From d235e2c6a5788ec4a6cff15a16f56b38a3876a0d Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Sun, 28 Jun 2020 14:47:41 -0400
Subject: ...

---
 core/vm/memory.go | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 core/vm/memory.go

(limited to 'core/vm/memory.go')

diff --git a/core/vm/memory.go b/core/vm/memory.go
new file mode 100644
index 0000000..5408707
--- /dev/null
+++ b/core/vm/memory.go
@@ -0,0 +1,124 @@
+// Copyright 2015 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 (
+	"fmt"
+	"math/big"
+
+	"github.com/ava-labs/go-ethereum/common/math"
+)
+
+// Memory implements a simple memory model for the ethereum virtual machine.
+type Memory struct {
+	store       []byte
+	lastGasCost uint64
+}
+
+// NewMemory returns a new memory model.
+func NewMemory() *Memory {
+	return &Memory{}
+}
+
+// Set sets offset + size to value
+func (m *Memory) Set(offset, size uint64, value []byte) {
+	// It's possible the offset is greater than 0 and size equals 0. This is because
+	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
+	if size > 0 {
+		// length of store may never be less than offset + size.
+		// The store should be resized PRIOR to setting the memory
+		if offset+size > uint64(len(m.store)) {
+			panic("invalid memory: store empty")
+		}
+		copy(m.store[offset:offset+size], value)
+	}
+}
+
+// Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
+// 32 bytes.
+func (m *Memory) Set32(offset uint64, val *big.Int) {
+	// length of store may never be less than offset + size.
+	// The store should be resized PRIOR to setting the memory
+	if offset+32 > uint64(len(m.store)) {
+		panic("invalid memory: store empty")
+	}
+	// Zero the memory area
+	copy(m.store[offset:offset+32], []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0})
+	// Fill in relevant bits
+	math.ReadBits(val, m.store[offset:offset+32])
+}
+
+// Resize resizes the memory to size
+func (m *Memory) Resize(size uint64) {
+	if uint64(m.Len()) < size {
+		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
+	}
+}
+
+// Get returns offset + size as a new slice
+func (m *Memory) Get(offset, size int64) (cpy []byte) {
+	if size == 0 {
+		return nil
+	}
+
+	if len(m.store) > int(offset) {
+		cpy = make([]byte, size)
+		copy(cpy, m.store[offset:offset+size])
+
+		return
+	}
+
+	return
+}
+
+// GetPtr returns the offset + size
+func (m *Memory) GetPtr(offset, size int64) []byte {
+	if size == 0 {
+		return nil
+	}
+
+	if len(m.store) > int(offset) {
+		return m.store[offset : offset+size]
+	}
+
+	return nil
+}
+
+// Len returns the length of the backing slice
+func (m *Memory) Len() int {
+	return len(m.store)
+}
+
+// Data returns the backing slice
+func (m *Memory) Data() []byte {
+	return m.store
+}
+
+// Print dumps the content of the memory.
+func (m *Memory) Print() {
+	fmt.Printf("### mem %d bytes ###\n", len(m.store))
+	if len(m.store) > 0 {
+		addr := 0
+		for i := 0; i+32 <= len(m.store); i += 32 {
+			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
+			addr++
+		}
+	} else {
+		fmt.Println("-- empty --")
+	}
+	fmt.Println("####################")
+}
-- 
cgit v1.2.3