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helpers: Make UniqueStringsReuse allocation free

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This should be faster for all of our use cases (small string slices), but more important, it makes UniqueStringsReuse allocation free.

```bash
name                                 old time/op    new time/op    delta
UniqueStrings/Safe-16                   776ns ± 0%     305ns ± 0%   -60.68%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice-16            621ns ± 3%     174ns ± 0%   -72.01%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice_sorted-16     319ns ± 4%     313ns ± 0%    -2.01%  (p=0.029 n=4+4)

name                                 old alloc/op   new alloc/op   delta
UniqueStrings/Safe-16                    224B ± 0%      128B ± 0%   -42.86%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice-16            96.0B ± 0%      0.0B       -100.00%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice_sorted-16     24.0B ± 0%     24.0B ± 0%      ~     (all equal)

name                                 old allocs/op  new allocs/op  delta
UniqueStrings/Safe-16                    7.00 ± 0%      1.00 ± 0%   -85.71%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice-16             6.00 ± 0%      0.00       -100.00%  (p=0.029 n=4+4)
UniqueStrings/Reuse_slice_sorted-16      1.00 ± 0%      1.00 ± 0%      ~     (all equal)
```
This commit is contained in:
Bjørn Erik Pedersen 2021-11-16 19:20:33 +01:00
parent 0b70b46aad
commit 5e0947c5b5
1 changed files with 20 additions and 8 deletions
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28
helpers/general.go
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@ -85,11 +85,16 @@ func FirstUpper(s string) string {
// UniqueStrings returns a new slice with any duplicates removed.
func UniqueStrings(s []string) []string {
unique := make([]string, 0, len(s))
set := map[string]interface{}{}
for _, val := range s {
if _, ok := set[val]; !ok {
for i, val := range s {
var seen bool
for j := 0; j < i; j++ {
if s[j] == val {
seen = true
break
}
}
if !seen {
unique = append(unique, val)
set[val] = val
}
}
return unique
@ -98,12 +103,19 @@ func UniqueStrings(s []string) []string {
// UniqueStringsReuse returns a slice with any duplicates removed.
// It will modify the input slice.
func UniqueStringsReuse(s []string) []string {
set := map[string]interface{}{}
result := s[:0]
for _, val := range s {
if _, ok := set[val]; !ok {
for i, val := range s {
var seen bool
for j := 0; j < i; j++ {
if s[j] == val {
seen = true
break
}
}
if !seen {
result = append(result, val)
set[val] = val
}
}
return result