sha1.hh

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#ifndef SHA1_HH
#define SHA1_HH
 
#include "xrange.hh"
#include <array>
#include <cstdint>
#include <ostream>
#include <span>
#include <string>
#include <string_view>
 
namespace openmsx {
 
class Sha1Sum
{
public:
        struct UninitializedTag {};
        Sha1Sum(UninitializedTag) {}
 
        // note: default copy and assign are ok
        Sha1Sum();
        explicit Sha1Sum(std::string_view hex);
 
        void parse40(std::span<const char, 40> str);
        [[nodiscard]] std::string toString() const;
 
        // Test or set 'null' value.
        [[nodiscard]] bool empty() const;
        void clear();
 
        // gcc-10.2 miscompiles this (fixed in gcc-11),
        //  so still manually implement operator==.
        //[[nodiscard]] constexpr bool operator==(const Sha1Sum&) const = default;
        [[nodiscard]] bool operator==(const Sha1Sum& other) const {
                for (int i : xrange(5)) {
                        if (a[i] != other.a[i]) return false;
                }
                return true;
        }
        [[nodiscard]] constexpr auto operator<=>(const Sha1Sum& other) const {
                for (int i : xrange(5 - 1)) {
                        if (auto cmp = a[i] <=> other.a[i]; cmp != 0) return cmp;
                }
                return a[5 - 1] <=> other.a[5 - 1];
        }
 
        friend std::ostream& operator<<(std::ostream& os, const Sha1Sum& sum) {
                os << sum.toString();
                return os;
        }
 
private:
        std::array<uint32_t, 5> a;
        friend class SHA1;
};
 
 
class SHA1
{
public:
        SHA1();
 
        void update(std::span<const uint8_t> data);
 
        [[nodiscard]] Sha1Sum digest();
 
        [[nodiscard]] static Sha1Sum calc(std::span<const uint8_t> data);
 
private:
        void transform(std::span<const uint8_t, 64> buffer);
        void finalize();
 
private:
        uint64_t m_count = 0; // in bytes (sha1 reference implementation counts in bits)
        Sha1Sum m_state;
        std::array<uint8_t, 64> m_buffer;
        bool m_finalized = false;
};
 
} // namespace openmsx
 
#endif