coerce numbers when appropriate

msgp/number.go

@@ -91,6 +91,70 @@ func (n *Number) Float() (float64, bool) {
 	}
 }
 
+// CoerceInt attempts to coerce the value of
+// the number into a signed integer, and returns
+// whether or not it was successful. "Success"
+// implies that no precision in the value of
+// the number was lost, which means that the
+// type of the number was an integer or 
+// a floating point 0.
+func (n *Number) CoerceInt() (int64, bool) {
+	switch n.typ {
+	case InvalidType, IntType:
+		return int64(n.bits), true
+	case UintType:
+		return int64(n.bits), n.bits <= math.MaxInt64
+	case Float32Type:
+		return 0, n.bits == 0 || n.bits == 1<<31
+	case Float64Type:
+		return 0, n.bits == 0 || n.bits == 1<<63
+	}
+	return 0, false
+}
+
+// CoerceUint attempts to coerce the value of
+// the number into an unsigned integer, and
+// returns whether or not it was successful.
+// "Success" implies that no precision in the
+// value of the number was lost (see CoerceInt()).
+func (n *Number) CoerceUint() (uint64, bool) {
+	switch n.typ {
+	case InvalidType:
+		return 0, true
+	case IntType:
+		return n.bits, int64(n.bits) >= 0
+	case UintType:
+		return n.bits, true
+	case Float32Type:
+		return 0, n.bits == 0 || n.bits == 1<<31
+	case Float64Type:
+		return 0, n.bits == 0 || n.bits == 1<<63
+	}
+	return 0, false
+}
+
+// CoerceFloat coerces the value of the
+// number to a float64. Some precision may
+// be lost in the conversion if the type
+// of the number was not originally a
+// float64. (However, zero is always
+// converted precisely.)
+func (n *Number) CoerceFloat() float64 {
+	switch n.typ {
+	case InvalidType:
+		return 0
+	case IntType:
+		return float64(int64(n.bits))
+	case UintType:
+		return float64(uint64(n.bits))
+	case Float32Type:
+		return float64(math.Float32frombits(uint32(n.bits)))
+	case Float64Type:
+		return math.Float64frombits(n.bits)
+	}
+	return 0
+}
+
 // Type will return one of:
 // Float64Type, Float32Type, UintType, or IntType.
 func (n *Number) Type() Type {

msgp/number_test.go

@@ -23,18 +23,33 @@ func TestNumber(t *testing.T) {
 		t.Errorf("%d in; %d out!", 248, i)
 	}
 
+	u, ok := n.CoerceUint()
+	if !ok || u != 248 {
+		t.Errorf("%d in, %d out!", 248, u)
+	}
+
 	n.AsFloat64(3.141)
 	f, ok := n.Float()
 	if !ok || f != 3.141 || n.Type() != Float64Type || n.String() != "3.141" {
 		t.Errorf("%f in; %f out!", 3.141, f)
 	}
 
+	f = n.CoerceFloat()
+	if f != 3.141 {
+		t.Errorf("%f in; %f out", 3.141, f)
+	}
+
 	n.AsUint(40000)
-	u, ok := n.Uint()
+	u, ok = n.Uint()
 	if !ok || u != 40000 || n.Type() != UintType || n.String() != "40000" {
 		t.Errorf("%d in; %d out!", 40000, u)
 	}
 
+	i, ok = n.CoerceInt()
+	if !ok || i != 40000 {
+		t.Errorf("%d in; %d out!", 40000, i)
+	}
+
 	nums := []interface{}{
 		float64(3.14159),
 		int64(-29081),