mirror of
https://github.com/go-sylixos/elvish.git
synced 2024-12-13 18:07:51 +08:00
53 lines
1.1 KiB
Go
53 lines
1.1 KiB
Go
package vals
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import (
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"errors"
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"unicode/utf8"
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)
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var errIndexNotAtRuneBoundary = errors.New("index not at rune boundary")
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func indexString(s string, index interface{}) (string, error) {
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i, j, err := convertStringIndex(index, s)
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if err != nil {
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return "", err
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}
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return s[i:j], nil
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}
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func convertStringIndex(rawIndex interface{}, s string) (int, int, error) {
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index, err := ConvertListIndex(rawIndex, len(s))
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if err != nil {
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return 0, 0, err
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}
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if index.Slice {
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lower, upper := index.Lower, index.Upper
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if startsWithRuneBoundary(s[lower:]) && endsWithRuneBoundary(s[:upper]) {
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return lower, upper, nil
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}
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return 0, 0, errIndexNotAtRuneBoundary
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}
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// Not slice
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r, size := utf8.DecodeRuneInString(s[index.Lower:])
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if r == utf8.RuneError {
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return 0, 0, errIndexNotAtRuneBoundary
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}
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return index.Lower, index.Lower + size, nil
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}
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func startsWithRuneBoundary(s string) bool {
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if s == "" {
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return true
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}
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r, _ := utf8.DecodeRuneInString(s)
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return r != utf8.RuneError
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}
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func endsWithRuneBoundary(s string) bool {
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if s == "" {
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return true
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}
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r, _ := utf8.DecodeLastRuneInString(s)
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return r != utf8.RuneError
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}
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