implement RangeCheck

pkg/vm/builtins/range_check.go

@@ -0,0 +1,31 @@
+package builtins
+
+import (
+	"fmt"
+
+	"github.com/NethermindEth/cairo-vm-go/pkg/vm/memory"
+	"github.com/consensys/gnark-crypto/ecc/stark-curve/fp"
+)
+
+type RangeCheck struct{}
+
+// 1 << 128
+var max, _ = new(fp.Element).SetString("0x100000000000000000000000000000000")
+
+func (r *RangeCheck) CheckWrite(segment *memory.Segment, offset uint64, value *memory.MemoryValue) error {
+	felt, err := value.ToFieldElement()
+	if err != nil {
+		return err
+	}
+
+	// felt >= (2^128)
+	if felt.Cmp(max) != -1 {
+		return fmt.Errorf("range check builtin failed for offset: %d value %s", offset, value)
+	}
+	return nil
+}
+
+func (r *RangeCheck) DeduceValue(segment *memory.Segment, offset uint64) error {
+	segment.Data[offset] = memory.EmptyMemoryValueAsFelt()
+	return nil
+}

pkg/vm/builtins/range_check_test.go

@@ -0,0 +1,39 @@
+package builtins
+
+import (
+	"testing"
+
+	"github.com/NethermindEth/cairo-vm-go/pkg/vm/memory"
+	"github.com/consensys/gnark-crypto/ecc/stark-curve/fp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRangeCheck(t *testing.T) {
+	builtin := RangeCheck{}
+
+	t.Run("write memory addr", func(t *testing.T) {
+		memoryAddress := memory.EmptyMemoryValueAsAddress()
+		assert.Error(t, builtin.CheckWrite(nil, 0, &memoryAddress))
+	})
+
+	t.Run("write out of range", func(t *testing.T) {
+		outOfRangeValueFelt, err := new(fp.Element).SetString("0x100000000000000000000000000000001")
+		require.NoError(t, err)
+		outOfRangeValue := memory.MemoryValueFromFieldElement(outOfRangeValueFelt)
+		assert.Error(t, builtin.CheckWrite(nil, 0, &outOfRangeValue))
+	})
+
+	t.Run("write in range", func(t *testing.T) {
+		f, err := new(fp.Element).SetString("0x44")
+		require.NoError(t, err)
+		v := memory.MemoryValueFromFieldElement(f)
+		assert.NoError(t, builtin.CheckWrite(nil, 0, &v))
+	})
+
+	t.Run("deduce", func(t *testing.T) {
+		segment := memory.EmptySegmentWithLength(3)
+		assert.NoError(t, builtin.DeduceValue(segment, 0))
+		require.Equal(t, memory.EmptyMemoryValueAsFelt(), segment.Data[0])
+	})
+}