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labels: cope with mutating Builder during Range call 

Although we had a different slice, the underlying memory was the same so
any changes meant we could skip some values.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2023-03-16 13:28:13 +00:00
parent 3c4ab7a069
commit 3743d87c56
2 changed files with 10 additions and 4 deletions
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7
model/labels/labels.go
View File

@ -545,9 +545,12 @@ func (b *Builder) Get(n string) string {
} }
// Range calls f on each label in the Builder. // Range calls f on each label in the Builder.
// If f calls Set or Del on b then this may affect what callbacks subsequently happen.
func (b *Builder) Range(f func(l Label)) { func (b *Builder) Range(f func(l Label)) {
origAdd, origDel := b.add, b.del // Stack-based arrays to avoid heap allocation in most cases.
var addStack [1024]Label
var delStack [1024]string
// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
b.base.Range(func(l Label) { b.base.Range(func(l Label) {
if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) { if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) {
f(l) f(l)

7
model/labels/labels_string.go
View File

@ -599,9 +599,12 @@ func (b *Builder) Get(n string) string {
} }
// Range calls f on each label in the Builder. // Range calls f on each label in the Builder.
// If f calls Set or Del on b then this may affect what callbacks subsequently happen.
func (b *Builder) Range(f func(l Label)) { func (b *Builder) Range(f func(l Label)) {
origAdd, origDel := b.add, b.del // Stack-based arrays to avoid heap allocation in most cases.
var addStack [1024]Label
var delStack [1024]string
// Take a copy of add and del, so they are unaffected by calls to Set() or Del().
origAdd, origDel := append(addStack[:0], b.add...), append(delStack[:0], b.del...)
b.base.Range(func(l Label) { b.base.Range(func(l Label) {
if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) { if !slices.Contains(origDel, l.Name) && !contains(origAdd, l.Name) {
f(l) f(l)