Step 2 - 地址生成与拆分

Assets/Scripts/Core/AddressTranslatorUtils.cs

@@ -0,0 +1,71 @@
+using System;
+
+namespace VMdemo.Core
+{
+    public static class AddressTranslatorUtils
+    {
+        public static AddressParts SplitVirtualAddress(ulong virtualAddress, int vaBits, int offsetBits)
+        {
+            if (vaBits <= 0 || vaBits > 64)
+            {
+                throw new ArgumentOutOfRangeException(nameof(vaBits), "vaBits 必须在 1 到 64 之间。");
+            }
+
+            if (offsetBits < 0 || offsetBits >= vaBits)
+            {
+                throw new ArgumentOutOfRangeException(nameof(offsetBits), "offsetBits 必须满足 0 <= offsetBits < vaBits。");
+            }
+
+            var vaMask = GetBitMask(vaBits);
+            if (vaBits < 64 && (virtualAddress & ~vaMask) != 0UL)
+            {
+                throw new ArgumentOutOfRangeException(nameof(virtualAddress), "virtualAddress 超出 vaBits 可表示范围。");
+            }
+
+            var vpnBits = vaBits - offsetBits;
+            GetPageTableBitLayout(vpnBits, out _, out var l2Bits);
+
+            var offset = virtualAddress & GetBitMask(offsetBits);
+            var vpn = virtualAddress >> offsetBits;
+            var l2Index = vpn & GetBitMask(l2Bits);
+            var l1Index = vpn >> l2Bits;
+
+            return new AddressParts(vpn, offset, l1Index, l2Index);
+        }
+
+        public static void GetPageTableBitLayout(int vpnBits, out int l1Bits, out int l2Bits)
+        {
+            if (vpnBits <= 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(vpnBits), "vpnBits 必须是正整数。");
+            }
+
+            l1Bits = (vpnBits + 1) / 2;
+            l2Bits = vpnBits / 2;
+        }
+
+        public static string FormatSplitResult(
+            ulong virtualAddress,
+            int vaBits,
+            int offsetBits,
+            AddressParts parts)
+        {
+            return $"VA={virtualAddress}, VPN={parts.Vpn}, Offset={parts.Offset}, L1={parts.L1Index}, L2={parts.L2Index}, vaBits={vaBits}, offsetBits={offsetBits}";
+        }
+
+        private static ulong GetBitMask(int bits)
+        {
+            if (bits <= 0)
+            {
+                return 0UL;
+            }
+
+            if (bits >= 64)
+            {
+                return ulong.MaxValue;
+            }
+
+            return (1UL << bits) - 1UL;
+        }
+    }
+}

Assets/Scripts/Core/AddressTranslatorUtils.cs.meta

@@ -0,0 +1,11 @@
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Assets/Scripts/Simulation/AddressGenerator.cs

@@ -0,0 +1,39 @@
+using System;
+
+namespace VMdemo.Simulation
+{
+    public class AddressGenerator
+    {
+        public const int DefaultSeed = 12345;
+
+        private readonly int _vaBits;
+        private readonly ulong _vaMask;
+        private readonly Random _random;
+        private readonly byte[] _buffer = new byte[8];
+
+        public AddressGenerator(int vaBits, int? seed = null)
+        {
+            if (vaBits != 32 && vaBits != 48 && vaBits != 64)
+            {
+                throw new ArgumentOutOfRangeException(nameof(vaBits), "vaBits 仅支持 32、48、64。");
+            }
+
+            _vaBits = vaBits;
+            _vaMask = vaBits == 64 ? ulong.MaxValue : (1UL << vaBits) - 1UL;
+            _random = new Random(seed ?? DefaultSeed);
+        }
+
+        public ulong MaxVirtualAddress => _vaMask;
+
+        public ulong NextVirtualAddress()
+        {
+            return NextRawUlong() & _vaMask;
+        }
+
+        private ulong NextRawUlong()
+        {
+            _random.NextBytes(_buffer);
+            return BitConverter.ToUInt64(_buffer, 0);
+        }
+    }
+}

Assets/Scripts/Simulation/AddressGenerator.cs.meta

@@ -0,0 +1,11 @@
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Assets/Tests/EditMode/Step2AddressSplitTests.cs

@@ -0,0 +1,113 @@
+using NUnit.Framework;
+using VMdemo.Core;
+using VMdemo.Simulation;
+
+namespace VMdemo.Tests.EditMode
+{
+    public class Step2AddressSplitTests
+    {
+        [TestCase(32)]
+        [TestCase(48)]
+        [TestCase(64)]
+        public void AddressGenerator_NextVirtualAddress_StaysWithinRange(int vaBits)
+        {
+            var generator = new AddressGenerator(vaBits, seed: 7);
+
+            for (var i = 0; i < 1000; i++)
+            {
+                var va = generator.NextVirtualAddress();
+                Assert.That(va, Is.LessThanOrEqualTo(generator.MaxVirtualAddress));
+            }
+        }
+
+        [Test]
+        public void AddressGenerator_SameSeed_GeneratesDeterministicSequence()
+        {
+            var a = new AddressGenerator(48, seed: 99);
+            var b = new AddressGenerator(48, seed: 99);
+
+            for (var i = 0; i < 20; i++)
+            {
+                Assert.That(a.NextVirtualAddress(), Is.EqualTo(b.NextVirtualAddress()));
+            }
+        }
+
+        [Test]
+        public void AddressGenerator_DifferentSeed_GeneratesDifferentSequence()
+        {
+            var a = new AddressGenerator(48, seed: 99);
+            var b = new AddressGenerator(48, seed: 100);
+            var hasDifference = false;
+
+            for (var i = 0; i < 20; i++)
+            {
+                if (a.NextVirtualAddress() != b.NextVirtualAddress())
+                {
+                    hasDifference = true;
+                    break;
+                }
+            }
+
+            Assert.IsTrue(hasDifference);
+        }
+
+        [TestCase(0x12345ABCUL, 32, 12, 0x12345UL, 0xABCUL, 0x48UL, 0x345UL)]
+        [TestCase(0x0000ABCDEF123456UL, 48, 12, 0xABCDEF123UL, 0x456UL, 0x2AF37UL, 0x2F123UL)]
+        [TestCase(0xFEDCBA9876543210UL, 64, 16, 0xFEDCBA987654UL, 0x3210UL, 0xFEDCBAUL, 0x987654UL)]
+        public void SplitVirtualAddress_SupportedVaBits_ReturnsExpectedParts(
+            ulong va,
+            int vaBits,
+            int offsetBits,
+            ulong expectedVpn,
+            ulong expectedOffset,
+            ulong expectedL1,
+            ulong expectedL2)
+        {
+            var parts = AddressTranslatorUtils.SplitVirtualAddress(va, vaBits, offsetBits);
+            TestContext.WriteLine(AddressTranslatorUtils.FormatSplitResult(va, vaBits, offsetBits, parts));
+
+            Assert.That(parts.Vpn, Is.EqualTo(expectedVpn));
+            Assert.That(parts.Offset, Is.EqualTo(expectedOffset));
+            Assert.That(parts.L1Index, Is.EqualTo(expectedL1));
+            Assert.That(parts.L2Index, Is.EqualTo(expectedL2));
+        }
+
+        [Test]
+        public void SplitVirtualAddress_OddVpnBits_UsesCeilFloorBitSplit()
+        {
+            const int vaBits = 32;
+            const int offsetBits = 13;
+            const ulong va = 0xDEADBEEFUL;
+
+            var parts = AddressTranslatorUtils.SplitVirtualAddress(va, vaBits, offsetBits);
+            AddressTranslatorUtils.GetPageTableBitLayout(vaBits - offsetBits, out var l1Bits, out var l2Bits);
+
+            Assert.That(l1Bits, Is.EqualTo(10));
+            Assert.That(l2Bits, Is.EqualTo(9));
+            Assert.That(parts.Vpn, Is.EqualTo(0x6F56DUL));
+            Assert.That(parts.Offset, Is.EqualTo(0x1EEFUL));
+            Assert.That(parts.L1Index, Is.EqualTo(0x37AUL));
+            Assert.That(parts.L2Index, Is.EqualTo(0x16DUL));
+        }
+
+        [Test]
+        public void GetPageTableBitLayout_AlwaysSumsToVpnBits()
+        {
+            for (var vpnBits = 1; vpnBits <= 63; vpnBits++)
+            {
+                AddressTranslatorUtils.GetPageTableBitLayout(vpnBits, out var l1Bits, out var l2Bits);
+
+                Assert.That(l1Bits + l2Bits, Is.EqualTo(vpnBits));
+                Assert.That(l1Bits, Is.GreaterThanOrEqualTo(l2Bits));
+                Assert.That(l1Bits - l2Bits, Is.LessThanOrEqualTo(1));
+            }
+        }
+
+        [Test]
+        public void SplitVirtualAddress_AddressOutOfRange_Throws()
+        {
+            Assert.Throws<System.ArgumentOutOfRangeException>(() =>
+                AddressTranslatorUtils.SplitVirtualAddress(0x1_0000_0000UL, 32, 12));
+        }
+    }
+}

Assets/Tests/EditMode/Step2AddressSplitTests.cs.meta

@@ -0,0 +1,11 @@
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doc/MVP-TODO.md

@@ -63,21 +63,21 @@
 
 ### TODO
 
-- [ ] 新建 `AddressGenerator.cs`：生成 `[0, 2^vaBits - 1]` 范围虚拟地址
+- [x] 新建 `AddressGenerator.cs`：生成 `[0, 2^vaBits - 1]` 范围虚拟地址
-- [ ] 新建 `AddressTranslatorUtils.cs`：拆分 `VPN + offset`
+- [x] 新建 `AddressTranslatorUtils.cs`：拆分 `VPN + offset`
-- [ ] 实现二级页表索引位拆分
+- [x] 实现二级页表索引位拆分
 
 ### 拆分规则
 
-- [ ] `vpnBits = vaBits - offsetBits`
+- [x] `vpnBits = vaBits - offsetBits`
-- [ ] `l1Bits = ceil(vpnBits / 2)`
+- [x] `l1Bits = ceil(vpnBits / 2)`
-- [ ] `l2Bits = floor(vpnBits / 2)`
+- [x] `l2Bits = floor(vpnBits / 2)`
-- [ ] 从 `VPN` 拆出 `L1Index` 和 `L2Index`
+- [x] 从 `VPN` 拆出 `L1Index` 和 `L2Index`
 
 ### 完成标准
 
-- [ ] 控制台可打印每次地址拆分结果
+- [x] 控制台可打印每次地址拆分结果
-- [ ] 32/48/64 三种位数下拆分结果均正确
+- [x] 32/48/64 三种位数下拆分结果均正确
 
 ## 4. Step 3 - TLB（全相联 + LRU）
 
@@ -206,5 +206,5 @@
 ## 11. 首日执行建议（直接开工）
 
 - [x] 先完成 Step 1（参数模型 + 校验）
-- [ ] 紧接 Step 2（地址拆分）
+- [x] 紧接 Step 2（地址拆分）
 - [ ] 当天收尾前完成 Step 3（TLB LRU 最小可运行）