80 lines
1.4 KiB
Go
80 lines
1.4 KiB
Go
package unpackstring
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import (
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"errors"
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"strconv"
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"strings"
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"unicode"
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)
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var ErrInvalidString = errors.New("invalid string")
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type state int
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const (
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start state = iota
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escape
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number
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)
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func Unpack(str string) (string, error) {
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var currentState state = start
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var result strings.Builder
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numOfRepeat := 1
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//if firstCheckString(&str) == true {
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// return "", ErrInvalidString
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//}
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var runeArray = []rune(str)
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if len(runeArray) > 0 && unicode.IsDigit(runeArray[0]) {
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return "first rune is digit", ErrInvalidString
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}
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for i, char := range runeArray {
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switch currentState {
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case start:
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if unicode.IsDigit(char) {
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currentState = number
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numOfRepeat, _ = strconv.Atoi(string(char))
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} else if char == '\\' {
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currentState = escape
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} else {
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currentState = start
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result.WriteRune(char)
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}
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case number:
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if unicode.IsDigit(char) {
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return "", ErrInvalidString
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}
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repStr, err := repeatRune(runeArray[i-2], numOfRepeat)
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if err != nil {
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res := result.String()
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result.Reset()
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result.WriteString(res[0 : len(res)-1])
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}
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result.WriteString(repStr)
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currentState = start
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result.WriteRune(char)
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case escape:
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result.WriteRune(char)
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}
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}
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return result.String(), nil
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}
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func repeatRune(char rune, numOfRepeat int) (string, error) {
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if numOfRepeat > 0 {
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return strings.Repeat(string(char), numOfRepeat-1), nil
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}
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if numOfRepeat == 0 {
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return "", errors.New("zero repeat")
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}
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return "", nil
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}
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