Convert function, minor improvements (#1)

* Convert function, minor improvements

* fix readme

* Should probably just retain the original license without adding all contributors

Author: Alexandr Stefurishin

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2023 Antonio Cheong
+Copyright (c) 2024 John C. Griffin
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -25,31 +25,20 @@ Function signatures: https://pkg.go.dev/github.com/g-utils/overflow
 ```go
 package overflow
 
-type number interface {
+type Int interface {
 	int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
 }
 
-func Add[T number](a, b T) (T, bool)
-func Sub[T number](a, b T) (T, bool)
-func Mul[T number](a, b T) (T, bool)
-func Div[T number](a, b T) (T, bool)
-func Quotient[T number](a, b T) (T, T, bool)
+func Add[T Int](a, b T) (T, bool)
+func Sub[T Int](a, b T) (T, bool)
+func Mul[T Int](a, b T) (T, bool)
+func Div[T Int](a, b T) (T, bool)
+func Quotient[T Int](a, b T) (T, T, bool)
+func Convert[T Int, U Int](a T) (U, bool)
 ```
 
-
-
 # Copyright / License
 
 This is a fork of https://github.com/JohnCGriffin/overflow. Generics were added to Golang in Go 1.18 (2022) and is used in place of build time code generators.
 
 Tests for unsigned integers have also been added from github.com/rwxe/overflow in case my logic is incorrect.
-
-```
-Copyright (c) 2017 John C. Griffin,
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-```

overflow.go

@@ -1,26 +1,26 @@
 package overflow
 
-type number interface {
+type Int interface {
 	int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64
 }
 
-func Add[T number](a, b T) (T, bool) {
+func Add[T Int](a, b T) (T, bool) {
 	c := a + b
 	if (c > a) == (b > 0) {
 		return c, true
 	}
 	return c, false
 }
 
-func Sub[T number](a, b T) (T, bool) {
+func Sub[T Int](a, b T) (T, bool) {
 	c := a - b
 	if (c < a) == (b > 0) {
 		return c, true
 	}
 	return c, false
 }
 
-func Mul[T number](a, b T) (T, bool) {
+func Mul[T Int](a, b T) (T, bool) {
 	if a == 0 || b == 0 {
 		return 0, true
 	}
@@ -32,15 +32,25 @@ func Mul[T number](a, b T) (T, bool) {
 	}
 	return c, false
 }
-func Div[T number](a, b T) (T, bool) {
+
+func Div[T Int](a, b T) (T, bool) {
 	q, _, ok := Quotient(a, b)
 	return q, ok
 }
-func Quotient[T number](a, b T) (T, T, bool) {
+
+func Quotient[T Int](a, b T) (T, T, bool) {
 	if b == 0 {
 		return 0, 0, false
 	}
 	c := a / b
-	status := (c < 0) == ((a < 0) != (b < 0))
-	return c, a % b, status
+	ok := (c < 0) == ((a < 0) != (b < 0))
+	return c, a % b, ok
+}
+
+func Convert[T Int, U Int](a T) (U, bool) {
+	b := U(a)
+	if T(b) == a && (a < 0) == (b < 0) {
+		return b, true
+	}
+	return b, false
 }

overflow_test.go

@@ -3,8 +3,9 @@ package overflow_test
 import (
 	"math"
 	"testing"
+
+	"github.com/g-utils/overflow"
 )
-import "github.com/g-utils/overflow"
 
 // sample all possibilities of 8 bit numbers
 // by checking against 64 bit numbers
@@ -287,3 +288,152 @@ func TestAlgorithmsUintImpl2(t *testing.T) {
 	}
 
 }
+
+func TestConvert(t *testing.T) {
+	// int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64
+
+	t.Run("positive: uint64->unsigned", func(t *testing.T) {
+		t.Parallel()
+		for i := uint64(0); i <= math.MaxUint8; i++ {
+			testConvert4[uint64, uint64, uint32, uint16, uint8](t, i, true)
+		}
+		testConvert3[uint64, uint64, uint32, uint16](t, math.MaxUint16-1, true)
+		testConvert3[uint64, uint64, uint32, uint16](t, math.MaxUint16, true)
+		testConvert2[uint64, uint64, uint32](t, math.MaxUint32-1, true)
+		testConvert2[uint64, uint64, uint32](t, math.MaxUint32, true)
+		testConvert1[uint64, uint64](t, math.MaxUint64-1, true)
+		testConvert1[uint64, uint64](t, math.MaxUint64, true)
+	})
+
+	t.Run("negative: uint64->unsigned", func(t *testing.T) {
+		for i := uint64(math.MaxUint32 + 1); i <= uint64(math.MaxUint32+math.MaxUint8+1); i++ {
+			testConvert3[uint64, uint32, uint16, uint8](t, i, false)
+		}
+		testConvert2[uint64, uint16, uint8](t, math.MaxUint16+1, false)
+		testConvert1[uint64, uint8](t, math.MaxUint8+1, false)
+	})
+
+	t.Run("positive: uint64->signed", func(t *testing.T) {
+		for i := uint64(0); i <= math.MaxInt8; i++ {
+			testConvert4[uint64, int64, int32, int16, int8](t, i, true)
+		}
+		testConvert3[uint64, int64, int32, int16](t, math.MaxInt16-1, true)
+		testConvert3[uint64, int64, int32, int16](t, math.MaxInt16, true)
+		testConvert2[uint64, int64, int32](t, math.MaxInt32-1, true)
+		testConvert2[uint64, int64, int32](t, math.MaxInt32, true)
+		testConvert1[uint64, int64](t, math.MaxInt64-1, true)
+		testConvert1[uint64, int64](t, math.MaxInt64, true)
+	})
+
+	t.Run("negative: uint64->signed", func(t *testing.T) {
+		for i := uint64(math.MaxInt64 + 1); i <= uint64(math.MaxInt64+math.MaxUint8+1); i++ {
+			testConvert4[uint64, int64, int32, int16, int8](t, i, false)
+		}
+		testConvert4[uint64, int64, int32, int16, int8](t, math.MaxUint64, false)
+		testConvert4[uint64, int64, int32, int16, int8](t, math.MaxUint64-1, false)
+		testConvert3[uint64, int32, int16, int8](t, math.MaxInt32+1, false)
+		testConvert2[uint64, int16, int8](t, math.MaxInt16+1, false)
+		testConvert1[uint64, int8](t, math.MaxInt8+1, false)
+	})
+
+	t.Run("positive: int64->signed", func(t *testing.T) {
+		for i := int64(math.MinInt8); i <= math.MaxInt8; i++ {
+			testConvert4[int64, int64, int32, int16, int8](t, i, true)
+		}
+		testConvert3[int64, int64, int32, int16](t, math.MinInt16, true)
+		testConvert3[int64, int64, int32, int16](t, math.MinInt16+1, true)
+		testConvert3[int64, int64, int32, int16](t, math.MaxInt16-1, true)
+		testConvert3[int64, int64, int32, int16](t, math.MaxInt16, true)
+		testConvert2[int64, int64, int32](t, math.MinInt32, true)
+		testConvert2[int64, int64, int32](t, math.MinInt32+1, true)
+		testConvert2[int64, int64, int32](t, math.MaxInt32-1, true)
+		testConvert2[int64, int64, int32](t, math.MaxInt32, true)
+		testConvert1[int64, int64](t, math.MinInt64, true)
+		testConvert1[int64, int64](t, math.MinInt64+1, true)
+		testConvert1[int64, int64](t, math.MaxInt64-1, true)
+		testConvert1[int64, int64](t, math.MaxInt64, true)
+	})
+
+	t.Run("negative: int64->signed", func(t *testing.T) {
+		for i := int64(math.MaxInt32 + 1); i <= int64(math.MaxInt32+math.MaxInt8+1); i++ {
+			testConvert3[int64, int32, int16, int8](t, i, false)
+		}
+		testConvert2[int64, int16, int8](t, math.MaxInt16+1, false)
+		testConvert1[int64, int8](t, math.MaxInt8+1, false)
+	})
+
+	t.Run("positive: int64->unsigned", func(t *testing.T) {
+		for i := int64(0); i <= math.MaxUint8; i++ {
+			testConvert4[int64, uint64, uint32, uint16, uint8](t, i, true)
+		}
+		testConvert3[int64, uint64, uint32, uint16](t, math.MaxUint16-1, true)
+		testConvert3[int64, uint64, uint32, uint16](t, math.MaxUint16, true)
+		testConvert2[int64, uint64, uint32](t, math.MaxUint32-1, true)
+		testConvert2[int64, uint64, uint32](t, math.MaxUint32, true)
+		testConvert1[int64, uint64](t, math.MaxInt64-1, true)
+		testConvert1[int64, uint64](t, math.MaxInt64, true)
+	})
+
+	t.Run("negative: int64->unsigned", func(t *testing.T) {
+		testConvert4[int64, uint64, uint32, uint16, uint8](t, math.MinInt64, false)
+		testConvert4[int64, uint64, uint32, uint16, uint8](t, math.MinInt64+1, false)
+		testConvert4[int64, uint64, uint32, uint16, uint8](t, -1, false)
+		testConvert3[int64, uint32, uint16, uint8](t, math.MaxUint32+1, false)
+		testConvert2[int64, uint16, int8](t, math.MaxUint16+1, false)
+		for i := int64(math.MaxUint8 + 1); i <= math.MaxUint8+math.MaxUint8+2; i++ {
+			testConvert1[int64, uint8](t, i, false)
+		}
+	})
+
+	t.Run("negative: int32|16|8->uint64", func(t *testing.T) {
+		testConvert1[int32, uint64](t, -1, false)
+		testConvert1[int32, uint64](t, math.MinInt32, false)
+		testConvert1[int16, uint64](t, -1, false)
+		testConvert1[int16, uint64](t, math.MinInt16, false)
+		testConvert1[int8, uint64](t, -1, false)
+		testConvert1[int8, uint64](t, math.MinInt8, false)
+	})
+
+	// already covered by reverse conversion checks:
+	// - "positive [u]int32|16|8 -> [u]int64"
+
+	// impossible cases:
+	// "negative uint32|16|8 -> [u]int64"
+	// "negative [u]int32|16|8 -> int64"
+}
+
+func testConvert4[T overflow.Int, U1 overflow.Int, U2 overflow.Int, U3 overflow.Int, U4 overflow.Int](t *testing.T, a T, expectOk bool) {
+	t.Helper()
+	testConvert2[T, U1, U2](t, a, expectOk)
+	testConvert2[T, U3, U4](t, a, expectOk)
+}
+
+func testConvert3[T overflow.Int, U1 overflow.Int, U2 overflow.Int, U3 overflow.Int](t *testing.T, a T, expectOk bool) {
+	t.Helper()
+	testConvert1[T, U1](t, a, expectOk)
+	testConvert1[T, U2](t, a, expectOk)
+	testConvert1[T, U3](t, a, expectOk)
+}
+
+func testConvert2[T overflow.Int, U1 overflow.Int, U2 overflow.Int](t *testing.T, a T, expectOk bool) {
+	t.Helper()
+	testConvert1[T, U1](t, a, expectOk)
+	testConvert1[T, U2](t, a, expectOk)
+}
+
+func testConvert1[T overflow.Int, U overflow.Int](t *testing.T, a T, expectOk bool) {
+	t.Helper()
+	if b, ok := overflow.Convert[T, U](a); expectOk && !ok {
+		t.Error("expected ok, got overflow: ", b)
+	} else if !expectOk && ok {
+		t.Error("expected overflow, got ok: ", b)
+	} else if a2, ok2 := overflow.Convert[U, T](b); ok && !ok2 {
+		t.Error("expected ok, got ok, but reverse conversion overflowed: ", a2)
+	}
+}
+
+func BenchmarkConvert(b *testing.B) {
+	for i := int64(-1_000_000_000); i < 1_000_000_000; i++ {
+		_, _ = overflow.Convert[int64, uint64](i)
+	}
+}