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Diffstat (limited to 'zen/base64.h')
| -rw-r--r-- | zen/base64.h | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/zen/base64.h b/zen/base64.h new file mode 100644 index 00000000..54a0a98b --- /dev/null +++ b/zen/base64.h @@ -0,0 +1,175 @@ +// ***************************************************************************** +// * This file is part of the FreeFileSync project. It is distributed under * +// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0 * +// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved * +// ***************************************************************************** + +#ifndef BASE64_H_08473021856321840873021487213453214 +#define BASE64_H_08473021856321840873021487213453214 + +#include <iterator> +#include "type_traits.h" + + +namespace zen +{ +//http://en.wikipedia.org/wiki/Base64 +/* +Usage: + const std::string input = "Sample text"; + std::string output; + zen::encodeBase64(input.begin(), input.end(), std::back_inserter(output)); + //output contains "U2FtcGxlIHRleHQ=" +*/ +template <class InputIterator, class OutputIterator> +OutputIterator encodeBase64(InputIterator first, InputIterator last, OutputIterator result); //nothrow! + +template <class InputIterator, class OutputIterator> +OutputIterator decodeBase64(InputIterator first, InputIterator last, OutputIterator result); //nothrow! + +std::string stringEncodeBase64(const std::string& str); +std::string stringDecodeBase64(const std::string& str); + + + + + + + + + + +//------------------------- implementation ------------------------------- +namespace impl +{ +//64 chars for base64 encoding + padding char +constexpr char ENCODING_MIME[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; +constexpr signed char DECODING_MIME[] = +{ + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, + -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, + 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, 64, -1, -1, + -1, 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, -1, -1, -1, -1, -1, + -1, 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, -1, -1, -1, -1, -1 + }; +const unsigned char INDEX_PAD = 64; //"=" +} + + +template <class InputIterator, class OutputIterator> inline +OutputIterator encodeBase64(InputIterator first, InputIterator last, OutputIterator result) +{ + using namespace impl; + static_assert(sizeof(typename std::iterator_traits<InputIterator>::value_type) == 1); + static_assert(arraySize(ENCODING_MIME) == 64 + 1 + 1); + static_assert(arrayAccumulate<int>(ENCODING_MIME) + INDEX_PAD == 5602); + + while (first != last) + { + const unsigned char a = static_cast<unsigned char>(*first++); + *result++ = ENCODING_MIME[a >> 2]; + + if (first == last) + { + *result++ = ENCODING_MIME[((a & 0x3) << 4)]; + *result++ = ENCODING_MIME[INDEX_PAD]; + *result++ = ENCODING_MIME[INDEX_PAD]; + break; + } + const unsigned char b = static_cast<unsigned char>(*first++); + *result++ = ENCODING_MIME[((a & 0x3) << 4) | (b >> 4)]; + + if (first == last) + { + *result++ = ENCODING_MIME[((b & 0xf) << 2)]; + *result++ = ENCODING_MIME[INDEX_PAD]; + break; + } + const unsigned char c = static_cast<unsigned char>(*first++); + *result++ = ENCODING_MIME[((b & 0xf) << 2) | (c >> 6)]; + *result++ = ENCODING_MIME[c & 0x3f]; + } + return result; +} + + +template <class InputIterator, class OutputIterator> inline +OutputIterator decodeBase64(InputIterator first, InputIterator last, OutputIterator result) +{ + using namespace impl; + static_assert(sizeof(typename std::iterator_traits<InputIterator>::value_type) == 1); + static_assert(arraySize(DECODING_MIME) == 128); + static_assert(arrayAccumulate<int>(DECODING_MIME) + INDEX_PAD == 2081); + + const unsigned char INDEX_END = INDEX_PAD + 1; + + auto readIndex = [&]() -> unsigned char //return index within [0, 64] or INDEX_END if end of input + { + for (;;) + { + if (first == last) + return INDEX_END; + + const unsigned char ch = static_cast<unsigned char>(*first++); + if (ch < 128) //we're in lower ASCII table half + { + const int index = DECODING_MIME[ch]; + if (0 <= index && index <= static_cast<int>(INDEX_PAD)) //skip all unknown characters (including carriage return, line-break, tab) + return static_cast<unsigned char>(index); + } + } + }; + + for (;;) + { + const unsigned char index1 = readIndex(); + const unsigned char index2 = readIndex(); + if (index1 >= INDEX_PAD || index2 >= INDEX_PAD) + { + assert(index1 == INDEX_END && index2 == INDEX_END); + break; + } + *result++ = static_cast<char>((index1 << 2) | (index2 >> 4)); + + const unsigned char index3 = readIndex(); + if (index3 >= INDEX_PAD) //padding + { + assert(index3 == INDEX_PAD); + break; + } + *result++ = static_cast<char>(((index2 & 0xf) << 4) | (index3 >> 2)); + + const unsigned char index4 = readIndex(); + if (index4 >= INDEX_PAD) //padding + { + assert(index4 == INDEX_PAD); + break; + } + *result++ = static_cast<char>(((index3 & 0x3) << 6) | index4); + } + return result; +} + + +inline +std::string stringEncodeBase64(const std::string& str) +{ + std::string out; + encodeBase64(str.begin(), str.end(), std::back_inserter(out)); + return out; +} + + +inline +std::string stringDecodeBase64(const std::string& str) +{ + std::string out; + decodeBase64(str.begin(), str.end(), std::back_inserter(out)); + return out; +} +} + +#endif //BASE64_H_08473021856321840873021487213453214 |