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8eabb4ff MW |
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}; | |
c8292b34 | 31 | import scala.util.control.{Breaks, ControlThrowable}; |
8eabb4ff | 32 | |
c8292b34 | 33 | import java.io.{BufferedReader, Closeable, File, InputStream, Reader}; |
8eabb4ff MW |
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); | |
c8292b34 MW |
44 | def unreachable(): Nothing = unreachable("unreachable"); |
45 | final val ok = (); | |
46 | final class Brand; | |
8eabb4ff MW |
47 | |
48 | /*----- Various pieces of implicit magic ----------------------------------*/ | |
49 | ||
50 | class InvalidCStringException(msg: String) extends Exception(msg); | |
8eabb4ff | 51 | |
25c35469 | 52 | object Implicits { |
8eabb4ff MW |
53 | |
54 | /* --- Syntactic sugar for locks --- */ | |
55 | ||
56 | implicit class LockOps(lk: Lock) { | |
57 | /* LK withLock { BODY } | |
58 | * LK.withLock(INTERRUPT) { BODY } | |
25c35469 MW |
59 | * LK.withLock(DUR, [INTERRUPT]) { BODY } orElse { ALT } |
60 | * LK.withLock(DL, [INTERRUPT]) { BODY } orElse { ALT } | |
8eabb4ff MW |
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 | ||
25c35469 | 86 | class PendingLock[T] private[Implicits] |
8eabb4ff MW |
87 | (val lk: Lock, val dur: Duration, |
88 | val interrupt: Boolean, body: => T) { | |
25c35469 | 89 | /* An auxiliary class for LockOps; provides the `orElse' qualifier. */ |
8eabb4ff | 90 | |
25c35469 | 91 | def orElse(alt: => T): T = { |
8eabb4ff MW |
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 | } | |
8eabb4ff MW |
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 | ||
c8292b34 MW |
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 | ||
8eabb4ff MW |
197 | /*----- A gadget for fetching URLs ----------------------------------------*/ |
198 | ||
199 | class URLFetchException(msg: String) extends Exception(msg); | |
200 | ||
201 | trait URLFetchCallbacks { | |
202 | def preflight(conn: URLConnection) { } | |
c8292b34 | 203 | def write(buf: Array[Byte], n: Int, len: Long): Unit; |
8eabb4ff MW |
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(); } | |
c8292b34 | 220 | val explen = c.getContentLength; |
8eabb4ff MW |
221 | |
222 | /* Read a buffer at a time, and give it to the callback. Maintain a | |
223 | * running total. | |
224 | */ | |
c8292b34 MW |
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 | } | |
8eabb4ff MW |
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 | ||
8eabb4ff MW |
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 | ||
c8292b34 MW |
354 | loopUnit { exit => nextToken(s, i) match { |
355 | case Some((w, j)) => b += w; i = j; | |
356 | case None => exit; | |
357 | } } | |
8eabb4ff MW |
358 | b.result |
359 | } | |
360 | ||
c8292b34 MW |
361 | /*----- Other random things -----------------------------------------------*/ |
362 | ||
8eabb4ff | 363 | trait LookaheadIterator[T] extends BufferedIterator[T] { |
c8292b34 MW |
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. */ | |
8eabb4ff | 374 | protected def fetch(): Option[T]; |
c8292b34 MW |
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; | |
8eabb4ff | 380 | private[this] def peek() { |
c8292b34 | 381 | /* Arrange to have a current item. */ |
8eabb4ff MW |
382 | if (st == None) fetch() match { |
383 | case None => st = null; | |
384 | case x@Some(_) => st = x; | |
385 | } | |
386 | } | |
c8292b34 MW |
387 | |
388 | /* The `BufferedIterator' protocol. */ | |
8eabb4ff | 389 | override def hasNext: Boolean = { peek(); st != null } |
c8292b34 | 390 | override def head: T = |
8eabb4ff | 391 | { peek(); if (st == null) throw new NoSuchElementException; st.get } |
c8292b34 | 392 | override def next(): T = { val it = head; st = None; it } |
8eabb4ff MW |
393 | } |
394 | ||
c8292b34 MW |
395 | def bufferedReader(r: Reader): BufferedReader = r match { |
396 | case br: BufferedReader => br | |
397 | case _ => new BufferedReader(r) | |
398 | } | |
8eabb4ff | 399 | |
c8292b34 MW |
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 | } | |
8eabb4ff | 431 | } |
c8292b34 MW |
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 | |
8eabb4ff MW |
455 | } |
456 | ||
457 | /*----- That's all, folks -------------------------------------------------*/ | |
458 | ||
459 | } |