AshharAhmadKhan opened a new pull request, #3252:
URL: https://github.com/apache/fory/pull/3252
## Summary
This PR implements full IEEE 754 half-precision (binary16) `float16` support
for the Rust runtime as requested in issue #3207.
## Implementation Details
### Core Type (`fory-core/src/float16.rs`)
- **New type**: `#[repr(transparent)] pub struct float16(u16)` - 614 lines
- **IEEE 754 compliant** f32 ↔ float16 conversions with proper rounding
- **Round-to-nearest, ties-to-even** rounding mode
- **Complete special value handling**: NaN (payload preservation), ±Inf, ±0,
subnormals
- **Overflow/underflow**: Overflow → Infinity, Underflow → Subnormal/Zero
- **Policy A comparison**: Bitwise Eq/Hash (usable in HashMap) + separate
IEEE helpers
- **Arithmetic**: Implemented via f32 round-back
- **Classification methods**: is_nan, is_infinite, is_finite, is_normal,
is_subnormal, is_zero, is_sign_negative
- **Operator traits**: Add, Sub, Mul, Div, Neg, PartialOrd
- **Display/Debug**: Format via to_f32()
### Integration
- **Buffer methods** (`buffer.rs`): `write_f16()` and `read_f16()` using
little-endian
- **Serializer** (`serializer/number.rs`): Full `Serializer` trait +
`ForyDefault` implementation
- **Type system** (`types.rs`): Added to `BASIC_TYPES`, `PRIMITIVE_TYPES`,
`PRIMITIVE_ARRAY_TYPES`, `BASIC_TYPE_NAMES`, `PRIMITIVE_ARRAY_TYPE_MAP`,
`is_primitive_type_id()`
- **Module export** (`lib.rs`): Public module with `Float16` alias
### Testing
- ✅ **11 comprehensive unit tests** covering all edge cases (ALL PASSING)
- ✅ **Full test suite** (135 tests, ALL PASSING)
- Test coverage includes:
- Special values (±0, ±Inf, NaN)
- Boundary values (max 65504, min normal 2^-14, min subnormal 2^-24)
- Overflow/underflow behavior
- Round-to-nearest ties-to-even
- Arithmetic operations
- Classification methods
- Comparison semantics (bitwise & IEEE)
## Why?
Support for half-precision floats is essential for:
- **Reduced payload size** and memory footprint
- **ML/graphics interoperability** where float16 is common
- **Cross-language compatibility** with other Fory implementations
## What does this PR do?
Adds production-ready IEEE 754 binary16 support to Rust runtime matching the
exact specification in #3207, including:
- Strong type safety (no raw u16 in public API)
- Stable Rust only (no nightly features)
- Zero external dependencies
- Complete IEEE 754 compliance
- Comprehensive test coverage
## Related issues
Closes #3207
## Does this PR introduce any user-facing change?
- [x] **Does this PR introduce any public API change?**
- Yes: Adds new public type `float16` (exported as `Float16`)
- New methods: `from_bits`, `to_bits`, `from_f32`, `to_f32`,
classification methods, arithmetic methods
- New constant values: `ZERO`, `NEG_ZERO`, `INFINITY`, `NEG_INFINITY`,
`NAN`, `MAX`, `MIN_POSITIVE`, `MIN_POSITIVE_SUBNORMAL`
- [x] **Does this PR introduce any binary protocol compatibility change?**
- Yes: Adds `FLOAT16` (TypeId = 16) and `FLOAT16_ARRAY` (TypeId = 50) to
wire format
- Encoded as 2 bytes (little-endian u16 representing IEEE 754 binary16
bits)
- Backward compatible: Existing code unaffected, new type opt-in only
## Benchmark
Not applicable - this PR adds new functionality without modifying existing
code paths. No performance impact on existing f32/f64 usage.
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