77 lines
1.9 KiB
Go
77 lines
1.9 KiB
Go
package main
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import (
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"fmt"
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"unicode"
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"unicode/utf8"
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)
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// no encoding
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func reverseBytes(s string) string {
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r := make([]byte, len(s))
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for i := 0; i < len(s); i++ {
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r[i] = s[len(s)-1-i]
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}
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return string(r)
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}
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// reverseCodePoints interprets its argument as UTF-8 and ignores bytes
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// that do not form valid UTF-8. return value is UTF-8.
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func reverseCodePoints(s string) string {
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r := make([]rune, len(s))
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start := len(s)
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for _, c := range s {
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// quietly skip invalid UTF-8
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if c != utf8.RuneError {
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start--
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r[start] = c
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}
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}
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return string(r[start:])
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}
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// reversePreservingCombiningCharacters interprets its argument as UTF-8
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// and ignores bytes that do not form valid UTF-8. return value is UTF-8.
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func reversePreservingCombiningCharacters(s string) string {
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if s == "" {
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return ""
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}
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p := []rune(s)
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r := make([]rune, len(p))
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start := len(r)
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for i := 0; i < len(p); {
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// quietly skip invalid UTF-8
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if p[i] == utf8.RuneError {
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i++
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continue
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}
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j := i + 1
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for j < len(p) && (unicode.Is(unicode.Mn, p[j]) ||
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unicode.Is(unicode.Me, p[j]) || unicode.Is(unicode.Mc, p[j])) {
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j++
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}
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for k := j - 1; k >= i; k-- {
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start--
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r[start] = p[k]
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}
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i = j
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}
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return (string(r[start:]))
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}
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func main() {
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test("asdf")
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test("as⃝df̅")
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}
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func test(s string) {
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fmt.Println("\noriginal: ", []byte(s), s)
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r := reverseBytes(s)
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fmt.Println("reversed bytes:", []byte(r), r)
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fmt.Println("original code points:", []rune(s), s)
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r = reverseCodePoints(s)
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fmt.Println("reversed code points:", []rune(r), r)
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r = reversePreservingCombiningCharacters(s)
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fmt.Println("combining characters:", []rune(r), r)
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}
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