v/base64/base64.v

50 lines
1.3 KiB
Go

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