bufio: add ReadLine

It matches encoding/line exactly and the tests are copied from there.
If we land this, then encoding/line will get marked as deprecated then
deleted in time.

R=rsc, rog, peterGo
CC=golang-dev
https://golang.org/cl/4389046

src/pkg/bufio/bufio.go

@@ -282,6 +282,33 @@ func (b *Reader) ReadSlice(delim byte) (line []byte, err os.Error) {
 	panic("not reached")
 }
 
+// ReadLine tries to return a single line, not including the end-of-line bytes.
+// If the line was too long for the buffer then isPrefix is set and the
+// beginning of the line is returned. The rest of the line will be returned
+// from future calls. isPrefix will be false when returning the last fragment
+// of the line. The returned buffer is only valid until the next call to
+// ReadLine. ReadLine either returns a non-nil line or it returns an error,
+// never both.
+func (b *Reader) ReadLine() (line []byte, isPrefix bool, err os.Error) {
+	line, err = b.ReadSlice('\n')
+	if err == ErrBufferFull {
+		return line, true, nil
+	}
+
+	if len(line) == 0 {
+		return
+	}
+	err = nil
+
+	if line[len(line)-1] == '\n' {
+		line = line[:len(line)-1]
+	}
+	if len(line) > 0 && line[len(line)-1] == '\r' {
+		line = line[:len(line)-1]
+	}
+	return
+}
+
 // ReadBytes reads until the first occurrence of delim in the input,
 // returning a slice containing the data up to and including the delimiter.
 // If ReadBytes encounters an error before finding a delimiter,

src/pkg/bufio/bufio_test.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"strings"
 	"testing"
@@ -570,3 +571,128 @@ func TestPeekThenUnreadRune(t *testing.T) {
 	r.UnreadRune()
 	r.ReadRune() // Used to panic here
 }
+
+var testOutput = []byte("0123456789abcdefghijklmnopqrstuvwxy")
+var testInput = []byte("012\n345\n678\n9ab\ncde\nfgh\nijk\nlmn\nopq\nrst\nuvw\nxy")
+var testInputrn = []byte("012\r\n345\r\n678\r\n9ab\r\ncde\r\nfgh\r\nijk\r\nlmn\r\nopq\r\nrst\r\nuvw\r\nxy\r\n\n\r\n")
+
+// TestReader wraps a []byte and returns reads of a specific length.
+type testReader struct {
+	data   []byte
+	stride int
+}
+
+func (t *testReader) Read(buf []byte) (n int, err os.Error) {
+	n = t.stride
+	if n > len(t.data) {
+		n = len(t.data)
+	}
+	if n > len(buf) {
+		n = len(buf)
+	}
+	copy(buf, t.data)
+	t.data = t.data[n:]
+	if len(t.data) == 0 {
+		err = os.EOF
+	}
+	return
+}
+
+func testReadLine(t *testing.T, input []byte) {
+	//for stride := 1; stride < len(input); stride++ {
+	for stride := 1; stride < 2; stride++ {
+		done := 0
+		reader := testReader{input, stride}
+		l, _ := NewReaderSize(&reader, len(input)+1)
+		for {
+			line, isPrefix, err := l.ReadLine()
+			if len(line) > 0 && err != nil {
+				t.Errorf("ReadLine returned both data and error: %s", err)
+			}
+			if isPrefix {
+				t.Errorf("ReadLine returned prefix")
+			}
+			if err != nil {
+				if err != os.EOF {
+					t.Fatalf("Got unknown error: %s", err)
+				}
+				break
+			}
+			if want := testOutput[done : done+len(line)]; !bytes.Equal(want, line) {
+				t.Errorf("Bad line at stride %d: want: %x got: %x", stride, want, line)
+			}
+			done += len(line)
+		}
+		if done != len(testOutput) {
+			t.Errorf("ReadLine didn't return everything: got: %d, want: %d (stride: %d)", done, len(testOutput), stride)
+		}
+	}
+}
+
+func TestReadLine(t *testing.T) {
+	testReadLine(t, testInput)
+	testReadLine(t, testInputrn)
+}
+
+func TestLineTooLong(t *testing.T) {
+	buf := bytes.NewBuffer([]byte("aaabbbcc\n"))
+	l, _ := NewReaderSize(buf, 3)
+	line, isPrefix, err := l.ReadLine()
+	if !isPrefix || !bytes.Equal(line, []byte("aaa")) || err != nil {
+		t.Errorf("bad result for first line: %x %s", line, err)
+	}
+	line, isPrefix, err = l.ReadLine()
+	if !isPrefix || !bytes.Equal(line, []byte("bbb")) || err != nil {
+		t.Errorf("bad result for second line: %x", line)
+	}
+	line, isPrefix, err = l.ReadLine()
+	if isPrefix || !bytes.Equal(line, []byte("cc")) || err != nil {
+		t.Errorf("bad result for third line: %x", line)
+	}
+	line, isPrefix, err = l.ReadLine()
+	if isPrefix || err == nil {
+		t.Errorf("expected no more lines: %x %s", line, err)
+	}
+}
+
+func TestReadAfterLines(t *testing.T) {
+	line1 := "line1"
+	restData := "line2\nline 3\n"
+	inbuf := bytes.NewBuffer([]byte(line1 + "\n" + restData))
+	outbuf := new(bytes.Buffer)
+	maxLineLength := len(line1) + len(restData)/2
+	l, _ := NewReaderSize(inbuf, maxLineLength)
+	line, isPrefix, err := l.ReadLine()
+	if isPrefix || err != nil || string(line) != line1 {
+		t.Errorf("bad result for first line: isPrefix=%v err=%v line=%q", isPrefix, err, string(line))
+	}
+	n, err := io.Copy(outbuf, l)
+	if int(n) != len(restData) || err != nil {
+		t.Errorf("bad result for Read: n=%d err=%v", n, err)
+	}
+	if outbuf.String() != restData {
+		t.Errorf("bad result for Read: got %q; expected %q", outbuf.String(), restData)
+	}
+}
+
+func TestReadEmptyBuffer(t *testing.T) {
+	l, _ := NewReaderSize(bytes.NewBuffer(nil), 10)
+	line, isPrefix, err := l.ReadLine()
+	if err != os.EOF {
+		t.Errorf("expected EOF from ReadLine, got '%s' %t %s", line, isPrefix, err)
+	}
+}
+
+func TestLinesAfterRead(t *testing.T) {
+	l, _ := NewReaderSize(bytes.NewBuffer([]byte("foo")), 10)
+	_, err := ioutil.ReadAll(l)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	line, isPrefix, err := l.ReadLine()
+	if err != os.EOF {
+		t.Errorf("expected EOF from ReadLine, got '%s' %t %s", line, isPrefix, err)
+	}
+}

src/pkg/crypto/openpgp/armor/armor.go

@@ -7,10 +7,10 @@
 package armor
 
 import (
+	"bufio"
 	"bytes"
 	"crypto/openpgp/error"
 	"encoding/base64"
-	"encoding/line"
 	"io"
 	"os"
 )
@@ -63,7 +63,7 @@ var armorEndOfLine = []byte("-----")
 // lineReader wraps a line based reader. It watches for the end of an armor
 // block and records the expected CRC value.
 type lineReader struct {
-	in  *line.Reader
+	in  *bufio.Reader
 	buf []byte
 	eof bool
 	crc uint32
@@ -156,7 +156,7 @@ func (r *openpgpReader) Read(p []byte) (n int, err os.Error) {
 // given Reader is not usable after calling this function: an arbitary amount
 // of data may have been read past the end of the block.
 func Decode(in io.Reader) (p *Block, err os.Error) {
-	r := line.NewReader(in, 100)
+	r, _ := bufio.NewReaderSize(in, 100)
 	var line []byte
 	ignoreNext := false
 

src/pkg/http/cgi/host.go

@@ -15,8 +15,8 @@
 package cgi
 
 import (
+	"bufio"
 	"bytes"
-	"encoding/line"
 	"exec"
 	"fmt"
 	"http"
@@ -142,7 +142,7 @@ func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		go io.Copy(cmd.Stdin, req.Body)
 	}
 
-	linebody := line.NewReader(cmd.Stdout, 1024)
+	linebody, _ := bufio.NewReaderSize(cmd.Stdout, 1024)
 	headers := rw.Header()
 	statusCode := http.StatusOK
 	for {