/
Processor.swift
477 lines (404 loc) · 11.4 KB
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Processor.swift
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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//
enum MatchMode {
case wholeString
case partialFromFront
}
typealias Program = MEProgram<String>
/// A concrete CU. Somehow will run the concrete logic and
/// feed stuff back to generic code
struct Controller {
var pc: InstructionAddress
mutating func step() {
pc.rawValue += 1
}
}
struct Processor<
Input: BidirectionalCollection
> where Input.Element: Equatable { // maybe Hashable?
typealias Element = Input.Element
let input: Input
let bounds: Range<Position>
let matchMode: MatchMode
var currentPosition: Position
let instructions: InstructionList<Instruction>
var controller: Controller
var cycleCount = 0
/// Our register file
var registers: Registers
// Used for back tracking
var savePoints: [SavePoint] = []
var callStack: [InstructionAddress] = []
var state: State = .inProgress
var failureReason: Error? = nil
var isTracingEnabled: Bool
var storedCaptures: Array<_StoredCapture>
}
extension Processor {
typealias Position = Input.Index
var start: Position { bounds.lowerBound }
var end: Position { bounds.upperBound }
}
extension Processor {
init(
program: MEProgram<Input>,
input: Input,
bounds: Range<Position>,
matchMode: MatchMode,
isTracingEnabled: Bool
) {
self.controller = Controller(pc: 0)
self.instructions = program.instructions
self.input = input
self.bounds = bounds
self.matchMode = matchMode
self.isTracingEnabled = isTracingEnabled
self.currentPosition = bounds.lowerBound
self.registers = Registers(program, bounds.upperBound)
self.storedCaptures = Array(
repeating: .init(), count: program.registerInfo.captures)
_checkInvariants()
}
func _checkInvariants() {
assert(end <= input.endIndex)
assert(start >= input.startIndex)
assert(currentPosition >= start)
assert(currentPosition <= end)
}
}
extension Processor {
var slice: Input.SubSequence {
// TODO: Should we whole-scale switch to slices, or
// does that depend on options for some anchors?
input[bounds]
}
// Advance in our input
//
// Returns whether the advance succeeded. On failure, our
// save point was restored
mutating func consume(_ n: Distance) -> Bool {
// Want Collection to provide this behavior...
if input.distance(from: currentPosition, to: end) < n.rawValue {
signalFailure()
return false
}
currentPosition = input.index(currentPosition, offsetBy: n.rawValue)
return true
}
mutating func advance(to nextIndex: Input.Index) {
assert(nextIndex >= bounds.lowerBound)
assert(nextIndex <= bounds.upperBound)
assert(nextIndex > currentPosition)
currentPosition = nextIndex
}
func doPrint(_ s: String) {
var enablePrinting: Bool { false }
if enablePrinting {
print(s)
}
}
func load() -> Element? {
currentPosition < end ? input[currentPosition] : nil
}
func load(count: Int) -> Input.SubSequence? {
let slice = self.slice[currentPosition...].prefix(count)
guard slice.count == count else { return nil }
return slice
}
mutating func match(_ e: Element) {
guard let cur = load(), cur == e else {
signalFailure()
return
}
if consume(1) {
controller.step()
}
}
mutating func matchSeq<C: Collection>(
_ seq: C
) where C.Element == Input.Element {
let count = seq.count
guard let inputSlice = load(count: count),
seq.elementsEqual(inputSlice)
else {
signalFailure()
return
}
guard consume(.init(count)) else {
fatalError("unreachable")
}
controller.step()
}
mutating func signalFailure() {
guard let (pc, pos, stackEnd, capEnds, intRegisters) =
savePoints.popLast()?.destructure
else {
state = .fail
return
}
assert(stackEnd.rawValue <= callStack.count)
assert(capEnds.count == storedCaptures.count)
controller.pc = pc
currentPosition = pos ?? currentPosition
callStack.removeLast(callStack.count - stackEnd.rawValue)
storedCaptures = capEnds
registers.ints = intRegisters
}
mutating func abort(_ e: Error? = nil) {
if let e = e {
self.failureReason = e
}
self.state = .fail
}
mutating func tryAccept() {
switch (currentPosition, matchMode) {
// When reaching the end of the match bounds or when we are only doing a
// prefix match, transition to accept.
case (bounds.upperBound, _), (_, .partialFromFront):
state = .accept
// When we are doing a full match but did not reach the end of the match
// bounds, backtrack if possible.
case (_, .wholeString):
signalFailure()
}
}
mutating func cycle() {
_checkInvariants()
assert(state == .inProgress)
if cycleCount == 0 { trace() }
defer {
cycleCount += 1
trace()
_checkInvariants()
}
let (opcode, payload) = fetch().destructure
switch opcode {
case .invalid:
fatalError("Invalid program")
case .nop:
if checkComments,
let s = payload.optionalString
{
doPrint(registers[s])
}
controller.step()
case .decrement:
let (bool, int) = payload.pairedBoolInt
let newValue = registers[int] - 1
registers[bool] = newValue == 0
registers[int] = newValue
controller.step()
case .moveImmediate:
let (imm, reg) = payload.pairedImmediateInt
let int = Int(asserting: imm)
assert(int == imm)
registers[reg] = int
controller.step()
case .movePosition:
let reg = payload.position
registers[reg] = currentPosition
controller.step()
case .branch:
controller.pc = payload.addr
case .condBranch:
let (addr, cond) = payload.pairedAddrBool
if registers[cond] {
controller.pc = addr
} else {
controller.step()
}
case .condBranchZeroElseDecrement:
let (addr, int) = payload.pairedAddrInt
if registers[int] == 0 {
controller.pc = addr
} else {
registers[int] -= 1
controller.step()
}
case .save:
let resumeAddr = payload.addr
let sp = makeSavePoint(resumeAddr)
savePoints.append(sp)
controller.step()
case .saveAddress:
let resumeAddr = payload.addr
let sp = makeSavePoint(resumeAddr, addressOnly: true)
savePoints.append(sp)
controller.step()
case .splitSaving:
let (nextPC, resumeAddr) = payload.pairedAddrAddr
let sp = makeSavePoint(resumeAddr)
savePoints.append(sp)
controller.pc = nextPC
case .clear:
if let _ = savePoints.popLast() {
controller.step()
} else {
fatalError("TODO: What should we do here?")
}
case .peek:
fatalError()
case .restore:
signalFailure()
case .push:
fatalError()
case .pop:
fatalError()
case .call:
controller.step()
callStack.append(controller.pc)
controller.pc = payload.addr
case .ret:
// TODO: Should empty stack mean success?
guard let r = callStack.popLast() else {
tryAccept()
return
}
controller.pc = r
case .abort:
// TODO: throw or otherwise propagate
if let s = payload.optionalString {
doPrint(registers[s])
}
state = .fail
case .accept:
tryAccept()
case .fail:
signalFailure()
case .advance:
if consume(payload.distance) {
controller.step()
}
case .match:
let reg = payload.element
match(registers[reg])
case .matchSequence:
let reg = payload.sequence
let seq = registers[reg]
matchSeq(seq)
case .matchSlice:
let (lower, upper) = payload.pairedPosPos
let range = registers[lower]..<registers[upper]
let slice = input[range]
matchSeq(slice)
case .consumeBy:
let reg = payload.consumer
guard currentPosition < bounds.upperBound,
let nextIndex = registers[reg](
input, currentPosition..<bounds.upperBound)
else {
signalFailure()
return
}
advance(to: nextIndex)
controller.step()
case .assertBy:
let reg = payload.assertion
let assertion = registers[reg]
do {
guard try assertion(input, currentPosition, bounds) else {
signalFailure()
return
}
} catch {
abort(error)
return
}
controller.step()
case .matchBy:
let (matcherReg, valReg) = payload.pairedMatcherValue
let matcher = registers[matcherReg]
do {
guard let (nextIdx, val) = try matcher(
input, currentPosition, bounds
) else {
signalFailure()
return
}
registers[valReg] = val
advance(to: nextIdx)
controller.step()
} catch {
abort(error)
return
}
case .print:
// TODO: Debug stream
doPrint(registers[payload.string])
case .assertion:
let (element, cond) =
payload.pairedElementBool
let result: Bool
if let cur = load(), cur == registers[element] {
result = true
} else {
result = false
}
registers[cond] = result
controller.step()
case .backreference:
let capNum = Int(
asserting: payload.capture.rawValue)
guard capNum < storedCaptures.count else {
fatalError("Should this be an assert?")
}
// TODO:
// Should we assert it's not finished yet?
// What's the behavior there?
let cap = storedCaptures[capNum]
guard let range = cap.latest else {
signalFailure()
return
}
matchSeq(input[range])
case .beginCapture:
let capNum = Int(
asserting: payload.capture.rawValue)
let sp = makeSavePoint(self.currentPC)
storedCaptures[capNum].startCapture(
currentPosition, initial: sp)
controller.step()
case .endCapture:
let capNum = Int(
asserting: payload.capture.rawValue)
storedCaptures[capNum].endCapture(currentPosition)
controller.step()
case .transformCapture:
let (cap, trans) = payload.pairedCaptureTransform
let transform = registers[trans]
let capNum = Int(asserting: cap.rawValue)
guard let range = storedCaptures[capNum].latest else {
fatalError(
"Unreachable: transforming without a capture")
}
do {
// FIXME: Pass input or the slice?
guard let value = try transform(input, range) else {
signalFailure()
return
}
storedCaptures[capNum].registerValue(value)
controller.step()
} catch {
abort(error)
return
}
case .captureValue:
let (val, cap) = payload.pairedValueCapture
let value = registers[val]
let capNum = Int(asserting: cap.rawValue)
let sp = makeSavePoint(self.currentPC)
storedCaptures[capNum].registerValue(
value, overwriteInitial: sp)
controller.step()
}
}
}