113 lines
2.5 KiB
Go
113 lines
2.5 KiB
Go
// 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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pub fn decode(data string) string {
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mut padding := 0
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if data.ends_with('=') {
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if data.ends_with('==') {
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padding = 2
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} else {
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padding = 1
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}
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}
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//input_length is the length of meaningful data
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input_length := data.len - padding
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output_length := input_length * 3 / 4
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mut i := 0
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mut j := 0
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mut str := malloc(output_length)
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for i < input_length {
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mut char_a := 0
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mut char_b := 0
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mut char_c := 0
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mut char_d := 0
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if i < input_length {
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char_a = Index[int(data[i])]
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i++
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}
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if i < input_length {
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char_b = Index[int(data[i])]
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i++
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}
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if i < input_length {
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char_c = Index[int(data[i])]
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i++
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}
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if i < input_length {
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char_d = Index[int(data[i])]
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i++
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}
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decoded_bytes := (char_a << 18) | (char_b << 12) | (char_c << 6) | (char_d << 0)
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str[j] = decoded_bytes >> 16
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str[j+1] = (decoded_bytes >> 8) & 0xff
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str[j+2] = (decoded_bytes >> 0) & 0xff
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j += 3
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}
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return tos(str, output_length)
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}
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const (
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EncodingTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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)
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pub fn encode(data string) string {
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input_length := data.len
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output_length := 4 * ((input_length + 2) / 3)
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mut i := 0
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mut j := 0
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mut str := malloc(output_length)
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for i < input_length {
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mut octet_a := 0
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mut octet_b := 0
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mut octet_c := 0
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if i < input_length {
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octet_a = int(data[i])
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i++
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}
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if i < input_length {
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octet_b = int(data[i])
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i++
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}
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if i < input_length {
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octet_c = int(data[i])
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i++
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}
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triple := ((octet_a << 0x10) + (octet_b << 0x08) + octet_c)
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str[j+0] = EncodingTable[(triple >> 3 * 6) & 63] // 63 is 0x3F
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str[j+1] = EncodingTable[(triple >> 2 * 6) & 63]
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str[j+2] = EncodingTable[(triple >> 1 * 6) & 63]
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str[j+3] = EncodingTable[(triple >> 0 * 6) & 63]
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j += 4
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}
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mod_table := [0, 2, 1]
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for i = 0; i < mod_table[input_length % 3]; i++ {
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str[output_length - 1 - i] = `=`
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}
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return tos(str, output_length)
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}
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