1 files changed, 99 insertions, 0 deletions
diff --git a/core/vm/common.go b/core/vm/common.go
new file mode 100644
index 0000000..ead30fc
--- /dev/null
+++ b/core/vm/common.go
@@ -0,0 +1,99 @@
+// Copyright 2014 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+import (
+	"math/big"
+
+	"github.com/ava-labs/go-ethereum/common"
+	"github.com/ava-labs/go-ethereum/common/math"
+)
+
+// calcMemSize64 calculates the required memory size, and returns
+// the size and whether the result overflowed uint64
+func calcMemSize64(off, l *big.Int) (uint64, bool) {
+	if !l.IsUint64() {
+		return 0, true
+	}
+	return calcMemSize64WithUint(off, l.Uint64())
+}
+
+// calcMemSize64WithUint calculates the required memory size, and returns
+// the size and whether the result overflowed uint64
+// Identical to calcMemSize64, but length is a uint64
+func calcMemSize64WithUint(off *big.Int, length64 uint64) (uint64, bool) {
+	// if length is zero, memsize is always zero, regardless of offset
+	if length64 == 0 {
+		return 0, false
+	}
+	// Check that offset doesn't overflow
+	if !off.IsUint64() {
+		return 0, true
+	}
+	offset64 := off.Uint64()
+	val := offset64 + length64
+	// if value < either of it's parts, then it overflowed
+	return val, val < offset64
+}
+
+// getData returns a slice from the data based on the start and size and pads
+// up to size with zero's. This function is overflow safe.
+func getData(data []byte, start uint64, size uint64) []byte {
+	length := uint64(len(data))
+	if start > length {
+		start = length
+	}
+	end := start + size
+	if end > length {
+		end = length
+	}
+	return common.RightPadBytes(data[start:end], int(size))
+}
+
+// getDataBig returns a slice from the data based on the start and size and pads
+// up to size with zero's. This function is overflow safe.
+func getDataBig(data []byte, start *big.Int, size *big.Int) []byte {
+	dlen := big.NewInt(int64(len(data)))
+
+	s := math.BigMin(start, dlen)
+	e := math.BigMin(new(big.Int).Add(s, size), dlen)
+	return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
+}
+
+// bigUint64 returns the integer casted to a uint64 and returns whether it
+// overflowed in the process.
+func bigUint64(v *big.Int) (uint64, bool) {
+	return v.Uint64(), !v.IsUint64()
+}
+
+// toWordSize returns the ceiled word size required for memory expansion.
+func toWordSize(size uint64) uint64 {
+	if size > math.MaxUint64-31 {
+		return math.MaxUint64/32 + 1
+	}
+
+	return (size + 31) / 32
+}
+
+func allZero(b []byte) bool {
+	for _, byte := range b {
+		if byte != 0 {
+			return false
+		}
+	}
+	return true
+}