# `EEVM.Precompiles.Blake2F`
[🔗](https://github.com/mw2000/eevm/blob/v0.1.0/lib/eevm/precompiles/blake2f.ex#L1)

Blake2f precompile — address `0x09` (EIP-152).

Implements the Blake2b compression function `F`.

### Gas schedule

Gas cost is exactly the `rounds` field from input bytes `0..3` (uint32,
big-endian).

### Input format

Input must be **exactly 213 bytes**:

- bytes `0..3`   — `rounds` (`uint32`, big-endian)
- bytes `4..67`  — `h` (8 × 64-bit words, little-endian)
- bytes `68..195` — `m` (16 × 64-bit words, little-endian)
- bytes `196..211` — `t` (2 × 64-bit words, little-endian)
- byte `212`     — `f` final block flag (`0` or `1` only)

Output is 64 bytes: the 8 updated state words in little-endian.

# `execute`

```elixir
@spec execute(binary(), non_neg_integer()) ::
  {:ok, binary(), non_neg_integer()} | {:error, :invalid_input | :out_of_gas}
```

Executes the Blake2f precompile.

Returns `{:ok, output, gas_used}` on success where `output` is 64 bytes and
`gas_used == rounds`.

Returns:
- `{:error, :invalid_input}` if input length is not 213 bytes or final flag is
  not `0` or `1`
- `{:error, :out_of_gas}` if `gas_limit < rounds`

---

*Consult [api-reference.md](api-reference.md) for complete listing*