TrimSpace remove space, also in sentence. like: " a \t\r\n b " -> "a b"

trimspace.go

package main

import (
	"fmt"

	"github.com/google/go-cmp/cmp"
)

func isSpace(b byte) bool {
	switch b {
	case '\t', '\n', '\v', '\f', '\r', ' ':
		return true
	}
	return false
}

// TrimSpace remove space, also in sentence.
// like:
// " a \t\r\n b " -> "a b"
func TrimSpace(b []byte) []byte {
	var l, r int
	r = len(b) - 1
	// skip left space
	for l < r && isSpace(b[l]) {
		l++
	}
	// skip right space
	for r >= 0 && isSpace(b[r]) {
		r--
	}
	var i int
	for l <= r {
		if isSpace(b[l]) {
			b[i] = ' '
			// skip multi spaces
			for l <= r && isSpace(b[l]) {
				l++
			}
		} else {
			b[i] = b[l]
			l++
		}
		i++
	}
	return b[:i]
}

func main() {
	datas := []struct {
		in  []byte
		out []byte
	}{
		{nil, nil},
		{[]byte("   "), []byte("")},
		{[]byte("hi"), []byte("hi")},
		{[]byte(" hi  world "), []byte("hi world")},
		{[]byte("\t hi\r\n world "), []byte("hi world")},
	}
	for _, data := range datas {
		d := cmp.Diff(TrimSpace(data.in), data.out)
		if d != "" {
			fmt.Println(d)
		}
	}
}