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50 lines
1.3 KiB
V
50 lines
1.3 KiB
V
// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module base64
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const (
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Index = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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62, 63, 62, 62, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0,
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0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
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17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 63, 0, 26, 27, 28, 29,
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30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
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47, 48, 49, 50, 51]
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)
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fn decode(data string) string {
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p := data.cstr()
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len := data.len
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mut pad := 0
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if len > 0 && (len % 4 != 0 || p[len - 1] == `=`) {
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pad = 1
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}
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L := ((len + 3) / 4 - pad) * 4
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str_len := L / 4 * 3 + pad
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mut str := malloc(str_len + 2)
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mut j := 0
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for i := 0; i < L; i += 4 {
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n := (Index[p[i]] << 18) | (Index[p[i + 1]] << 12) |
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(Index[p[i + 2]] << 6) | (Index[p[i + 3]])
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str[j] = n >> 16
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j++
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str[j] = n >> 8 & 0xff
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j++
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str[j] = n & 0xff
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j++
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}
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if pad > 0 {
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mut nn := (Index[p[L]] << 18) | (Index[p[L + 1]] << 12)
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str[str_len - 1] = nn >> 16
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if len > L + 2 && p[L + 2] != `=` {
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nn = nn | (Index[p[L + 2]] << 6)
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str[str_len] = nn >> 8 & 0xff
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}
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}
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str[str_len + 1] = `\0`
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return string(str)
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}
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