[frankslin]

Inspection of OPENCCDARTS1 files produced by opencc_dict 1.3.2 on 64-bit platforms confirms that the high 32 bits of every unit are zero, so the logical double-array structure is identical to the 32-bit layout. Switching id_type from size_t to uint32_t is therefore safe, makes all future output platform-independent, and keeps the vendored copy as close to upstream darts-clone 0.32h as possible (one typedef change plus one added include). A compatibility layer in DartsDict auto-detects old 64-bit files at load time via a zero-bytes heuristic and reads them without altering the magic string or on-disk format.

Detailed Changes:

• deps/darts-clone-0.32h/include/darts.h:
  • Add #include <cstdint>.
  • Change typedef size_t id_type → typedef uint32_t id_type; all other code is left untouched to stay in sync with upstream.
• src/DartsDict.cpp:
  • Add LegacyUnit64 struct mirroring DoubleArrayUnit bit operations on uint64_t units.
  • Add Legacy64ExactMatch mirroring exactMatchSearch with the correct three-way pos ^= offset ^ c traversal and pos ^ offset leaf access.
  • Add Legacy64PrefixSearch mirroring commonPrefixSearch: continues traversal to maxLen even after the result buffer is full, always returning the true total match count so the caller's re-search path can allocate a correctly-sized buffer and retrieve the true longest match.
  • Add ValidateLegacy64 mirroring DoubleArrayImpl::validate to check root sanity, offset bounds, and leaf value bounds before any traversal.
  • NewFromFile: read an 8-byte probe after the magic; bytes [4..7] all zero → old 64-bit layout (uint64_t dartsSize + 8-byte units, loaded into legacyArray64 and validated); otherwise → 32-bit layout (uint32_t dartsSize + 4-byte units, seek back 4, existing path).
  • MatchPrefix legacy branch: restructure re-search to read maxVal from rematchedResults, not the original stack-allocated results[64] (was out-of-bounds and returned the wrong longest match).
  • SerializeToFile: write dartsSize as uint32_t instead of size_t so output is platform-independent; throw InvalidFormat early when called on a legacy-loaded dict whose doubleArray is nullptr.
• src/DartsDictTest.cpp:
  • Update WriteMalformedDartsFile / CorruptDartsRootUnit / CorruptFirstDartsValue to use uint32_t sizes.
  • Add SerializeAsLegacy64 helper that zero-extends each 32-bit unit to 64 bits to reproduce old build output.
  • Add LoadsLegacy64bitFormat: round-trip correctness via TestDict and an explicit Chinese-key lookup.
  • Add RejectsInvalidLegacy64Root: zeroed root unit must throw.
  • Add Legacy64SerializeToFileThrows: SerializeToFile on a legacy-loaded dict must throw InvalidFormat rather than segfault.
  • Add Legacy64PrefixSearchBeyond64Matches: 65-entry purely-nested dict round-tripped through legacy 64-bit OCD; MatchPrefix must return "v65" (the true longest match), not "v64" as it did when traversal stopped as soon as the result buffer was full.
  • Total DartsDictTest count: 12.