port over overflow stdlib

gnovm/stdlibs/overflow/overflow.gno

@@ -0,0 +1,131 @@
+/*
+Package overflow offers overflow-checked integer arithmetic operations
+for int, int32, and int64. Each of the operations returns a
+result,bool combination.  This was prompted by the need to know when
+to flow into higher precision types from the math.big library.
+
+For instance, assuing a 64 bit machine:
+
+10 + 20 -> 30
+int(math.MaxInt64) + 1 -> -9223372036854775808
+
+whereas
+
+overflow.Add(10,20) -> (30, true)
+overflow.Add(math.MaxInt64,1) -> (0, false)
+
+Add, Sub, Mul, Div are for int.  Add64, Add32, etc. are specifically sized.
+
+If anybody wishes an unsigned version, submit a pull request for code
+and new tests.
+*/
+package overflow
+
+//go:generate ./overflow_template.sh
+
+import "math"
+
+func _is64Bit() bool {
+	maxU32 := uint(math.MaxUint32)
+	return ((maxU32 << 1) >> 1) == maxU32
+}
+
+/********** PARTIAL TEST COVERAGE FROM HERE DOWN *************
+
+The only way that I could see to do this is a combination of
+my normal 64 bit system and a GopherJS running on Node.  My
+understanding is that its ints are 32 bit.
+
+So, FEEL FREE to carefully review the code visually.
+
+*************************************************************/
+
+// Unspecified size, i.e. normal signed int
+
+// Add sums two ints, returning the result and a boolean status.
+func Add(a, b int) (int, bool) {
+	if _is64Bit() {
+		r64, ok := Add64(int64(a), int64(b))
+		return int(r64), ok
+	}
+	r32, ok := Add32(int32(a), int32(b))
+	return int(r32), ok
+}
+
+// Sub returns the difference of two ints and a boolean status.
+func Sub(a, b int) (int, bool) {
+	if _is64Bit() {
+		r64, ok := Sub64(int64(a), int64(b))
+		return int(r64), ok
+	}
+	r32, ok := Sub32(int32(a), int32(b))
+	return int(r32), ok
+}
+
+// Mul returns the product of two ints and a boolean status.
+func Mul(a, b int) (int, bool) {
+	if _is64Bit() {
+		r64, ok := Mul64(int64(a), int64(b))
+		return int(r64), ok
+	}
+	r32, ok := Mul32(int32(a), int32(b))
+	return int(r32), ok
+}
+
+// Div returns the quotient of two ints and a boolean status
+func Div(a, b int) (int, bool) {
+	if _is64Bit() {
+		r64, ok := Div64(int64(a), int64(b))
+		return int(r64), ok
+	}
+	r32, ok := Div32(int32(a), int32(b))
+	return int(r32), ok
+}
+
+// Quotient returns the quotient, remainder and status of two ints
+func Quotient(a, b int) (int, int, bool) {
+	if _is64Bit() {
+		q64, r64, ok := Quotient64(int64(a), int64(b))
+		return int(q64), int(r64), ok
+	}
+	q32, r32, ok := Quotient32(int32(a), int32(b))
+	return int(q32), int(r32), ok
+}
+
+/************* Panic versions for int ****************/
+
+// Addp returns the sum of two ints, panicking on overflow
+func Addp(a, b int) int {
+	r, ok := Add(a, b)
+	if !ok {
+		panic("addition overflow")
+	}
+	return r
+}
+
+// Subp returns the difference of two ints, panicking on overflow.
+func Subp(a, b int) int {
+	r, ok := Sub(a, b)
+	if !ok {
+		panic("subtraction overflow")
+	}
+	return r
+}
+
+// Mulp returns the product of two ints, panicking on overflow.
+func Mulp(a, b int) int {
+	r, ok := Mul(a, b)
+	if !ok {
+		panic("multiplication overflow")
+	}
+	return r
+}
+
+// Divp returns the quotient of two ints, panicking on overflow.
+func Divp(a, b int) int {
+	r, ok := Div(a, b)
+	if !ok {
+		panic("division failure")
+	}
+	return r
+}