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88794a1ea9
Bulk documentation pass covering 702 C++ source files in src/libxrpl, src/xrpld, and include/xrpl. Adds class, function, parameter, and invariant docs per docs/DOCUMENTATION_STANDARDS.md. Squashed from the original three-part series (part 1 / part 2 / part 3) to avoid merge-conflict noise when rebasing the work onto current develop.
42 lines
1.9 KiB
C++
42 lines
1.9 KiB
C++
#pragma once
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#include <xrpl/basics/base_uint.h>
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#include <string_view>
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namespace xrpl::nft {
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/** Bitmask that separates the owner-identity region of an NFToken page key
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* from its token-ordering region.
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*
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* Every `NFTokenID` encodes the issuing `AccountID` in its high 160 bits and
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* token-specific data (taxon + sequence) in its low 96 bits. Ledger page keys
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* for `ltNFTOKEN_PAGE` SLEs fuse those two regions into a single `uint256`.
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* `kPAGE_MASK` — 96 bits of `1` in the least-significant position, 160 bits
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* of `0` above — is the canonical tool for splitting them:
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*
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* - `token & kPAGE_MASK` → low 96 bits (token-ordering portion)
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* - `key & ~kPAGE_MASK` → high 160 bits (owner AccountID portion)
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*
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* Typical uses:
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* - **Page key construction** (`Indexes.cpp`): `(k.key & ~kPAGE_MASK) + (token & kPAGE_MASK)`
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* - **Max-page sentinel** (`keylet::nftpage_max`): initialize the full `uint256`
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* to `kPAGE_MASK` (all-ones in the low 96 bits), then overwrite the high
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* bytes with the owner's `AccountID` to form the lexicographically largest
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* page key for that owner.
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* - **RPC pagination** (`AccountNFTs.cpp`, `AccountObjects.cpp`): validate
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* that a client-supplied marker or `entryIndex` belongs to the correct page.
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* - **Sort-order comparisons** (`NFTokenHelpers.cpp`): tokens with different
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* low-96-bit values belong to different pages.
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* - **Invariant checks** (`NFTInvariant.cpp`): verify that a page being deleted
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* carries the all-ones sentinel in its low 96 bits.
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*
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* @note The value is `constexpr`, resolved entirely at compile time via
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* `base_uint`'s `std::string_view` constructor, so including this header
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* has no runtime cost and raises no ODR concerns.
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*/
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uint256 constexpr kPAGE_MASK(
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std::string_view("0000000000000000000000000000000000000000ffffffffffffffffffffffff"));
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} // namespace xrpl::nft
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