PolkaVM

PolkaVM/Package.resolved

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+{
+  "originHash" : "83027e22d1c1e6e15dd98a1719eec3b0aa70fd540013d36d77223e0931d6f7a8",
+  "pins" : [
+    {
+      "identity" : "blake2.swift",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/tesseract-one/Blake2.swift.git",
+      "state" : {
+        "revision" : "29c55c8fe42d6661e5a32cc5bbbad1fff64fd01e",
+        "version" : "0.2.0"
+      }
+    },
+    {
+      "identity" : "scalecodec.swift",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/AcalaNetwork/ScaleCodec.swift.git",
+      "state" : {
+        "branch" : "main",
+        "revision" : "dac3e7161de34c60c82794d031de0231b5a5746e"
+      }
+    },
+    {
+      "identity" : "swift-crypto",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-crypto.git",
+      "state" : {
+        "revision" : "46072478ca365fe48370993833cb22de9b41567f",
+        "version" : "3.5.2"
+      }
+    },
+    {
+      "identity" : "swift-log",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-log.git",
+      "state" : {
+        "revision" : "9cb486020ebf03bfa5b5df985387a14a98744537",
+        "version" : "1.6.1"
+      }
+    },
+    {
+      "identity" : "swift-syntax",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-syntax.git",
+      "state" : {
+        "revision" : "4c6cc0a3b9e8f14b3ae2307c5ccae4de6167ac2c",
+        "version" : "600.0.0-prerelease-2024-06-12"
+      }
+    },
+    {
+      "identity" : "swift-testing",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-testing.git",
+      "state" : {
+        "branch" : "0.10.0",
+        "revision" : "69d59cfc76e5daf498ca61f5af409f594768eef9"
+      }
+    },
+    {
+      "identity" : "tuples.swift",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/tesseract-one/Tuples.swift.git",
+      "state" : {
+        "revision" : "4d2cf7c64443cdf4df833d0bedd767bf9dbc49d9",
+        "version" : "0.1.3"
+      }
+    }
+  ],
+  "version" : 3
+}

PolkaVM/Package.swift

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+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "PolkaVM",
+    platforms: [
+        .macOS(.v14),
+    ],
+    products: [
+        .library(
+            name: "PolkaVM",
+            targets: ["PolkaVM"]
+        ),
+    ],
+    dependencies: [
+        .package(path: "../Utils"),
+        .package(url: "https://github.com/apple/swift-testing.git", branch: "0.10.0"),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.6.0"),
+    ],
+    targets: [
+        .target(
+            name: "PolkaVM",
+            dependencies: [
+                "Utils",
+                .product(name: "Logging", package: "swift-log"),
+            ]
+        ),
+        .testTarget(
+            name: "PolkaVMTests",
+            dependencies: [
+                "PolkaVM",
+                .product(name: "Testing", package: "swift-testing"),
+            ]
+        ),
+    ],
+    swiftLanguageVersions: [.version("6")]
+)

PolkaVM/Sources/PolkaVM/Engine.swift

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+public class Engine {
+    public init() {}
+
+    public func execute(program: ProgramCode, state: VMState) -> ExitReason {
+        while true {
+            guard state.gas > 0 else {
+                return .outOfGas
+            }
+            if let exitReason = step(program: program, state: state) {
+                return exitReason
+            }
+        }
+    }
+
+    public func step(program: ProgramCode, state: VMState) -> ExitReason? {
+        let pc = state.pc
+        guard let skip = program.skip(state.pc) else {
+            return .halt(.invalidInstruction)
+        }
+        guard let inst = InstructionTable.parse(program.code[Int(pc) ..< Int(pc + 1 + skip)]) else {
+            return .halt(.invalidInstruction)
+        }
+
+        return inst.execute(state: state, skip: skip)
+    }
+}

PolkaVM/Sources/PolkaVM/ExitReason.swift

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+public enum ExitReason {
+    public enum HaltReason {
+        case trap
+        case invalidInstruction
+    }
+
+    case halt(HaltReason)
+    case panic
+    case outOfGas
+    case hostCall(UInt32)
+    case pageFault(UInt32)
+}

PolkaVM/Sources/PolkaVM/Instruction.swift

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+import Foundation
+
+public protocol Instruction {
+    static var opcode: UInt8 { get }
+
+    init?(data: Data)
+
+    func execute(state: VMState, skip: UInt32) -> ExitReason?
+    func executeImpl(state: VMState) -> ExitReason?
+
+    func gasCost() -> UInt64
+    func updatePC(state: VMState, skip: UInt32)
+}
+
+extension Instruction {
+    public func execute(state: VMState, skip: UInt32) -> ExitReason? {
+        state.consumeGas(gasCost())
+        let res = executeImpl(state: state)
+        if res == nil {
+            state.updatePC(state.pc + skip + 1)
+        }
+        return res
+    }
+
+    public func gasCost() -> UInt64 {
+        1
+    }
+
+    public func updatePC(state: VMState, skip: UInt32) {
+        state.increasePC(skip + 1)
+    }
+}

PolkaVM/Sources/PolkaVM/InstructionTable.swift

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+import Foundation
+
+public class InstructionTable {
+    public static let table: [Instruction.Type?] = {
+        let insts: [Instruction.Type] = [
+            Instructions.Trap.self,
+            Instructions.Fallthrough.self,
+            Instructions.Ecalli.self,
+            Instructions.StoreImmU8.self,
+            Instructions.StoreImmU16.self,
+            Instructions.StoreImmU32.self,
+        ]
+        var table: [Instruction.Type?] = Array(repeating: nil, count: 256)
+        for i in 0 ..< insts.count {
+            table[Int(insts[i].opcode)] = insts[i]
+        }
+        return table
+    }()
+
+    public static func parse(_ data: Data) -> (any Instruction)? {
+        guard data.count >= 1 else {
+            return nil
+        }
+        let opcode = data[data.startIndex]
+        guard let instType = table[Int(opcode)] else {
+            return nil
+        }
+        return instType.init(data: data)
+    }
+}

PolkaVM/Sources/PolkaVM/Instructions.swift

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+import Foundation
+import Utils
+
+public enum Instructions {
+    static func decodeImmidate(_ data: Data) -> UInt32 {
+        let len = min(data.count, 4)
+        if len == 0 {
+            return 0
+        }
+        var value: UInt32 = 0
+        for i in 0 ..< len {
+            value = value | (UInt32(data[i]) << (8 * i))
+        }
+        let shift = (4 - len) * 8
+        // shift left so that the MSB is the sign bit
+        // and then do signed shift right to fill the empty bits using the sign bit
+        // and then convert back to UInt32
+        return UInt32(bitPattern: Int32(bitPattern: value << shift) >> shift)
+    }
+
+    static func decodeImmidate2(_ data: Data) -> (UInt32, UInt32)? {
+        do {
+            let lA = try Int(data.at(0) & 0b111)
+            let lX = min(4, lA)
+            let lY1 = min(4, max(0, data.count - Int(lA) - 1))
+            let lY2 = min(lY1, 8 - lA)
+            let vX = try decodeImmidate(data.at(1 ..< lX))
+            let vY = try decodeImmidate(data.at((1 + lA) ..< lY2))
+            return (vX, vY)
+        } catch {
+            return nil
+        }
+    }
+
+    // MARK: Instructions without Arguments
+
+    public struct Trap: Instruction {
+        public static var opcode: UInt8 { 0 }
+
+        public init(data _: Data) {}
+
+        public func executeImpl(state _: VMState) -> ExitReason? {
+            .halt(.trap)
+        }
+    }
+
+    public struct Fallthrough: Instruction {
+        public static var opcode: UInt8 { 1 }
+
+        public init(data _: Data) {}
+
+        public func executeImpl(state _: VMState) -> ExitReason? {
+            nil
+        }
+    }
+
+    // MARK: Instructions with Arguments of One Immediate
+
+    public struct Ecalli: Instruction {
+        public static var opcode: UInt8 { 78 }
+
+        public let callIndex: UInt32
+
+        public init(data: Data) {
+            callIndex = Instructions.decodeImmidate(data)
+        }
+
+        public func executeImpl(state _: VMState) -> ExitReason? {
+            .hostCall(callIndex)
+        }
+    }
+
+    // MARK: Instructions with Arguments of Two Immediates
+
+    public struct StoreImmU8: Instruction {
+        public static var opcode: UInt8 { 62 }
+
+        public let address: UInt32
+        public let value: UInt8
+
+        public init(data: Data) {
+            let (x, y) = Instructions.decodeImmidate2(data)!
+            address = x
+            value = UInt8(truncatingIfNeeded: y)
+        }
+
+        public func executeImpl(state: VMState) -> ExitReason? {
+            if (try? state.memory.write(address: address, value: value)) != nil {
+                return nil
+            }
+            return .pageFault(address)
+        }
+    }
+
+    public struct StoreImmU16: Instruction {
+        public static var opcode: UInt8 { 79 }
+
+        public let address: UInt32
+        public let value: UInt16
+
+        public init(data: Data) {
+            let (x, y) = Instructions.decodeImmidate2(data)!
+            address = x
+            value = UInt16(truncatingIfNeeded: y)
+        }
+
+        public func executeImpl(state: VMState) -> ExitReason? {
+            if (try? state.memory.write(address: address, values: value.encode(method: .fixedWidth(2)))) != nil {
+                return nil
+            }
+            return .pageFault(address)
+        }
+    }
+
+    public struct StoreImmU32: Instruction {
+        public static var opcode: UInt8 { 38 }
+
+        public let address: UInt32
+        public let value: UInt32
+
+        public init(data: Data) {
+            let (x, y) = Instructions.decodeImmidate2(data)!
+            address = x
+            value = y
+        }
+
+        public func executeImpl(state: VMState) -> ExitReason? {
+            if (try? state.memory.write(address: address, values: value.encode(method: .fixedWidth(4)))) != nil {
+                return nil
+            }
+            return .pageFault(address)
+        }
+    }
+}