| 1 | /* -*-scala-*- |
| 2 | * |
| 3 | * Miscellaneous utilities |
| 4 | * |
| 5 | * (c) 2018 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of the Trivial IP Encryption (TrIPE) Android app. |
| 11 | * |
| 12 | * TrIPE is free software: you can redistribute it and/or modify it under |
| 13 | * the terms of the GNU General Public License as published by the Free |
| 14 | * Software Foundation; either version 3 of the License, or (at your |
| 15 | * option) any later version. |
| 16 | * |
| 17 | * TrIPE is distributed in the hope that it will be useful, but WITHOUT |
| 18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 20 | * for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with TrIPE. If not, see <https://www.gnu.org/licenses/>. |
| 24 | */ |
| 25 | |
| 26 | package uk.org.distorted; package object tripe { |
| 27 | |
| 28 | /*----- Imports -----------------------------------------------------------*/ |
| 29 | |
| 30 | import scala.concurrent.duration.{Deadline, Duration}; |
| 31 | import scala.util.control.{Breaks, ControlThrowable}; |
| 32 | |
| 33 | import java.io.{BufferedReader, Closeable, File, InputStream, Reader}; |
| 34 | import java.net.{URL, URLConnection}; |
| 35 | import java.nio.{ByteBuffer, CharBuffer}; |
| 36 | import java.nio.charset.Charset; |
| 37 | import java.util.concurrent.locks.{Lock, ReentrantLock}; |
| 38 | |
| 39 | /*----- Miscellaneous useful things ---------------------------------------*/ |
| 40 | |
| 41 | val rng = new java.security.SecureRandom; |
| 42 | |
| 43 | def unreachable(msg: String): Nothing = throw new AssertionError(msg); |
| 44 | def unreachable(): Nothing = unreachable("unreachable"); |
| 45 | final val ok = (); |
| 46 | final class Brand; |
| 47 | |
| 48 | /*----- Various pieces of implicit magic ----------------------------------*/ |
| 49 | |
| 50 | class InvalidCStringException(msg: String) extends Exception(msg); |
| 51 | |
| 52 | object Implicits { |
| 53 | |
| 54 | /* --- Syntactic sugar for locks --- */ |
| 55 | |
| 56 | implicit class LockOps(lk: Lock) { |
| 57 | /* LK withLock { BODY } |
| 58 | * LK.withLock(INTERRUPT) { BODY } |
| 59 | * LK.withLock(DUR, [INTERRUPT]) { BODY } orElse { ALT } |
| 60 | * LK.withLock(DL, [INTERRUPT]) { BODY } orElse { ALT } |
| 61 | * |
| 62 | * Acquire a lock while executing a BODY. If a duration or deadline is |
| 63 | * given then wait so long for the lock, and then give up and run ALT |
| 64 | * instead. |
| 65 | */ |
| 66 | |
| 67 | def withLock[T](dur: Duration, interrupt: Boolean) |
| 68 | (body: => T): PendingLock[T] = |
| 69 | new PendingLock(lk, if (dur > Duration.Zero) dur else Duration.Zero, |
| 70 | interrupt, body); |
| 71 | def withLock[T](dur: Duration)(body: => T): PendingLock[T] = |
| 72 | withLock(dur, true)(body); |
| 73 | def withLock[T](dl: Deadline, interrupt: Boolean) |
| 74 | (body: => T): PendingLock[T] = |
| 75 | new PendingLock(lk, dl.timeLeft, interrupt, body); |
| 76 | def withLock[T](dl: Deadline)(body: => T): PendingLock[T] = |
| 77 | withLock(dl, true)(body); |
| 78 | def withLock[T](interrupt: Boolean)(body: => T): T = { |
| 79 | if (interrupt) lk.lockInterruptibly(); |
| 80 | else lk.lock(); |
| 81 | try { body; } finally lk.unlock(); |
| 82 | } |
| 83 | def withLock[T](body: => T): T = withLock(true)(body); |
| 84 | } |
| 85 | |
| 86 | class PendingLock[T] private[Implicits] |
| 87 | (val lk: Lock, val dur: Duration, |
| 88 | val interrupt: Boolean, body: => T) { |
| 89 | /* An auxiliary class for LockOps; provides the `orElse' qualifier. */ |
| 90 | |
| 91 | def orElse(alt: => T): T = { |
| 92 | val locked = (dur, interrupt) match { |
| 93 | case (Duration.Inf, true) => lk.lockInterruptibly(); true |
| 94 | case (Duration.Inf, false) => lk.lock(); true |
| 95 | case (Duration.Zero, false) => lk.tryLock() |
| 96 | case (_, true) => lk.tryLock(dur.length, dur.unit) |
| 97 | case _ => unreachable("timed wait is always interruptible"); |
| 98 | } |
| 99 | if (!locked) alt; |
| 100 | else try { body; } finally lk.unlock(); |
| 101 | } |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | /*----- Cleanup assistant -------------------------------------------------*/ |
| 106 | |
| 107 | class Cleaner { |
| 108 | /* A helper class for avoiding deep nests of `try'/`finally'. |
| 109 | * |
| 110 | * Make a `Cleaner' instance CL at the start of your operation. Apply it |
| 111 | * to blocks of code -- as CL { ACTION } -- as you proceed, to accumulate |
| 112 | * cleanup actions. Finally, call CL.cleanup() to invoke the accumulated |
| 113 | * actions, in reverse order. |
| 114 | */ |
| 115 | |
| 116 | var cleanups: List[() => Unit] = Nil; |
| 117 | def apply(cleanup: => Unit) { cleanups +:= { () => cleanup; } } |
| 118 | def cleanup() { cleanups foreach { _() } } |
| 119 | } |
| 120 | |
| 121 | def withCleaner[T](body: Cleaner => T): T = { |
| 122 | /* An easier way to use the `Cleaner' class. Just |
| 123 | * |
| 124 | * withCleaner { CL => BODY } |
| 125 | * |
| 126 | * The BODY can attach cleanup actions to the cleaner CL by saying |
| 127 | * CL { ACTION } as usual. When the BODY exits, normally or otherwise, the |
| 128 | * cleanup actions are invoked in reverse order. |
| 129 | */ |
| 130 | |
| 131 | val cleaner = new Cleaner; |
| 132 | try { body(cleaner) } |
| 133 | finally { cleaner.cleanup(); } |
| 134 | } |
| 135 | |
| 136 | def closing[T, U <: Closeable](thing: U)(body: U => T): T = |
| 137 | try { body(thing) } |
| 138 | finally { thing.close(); } |
| 139 | |
| 140 | /*----- Control structures ------------------------------------------------*/ |
| 141 | |
| 142 | private case class ExitBlock[T](brand: Brand, result: T) |
| 143 | extends ControlThrowable; |
| 144 | |
| 145 | def block[T](body: (T => Nothing) => T): T = { |
| 146 | /* block { exit[T] => ...; exit(x); ... } |
| 147 | * |
| 148 | * Execute the body until it calls the `exit' function or finishes. |
| 149 | * Annoyingly, Scala isn't clever enough to infer the return type, so |
| 150 | * you'll have to write it explicitly. |
| 151 | */ |
| 152 | |
| 153 | val mybrand = new Brand; |
| 154 | try { body { result => throw new ExitBlock(mybrand, result) } } |
| 155 | catch { |
| 156 | case ExitBlock(brand, result) if brand eq mybrand => |
| 157 | result.asInstanceOf[T] |
| 158 | } |
| 159 | } |
| 160 | |
| 161 | def blockUnit(body: (=> Nothing) => Unit) { |
| 162 | /* blockUnit { exit => ...; exit; ... } |
| 163 | * |
| 164 | * Like `block'; it just saves you having to write `exit[Unit] => ...; |
| 165 | * exit(ok); ...'. |
| 166 | */ |
| 167 | |
| 168 | val mybrand = new Brand; |
| 169 | try { body { throw new ExitBlock(mybrand, null) }; } |
| 170 | catch { case ExitBlock(brand, result) if brand eq mybrand => ok; } |
| 171 | } |
| 172 | |
| 173 | def loop[T](body: (T => Nothing) => Unit): T = { |
| 174 | /* loop { exit[T] => ...; exit(x); ... } |
| 175 | * |
| 176 | * Repeatedly execute the body until it calls the `exit' function. |
| 177 | * Annoyingly, Scala isn't clever enough to infer the return type, so |
| 178 | * you'll have to write it explicitly. |
| 179 | */ |
| 180 | |
| 181 | block { exit => while (true) body(exit); unreachable } |
| 182 | } |
| 183 | |
| 184 | def loopUnit(body: (=> Nothing) => Unit): Unit = { |
| 185 | /* loopUnit { exit => ...; exit; ... } |
| 186 | * |
| 187 | * Like `loop'; it just saves you having to write `exit[Unit] => ...; |
| 188 | * exit(()); ...'. |
| 189 | */ |
| 190 | |
| 191 | blockUnit { exit => while (true) body(exit); } |
| 192 | } |
| 193 | |
| 194 | val BREAKS = new Breaks; |
| 195 | import BREAKS.{breakable, break}; |
| 196 | |
| 197 | /*----- A gadget for fetching URLs ----------------------------------------*/ |
| 198 | |
| 199 | class URLFetchException(msg: String) extends Exception(msg); |
| 200 | |
| 201 | trait URLFetchCallbacks { |
| 202 | def preflight(conn: URLConnection) { } |
| 203 | def write(buf: Array[Byte], n: Int, len: Long): Unit; |
| 204 | def done(win: Boolean) { } |
| 205 | } |
| 206 | |
| 207 | def fetchURL(url: URL, cb: URLFetchCallbacks) { |
| 208 | /* Fetch the URL, feeding the data through the callbacks CB. */ |
| 209 | |
| 210 | withCleaner { clean => |
| 211 | var win: Boolean = false; |
| 212 | clean { cb.done(win); } |
| 213 | |
| 214 | /* Set up the connection, and run a preflight check. */ |
| 215 | val c = url.openConnection(); |
| 216 | cb.preflight(c); |
| 217 | |
| 218 | /* Start fetching data. */ |
| 219 | val in = c.getInputStream; clean { in.close(); } |
| 220 | val explen = c.getContentLength; |
| 221 | |
| 222 | /* Read a buffer at a time, and give it to the callback. Maintain a |
| 223 | * running total. |
| 224 | */ |
| 225 | var len: Long = 0; |
| 226 | blockUnit { exit => |
| 227 | for ((buf, n) <- blocks(in)) { |
| 228 | cb.write(buf, n, len); |
| 229 | len += n; |
| 230 | if (explen != -1 && len > explen) exit; |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | /* I can't find it documented anywhere that the existing machinery |
| 235 | * checks the received stream against the advertised content length. |
| 236 | * It doesn't hurt to check again, anyway. |
| 237 | */ |
| 238 | if (explen != -1 && explen != len) { |
| 239 | throw new URLFetchException( |
| 240 | s"received $len /= $explen bytes from `$url'"); |
| 241 | } |
| 242 | |
| 243 | /* Glorious success is ours. */ |
| 244 | win = true; |
| 245 | } |
| 246 | } |
| 247 | |
| 248 | /*----- Threading things --------------------------------------------------*/ |
| 249 | |
| 250 | def thread[T](name: String, run: Boolean = true, daemon: Boolean = true) |
| 251 | (f: => T): Thread = { |
| 252 | /* Make a thread with a given name, and maybe start running it. */ |
| 253 | |
| 254 | val t = new Thread(new Runnable { def run() { f; } }, name); |
| 255 | if (daemon) t.setDaemon(true); |
| 256 | if (run) t.start(); |
| 257 | t |
| 258 | } |
| 259 | |
| 260 | /*----- Quoting and parsing tokens ----------------------------------------*/ |
| 261 | |
| 262 | def quoteTokens(v: Seq[String]): String = { |
| 263 | /* Return a string representing the token sequence V. |
| 264 | * |
| 265 | * The tokens are quoted as necessary. |
| 266 | */ |
| 267 | |
| 268 | val b = new StringBuilder; |
| 269 | var sep = false; |
| 270 | for (s <- v) { |
| 271 | |
| 272 | /* If this isn't the first word, then write a separating space. */ |
| 273 | if (!sep) sep = true; |
| 274 | else b += ' '; |
| 275 | |
| 276 | /* Decide how to handle this token. */ |
| 277 | if (s.length > 0 && |
| 278 | (s forall { ch => (ch != ''' && ch != '"' && ch != '\\' && |
| 279 | !ch.isWhitespace) })) { |
| 280 | /* If this word is nonempty and contains no problematic characters, |
| 281 | * we can write it literally. |
| 282 | */ |
| 283 | |
| 284 | b ++= s; |
| 285 | } else { |
| 286 | /* Otherwise, we shall have to do this the hard way. We could be |
| 287 | * cleverer about this, but it's not worth the effort. |
| 288 | */ |
| 289 | |
| 290 | b += '"'; |
| 291 | s foreach { ch => |
| 292 | if (ch == '"' || ch == '\\') b += '\\'; |
| 293 | b += ch; |
| 294 | } |
| 295 | b += '"'; |
| 296 | } |
| 297 | } |
| 298 | b.result |
| 299 | } |
| 300 | |
| 301 | class InvalidQuotingException(msg: String) extends Exception(msg); |
| 302 | |
| 303 | def nextToken(s: String, pos: Int = 0): Option[(String, Int)] = { |
| 304 | /* Parse the next token from a string S. |
| 305 | * |
| 306 | * If there is a token in S starting at or after index POS, then return |
| 307 | * it, and the index for the following token; otherwise return `None'. |
| 308 | */ |
| 309 | |
| 310 | val b = new StringBuilder; |
| 311 | val n = s.length; |
| 312 | var i = pos; |
| 313 | var q = 0; |
| 314 | |
| 315 | /* Skip whitespace while we find the next token. */ |
| 316 | while (i < n && s(i).isWhitespace) i += 1; |
| 317 | |
| 318 | /* Maybe there just isn't anything to find. */ |
| 319 | if (i >= n) return None; |
| 320 | |
| 321 | /* There is something there. Unpick the quoting and escaping. */ |
| 322 | while (i < n && (q != 0 || !s(i).isWhitespace)) { |
| 323 | s(i) match { |
| 324 | case '\\' => |
| 325 | if (i + 1 >= n) throw new InvalidQuotingException("trailing `\\'"); |
| 326 | b += s(i + 1); i += 2; |
| 327 | case ch@('"' | ''') => |
| 328 | if (q == 0) q = ch; |
| 329 | else if (q == ch) q = 0; |
| 330 | else b += ch; |
| 331 | i += 1; |
| 332 | case ch => |
| 333 | b += ch; |
| 334 | i += 1; |
| 335 | } |
| 336 | } |
| 337 | |
| 338 | /* Check that the quoting was valid. */ |
| 339 | if (q != 0) throw new InvalidQuotingException(s"unmatched `$q'"); |
| 340 | |
| 341 | /* Skip whitespace before the next token. */ |
| 342 | while (i < n && s(i).isWhitespace) i += 1; |
| 343 | |
| 344 | /* We're done. */ |
| 345 | Some((b.result, i)) |
| 346 | } |
| 347 | |
| 348 | def splitTokens(s: String, pos: Int = 0): Seq[String] = { |
| 349 | /* Return all of the tokens in string S into tokens, starting at POS. */ |
| 350 | |
| 351 | val b = List.newBuilder[String]; |
| 352 | var i = pos; |
| 353 | |
| 354 | loopUnit { exit => nextToken(s, i) match { |
| 355 | case Some((w, j)) => b += w; i = j; |
| 356 | case None => exit; |
| 357 | } } |
| 358 | b.result |
| 359 | } |
| 360 | |
| 361 | /*----- Other random things -----------------------------------------------*/ |
| 362 | |
| 363 | trait LookaheadIterator[T] extends BufferedIterator[T] { |
| 364 | /* An iterator in terms of a single `maybe there's another item' function. |
| 365 | * |
| 366 | * It seems like every time I write an iterator in Scala, the only way to |
| 367 | * find out whether there's a next item, for `hasNext', is to actually try |
| 368 | * to fetch it. So here's an iterator in terms of a function which goes |
| 369 | * off and maybe returns a next thing. It turns out to be easy to satisfy |
| 370 | * the additional requirements for `BufferedIterator', so why not? |
| 371 | */ |
| 372 | |
| 373 | /* Subclass responsibility. */ |
| 374 | protected def fetch(): Option[T]; |
| 375 | |
| 376 | /* The machinery. `st' is `None' if there's no current item, null if we've |
| 377 | * actually hit the end, or `Some(x)' if the current item is x. |
| 378 | */ |
| 379 | private[this] var st: Option[T] = None; |
| 380 | private[this] def peek() { |
| 381 | /* Arrange to have a current item. */ |
| 382 | if (st == None) fetch() match { |
| 383 | case None => st = null; |
| 384 | case x@Some(_) => st = x; |
| 385 | } |
| 386 | } |
| 387 | |
| 388 | /* The `BufferedIterator' protocol. */ |
| 389 | override def hasNext: Boolean = { peek(); st != null } |
| 390 | override def head: T = |
| 391 | { peek(); if (st == null) throw new NoSuchElementException; st.get } |
| 392 | override def next(): T = { val it = head; st = None; it } |
| 393 | } |
| 394 | |
| 395 | def bufferedReader(r: Reader): BufferedReader = r match { |
| 396 | case br: BufferedReader => br |
| 397 | case _ => new BufferedReader(r) |
| 398 | } |
| 399 | |
| 400 | def lines(r: BufferedReader): BufferedIterator[String] = |
| 401 | new LookaheadIterator[String] { |
| 402 | /* Iterates over the lines of text in a `Reader' object. */ |
| 403 | override protected def fetch() = Option(r.readLine()); |
| 404 | } |
| 405 | def lines(r: Reader): BufferedIterator[String] = lines(bufferedReader(r)); |
| 406 | |
| 407 | def blocks(in: InputStream, blksz: Int): |
| 408 | BufferedIterator[(Array[Byte], Int)] = |
| 409 | /* Iterates over (possibly irregularly sized) blocks in a stream. */ |
| 410 | new LookaheadIterator[(Array[Byte], Int)] { |
| 411 | val buf = new Array[Byte](blksz) |
| 412 | override protected def fetch() = { |
| 413 | val n = in.read(buf); |
| 414 | if (n < 0) None |
| 415 | else Some((buf, n)) |
| 416 | } |
| 417 | } |
| 418 | def blocks(in: InputStream): |
| 419 | BufferedIterator[(Array[Byte], Int)] = blocks(in, 4096); |
| 420 | |
| 421 | def blocks(in: BufferedReader, blksz: Int): |
| 422 | BufferedIterator[(Array[Char], Int)] = |
| 423 | /* Iterates over (possibly irregularly sized) blocks in a reader. */ |
| 424 | new LookaheadIterator[(Array[Char], Int)] { |
| 425 | val buf = new Array[Char](blksz) |
| 426 | override protected def fetch() = { |
| 427 | val n = in.read(buf); |
| 428 | if (n < 0) None |
| 429 | else Some((buf, n)) |
| 430 | } |
| 431 | } |
| 432 | def blocks(in: BufferedReader): |
| 433 | BufferedIterator[(Array[Char], Int)] = blocks(in, 4096); |
| 434 | def blocks(r: Reader, blksz: Int): BufferedIterator[(Array[Char], Int)] = |
| 435 | blocks(bufferedReader(r), blksz); |
| 436 | def blocks(r: Reader): BufferedIterator[(Array[Char], Int)] = |
| 437 | blocks(bufferedReader(r)); |
| 438 | |
| 439 | def oxford(conj: String, things: Seq[String]): String = things match { |
| 440 | case Seq() => "<nothing>" |
| 441 | case Seq(a) => a |
| 442 | case Seq(a, b) => s"$a $conj $b" |
| 443 | case Seq(a, tail@_*) => |
| 444 | val sb = new StringBuilder; |
| 445 | sb ++= a; sb ++= ", "; |
| 446 | def iter(rest: Seq[String]) { |
| 447 | rest match { |
| 448 | case Seq() => unreachable; |
| 449 | case Seq(a) => sb ++= conj; sb += ' '; sb ++= a; |
| 450 | case Seq(a, tail@_*) => sb ++= a; sb ++= ", "; iter(tail); |
| 451 | } |
| 452 | } |
| 453 | iter(tail); |
| 454 | sb.result |
| 455 | } |
| 456 | |
| 457 | /*----- That's all, folks -------------------------------------------------*/ |
| 458 | |
| 459 | } |