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Code Issues Releases Wiki Activity

internal/ui/termstatus: Optimize and publish Truncate

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name               old time/op  new time/op  delta
TruncateASCII-8     347ns ± 1%    69ns ± 1%  -80.02%  (p=0.000 n=9+10)
TruncateUnicode-8   447ns ± 3%   348ns ± 1%  -22.04%  (p=0.000 n=10+10)
This commit is contained in:
greatroar 2021-08-29 14:54:15 +02:00
parent 10b39d7591
commit 5aaa3e93c1
2 changed files with 41 additions and 13 deletions
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24
internal/ui/termstatus/status.go
View File

@ -8,6 +8,7 @@ import (
"io"
"os"
"strings"
"unicode"
"golang.org/x/crypto/ssh/terminal"
"golang.org/x/text/width"
@ -280,7 +281,7 @@ func (t *Terminal) Errorf(msg string, args ...interface{}) {
// Truncate s to fit in width (number of terminal cells) w.
// If w is negative, returns the empty string.
func truncate(s string, w int) string {
func Truncate(s string, w int) string {
if len(s) < w {
// Since the display width of a character is at most 2
// and all of ASCII (single byte per rune) has width 1,
@ -289,16 +290,11 @@ func truncate(s string, w int) string {
}
for i, r := range s {
// Determine width of the rune. This cannot be determined without
// knowing the terminal font, so let's just be careful and treat
// all ambigous characters as full-width, i.e., two cells.
wr := 2
switch width.LookupRune(r).Kind() {
case width.Neutral, width.EastAsianNarrow:
wr = 1
w--
if r > unicode.MaxASCII && wideRune(r) {
w--
}
w -= wr
if w < 0 {
return s[:i]
}
@ -307,6 +303,14 @@ func truncate(s string, w int) string {
return s
}
// Guess whether r would occupy two terminal cells instead of one.
// This cannot be determined exactly without knowing the terminal font,
// so we treat all ambigous runes as full-width, i.e., two cells.
func wideRune(r rune) bool {
kind := width.LookupRune(r).Kind()
return kind != width.Neutral && kind != width.EastAsianNarrow
}
// SetStatus updates the status lines.
func (t *Terminal) SetStatus(lines []string) {
if len(lines) == 0 {
@ -328,7 +332,7 @@ func (t *Terminal) SetStatus(lines []string) {
for i, line := range lines {
line = strings.TrimRight(line, "\n")
if width > 0 {
line = truncate(line, width-2)
line = Truncate(line, width-2)
}
lines[i] = line + "\n"
}

30
internal/ui/termstatus/status_test.go
View File

@ -19,13 +19,14 @@ func TestTruncate(t *testing.T) {
{"foo", 0, ""},
{"foo", -1, ""},
{"Löwen", 4, "Löwe"},
{"あああああああああ/data", 10, "あああああ"},
{"あああああああああ/data", 11, "あああああ"},
{"あああああ/data", 7, "あああ"},
{"あああああ/data", 10, "あああああ"},
{"あああああ/data", 11, "あああああ/"},
}
for _, test := range tests {
t.Run("", func(t *testing.T) {
out := truncate(test.input, test.width)
out := Truncate(test.input, test.width)
if out != test.output {
t.Fatalf("wrong output for input %v, width %d: want %q, got %q",
test.input, test.width, test.output, out)
@ -33,3 +34,26 @@ func TestTruncate(t *testing.T) {
})
}
}
func benchmarkTruncate(b *testing.B, s string, w int) {
for i := 0; i < b.N; i++ {
Truncate(s, w)
}
}
func BenchmarkTruncateASCII(b *testing.B) {
s := "This is an ASCII-only status message...\r\n"
benchmarkTruncate(b, s, len(s)-1)
}
func BenchmarkTruncateUnicode(b *testing.B) {
s := "Hello World or Καλημέρα κόσμε or こんにちは 世界"
w := 0
for _, r := range s {
w++
if wideRune(r) {
w++
}
}
benchmarkTruncate(b, s, w-1)
}