jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#include <AK/Array.h>
8#include <AK/Assertions.h>
9#include <AK/Base64.h>
10#include <AK/CharacterTypes.h>
11#include <AK/Error.h>
12#include <AK/StringBuilder.h>
13#include <AK/Types.h>
14#include <AK/Vector.h>
15
16namespace AK {
17
18size_t calculate_base64_decoded_length(StringView input)
19{
20 return input.length() * 3 / 4;
21}
22
23size_t calculate_base64_encoded_length(ReadonlyBytes input)
24{
25 return ((4 * input.size() / 3) + 3) & ~3;
26}
27
28ErrorOr<ByteBuffer> decode_base64(StringView input)
29{
30 auto alphabet_lookup_table = base64_lookup_table();
31
32 auto get = [&](size_t& offset, bool* is_padding, bool& parsed_something) -> ErrorOr<u8> {
33 while (offset < input.length() && is_ascii_space(input[offset]))
34 ++offset;
35 if (offset >= input.length())
36 return 0;
37 auto ch = static_cast<unsigned char>(input[offset++]);
38 parsed_something = true;
39 if (ch == '=') {
40 if (!is_padding)
41 return Error::from_string_literal("Invalid '=' character outside of padding in base64 data");
42 *is_padding = true;
43 return 0;
44 }
45 i16 result = alphabet_lookup_table[ch];
46 if (result < 0)
47 return Error::from_string_literal("Invalid character in base64 data");
48 VERIFY(result < 256);
49 return { result };
50 };
51
52 Vector<u8> output;
53 output.ensure_capacity(calculate_base64_decoded_length(input));
54
55 size_t offset = 0;
56 while (offset < input.length()) {
57 bool in2_is_padding = false;
58 bool in3_is_padding = false;
59
60 bool parsed_something = false;
61
62 const u8 in0 = TRY(get(offset, nullptr, parsed_something));
63 const u8 in1 = TRY(get(offset, nullptr, parsed_something));
64 const u8 in2 = TRY(get(offset, &in2_is_padding, parsed_something));
65 const u8 in3 = TRY(get(offset, &in3_is_padding, parsed_something));
66
67 if (!parsed_something)
68 break;
69
70 const u8 out0 = (in0 << 2) | ((in1 >> 4) & 3);
71 const u8 out1 = ((in1 & 0xf) << 4) | ((in2 >> 2) & 0xf);
72 const u8 out2 = ((in2 & 0x3) << 6) | in3;
73
74 output.append(out0);
75 if (!in2_is_padding)
76 output.append(out1);
77 if (!in3_is_padding)
78 output.append(out2);
79 }
80
81 return ByteBuffer::copy(output);
82}
83
84ErrorOr<String> encode_base64(ReadonlyBytes input)
85{
86 StringBuilder output(calculate_base64_encoded_length(input));
87
88 auto get = [&](const size_t offset, bool* need_padding = nullptr) -> u8 {
89 if (offset >= input.size()) {
90 if (need_padding)
91 *need_padding = true;
92 return 0;
93 }
94 return input[offset];
95 };
96
97 for (size_t i = 0; i < input.size(); i += 3) {
98 bool is_8bit = false;
99 bool is_16bit = false;
100
101 const u8 in0 = get(i);
102 const u8 in1 = get(i + 1, &is_16bit);
103 const u8 in2 = get(i + 2, &is_8bit);
104
105 const u8 index0 = (in0 >> 2) & 0x3f;
106 const u8 index1 = ((in0 << 4) | (in1 >> 4)) & 0x3f;
107 const u8 index2 = ((in1 << 2) | (in2 >> 6)) & 0x3f;
108 const u8 index3 = in2 & 0x3f;
109
110 char const out0 = base64_alphabet[index0];
111 char const out1 = base64_alphabet[index1];
112 char const out2 = is_16bit ? '=' : base64_alphabet[index2];
113 char const out3 = is_8bit ? '=' : base64_alphabet[index3];
114
115 TRY(output.try_append(out0));
116 TRY(output.try_append(out1));
117 TRY(output.try_append(out2));
118 TRY(output.try_append(out3));
119 }
120
121 return output.to_string();
122}
123
124}