New APIs

XXHash3 (XxHash3Native):

• 64-bit and 128-bit one-shot hashing
• Streaming (incremental) hashing with XxHash3Hasher / XxHash3Hasher128
• Seeded variants for all methods

XXHash64 (XxHash64Hasher):

• One-shot and streaming hashing
• Both native (FFM) and pure Java (VarHandle) implementations
• Automatically selects native when available

Performance Summary

Benchmarked on Apple M1 (aarch64), throughput in ops/ms (higher is better):

Key observations:

• XXHash3 is ~2.5x faster than XXHash64 for large inputs (1KB+)
• XXHash3 64-bit has minimal FFM overhead and is faster at all sizes
• XXHash3 128-bit has FFM struct-return overhead at small inputs (<512 bytes), but converges with 64-bit at larger sizes (8KB+)
• For 128-bit hashes on small inputs, the overhead is the cost of the simpler API—no known workarounds exist
• XXHash64 native, Java, and legacy Unsafe implementations all have equivalent performance (not shown)

Implementation Notes

• Internal Unsafe-based XXHash64 in zstd package retained for Zstd Java implementation compatibility