feat: add dereferencing with default value

This allows you to extract a value from a pointer by setting values for
nil pointers instead of getting the default value.

LICENSE

@@ -1,6 +1,6 @@
 BSD 3-Clause License
 
-Copyright © 2019 Vasiliy Vasilyuk <xorcare@gmail.com>
+Copyright © 2019-2020 Vasiliy Vasilyuk <xorcare@gmail.com>
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

derefed/derefed.go

@@ -0,0 +1,180 @@
+// Copyright © 2019-2020 Vasiliy Vasilyuk. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package derefed contains helper routines for simplifying the getting of
+// optional fields of basic type. This allows you to get the value from the
+// pointer even if it is nil, and if the pointer is nil it returns a value of
+// second parameter.
+package derefed
+
+// Bool dereference a pointer bool from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Bool(v *bool, def bool) bool {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Byte dereference a pointer byte from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Byte(v *byte, def byte) byte {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Complex64 dereference a pointer complex64 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Complex64(v *complex64, def complex64) complex64 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Complex128 dereference a pointer complex128 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Complex128(v *complex128, def complex128) complex128 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Float32 dereference a pointer float32 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Float32(v *float32, def float32) float32 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Float64 dereference a pointer float64 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Float64(v *float64, def float64) float64 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Int dereference a pointer int from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Int(v *int, def int) int {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Int8 dereference a pointer int8 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Int8(v *int8, def int8) int8 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Int16 dereference a pointer int16 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Int16(v *int16, def int16) int16 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Int32 dereference a pointer int32 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Int32(v *int32, def int32) int32 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Int64 dereference a pointer int64 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Int64(v *int64, def int64) int64 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Rune dereference a pointer rune from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Rune(v *rune, def rune) rune {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// String dereference a pointer string from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func String(v *string, def string) string {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uint dereference a pointer uint from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uint(v *uint, def uint) uint {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uint8 dereference a pointer uint8 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uint8(v *uint8, def uint8) uint8 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uint16 dereference a pointer uint16 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uint16(v *uint16, def uint16) uint16 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uint32 dereference a pointer uint32 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uint32(v *uint32, def uint32) uint32 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uint64 dereference a pointer uint64 from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uint64(v *uint64, def uint64) uint64 {
+	if v == nil {
+		return def
+	}
+	return *v
+}
+
+// Uintptr dereference a pointer uintptr from the structure of a literal or
+// variable, and if the pointer is nil it returns a value of second parameter.
+func Uintptr(v *uintptr, def uintptr) uintptr {
+	if v == nil {
+		return def
+	}
+	return *v
+}

derefed/derefed_test.go

@@ -0,0 +1,176 @@
+// Copyright © 2019-2020 Vasiliy Vasilyuk. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package derefed
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+func equal(t testing.TB, expected, actual interface{}) {
+	if h, ok := t.(interface{ Helper() }); ok {
+		h.Helper()
+	}
+
+	t.Logf("expected: %q (%T), actual: %q (%T)", fmt.Sprint(expected), expected, fmt.Sprint(actual), actual)
+
+	if !reflect.DeepEqual(expected, actual) {
+		t.Fatalf("values obtained are not equal, expected: %v, actual: %v", expected, actual)
+	}
+}
+
+var _bool = true
+var _byte = byte(1)
+var _complex64 = complex64(1.1)
+var _complex128 = complex128(1.1)
+var _float32 = float32(1.1)
+var _float64 = float64(1.1)
+var _int = int(1)
+var _int8 = int8(8)
+var _int16 = int16(16)
+var _int32 = int32(32)
+var _int64 = int64(64)
+var _rune = rune(1)
+var _string = "derefed"
+var _uint = uint(1)
+var _uint8 = uint8(8)
+var _uint16 = uint16(16)
+var _uint32 = uint32(32)
+var _uint64 = uint64(64)
+var _uintptr = uintptr(64)
+
+func TestBool(t *testing.T) {
+	equal(t, false, Bool(nil, false))
+	equal(t, true, Bool(nil, true))
+	equal(t, false, Bool(new(bool), true))
+	equal(t, true, Bool(&_bool, false))
+}
+
+func TestByte(t *testing.T) {
+	equal(t, byte(0), Byte(nil, 0))
+	equal(t, byte(1), Byte(nil, 1))
+	equal(t, byte(0), Byte(new(byte), 1))
+	equal(t, byte(1), Byte(&_byte, 2))
+}
+
+func TestComplex64(t *testing.T) {
+	equal(t, complex64(0), Complex64(nil, 0))
+	equal(t, complex64(1.1), Complex64(nil, 1.1))
+	equal(t, complex64(0), Complex64(new(complex64), 2.2))
+	equal(t, complex64(1.1), Complex64(&_complex64, 2.2))
+}
+
+func TestComplex128(t *testing.T) {
+	equal(t, complex128(0), Complex128(nil, 0))
+	equal(t, complex128(1.1), Complex128(nil, 1.1))
+	equal(t, complex128(0), Complex128(new(complex128), 1.1))
+	equal(t, complex128(1.1), Complex128(&_complex128, 2.2))
+}
+
+func TestFloat32(t *testing.T) {
+	equal(t, float32(0), Float32(nil, 0))
+	equal(t, float32(1.1), Float32(nil, 1.1))
+	equal(t, float32(0), Float32(new(float32), 1.1))
+	equal(t, float32(1.1), Float32(&_float32, 2.2))
+}
+
+func TestFloat64(t *testing.T) {
+	equal(t, float64(0), Float64(nil, 0))
+	equal(t, float64(1.1), Float64(nil, 1.1))
+	equal(t, float64(0), Float64(new(float64), 1.1))
+	equal(t, float64(1.1), Float64(&_float64, 2.2))
+}
+
+func TestInt(t *testing.T) {
+	equal(t, 0, Int(nil, 0))
+	equal(t, 1, Int(nil, 1))
+	equal(t, 0, Int(new(int), 1))
+	equal(t, 1, Int(&_int, 2))
+}
+
+func TestInt8(t *testing.T) {
+	equal(t, int8(0), Int8(nil, 0))
+	equal(t, int8(1), Int8(nil, 1))
+	equal(t, int8(0), Int8(new(int8), 1))
+	equal(t, int8(8), Int8(&_int8, 2))
+}
+
+func TestInt16(t *testing.T) {
+	equal(t, int16(0), Int16(nil, 0))
+	equal(t, int16(1), Int16(nil, 1))
+	equal(t, int16(0), Int16(new(int16), 1))
+	equal(t, int16(16), Int16(&_int16, 2))
+}
+
+func TestInt32(t *testing.T) {
+	equal(t, int32(0), Int32(nil, 0))
+	equal(t, int32(1), Int32(nil, 1))
+	equal(t, int32(0), Int32(new(int32), 1))
+	equal(t, int32(32), Int32(&_int32, 2))
+}
+
+func TestInt64(t *testing.T) {
+	equal(t, int64(0), Int64(nil, 0))
+	equal(t, int64(1), Int64(nil, 1))
+	equal(t, int64(0), Int64(new(int64), 1))
+	equal(t, int64(64), Int64(&_int64, 2))
+}
+
+func TestRune(t *testing.T) {
+	equal(t, rune(0), Rune(nil, 0))
+	equal(t, rune(1), Rune(nil, 1))
+	equal(t, rune(0), Rune(new(rune), 1))
+	equal(t, rune(1), Rune(&_rune, 1))
+}
+
+func TestString(t *testing.T) {
+	equal(t, "", String(nil, ""))
+	equal(t, "derefer", String(nil, "derefer"))
+	equal(t, "", String(new(string), "derefed"))
+	equal(t, "derefed", String(&_string, "derefer"))
+}
+
+func TestUint(t *testing.T) {
+	equal(t, uint(0), Uint(nil, 0))
+	equal(t, uint(1), Uint(nil, 1))
+	equal(t, uint(0), Uint(new(uint), 1))
+	equal(t, uint(1), Uint(&_uint, 2))
+}
+
+func TestUint8(t *testing.T) {
+	equal(t, uint8(0), Uint8(nil, 0))
+	equal(t, uint8(1), Uint8(nil, 1))
+	equal(t, uint8(0), Uint8(new(uint8), 1))
+	equal(t, uint8(8), Uint8(&_uint8, 2))
+}
+
+func TestUint16(t *testing.T) {
+	equal(t, uint16(0), Uint16(nil, 0))
+	equal(t, uint16(1), Uint16(nil, 1))
+	equal(t, uint16(0), Uint16(new(uint16), 1))
+	equal(t, uint16(16), Uint16(&_uint16, 2))
+}
+
+func TestUint32(t *testing.T) {
+	equal(t, uint32(0), Uint32(nil, 0))
+	equal(t, uint32(1), Uint32(nil, 1))
+	equal(t, uint32(0), Uint32(new(uint32), 1))
+	equal(t, uint32(32), Uint32(&_uint32, 2))
+}
+
+func TestUint64(t *testing.T) {
+	equal(t, uint64(0), Uint64(nil, 0))
+	equal(t, uint64(1), Uint64(nil, 1))
+	equal(t, uint64(0), Uint64(new(uint64), 1))
+	equal(t, uint64(64), Uint64(&_uint64, 2))
+}
+
+func TestUintptr(t *testing.T) {
+	equal(t, uintptr(0), Uintptr(nil, 0))
+	equal(t, uintptr(1), Uintptr(nil, 1))
+	equal(t, uintptr(0), Uintptr(new(uintptr), 1))
+	equal(t, uintptr(64), Uintptr(&_uintptr, 2))
+}