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| author | Jes Cok <xigua67damn@gmail.com> | 2024-08-01 16:18:06 +0000 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2024-08-01 21:32:50 +0000 |
| commit | 67c3f012cf5bfd69841c74666243281f0698e09f (patch) | |
| tree | ee612f3b0c4d16414946cd84919fb152d42aed7f /src/strings/strings.go | |
| parent | e50913cefcdb590cdf7d9432455de2847ef93851 (diff) | |
| download | go-67c3f012cf5bfd69841c74666243281f0698e09f.tar.xz | |
bytes,slices,strings: optimize Repeat a bit
Like slices.Repeat, use math/bits.Mul to detect overflow in order to
avoid a divide which is slow.
While here, also use builtin min/max to simplify code.
Change-Id: I4a6d8cd5df97fa75f4e324d4be1405ce53c03d31
GitHub-Last-Rev: 54ba5c7126b1d4a301e95d664b5f6deee6d579d9
GitHub-Pull-Request: golang/go#68704
Reviewed-on: https://go-review.googlesource.com/c/go/+/602475
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Diffstat (limited to 'src/strings/strings.go')
| -rw-r--r-- | src/strings/strings.go | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/src/strings/strings.go b/src/strings/strings.go index 0bd3c1c233..0729c4ad42 100644 --- a/src/strings/strings.go +++ b/src/strings/strings.go @@ -10,6 +10,7 @@ package strings import ( "internal/bytealg" "internal/stringslite" + "math/bits" "unicode" "unicode/utf8" ) @@ -568,10 +569,11 @@ func Repeat(s string, count int) string { if count < 0 { panic("strings: negative Repeat count") } - if len(s) > maxInt/count { + hi, lo := bits.Mul(uint(len(s)), uint(count)) + if hi > 0 || lo > uint(maxInt) { panic("strings: Repeat output length overflow") } - n := len(s) * count + n := int(lo) // lo = len(s) * count if len(s) == 0 { return "" @@ -617,13 +619,7 @@ func Repeat(s string, count int) string { b.Grow(n) b.WriteString(s) for b.Len() < n { - chunk := n - b.Len() - if chunk > b.Len() { - chunk = b.Len() - } - if chunk > chunkMax { - chunk = chunkMax - } + chunk := min(n-b.Len(), b.Len(), chunkMax) b.WriteString(b.String()[:chunk]) } return b.String() |