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encoding/binary: PutX functions require buffer of sufficient size.

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R=rsc
CC=golang-dev
https://golang.org/cl/5163041
This commit is contained in:
Robert Griesemer 2011-09-29 09:40:59 -07:00
parent 092a211fb9
commit 61cc8728fb
2 changed files with 7 additions and 32 deletions
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24
src/pkg/encoding/binary/varint.go
View File

@ -37,27 +37,15 @@ const (
)
// PutUvarint encodes a uint64 into buf and returns the number of bytes written.
// If the buffer is too small, the result is the negated number of bytes required
// (that is, -PutUvarint(nil, x) is the number of bytes required to encode x).
func PutUvarint(buf []byte, x uint64) int {
var i int
for i = range buf {
if x < 0x80 {
buf[i] = byte(x)
return i + 1
}
i := 0
for x >= 0x80 {
buf[i] = byte(x) | 0x80
x >>= 7
}
// buffer too small; compute number of bytes required
for x >= 0x4000 {
x >>= 2 * 7
i += 2
}
if x >= 0x80 {
i++
}
return -(i + 1)
buf[i] = byte(x)
return i + 1
}
// Uvarint decodes a uint64 from buf and returns that value and the
@ -85,8 +73,6 @@ func Uvarint(buf []byte) (uint64, int) {
}
// PutVarint encodes an int64 into buf and returns the number of bytes written.
// If the buffer is too small, the result is the negated number of bytes required
// (that is, -PutVarint(nil, x) is the number of bytes required to encode x).
func PutVarint(buf []byte, x int64) int {
ux := uint64(x) << 1
if x < 0 {
@ -115,7 +101,7 @@ func Varint(buf []byte) (int64, int) {
// WriteUvarint encodes x and writes the result to w.
func WriteUvarint(w io.Writer, x uint64) os.Error {
var buf [MaxVarintLen64]byte
n := PutUvarint(buf[:], x) // won't fail
n := PutUvarint(buf[:], x)
_, err := w.Write(buf[0:n])
return err
}

15
src/pkg/encoding/binary/varint_test.go
View File

@ -11,7 +11,8 @@ import (
)
func testConstant(t *testing.T, w uint, max int) {
n := -PutUvarint(nil, 1<<w-1)
var buf [MaxVarintLen64]byte
n := PutUvarint(buf[:], 1<<w-1)
if n != max {
t.Errorf("MaxVarintLen%d = %d; want %d", w, max, n)
}
@ -121,18 +122,6 @@ func TestUvarint(t *testing.T) {
}
func TestBufferTooSmall(t *testing.T) {
for i := 0; i < 10; i++ {
buf := make([]byte, i)
x := uint64(1) << (uint(i) * 7)
n0 := -i
if i == 0 {
n0 = -1 // encoding 0 takes one byte
}
if n := PutUvarint(buf, x); n != n0 {
t.Errorf("PutUvarint([%d]byte, %d): got n = %d; want %d", len(buf), x, n, n0)
}
}
buf := []byte{0x80, 0x80, 0x80, 0x80}
for i := 0; i <= len(buf); i++ {
buf := buf[0:i]