ErrEOF is the error returned by FullRead and Copyn when they encounter EOF.
+// Error represents an unexpected I/O behavior.
 type Error struct {
 	os.ErrorString
 }
+
+// ErrEOF means that data was expected, but a read got EOF instead.
 var ErrEOF os.Error = &Error{"EOF"}
 
+// ErrShortWrite means that a write accepted fewer bytes than requested
+// but failed to return an explicit error.
+var ErrShortWrite os.Error = &Error{"short write"}
+
+
 // Reader is the interface that wraps the basic Read method.
 type Reader interface {
 	Read(p []byte) (n int, err os.Error);