Merge pull request #3 from lunemec/go_generics

Add Go generics support.

README.md

@@ -34,6 +34,58 @@ func main() {
 }
 ```
 
+## Example using generics
+```go
+package main
+
+import (
+    "fmt"
+
+    "github.com/lunemec/as"
+)
+
+func main() {
+	for _, n := range []int{127, 128} {
+		num, err := as.T[int8](n)
+		if err != nil {
+			fmt.Printf("Input invalid: %d, err: %s\n", num, err)
+		} else {
+			fmt.Printf("Input valid: %d\n", num)
+		}
+	}
+	// Output: Input valid: 127
+	// Input invalid: -128, err: 128 (int) overflows int8
+}
+```
+
+## Example slices type conversion with overflow check
+```go
+package main
+
+import (
+    "fmt"
+
+    "github.com/lunemec/as"
+)
+
+func main() {
+	out, err := as.SliceT[int, int8]([]int{127, 128})
+	fmt.Printf("Output: %+v, error: %+v\n", out, err)
+	// Output: Output: [127 0], error: 1 error occurred:
+	// 	* at index [1]: 128 (int) overflows int8
+}
+```
+
+## Other considerations
+Note this checking is not free, check benchmarks for each checked cast.
+
+There are several [Go proposals](https://github.com/golang/go/issues/30613) to have this functionality in the language
+but many of them even predate this library.
+
+
+There are also [libraries](https://github.com/JohnCGriffin/overflow) that
+allow for math operations while checking for overflow at the output.
+
 ## Architecture support
 `As` currently supports these architectures and correctly handles overflows for 64/32 bit numbers:
 * 386

as.go

@@ -4,6 +4,8 @@ package as
 import (
 	"fmt"
 	"reflect"
+
+	"golang.org/x/exp/constraints"
 )
 
 // InvalidTypeError is returned when user supplied invalid type to convert.
@@ -26,6 +28,69 @@ func (e OverflowError) Error() string {
 	return fmt.Sprintf("%d (%T) overflows %s", e.Value, e.Value, e.ToType)
 }
 
+// Number constraint is used for type cast into any number.
+// Only Integers for now until float support is added.
+type Number interface {
+	constraints.Integer
+}
+
+// T is generic function to allow for easier checked
+// type cast from any type to any Number type.
+func T[To Number](v any) (To, error) {
+	var (
+		err error
+		out To
+	)
+	switch any(out).(type) {
+	case int:
+		var n int
+		n, err = Int(v)
+		out = To(n)
+	case int8:
+		var n int8
+		n, err = Int8(v)
+		out = To(n)
+	case int16:
+		var n int16
+		n, err = Int16(v)
+		out = To(n)
+	case int32:
+		var n int32
+		n, err = Int32(v)
+		out = To(n)
+	case int64:
+		var n int64
+		n, err = Int64(v)
+		out = To(n)
+	case uint:
+		var n uint
+		n, err = Uint(v)
+		out = To(n)
+	case uint8:
+		var n uint8
+		n, err = Uint8(v)
+		out = To(n)
+	case uint16:
+		var n uint16
+		n, err = Uint16(v)
+		out = To(n)
+	case uint32:
+		var n uint32
+		n, err = Uint32(v)
+		out = To(n)
+	case uint64:
+		var n uint64
+		n, err = Uint64(v)
+		out = To(n)
+	default:
+		return out, InvalidTypeError{
+			ToType: fmt.Sprintf("%T", out),
+			Value:  v,
+		}
+	}
+	return To(out), err
+}
+
 // From html/template/content.go
 // Copyright 2011 The Go Authors. All rights reserved.
 // indirect returns the value, after dereferencing as many times

as_32b_test.go

@@ -0,0 +1,16 @@
+//go:build 386 || arm
+// +build 386 arm
+
+package as_test
+
+import (
+	"testing"
+)
+
+func TestT32b(t *testing.T) {
+	assertNoError(t, as.T[int], int64(math.MaxInt32))
+	assertNoError(t, as.T[int], int64(math.MinInt32))
+	assertError(t, as.T[int], int64(math.MaxInt64))
+	assertError(t, as.T[int], int64(math.MinInt64))
+	assertError(t, as.T[int], uint64(math.MaxUint64))
+}

as_test.go

@@ -1,8 +1,11 @@
 package as_test
 
 import (
+	"math"
 	"reflect"
 	"testing"
+
+	"github.com/lunemec/as"
 )
 
 // assertError tests if function called with given parameters raises error, if not
@@ -35,3 +38,33 @@ func callfn(fn interface{}, args interface{}) (reflect.Type, interface{}) {
 	err := outValue[1].Interface()
 	return outType, err
 }
+
+func TestT(t *testing.T) {
+	assertNoError(t, as.T[int], int64(math.MaxInt64))
+	assertNoError(t, as.T[int], int64(math.MinInt64))
+	assertError(t, as.T[int], uint64(math.MaxUint64))
+	// uintptr is not supported, will error
+	assertError(t, as.T[uintptr], uint64(math.MaxUint64))
+}
+
+var out int
+
+// BenchmarkT-8   	91144112	        12.90 ns/op	       8 B/op	       0 allocs/op
+func BenchmarkT(b *testing.B) {
+	var t int
+	for n := 0; n < b.N; n++ {
+		t, _ = as.T[int](n)
+	}
+
+	out = t
+}
+
+// BenchmarkInt-8   	108703077	        10.98 ns/op	       8 B/op	       0 allocs/op
+func BenchmarkInt(b *testing.B) {
+	var t int
+	for n := 0; n < b.N; n++ {
+		t, _ = as.Int(n)
+	}
+
+	out = t
+}

example_test.go

@@ -18,3 +18,29 @@ func Example() {
 	// Output: Input valid: 127
 	// Input invalid: -128, err: 128 (int) overflows int8
 }
+
+func ExampleT() {
+	for _, n := range []int{127, 128} {
+		num, err := as.T[int8](n)
+		if err != nil {
+			fmt.Printf("Input invalid: %d, err: %s\n", num, err)
+		} else {
+			fmt.Printf("Input valid: %d\n", num)
+		}
+	}
+	// Output: Input valid: 127
+	// Input invalid: -128, err: 128 (int) overflows int8
+}
+
+func ExampleSliceT() {
+	out, err := as.SliceT[int, int8]([]int{127, 128})
+	fmt.Printf("Output: %+v, error: %+v\n", out, err)
+	// Output: Output: [127 0], error: 1 error occurred:
+	// 	* at index [1]: 128 (int) overflows int8
+}
+
+func ExampleSliceTUnchecked() {
+	out := as.SliceTUnchecked[int, int8]([]int{127, 128})
+	fmt.Printf("Output: %+v\n", out)
+	// Output: Output: [127 -128]
+}

go.mod

@@ -1,3 +1,17 @@
 module github.com/lunemec/as
 
-go 1.12
+go 1.19
+
+require (
+	github.com/hashicorp/go-multierror v1.1.1
+	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.8.1
+	golang.org/x/exp v0.0.0-20221031165847-c99f073a8326
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/hashicorp/errwrap v1.0.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,25 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/hashicorp/errwrap v1.0.0 h1:hLrqtEDnRye3+sgx6z4qVLNuviH3MR5aQ0ykNJa/UYA=
+github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
+github.com/hashicorp/go-multierror v1.1.1 h1:H5DkEtf6CXdFp0N0Em5UCwQpXMWke8IA0+lD48awMYo=
+github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9/fmwbPZ6JB6eMoM=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+golang.org/x/exp v0.0.0-20221031165847-c99f073a8326 h1:QfTh0HpN6hlw6D3vu8DAwC8pBIwikq0AI1evdm+FksE=
+golang.org/x/exp v0.0.0-20221031165847-c99f073a8326/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

int16_32b_test.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as_test

int16_64b_test.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as_test
@@ -42,3 +43,26 @@ func TestInt16(t *testing.T) {
 	assertNoError(t, as.Int16, uint(0))
 	assertError(t, as.Int16, uint(math.MaxUint64))
 }
+
+var out16 int16
+
+// BenchmarkAs16-8   	36798218	        32.61 ns/op	      39 B/op	       1 allocs/op
+
+func BenchmarkAs16(b *testing.B) {
+	var t int16
+	for n := 0; n < b.N; n++ {
+		t, _ = as.Int16(n)
+	}
+
+	out16 = t
+}
+
+// BenchmarkInt16-8   	1000000000	         0.3211 ns/op	       0 B/op	       0 allocs/op
+func BenchmarkInt16(b *testing.B) {
+	var t int16
+	for n := 0; n < b.N; n++ {
+		t = int16(n)
+	}
+
+	out16 = t
+}

int32_32b_test.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as_test

int32_64b_test.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as_test

int64_32b.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as

int64_32b_test.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as_test

int64_64b.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as

int64_64b_test.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as_test

int8_32b_test.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as_test

int8_64b_test.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as_test

int_32b_test.go

@@ -1,3 +1,4 @@
+//go:build 386 || arm
 // +build 386 arm
 
 package as_test

int_64b.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as

int_64b_test.go

@@ -1,3 +1,4 @@
+//go:build amd64 || arm64
 // +build amd64 arm64
 
 package as_test