bufio: fix potential endless loop in ReadByte
Also: Simplify ReadSlice implementation and
ensure that it doesn't call fill() with a full
buffer (this caused a failure in net/textproto
TestLargeReadMIMEHeader because fill() wasn't able
to read more data).
Fixes #7745.
LGTM=bradfitz
R=r, bradfitz
CC=golang-codereviews
https://golang.org/cl/86590043
diff --git a/src/pkg/bufio/bufio.go b/src/pkg/bufio/bufio.go
index 1e0cdae..ecd2708 100644
--- a/src/pkg/bufio/bufio.go
+++ b/src/pkg/bufio/bufio.go
@@ -88,15 +88,26 @@
b.r = 0
}
- // Read new data.
- n, err := b.rd.Read(b.buf[b.w:])
- if n < 0 {
- panic(errNegativeRead)
+ if b.w >= len(b.buf) {
+ panic("bufio: tried to fill full buffer")
}
- b.w += n
- if err != nil {
- b.err = err
+
+ // Read new data: try a limited number of times.
+ for i := maxConsecutiveEmptyReads; i > 0; i-- {
+ n, err := b.rd.Read(b.buf[b.w:])
+ if n < 0 {
+ panic(errNegativeRead)
+ }
+ b.w += n
+ if err != nil {
+ b.err = err
+ return
+ }
+ if n > 0 {
+ return
+ }
}
+ b.err = io.ErrNoProgress
}
func (b *Reader) readErr() error {
@@ -116,8 +127,9 @@
if n > len(b.buf) {
return nil, ErrBufferFull
}
+ // 0 <= n <= len(b.buf)
for b.w-b.r < n && b.err == nil {
- b.fill()
+ b.fill() // b.w-b.r < len(b.buf) => buffer is not full
}
m := b.w - b.r
if m > n {
@@ -143,7 +155,7 @@
if n == 0 {
return 0, b.readErr()
}
- if b.w == b.r {
+ if b.r == b.w {
if b.err != nil {
return 0, b.readErr()
}
@@ -151,13 +163,16 @@
// Large read, empty buffer.
// Read directly into p to avoid copy.
n, b.err = b.rd.Read(p)
+ if n < 0 {
+ panic(errNegativeRead)
+ }
if n > 0 {
b.lastByte = int(p[n-1])
b.lastRuneSize = -1
}
return n, b.readErr()
}
- b.fill()
+ b.fill() // buffer is empty
if b.w == b.r {
return 0, b.readErr()
}
@@ -181,7 +196,7 @@
if b.err != nil {
return 0, b.readErr()
}
- b.fill()
+ b.fill() // buffer is empty
}
c = b.buf[b.r]
b.r++
@@ -211,8 +226,8 @@
// rune and its size in bytes. If the encoded rune is invalid, it consumes one byte
// and returns unicode.ReplacementChar (U+FFFD) with a size of 1.
func (b *Reader) ReadRune() (r rune, size int, err error) {
- for b.r+utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) && b.err == nil {
- b.fill()
+ for b.r+utf8.UTFMax > b.w && !utf8.FullRune(b.buf[b.r:b.w]) && b.err == nil && b.w-b.r < len(b.buf) {
+ b.fill() // b.w-b.r < len(buf) => buffer is not full
}
b.lastRuneSize = -1
if b.r == b.w {
@@ -256,36 +271,28 @@
// ReadBytes or ReadString instead.
// ReadSlice returns err != nil if and only if line does not end in delim.
func (b *Reader) ReadSlice(delim byte) (line []byte, err error) {
- // Look in buffer.
- if i := bytes.IndexByte(b.buf[b.r:b.w], delim); i >= 0 {
- line1 := b.buf[b.r : b.r+i+1]
- b.r += i + 1
- return line1, nil
- }
-
- // Read more into buffer, until buffer fills or we find delim.
for {
+ // Search buffer.
+ if i := bytes.IndexByte(b.buf[b.r:b.w], delim); i >= 0 {
+ line := b.buf[b.r : b.r+i+1]
+ b.r += i + 1
+ return line, nil
+ }
+
+ // Pending error?
if b.err != nil {
line := b.buf[b.r:b.w]
b.r = b.w
return line, b.readErr()
}
- n := b.Buffered()
- b.fill()
-
- // Search new part of buffer
- if i := bytes.IndexByte(b.buf[n:b.w], delim); i >= 0 {
- line := b.buf[0 : n+i+1]
- b.r = n + i + 1
- return line, nil
- }
-
- // Buffer is full?
- if b.Buffered() >= len(b.buf) {
+ // Buffer full?
+ if n := b.Buffered(); n >= len(b.buf) {
b.r = b.w
return b.buf, ErrBufferFull
}
+
+ b.fill() // buffer is not full
}
}
@@ -417,12 +424,18 @@
return n, err
}
- for b.fill(); b.r < b.w; b.fill() {
+ if b.w-b.r < len(b.buf) {
+ b.fill() // buffer not full
+ }
+
+ for b.r < b.w {
+ // b.r < b.w => buffer is not empty
m, err := b.writeBuf(w)
n += m
if err != nil {
return n, err
}
+ b.fill() // buffer is empty
}
if b.err == io.EOF {
@@ -435,6 +448,9 @@
// writeBuf writes the Reader's buffer to the writer.
func (b *Reader) writeBuf(w io.Writer) (int64, error) {
n, err := w.Write(b.buf[b.r:b.w])
+ if n < b.r-b.w {
+ panic(errors.New("bufio: writer did not write all data"))
+ }
b.r += n
return int64(n), err
}
