66 lines
2.1 KiB
Go
66 lines
2.1 KiB
Go
/*
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https://github.com/fs111/kurz.go/blob/master/src/codec.go
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Originally written and Copyright (c) 2011 André Kelpe
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Modifications Copyright (c) 2015 John Ko
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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the Software, and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package server
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import (
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"math"
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"strings"
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)
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const (
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// characters used for short-urls
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SYMBOLS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
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// someone set us up the bomb !!
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BASE = int64(len(SYMBOLS))
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)
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// encodes a number into our *base* representation
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// TODO can this be made better with some bitshifting?
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func Encode(number int64) string {
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rest := number % BASE
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// strings are a bit weird in go...
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result := string(SYMBOLS[rest])
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if number-rest != 0 {
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newnumber := (number - rest) / BASE
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result = Encode(newnumber) + result
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}
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return result
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}
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// Decodes a string given in our encoding and returns the decimal
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// integer.
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func Decode(input string) int64 {
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const floatbase = float64(BASE)
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l := len(input)
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var sum int = 0
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for index := l - 1; index > -1; index -= 1 {
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current := string(input[index])
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pos := strings.Index(SYMBOLS, current)
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sum = sum + (pos * int(math.Pow(floatbase, float64((l-index-1)))))
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}
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return int64(sum)
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}
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