248 lines
12 KiB
C++
248 lines
12 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2017 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_UTIL_BASE64_HPP
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#define CRUFT_UTIL_BASE64_HPP
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#include "../view.hpp"
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#include "../debug.hpp"
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#include <cstdint>
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#include <array>
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namespace util::encode {
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///////////////////////////////////////////////////////////////////////////
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template <int Size>
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struct alphabet {
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static const char enc[Size];
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static const uint8_t dec[256];
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};
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///////////////////////////////////////////////////////////////////////////
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template <>
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const char alphabet<64>::enc[64] = {
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'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
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'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
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'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
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'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',
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};
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//-------------------------------------------------------------------------
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template <>
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const uint8_t alphabet<64>::dec[256] = {
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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,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x3E, 0, 0, 0, 0x3F,
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0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0, 0, 0, 0, 0, 0,
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0, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E,
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0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0, 0, 0, 0, 0,
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0, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
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0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 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,
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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,
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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,
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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,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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};
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///////////////////////////////////////////////////////////////////////////
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template <>
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const char alphabet<32>::enc[32] {
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'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
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'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
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'2', '3', '4', '5', '6', '7',
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};
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//-------------------------------------------------------------------------
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template <>
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const uint8_t alphabet<32>::dec[256] = {
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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,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
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0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 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,
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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,
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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,
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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,
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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,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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};
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///////////////////////////////////////////////////////////////////////////
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template <>
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const char alphabet<16>::enc[16] {
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'0', '1', '2', '3', '4', '5', '6', '7',
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'8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
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};
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template <>
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const uint8_t alphabet<16>::dec[256] = {
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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,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0, 0, 0, 0, 0, 0,
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0, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 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,
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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,
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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,
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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,
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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,
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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
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};
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//-------------------------------------------------------------------------
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template <int Size> constexpr auto enc_v = alphabet<Size>::enc;
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template <int Size> constexpr auto dec_v = alphabet<Size>::dec;
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///////////////////////////////////////////////////////////////////////////
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/// rfc4648 base16, base32, and base64 encoding
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template <int Size>
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struct base {
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static constexpr auto symbol_bits = log2 (Size);
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static constexpr auto group_bits = std::lcm (symbol_bits, 8);
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static constexpr auto group_symbols = group_bits / symbol_bits;
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static constexpr auto group_bytes = group_bits / 8;
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static constexpr uint_fast32_t mask = (1<<symbol_bits)-1;
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template <typename InputT, typename OutputT>
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static OutputT
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encode (OutputT dst, const util::view<InputT> src)
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{
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// convert whole groups of symbols while we have enough bytes remaining
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auto cursor = std::cbegin (src);
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for (size_t i = 0, last = std::size (src) / group_bytes; i != last; ++i) {
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auto tally = std::accumulate (
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cursor, cursor + group_bytes,
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uint_fast32_t {0},
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[] (auto a, auto b) { return a << 8 | b; }
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);
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cursor += group_bytes;
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for (int j = group_symbols - 1; j >= 0; --j)
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*dst++ = enc_v<Size>[tally >> (j * symbol_bits) & mask];
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}
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// we don't need to pad the output so we can early exit
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if (cursor == std::cend (src))
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return dst;
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// accumulate the remaining bits and pad to a multiple of the
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// output group length
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auto tally = std::accumulate (
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cursor,
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std::cend (src),
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uint_fast32_t {0},
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[] (auto a, auto b) { return a << 8 | b; }
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);
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auto input_remain = std::cend (src) - cursor;
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tally <<= symbol_bits - input_remain * 8 % symbol_bits;
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// write each of the remaining symbols
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auto output_remain = (input_remain * 8 + symbol_bits - 1) / symbol_bits;
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for (auto i = output_remain - 1; i >= 0; --i)
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*dst++ = enc_v<Size>[tally >> (i * symbol_bits) & mask];
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// pad the output to the symbol group size with '=' characters
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auto fill = (group_bytes - input_remain) * 8 / symbol_bits;
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return std::fill_n (dst, fill, '=');
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}
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//---------------------------------------------------------------------
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template <typename InputT, typename OutputT>
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static OutputT
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decode (OutputT dst, util::view<InputT> src)
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{
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if (src.empty ())
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return dst;
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if (src.size () % group_symbols)
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throw std::invalid_argument ("base-encoded strings must be a proper multiple of symbols");
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union {
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uint_fast32_t num;
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uint8_t bytes[group_bytes];
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};
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const bool padded = src.end ()[-1] == '=';
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auto cursor = std::cbegin (src);
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for (size_t i = 0, last = std::size (src) / group_symbols - padded?1:0;
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i != last;
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++i)
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{
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num = std::accumulate (
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cursor, cursor + group_symbols,
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uint_fast32_t {0},
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[] (auto a, auto b) { return a << symbol_bits | dec_v<Size>[b]; }
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);
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cursor += group_symbols;
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dst = std::copy (std::crbegin (bytes), std::crend (bytes), dst);
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}
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if (cursor != std::end (src)) {
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auto last = std::find (cursor, std::cend (src), '=');
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num = std::accumulate (
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cursor, last,
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uint_fast32_t{0},
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[] (auto a, auto b) { return a << symbol_bits | dec_v<Size>[b]; }
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);
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auto symbols = last - cursor;
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auto bits = symbols * symbol_bits;
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auto shift = bits%8;
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num >>= shift;
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for (auto i = bits / 8; i; )
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*dst++ = bytes[--i];
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}
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return dst;
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}
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};
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};
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#endif
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