net/textproto: avoid 1 copy in ReadLine, ReadContinuedLine

Fixes #2083.

R=msolo, bradfitz
CC=golang-dev
https://golang.org/cl/4812042

diff --git a/src/pkg/net/textproto/reader.go b/src/pkg/net/textproto/reader.go
index e65374903acda1cb8cb15d2e3d0cabc5d6104eee..9b5befe9aa5b78717ff25eaf26b316cba0271823 100644 (file)
--- a/src/pkg/net/textproto/reader.go
+++ b/src/pkg/net/textproto/reader.go
@@ -33,22 +33,25 @@ func NewReader(r *bufio.Reader) *Reader {
 // ReadLine reads a single line from r,
 // eliding the final \n or \r\n from the returned string.
 func (r *Reader) ReadLine() (string, os.Error) {
-       line, err := r.ReadLineBytes()
+       line, err := r.readLineSlice()
        return string(line), err
 }
 
 // ReadLineBytes is like ReadLine but returns a []byte instead of a string.
 func (r *Reader) ReadLineBytes() ([]byte, os.Error) {
-       r.closeDot()
-       line, err := r.R.ReadBytes('\n')
-       n := len(line)
-       if n > 0 && line[n-1] == '\n' {
-               n--
-               if n > 0 && line[n-1] == '\r' {
-                       n--
-               }
+       line, err := r.readLineSlice()
+       if line != nil {
+               buf := make([]byte, len(line))
+               copy(buf, line)
+               line = buf
        }
-       return line[0:n], err
+       return line, err
+}
+
+func (r *Reader) readLineSlice() ([]byte, os.Error) {
+       r.closeDot()
+       line, _, err := r.R.ReadLine()
+       return line, err
 }
 
 // ReadContinuedLine reads a possibly continued line from r,
@@ -71,7 +74,7 @@ func (r *Reader) ReadLineBytes() ([]byte, os.Error) {
 // A line consisting of only white space is never continued.
 //
 func (r *Reader) ReadContinuedLine() (string, os.Error) {
-       line, err := r.ReadContinuedLineBytes()
+       line, err := r.readContinuedLineSlice()
        return string(line), err
 }
 
@@ -92,8 +95,18 @@ func trim(s []byte) []byte {
 // ReadContinuedLineBytes is like ReadContinuedLine but
 // returns a []byte instead of a string.
 func (r *Reader) ReadContinuedLineBytes() ([]byte, os.Error) {
+       line, err := r.readContinuedLineSlice()
+       if line != nil {
+               buf := make([]byte, len(line))
+               copy(buf, line)
+               line = buf
+       }
+       return line, err
+}
+
+func (r *Reader) readContinuedLineSlice() ([]byte, os.Error) {
        // Read the first line.
-       line, err := r.ReadLineBytes()
+       line, err := r.readLineSlice()
        if err != nil {
                return line, err
        }
@@ -127,8 +140,11 @@ func (r *Reader) ReadContinuedLineBytes() ([]byte, os.Error) {
                                break
                        }
                }
+               // copy now since the next call to read a slice invalidates line
+               line = append(make([]byte, 0, len(line)*2), line...)
+
                var cont []byte
-               cont, err = r.ReadLineBytes()
+               cont, err = r.readLineSlice()
                cont = trim(cont)
                line = append(line, ' ')
                line = append(line, cont...)
@@ -422,7 +438,7 @@ func (r *Reader) ReadDotLines() ([]string, os.Error) {
 func (r *Reader) ReadMIMEHeader() (MIMEHeader, os.Error) {
        m := make(MIMEHeader)
        for {
-               kv, err := r.ReadContinuedLineBytes()
+               kv, err := r.readContinuedLineSlice()
                if len(kv) == 0 {
                        return m, err
                }