81 lines
1.9 KiB
C++
81 lines
1.9 KiB
C++
#ifndef CHAOS_PADDING_PADDERPKCS7_HPP
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#define CHAOS_PADDING_PADDERPKCS7_HPP
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#include <cstddef>
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#include <cstdint>
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#include <iterator>
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#include <limits>
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#include "Padding/Padder.hpp"
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#include "Service/Branchless.hpp"
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#include "Service/ChaosException.hpp"
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namespace Chaos::Padding
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{
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class PadderPkcs7 : public Padder<PadderPkcs7>
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{
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public:
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template<typename OutputIt>
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static void Pad(OutputIt begin, OutputIt end)
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{
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auto dist = std::distance(begin, end);
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if (dist > 0 && dist <= std::numeric_limits<uint8_t>::max())
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{
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for (OutputIt it = begin; it != end; ++it)
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{
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*it = static_cast<uint8_t>(dist);
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}
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}
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else
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{
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throw Service::ChaosException("PadderPkcs7::Pad(): invalid range");
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}
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}
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struct ComputeUnpadResult
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{
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bool IsOkay_;
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uint8_t PadSize_;
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};
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template<typename InputIt>
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static ComputeUnpadResult ComputeUnpad(InputIt begin, InputIt end) noexcept
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{
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if (begin == end)
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{
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return { .IsOkay_ = false, .PadSize_ = 0 };
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}
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const uint8_t padSize = *std::prev(end);
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uint8_t isOkay = ~Branchless::IsZero<uint8_t>(padSize);
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size_t suffixSize = 0;
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InputIt it = end;
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while (it != begin && suffixSize < std::numeric_limits<uint8_t>::max())
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{
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--it;
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++suffixSize;
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isOkay &= (Branchless::Eq<uint8_t>(*it, padSize) |
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Branchless::Gt<uint8_t, size_t>(suffixSize, padSize));
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}
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isOkay &= Branchless::Ge<uint8_t, size_t>(suffixSize, padSize);
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return
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{
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.IsOkay_ = static_cast<bool>(isOkay),
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.PadSize_ = Branchless::Sel<uint8_t>(isOkay, padSize, 0)
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};
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}
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private:
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using Branchless = Service::Branchless;
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};
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} // namespace Chaos::Padding
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#endif // CHAOS_PADDING_PADDERPKCS7_HPP
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