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/*
* Envoy
* Copyright 2016-2017 Lyft Inc.
*
* Licensed under Apache License 2.0. See LICENSE.apache for terms.
*/
#include "base64.h"
#include <cstdint>
#include <string>
namespace opentracing {
BEGIN_OPENTRACING_ABI_NAMESPACE
namespace mocktracer {
static constexpr char CHAR_TABLE[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
// Conversion table is taken from
// https://opensource.apple.com/source/QuickTimeStreamingServer/QuickTimeStreamingServer-452/CommonUtilitiesLib/base64.c
static const unsigned char REVERSE_LOOKUP_TABLE[256] = {
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60,
61, 64, 64, 64, 64, 64, 64, 64, 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, 64, 64, 64, 64,
64, 64, 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, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
64, 64, 64, 64, 64, 64, 64, 64, 64};
std::string Base64::decode(const char* input, size_t length) {
if (length % 4 || length == 0) {
return {};
}
// First position of "valid" padding character.
uint64_t first_padding_index = length;
int max_length = static_cast<int>(length) / 4 * 3;
// At most last two chars can be '='.
if (input[length - 1] == '=') {
max_length--;
first_padding_index = length - 1;
if (input[length - 2] == '=') {
max_length--;
first_padding_index = length - 2;
}
}
std::string result;
result.reserve(static_cast<size_t>(max_length));
uint64_t bytes_left = length;
uint64_t cur_read = 0;
// Read input string by group of 4 chars, length of input string must be
// divided evenly by 4. Decode 4 chars 6 bits each into 3 chars 8 bits each.
while (bytes_left > 0) {
// Take first 6 bits from 1st converted char and first 2 bits from 2nd
// converted char, make 8 bits char from it. Use conversion table to map
// char to decoded value (value is between 0 and 63 inclusive for a valid
// character).
const unsigned char a =
REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read])];
const unsigned char b =
REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 1])];
if (a == 64 || b == 64) {
// Input contains an invalid character.
return {};
}
result.push_back(static_cast<char>(a << 2 | b >> 4));
const unsigned char c =
REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 2])];
// Decoded value 64 means invalid character unless we already know it is a
// valid padding. If so, following characters are all padding. Also we
// should check there are no unused bits.
if (c == 64) {
if (first_padding_index != cur_read + 2) {
// Input contains an invalid character.
return {};
} else if (b & 15) {
// There are unused bits at tail.
return {};
} else {
return result;
}
}
// Take last 4 bits from 2nd converted char and 4 first bits from 3rd
// converted char.
result.push_back(static_cast<char>(b << 4 | c >> 2));
const unsigned char d =
REVERSE_LOOKUP_TABLE[static_cast<uint32_t>(input[cur_read + 3])];
if (d == 64) {
if (first_padding_index != cur_read + 3) {
// Input contains an invalid character.
return {};
} else if (c & 3) {
// There are unused bits at tail.
return {};
} else {
return result;
}
}
// Take last 2 bits from 3rd converted char and all(6) bits from 4th
// converted char.
result.push_back(static_cast<char>(c << 6 | d));
cur_read += 4;
bytes_left -= 4;
}
return result;
}
void Base64::encodeBase(const uint8_t cur_char, uint64_t pos, uint8_t& next_c,
std::string& ret) {
switch (pos % 3) {
case 0:
ret.push_back(CHAR_TABLE[cur_char >> 2]);
next_c = static_cast<uint8_t>((cur_char & 0x03) << 4);
break;
case 1:
ret.push_back(CHAR_TABLE[next_c | (cur_char >> 4)]);
next_c = static_cast<uint8_t>((cur_char & 0x0f) << 2);
break;
case 2:
ret.push_back(CHAR_TABLE[next_c | (cur_char >> 6)]);
ret.push_back(CHAR_TABLE[cur_char & 0x3f]);
next_c = 0;
break;
}
}
void Base64::encodeLast(uint64_t pos, uint8_t last_char, std::string& ret) {
switch (pos % 3) {
case 1:
ret.push_back(CHAR_TABLE[last_char]);
ret.push_back('=');
ret.push_back('=');
break;
case 2:
ret.push_back(CHAR_TABLE[last_char]);
ret.push_back('=');
break;
default:
break;
}
}
std::string Base64::encode(const char* input, uint64_t length) {
uint64_t output_length = (length + 2) / 3 * 4;
std::string ret;
ret.reserve(output_length);
uint64_t pos = 0;
uint8_t next_c = 0;
for (uint64_t i = 0; i < length; ++i) {
encodeBase(static_cast<uint8_t>(input[i]), pos++, next_c, ret);
}
encodeLast(pos, next_c, ret);
return ret;
}
} // namespace mocktracer
END_OPENTRACING_ABI_NAMESPACE
} // namespace opentracing
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