Enable fixed point u128 (#6214)

* Add fixed u128.

* remove move

* Change sat_from_integer impl.

* checked_pow is always positive

* Revert.

* rename fixed file

* Rename to FixedI

* rename fixed file

* Add newline.

* Use Multiplier in impls.

* Renames negate() to saturating_negate().

* Uncomment test.

* Add Signed to macro.

* Add some tests for Saturating trait.

substrate/primitives/arithmetic/fuzzer/src/fixed_point.rs

@@ -0,0 +1,82 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! # Running
+//! Running this fuzzer can be done with `cargo hfuzz run fixed_point`. `honggfuzz` CLI options can
+//! be used by setting `HFUZZ_RUN_ARGS`, such as `-n 4` to use 4 threads.
+//!
+//! # Debugging a panic
+//! Once a panic is found, it can be debugged with
+//! `cargo hfuzz run-debug fixed_point hfuzz_workspace/fixed_point/*.fuzz`.
+//!
+//! # More information
+//! More information about `honggfuzz` can be found
+//! [here](https://docs.rs/honggfuzz/).
+
+use honggfuzz::fuzz;
+use sp_arithmetic::{FixedPointNumber, FixedI64, traits::Saturating};
+
+fn main() {
+	loop {
+		fuzz!(|data: (i32, i32)| {
+			let x: i128 = data.0.into();
+			let y: i128 = data.1.into();
+
+			// Check `from_rational` and division are consistent.
+			if y != 0 {
+				let f1 = FixedI64::saturating_from_integer(x) / FixedI64::saturating_from_integer(y);
+				let f2 = FixedI64::saturating_from_rational(x, y);
+				assert_eq!(f1.into_inner(), f2.into_inner());
+			}
+
+			// Check `saturating_mul`.
+			let a = FixedI64::saturating_from_rational(2, 5);
+			let b = a.saturating_mul(FixedI64::saturating_from_integer(x));
+			let n = b.into_inner() as i128;
+			let m = 2i128 * x * FixedI64::accuracy() as i128 / 5i128;
+			assert_eq!(n, m);
+
+			// Check `saturating_mul` and division are inverse.
+			if x != 0 {
+				assert_eq!(a, b / FixedI64::saturating_from_integer(x));
+			}
+
+			// Check `reciprocal`.
+			let r = a.reciprocal().unwrap().reciprocal().unwrap();
+			assert_eq!(a, r);
+
+			// Check addition.
+			let a = FixedI64::saturating_from_integer(x);
+			let b = FixedI64::saturating_from_integer(y);
+			let c = FixedI64::saturating_from_integer(x.saturating_add(y));
+			assert_eq!(a.saturating_add(b), c);
+
+			// Check substraction.
+			let a = FixedI64::saturating_from_integer(x);
+			let b = FixedI64::saturating_from_integer(y);
+			let c = FixedI64::saturating_from_integer(x.saturating_sub(y));
+			assert_eq!(a.saturating_sub(b), c);
+
+			// Check `saturating_mul_acc_int`.
+			let a = FixedI64::saturating_from_rational(2, 5);
+			let b = a.saturating_mul_acc_int(x);
+			let xx = FixedI64::saturating_from_integer(x);
+			let d = a.saturating_mul(xx).saturating_add(xx).into_inner() as i128 / FixedI64::accuracy() as i128;
+			assert_eq!(b, d);
+		});
+	}
+}