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23c87d8a21
This keeps things fast by making the function inline, but also prevents people from having to know about the `0xFF` implementation detail directly, instead making one go through a `std::optional` (which could be fused away with a sufficiently smart compiler). Additionally, the base "nix32" implementation is moved to its own header file pair, as it is logically distinct and prior to the `Hash` data type. It would probably be nice to do this with all the hash format implementations.
42 lines
1,011 B
C++
42 lines
1,011 B
C++
#include <cassert>
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#include "nix/util/base-nix-32.hh"
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namespace nix {
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constexpr const std::array<unsigned char, 256> BaseNix32::reverseMap = [] {
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std::array<unsigned char, 256> map{};
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for (size_t i = 0; i < map.size(); ++i)
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map[i] = invalid; // invalid
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for (unsigned char i = 0; i < 32; ++i)
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map[static_cast<unsigned char>(characters[i])] = i;
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return map;
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}();
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std::string BaseNix32::encode(std::span<const uint8_t> originalData)
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{
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if (originalData.size() == 0)
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return {};
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size_t len = encodedLength(originalData.size());
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assert(len);
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std::string s;
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s.reserve(len);
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for (int n = (int) len - 1; n >= 0; n--) {
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unsigned int b = n * 5;
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unsigned int i = b / 8;
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unsigned int j = b % 8;
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unsigned char c =
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(originalData.data()[i] >> j) | (i >= originalData.size() - 1 ? 0 : originalData.data()[i + 1] << (8 - j));
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s.push_back(characters[c & 0x1f]);
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}
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return s;
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}
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} // namespace nix
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