v/vlib/encoding/base64/base64.v

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// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module base64
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,
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,
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47, 48, 49, 50, 51]
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ending_table = [0, 2, 1]
enc_table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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)
/**
* decode - expects a base64 encoded string. Returns its decoded version.
* @param data - the encoded input string.
* @return the decoded version of the input string data.
* NB: if you need to decode many strings repeatedly, take a look at decode_in_buffer too.
*/
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pub fn decode(data string) string {
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size := data.len * 3 / 4
if size <= 0 {
return ''
}
buffer := malloc(size)
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return tos(buffer, decode_in_buffer(data, buffer) )
}
/**
* decode - expects a string. Returns its base64 encoded version.
* @param data - the input string.
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* @return the base64 encoded version of the input string.
* NB: base64 encoding returns a string that is ~ 4/3 larger than the input.
* NB: if you need to encode many strings repeatedly, take a look at encode_in_buffer too.
*/
pub fn encode(data string) string {
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size := 4 * ((data.len + 2) / 3)
if size <= 0 {
return ''
}
buffer := malloc(size)
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return tos(buffer, encode_in_buffer(data, buffer))
}
/**
* decode_in_buffer - expects a string reference, and a buffer in which to store its decoded version.
* @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.
* The buffer should be large enough (i.e. 3/4 of the data.len, or larger) to hold the decoded data.
* @return the actual size of the decoded data in the buffer.
* NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
*/
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pub fn decode_in_buffer(data &string, buffer byteptr) int {
mut padding := 0
if data.ends_with('=') {
if data.ends_with('==') {
padding = 2
} else {
padding = 1
}
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}
//input_length is the length of meaningful data
input_length := data.len - padding
output_length := input_length * 3 / 4
mut i := 0
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mut j := 0
mut b := &byte(0)
mut d := &byte(0)
unsafe{
d = byteptr(data.str)
b = byteptr(buffer)
}
for i < input_length {
mut char_a := 0
mut char_b := 0
mut char_c := 0
mut char_d := 0
if i < input_length {
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char_a = index[d[i]]
i++
}
if i < input_length {
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char_b = index[d[i]]
i++
}
if i < input_length {
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char_c = index[d[i]]
i++
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}
if i < input_length {
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char_d = index[d[i]]
i++
}
decoded_bytes := (char_a << 18) | (char_b << 12) | (char_c << 6) | (char_d << 0)
b[j] = decoded_bytes >> 16
b[j+1] = (decoded_bytes >> 8) & 0xff
b[j+2] = (decoded_bytes >> 0) & 0xff
j += 3
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}
return output_length
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}
/**
* encode_in_buffer - expects a string reference, and a buffer in which to store its base64 encoded version.
* @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.
* The buffer should be large enough (i.e. 4/3 of the data.len, or larger) to hold the encoded data.
* @return the actual size of the encoded data in the buffer.
* NB: this function does NOT allocate new memory, and is suitable for handling very large strings.
*/
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pub fn encode_in_buffer(data &string, buffer byteptr) int {
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input_length := data.len
output_length := 4 * ((input_length + 2) / 3)
mut i := 0
mut j := 0
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mut d := byteptr(0)
mut b := byteptr(0)
mut etable := byteptr(0)
unsafe{
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d = data.str
b = buffer
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etable = enc_table.str
}
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for i < input_length {
mut octet_a := 0
mut octet_b := 0
mut octet_c := 0
if i < input_length {
octet_a = int(d[i])
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i++
}
if i < input_length {
octet_b = int(d[i])
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i++
}
if i < input_length {
octet_c = int(d[i])
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i++
}
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triple := ((octet_a << 0x10) + (octet_b << 0x08) + octet_c)
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b[j] = etable[ (triple >> 3 * 6) & 63 ] // 63 is 0x3F
b[j+1] = etable[ (triple >> 2 * 6) & 63 ]
b[j+2] = etable[ (triple >> 1 * 6) & 63 ]
b[j+3] = etable[ (triple >> 0 * 6) & 63 ]
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j += 4
}
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padding_length := ending_table[input_length % 3]
for i = 0; i < padding_length; i++ {
b[output_length - 1 - i] = `=`
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}
return output_length
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}