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1d42c4f6de
Per XLS-0095, we are taking steps to rename ripple(d) to xrpl(d). This change specifically removes all copyright notices referencing Ripple, XRPLF, and certain affiliated contributors upon mutual agreement, so the notice in the LICENSE.md file applies throughout. Copyright notices referencing external contributions remain as-is. Duplicate verbiage is also removed.
110 lines
2.9 KiB
C++
110 lines
2.9 KiB
C++
#ifndef XRPL_PROTOCOL_NFT_H_INCLUDED
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#define XRPL_PROTOCOL_NFT_H_INCLUDED
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#include <xrpl/basics/base_uint.h>
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#include <xrpl/basics/tagged_integer.h>
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#include <xrpl/protocol/AccountID.h>
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#include <boost/endian/conversion.hpp>
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#include <cstdint>
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#include <cstring>
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namespace ripple {
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namespace nft {
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// Separate taxons from regular integers.
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struct TaxonTag
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{
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};
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using Taxon = tagged_integer<std::uint32_t, TaxonTag>;
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inline Taxon
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toTaxon(std::uint32_t i)
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{
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return static_cast<Taxon>(i);
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}
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inline std::uint32_t
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toUInt32(Taxon t)
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{
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return static_cast<std::uint32_t>(t);
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}
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constexpr std::uint16_t const flagBurnable = 0x0001;
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constexpr std::uint16_t const flagOnlyXRP = 0x0002;
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constexpr std::uint16_t const flagCreateTrustLines = 0x0004;
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constexpr std::uint16_t const flagTransferable = 0x0008;
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constexpr std::uint16_t const flagMutable = 0x0010;
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inline std::uint16_t
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getFlags(uint256 const& id)
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{
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std::uint16_t flags;
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memcpy(&flags, id.begin(), 2);
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return boost::endian::big_to_native(flags);
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}
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inline std::uint16_t
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getTransferFee(uint256 const& id)
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{
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std::uint16_t fee;
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memcpy(&fee, id.begin() + 2, 2);
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return boost::endian::big_to_native(fee);
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}
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inline std::uint32_t
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getSerial(uint256 const& id)
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{
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std::uint32_t seq;
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memcpy(&seq, id.begin() + 28, 4);
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return boost::endian::big_to_native(seq);
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}
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inline Taxon
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cipheredTaxon(std::uint32_t tokenSeq, Taxon taxon)
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{
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// An issuer may issue several NFTs with the same taxon; to ensure that NFTs
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// are spread across multiple pages we lightly mix the taxon up by using the
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// sequence (which is not under the issuer's direct control) as the seed for
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// a simple linear congruential generator.
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//
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// From the Hull-Dobell theorem we know that f(x)=(m*x+c) mod n will yield a
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// permutation of [0, n) when n is a power of 2 if m is congruent to 1 mod 4
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// and c is odd.
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//
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// Here we use m = 384160001 and c = 2459. The modulo is implicit because we
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// use 2^32 for n and the arithmetic gives it to us for "free".
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//
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// Note that the scramble value we calculate is not cryptographically secure
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// but that's fine since all we're looking for is some dispersion.
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//
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// **IMPORTANT** Changing these numbers would be a breaking change requiring
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// an amendment along with a way to distinguish token IDs that
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// were generated with the old code.
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return taxon ^ toTaxon(((384160001 * tokenSeq) + 2459));
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}
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inline Taxon
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getTaxon(uint256 const& id)
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{
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std::uint32_t taxon;
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memcpy(&taxon, id.begin() + 24, 4);
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taxon = boost::endian::big_to_native(taxon);
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// The taxon cipher is just an XOR, so it is reversible by applying the
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// XOR a second time.
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return cipheredTaxon(getSerial(id), toTaxon(taxon));
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}
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inline AccountID
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getIssuer(uint256 const& id)
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{
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return AccountID::fromVoid(id.data() + 4);
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}
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} // namespace nft
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} // namespace ripple
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#endif
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