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bytes: set cap of slices returned by Split and Fields and friends

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This avoids the problem in which appending to a slice returned by
Split can affect subsequent slices.

Fixes #21149.

Change-Id: Ie3df2b9ceeb9605d4625f47d49073c5f348cf0a1
Reviewed-on: https://go-review.googlesource.com/74510
Reviewed-by: Jelte Fennema <github-tech@jeltef.nl>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Ian Lance Taylor 2017-10-30 16:05:18 -07:00
parent 3043c355f4
commit a9e2479a44
2 changed files with 65 additions and 7 deletions
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10
src/bytes/bytes.go
View File

@ -39,7 +39,7 @@ func explode(s []byte, n int) [][]byte {
break
}
_, size = utf8.DecodeRune(s)
a[na] = s[0:size]
a[na] = s[0:size:size]
s = s[size:]
na++
}
@ -219,7 +219,7 @@ func genSplit(s, sep []byte, sepSave, n int) [][]byte {
if m < 0 {
break
}
a[i] = s[:m+sepSave]
a[i] = s[: m+sepSave : m+sepSave]
s = s[m+len(sep):]
i++
}
@ -302,7 +302,7 @@ func Fields(s []byte) [][]byte {
i++
continue
}
a[na] = s[fieldStart:i]
a[na] = s[fieldStart:i:i]
na++
i++
// Skip spaces in between fields.
@ -312,7 +312,7 @@ func Fields(s []byte) [][]byte {
fieldStart = i
}
if fieldStart < len(s) { // Last field might end at EOF.
a[na] = s[fieldStart:]
a[na] = s[fieldStart:len(s):len(s)]
}
return a
}
@ -363,7 +363,7 @@ func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
// Create subslices from recorded field indices.
a := make([][]byte, len(spans))
for i, span := range spans {
a[i] = s[span.start:span.end]
a[i] = s[span.start:span.end:span.end]
}
return a

62
src/bytes/bytes_test.go
View File

@ -736,6 +736,13 @@ var splittests = []SplitTest{
func TestSplit(t *testing.T) {
for _, tt := range splittests {
a := SplitN([]byte(tt.s), []byte(tt.sep), tt.n)
// Appending to the results should not change future results.
var x []byte
for _, v := range a {
x = append(v, 'z')
}
result := sliceOfString(a)
if !eq(result, tt.a) {
t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
@ -744,6 +751,11 @@ func TestSplit(t *testing.T) {
if tt.n == 0 {
continue
}
if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
t.Errorf("last appended result was %s; want %s", x, want)
}
s := Join(a, []byte(tt.sep))
if string(s) != tt.s {
t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
@ -782,11 +794,23 @@ var splitaftertests = []SplitTest{
func TestSplitAfter(t *testing.T) {
for _, tt := range splitaftertests {
a := SplitAfterN([]byte(tt.s), []byte(tt.sep), tt.n)
// Appending to the results should not change future results.
var x []byte
for _, v := range a {
x = append(v, 'z')
}
result := sliceOfString(a)
if !eq(result, tt.a) {
t.Errorf(`Split(%q, %q, %d) = %v; want %v`, tt.s, tt.sep, tt.n, result, tt.a)
continue
}
if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
t.Errorf("last appended result was %s; want %s", x, want)
}
s := Join(a, nil)
if string(s) != tt.s {
t.Errorf(`Join(Split(%q, %q, %d), %q) = %q`, tt.s, tt.sep, tt.n, tt.sep, s)
@ -821,12 +845,29 @@ var fieldstests = []FieldsTest{
func TestFields(t *testing.T) {
for _, tt := range fieldstests {
a := Fields([]byte(tt.s))
b := []byte(tt.s)
a := Fields(b)
// Appending to the results should not change future results.
var x []byte
for _, v := range a {
x = append(v, 'z')
}
result := sliceOfString(a)
if !eq(result, tt.a) {
t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
continue
}
if string(b) != tt.s {
t.Errorf("slice changed to %s; want %s", string(b), tt.s)
}
if len(tt.a) > 0 {
if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
t.Errorf("last appended result was %s; want %s", x, want)
}
}
}
}
@ -847,11 +888,28 @@ func TestFieldsFunc(t *testing.T) {
{"aXXbXXXcX", []string{"a", "b", "c"}},
}
for _, tt := range fieldsFuncTests {
a := FieldsFunc([]byte(tt.s), pred)
b := []byte(tt.s)
a := FieldsFunc(b, pred)
// Appending to the results should not change future results.
var x []byte
for _, v := range a {
x = append(v, 'z')
}
result := sliceOfString(a)
if !eq(result, tt.a) {
t.Errorf("FieldsFunc(%q) = %v, want %v", tt.s, a, tt.a)
}
if string(b) != tt.s {
t.Errorf("slice changed to %s; want %s", b, tt.s)
}
if len(tt.a) > 0 {
if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
t.Errorf("last appended result was %s; want %s", x, want)
}
}
}
}