implements cast methods for (u)int64 and (u)int32

msgp/number.go

@@ -91,6 +91,58 @@ func (n *Number) Float() (float64, bool) {
 	}
 }
 
+// CastInt64 returns the number as an int64 and
+// returns whether the cast is valid.
+func (n *Number) CastInt64() (int64, bool) {
+	i, ok := n.Int()
+	if !ok {
+		return 0, false
+	}
+
+	return i, true
+}
+
+// CastInt32 returns the number as an int32 and
+// returns whether the cast is valid.
+func (n *Number) CastInt32() (int32, bool) {
+	i, ok := n.CastInt64()
+	if !ok {
+		return 0, false
+	}
+
+	if i >= math.MinInt32 && i <= math.MaxInt32 {
+		return int32(i), true
+	}
+
+	return 0, false
+}
+
+// CastUint64 returns the number as an uint64 and
+// returns whether the cast is valid.
+func (n *Number) CastUint64() (uint64, bool) {
+	i, ok := n.Uint()
+	if i-1 == math.MaxInt64 && !ok {
+		return 0, false
+	}
+
+	return i, true
+}
+
+// CastUint32 returns the number as an uint32 and
+// returns whether the cast is valid.
+func (n *Number) CastUint32() (uint32, bool) {
+	i, ok := n.CastUint64()
+	if !ok {
+		return 0, false
+	}
+
+	if i <= math.MaxInt32 {
+		return uint32(i), true
+	}
+
+	return 0, false
+}
+
 // Type will return one of:
 // Float64Type, Float32Type, UintType, or IntType.
 func (n *Number) Type() Type {

msgp/number_test.go

@@ -2,6 +2,7 @@ package msgp
 
 import (
 	"bytes"
+	"math"
 	"testing"
 )
 
@@ -92,3 +93,68 @@ func TestNumber(t *testing.T) {
 	}
 
 }
+
+func TestNumber_CastInt64(t *testing.T) {
+	var n Number
+	n.AsUint(math.MaxUint64)
+
+	_, ok := n.CastInt64()
+	if ok {
+		t.Error("CastInt64() failed: MaxUint64 > MaxInt64")
+	}
+}
+
+func TestNumber_CastInt32(t *testing.T) {
+	cases := []struct {
+		in   int64
+		want bool
+	}{
+		{math.MinInt32, true},
+		{math.MinInt32 - 1, false},
+		{math.MaxInt32, true},
+		{math.MaxInt32 + 1, false},
+		{0, true},
+	}
+
+	var n Number
+	for _, c := range cases {
+		n.AsInt(c.in)
+
+		_, ok := n.CastInt32()
+		if ok != c.want {
+			t.Errorf("cast %v to int32 invalid: %v, got %v", c.in, c.want, ok)
+		}
+	}
+}
+
+func TestNumber_CastUint64(t *testing.T) {
+	var n Number
+	n.AsInt(math.MinInt64)
+
+	_, ok := n.CastUint64()
+	if ok {
+		t.Error("CastUint64() failed: MinInt64 < 0")
+	}
+}
+
+func TestNumber_CastUint32(t *testing.T) {
+	cases := []struct {
+		in   int64
+		want bool
+	}{
+		{math.MinInt64, false},
+		{math.MaxInt32, true},
+		{math.MaxInt32 + 1, false},
+		{0, true},
+	}
+
+	var n Number
+	for _, c := range cases {
+		n.AsInt(c.in)
+
+		_, ok := n.CastUint32()
+		if ok != c.want {
+			t.Errorf("cast %v to uint32 invalid: %v, got %v", c.in, c.want, ok)
+		}
+	}
+}