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Diffstat (limited to 'mocktracer/src/base64.cpp')
| -rw-r--r-- | mocktracer/src/base64.cpp | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/mocktracer/src/base64.cpp b/mocktracer/src/base64.cpp new file mode 100644 index 0000000..d039dcf --- /dev/null +++ b/mocktracer/src/base64.cpp @@ -0,0 +1,174 @@ +/* + * 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 |