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161 lines
4.6 KiB
V
161 lines
4.6 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 = [int(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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EndingTable = [0, 2, 1]
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EncodingTable = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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)
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/**
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* decode - expects a base64 encoded string. Returns its decoded version.
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* @param data - the encoded input string.
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* @return the decoded version of the input string data.
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* NB: if you need to decode many strings repeatedly, take a look at decode_in_buffer too.
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*/
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pub fn decode(data string) string {
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buffer := malloc( data.len * 3 / 4 )
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return tos(buffer, decode_in_buffer(data, buffer) )
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}
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/**
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* decode - expects a string. Returns its base64 encoded version.
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* @param data - the input string.
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* @return the base64 encoded version of the input string.
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* NB: base64 encoding returns a string that is ~ 4/3 larger than the input.
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* NB: if you need to encode many strings repeatedly, take a look at encode_in_buffer too.
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*/
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pub fn encode(data string) string {
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buffer := malloc( 4 * ((data.len + 2) / 3) )
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return tos(buffer, encode_in_buffer(data, buffer))
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}
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/**
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* decode_in_buffer - expects a string reference, and a buffer in which to store its decoded version.
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* @param data - a reference/pointer to the input string that will be decoded.
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* @param buffer - a reference/pointer to the buffer that will hold the result.
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* The buffer should be large enough (i.e. 3/4 of the data.len, or larger) to hold the decoded data.
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* @return the actual size of the decoded data in the buffer.
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* NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
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*/
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pub fn decode_in_buffer(data &string, buffer byteptr) int {
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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 b := &byte(0)
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mut d := &byte(0)
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unsafe{
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d = byteptr(data.str)
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b = byteptr(buffer)
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}
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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[d[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[d[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[d[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[d[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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b[j] = decoded_bytes >> 16
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b[j+1] = (decoded_bytes >> 8) & 0xff
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b[j+2] = (decoded_bytes >> 0) & 0xff
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j += 3
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}
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return output_length
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}
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/**
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* encode_in_buffer - expects a string reference, and a buffer in which to store its base64 encoded version.
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* @param data - a reference/pointer to the input string.
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* @param buffer - a reference/pointer to the buffer that will hold the result.
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* The buffer should be large enough (i.e. 4/3 of the data.len, or larger) to hold the encoded data.
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* @return the actual size of the encoded data in the buffer.
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* NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
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*/
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pub fn encode_in_buffer(data &string, buffer byteptr) int {
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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 d := &byte(0)
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mut b := &byte(0)
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mut etable := &byte(0)
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unsafe{
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d = &byte(data.str)
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b = &byte(buffer)
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etable = &byte(EncodingTable.str)
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}
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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(d[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(d[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(d[i])
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i++
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}
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triple := ((int(octet_a) << 0x10) + (int(octet_b) << 0x08) + int(octet_c))
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b[j] = etable[ (triple >> 3 * 6) & 63 ] // 63 is 0x3F
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b[j+1] = etable[ (triple >> 2 * 6) & 63 ]
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b[j+2] = etable[ (triple >> 1 * 6) & 63 ]
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b[j+3] = etable[ (triple >> 0 * 6) & 63 ]
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j += 4
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}
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padding_length := EndingTable[input_length % 3]
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for i = 0; i < padding_length; i++ {
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b[output_length - 1 - i] = `=`
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}
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return output_length
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}
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