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bytes.Buffer: turn buffer size overflows into errors

Fixes #2743.

R=golang-dev, gri, r
CC=golang-dev
https://golang.org/cl/5556072
This commit is contained in:
Rob Pike 2012-01-20 13:51:49 -08:00
parent 0796c1c3ec
commit 696bf79350
2 changed files with 52 additions and 4 deletions

View File

@ -33,6 +33,9 @@ const (
opRead // Any other read operation.
)
// ErrTooLarge is returned if there is too much data to fit in a buffer.
var ErrTooLarge = errors.New("bytes.Buffer: too large")
// Bytes returns a slice of the contents of the unread portion of the buffer;
// len(b.Bytes()) == b.Len(). If the caller changes the contents of the
// returned slice, the contents of the buffer will change provided there
@ -68,8 +71,10 @@ func (b *Buffer) Truncate(n int) {
// b.Reset() is the same as b.Truncate(0).
func (b *Buffer) Reset() { b.Truncate(0) }
// Grow buffer to guarantee space for n more bytes.
// Return index where bytes should be written.
// grow grows the buffer to guarantee space for n more bytes.
// It returns the index where bytes should be written.
// If the buffer can't grow, it returns -1, which will
// become ErrTooLarge in the caller.
func (b *Buffer) grow(n int) int {
m := b.Len()
// If buffer is empty, reset to recover space.
@ -82,7 +87,10 @@ func (b *Buffer) grow(n int) int {
buf = b.bootstrap[0:]
} else {
// not enough space anywhere
buf = make([]byte, 2*cap(b.buf)+n)
buf = makeSlice(2*cap(b.buf) + n)
if buf == nil {
return -1
}
copy(buf, b.buf[b.off:])
}
b.buf = buf
@ -97,6 +105,9 @@ func (b *Buffer) grow(n int) int {
func (b *Buffer) Write(p []byte) (n int, err error) {
b.lastRead = opInvalid
m := b.grow(len(p))
if m < 0 {
return 0, ErrTooLarge
}
return copy(b.buf[m:], p), nil
}
@ -105,6 +116,9 @@ func (b *Buffer) Write(p []byte) (n int, err error) {
func (b *Buffer) WriteString(s string) (n int, err error) {
b.lastRead = opInvalid
m := b.grow(len(s))
if m < 0 {
return 0, ErrTooLarge
}
return copy(b.buf[m:], s), nil
}
@ -133,7 +147,10 @@ func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
newBuf = b.buf[0 : len(b.buf)-b.off]
} else {
// not enough space at end; put space on end
newBuf = make([]byte, len(b.buf)-b.off, 2*(cap(b.buf)-b.off)+MinRead)
newBuf = makeSlice(2*(cap(b.buf)-b.off) + MinRead)[:len(b.buf)-b.off]
if newBuf == nil {
return n, ErrTooLarge
}
}
copy(newBuf, b.buf[b.off:])
b.buf = newBuf
@ -152,6 +169,18 @@ func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
return n, nil // err is EOF, so return nil explicitly
}
// makeSlice allocates a slice of size n, returning nil if the slice cannot be allocated.
func makeSlice(n int) []byte {
if n < 0 {
return nil
}
// Catch out of memory panics.
defer func() {
recover()
}()
return make([]byte, n)
}
// WriteTo writes data to w until the buffer is drained or an error
// occurs. The return value n is the number of bytes written; it always
// fits into an int, but it is int64 to match the io.WriterTo interface.
@ -179,6 +208,9 @@ func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
func (b *Buffer) WriteByte(c byte) error {
b.lastRead = opInvalid
m := b.grow(1)
if m < 0 {
return ErrTooLarge
}
b.buf[m] = c
return nil
}

View File

@ -386,3 +386,19 @@ func TestReadEmptyAtEOF(t *testing.T) {
t.Errorf("wrong count; got %d want 0", n)
}
}
func TestHuge(t *testing.T) {
// About to use tons of memory, so avoid for simple installation testing.
if testing.Short() {
return
}
b := new(Buffer)
big := make([]byte, 500e6)
for i := 0; i < 1000; i++ {
if _, err := b.Write(big); err != nil {
// Got error as expected. Stop
return
}
}
t.Error("error expected")
}