premiere-libtorrent/include/libtorrent/sha1_hash.hpp

/*

Copyright (c) 2003-2018, Arvid Norberg
All rights reserved.

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    * Redistributions in binary form must reproduce the above copyright
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      from this software without specific prior written permission.

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*/

#ifndef TORRENT_SHA1_HASH_HPP_INCLUDED
#define TORRENT_SHA1_HASH_HPP_INCLUDED

#include <cctype>
#include <algorithm>
#include <string>
#include <cstring>
#include <array>

#include "libtorrent/aux_/disable_warnings_push.hpp"
#include <boost/range/combine.hpp>
#include "libtorrent/aux_/disable_warnings_pop.hpp"

#include "libtorrent/config.hpp"
#include "libtorrent/assert.hpp"
#include "libtorrent/aux_/byteswap.hpp"
#include "libtorrent/aux_/ffs.hpp"
#include "libtorrent/span.hpp"

#if TORRENT_USE_IOSTREAM
#include <iosfwd>
#endif // TORRENT_USE_IOSTREAM

namespace libtorrent {

	// TODO: find a better place for these functions
namespace aux {

		TORRENT_EXTRA_EXPORT void bits_shift_left(span<std::uint32_t> number, int n);
		TORRENT_EXTRA_EXPORT void bits_shift_right(span<std::uint32_t> number, int n);
	}

	// This type holds an N digest or any other kind of N bits
	// sequence. It implements a number of convenience functions, such
	// as bit operations, comparison operators etc.
	//
	// This data structure is 32 bits aligned, like it's the case for
	// each SHA-N specification.
	template <std::ptrdiff_t N>
	class digest32
	{
		static_assert(N % 32 == 0, "N must be a multiple of 32");
		static constexpr std::ptrdiff_t number_size = N / 32;
		static constexpr int bits_in_byte = 8;
	public:

		using difference_type = std::ptrdiff_t;
		using index_type = std::ptrdiff_t;

		// the size of the hash in bytes
		static constexpr difference_type size() noexcept { return N / bits_in_byte; }

		// constructs an all-zero digest
		digest32() noexcept { clear(); }

		digest32(digest32 const&) noexcept = default;
		digest32& operator=(digest32 const&) noexcept = default;

		// returns an all-F digest. i.e. the maximum value
		// representable by an N bit number (N/8 bytes). This is
		// a static member function.
		static digest32 (max)() noexcept
		{
			digest32 ret;
			ret.m_number.fill(0xffffffff);
			return ret;
		}

		// returns an all-zero digest. i.e. the minimum value
		// representable by an N bit number (N/8 bytes). This is
		// a static member function.
		static digest32 (min)() noexcept
		{
			digest32 ret;
			// all bits are already 0
			return ret;
		}

		// copies N/8 bytes from the pointer provided, into the digest.
		// The passed in string MUST be at least N/8 bytes. 0-terminators
		// are ignored, ``s`` is treated like a raw memory buffer.
		explicit digest32(char const* s) noexcept
		{
			if (s == nullptr) clear();
			else std::memcpy(m_number.data(), s, size());
		}
#if TORRENT_ABI_VERSION == 1
		TORRENT_DEPRECATED
		explicit digest32(std::string const& s)
		{
			assign(s.data());
		}
#endif
		explicit digest32(span<char const> s) noexcept
		{
			assign(s);
		}
		void assign(span<char const> s) noexcept
		{
			TORRENT_ASSERT(s.size() >= N / bits_in_byte);
			auto const sl = s.size() < size() ? s.size() : size();
			std::memcpy(m_number.data(), s.data(), static_cast<std::size_t>(sl));
		}
		void assign(char const* str) noexcept { std::memcpy(m_number.data(), str, size()); }

		char const* data() const noexcept { return reinterpret_cast<char const*>(m_number.data()); }
		char* data() noexcept { return reinterpret_cast<char*>(m_number.data()); }

		// set the digest to all zeros.
		void clear() noexcept { m_number.fill(0); }

		// return true if the digest is all zero.
		bool is_all_zeros() const noexcept
		{
			return std::all_of(m_number.begin(), m_number.end()
				, [](std::uint32_t v) { return v == 0; });
		}

		// shift left ``n`` bits.
		digest32& operator<<=(int const n) noexcept
		{
			aux::bits_shift_left(m_number, n);
			return *this;
		}

		// shift right ``n`` bits.
		digest32& operator>>=(int const n) noexcept
		{
			aux::bits_shift_right(m_number, n);
			return *this;
		}

		// standard comparison operators
		bool operator==(digest32 const& n) const noexcept
		{
			return std::equal(n.m_number.begin(), n.m_number.end(), m_number.begin());
		}
		bool operator!=(digest32 const& n) const noexcept
		{
			return !std::equal(n.m_number.begin(), n.m_number.end(), m_number.begin());
		}
		bool operator<(digest32 const& n) const noexcept
		{
			for (auto const v : boost::combine(m_number, n.m_number))
			{
				std::uint32_t const lhs = aux::network_to_host(boost::get<0>(v));
				std::uint32_t const rhs = aux::network_to_host(boost::get<1>(v));
				if (lhs < rhs) return true;
				if (lhs > rhs) return false;
			}
			return false;
		}

		int count_leading_zeroes() const noexcept
		{
			return aux::count_leading_zeros(m_number);
		}

		// returns a bit-wise negated copy of the digest
		digest32 operator~() const noexcept
		{
			digest32 ret;
			for (auto const v : boost::combine(m_number, ret.m_number))
				boost::get<1>(v) = ~boost::get<0>(v);
			return ret;
		}

		// returns the bit-wise XOR of the two digests.
		digest32 operator^(digest32 const& n) const noexcept
		{
			digest32 ret = *this;
			ret ^= n;
			return ret;
		}

		// in-place bit-wise XOR with the passed in digest.
		digest32& operator^=(digest32 const& n) noexcept
		{
			for (auto const v : boost::combine(m_number, n.m_number))
				boost::get<0>(v) ^= boost::get<1>(v);
			return *this;
		}

		// returns the bit-wise AND of the two digests.
		digest32 operator&(digest32 const& n) const noexcept
		{
			digest32 ret = *this;
			ret &= n;
			return ret;
		}

		// in-place bit-wise AND of the passed in digest
		digest32& operator&=(digest32 const& n) noexcept
		{
			for (auto const v : boost::combine(m_number, n.m_number))
				boost::get<0>(v) &= boost::get<1>(v);
			return *this;
		}

		// in-place bit-wise OR of the two digests.
		digest32& operator|=(digest32 const& n) noexcept
		{
			for (auto const v : boost::combine(m_number, n.m_number))
				boost::get<0>(v) |= boost::get<1>(v);
			return *this;
		}

		// accessors for specific bytes
		std::uint8_t& operator[](index_type i) noexcept
		{
			TORRENT_ASSERT(i < size());
			return reinterpret_cast<std::uint8_t*>(m_number.data())[i];
		}
		std::uint8_t const& operator[](index_type i) const noexcept
		{
			TORRENT_ASSERT(i < size());
			return reinterpret_cast<std::uint8_t const*>(m_number.data())[i];
		}

		using const_iterator = std::uint8_t const*;
		using iterator = std::uint8_t*;

		// start and end iterators for the hash. The value type
		// of these iterators is ``std::uint8_t``.
		const_iterator begin() const
		{ return reinterpret_cast<std::uint8_t const*>(m_number.data()); }
		const_iterator end() const
		{ return reinterpret_cast<std::uint8_t const*>(m_number.data()) + size(); }
		iterator begin()
		{ return reinterpret_cast<std::uint8_t*>(m_number.data()); }
		iterator end()
		{ return reinterpret_cast<std::uint8_t*>(m_number.data()) + size(); }

		// return a copy of the N/8 bytes representing the digest as a std::string.
		// It's still a binary string with N/8 binary characters.
		std::string to_string() const
		{
			return std::string(reinterpret_cast<char const*>(m_number.data()), size());
		}

	private:

		std::array<std::uint32_t, number_size> m_number;

	};

	// This type holds a SHA-1 digest or any other kind of 20 byte
	// sequence. It implements a number of convenience functions, such
	// as bit operations, comparison operators etc.
	//
	// In libtorrent it is primarily used to hold info-hashes, piece-hashes,
	// peer IDs, node IDs etc.
	using sha1_hash = digest32<160>;

#if TORRENT_USE_IOSTREAM

	// print a sha1_hash object to an ostream as 40 hexadecimal digits
	TORRENT_EXPORT std::ostream& operator<<(std::ostream& os, sha1_hash const& peer);

	// read 40 hexadecimal digits from an istream into a sha1_hash
	TORRENT_EXPORT std::istream& operator>>(std::istream& is, sha1_hash& peer);

#endif // TORRENT_USE_IOSTREAM
}

namespace std
{
	template <>
	struct hash<libtorrent::sha1_hash>
	{
		std::size_t operator()(libtorrent::sha1_hash const& k) const
		{
			std::size_t ret;
			// this is OK because sha1_hash is already a hash
			std::memcpy(&ret, k.data(), sizeof(ret));
			return ret;
		}
	};
}

#endif // TORRENT_SHA1_HASH_HPP_INCLUDED