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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; | |
32 | ||
33 | import java.io.{BufferedReader, Closeable, File, 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 | ||
45 | /*----- Various pieces of implicit magic ----------------------------------*/ | |
46 | ||
47 | class InvalidCStringException(msg: String) extends Exception(msg); | |
48 | type CString = Array[Byte]; | |
49 | ||
50 | object Magic { | |
51 | ||
52 | /* --- Syntactic sugar for locks --- */ | |
53 | ||
54 | implicit class LockOps(lk: Lock) { | |
55 | /* LK withLock { BODY } | |
56 | * LK.withLock(INTERRUPT) { BODY } | |
57 | * LK.withLock(DUR, [INTERRUPT]) { BODY } orelse { ALT } | |
58 | * LK.withLock(DL, [INTERRUPT]) { BODY } orelse { ALT } | |
59 | * | |
60 | * Acquire a lock while executing a BODY. If a duration or deadline is | |
61 | * given then wait so long for the lock, and then give up and run ALT | |
62 | * instead. | |
63 | */ | |
64 | ||
65 | def withLock[T](dur: Duration, interrupt: Boolean) | |
66 | (body: => T): PendingLock[T] = | |
67 | new PendingLock(lk, if (dur > Duration.Zero) dur else Duration.Zero, | |
68 | interrupt, body); | |
69 | def withLock[T](dur: Duration)(body: => T): PendingLock[T] = | |
70 | withLock(dur, true)(body); | |
71 | def withLock[T](dl: Deadline, interrupt: Boolean) | |
72 | (body: => T): PendingLock[T] = | |
73 | new PendingLock(lk, dl.timeLeft, interrupt, body); | |
74 | def withLock[T](dl: Deadline)(body: => T): PendingLock[T] = | |
75 | withLock(dl, true)(body); | |
76 | def withLock[T](interrupt: Boolean)(body: => T): T = { | |
77 | if (interrupt) lk.lockInterruptibly(); | |
78 | else lk.lock(); | |
79 | try { body; } finally lk.unlock(); | |
80 | } | |
81 | def withLock[T](body: => T): T = withLock(true)(body); | |
82 | } | |
83 | ||
84 | class PendingLock[T] private[Magic] | |
85 | (val lk: Lock, val dur: Duration, | |
86 | val interrupt: Boolean, body: => T) { | |
87 | /* An auxiliary class for LockOps; provides the `orelse' qualifier. */ | |
88 | ||
89 | def orelse(alt: => T): T = { | |
90 | val locked = (dur, interrupt) match { | |
91 | case (Duration.Inf, true) => lk.lockInterruptibly(); true | |
92 | case (Duration.Inf, false) => lk.lock(); true | |
93 | case (Duration.Zero, false) => lk.tryLock() | |
94 | case (_, true) => lk.tryLock(dur.length, dur.unit) | |
95 | case _ => unreachable("timed wait is always interruptible"); | |
96 | } | |
97 | if (!locked) alt; | |
98 | else try { body; } finally lk.unlock(); | |
99 | } | |
100 | } | |
101 | ||
102 | /* --- Conversion to/from C strings --- */ | |
103 | ||
104 | implicit class ConvertJStringToCString(s: String) { | |
105 | /* Magic to convert a string into a C string (null-terminated bytes). */ | |
106 | ||
107 | def toCString: CString = { | |
108 | /* Convert the receiver to a C string. | |
109 | * | |
110 | * We do this by hand, rather than relying on the JNI's built-in | |
111 | * conversions, because we use the default encoding taken from the | |
112 | * locale settings, rather than the ridiculous `modified UTF-8' which | |
113 | * is (a) insensitive to the user's chosen locale and (b) not actually | |
114 | * UTF-8 either. | |
115 | */ | |
116 | ||
117 | val enc = Charset.defaultCharset.newEncoder; | |
118 | val in = CharBuffer.wrap(s); | |
119 | var sz: Int = (s.length*enc.averageBytesPerChar + 1).toInt; | |
120 | var out = ByteBuffer.allocate(sz); | |
121 | ||
122 | while (true) { | |
123 | /* If there's still stuff to encode, then encode it. Otherwise, | |
124 | * there must be some dregs left in the encoder, so flush them out. | |
125 | */ | |
126 | val r = if (in.hasRemaining) enc.encode(in, out, true) | |
127 | else enc.flush(out); | |
128 | ||
129 | /* Sift through the wreckage to figure out what to do. */ | |
130 | if (r.isError) r.throwException(); | |
131 | else if (r.isOverflow) { | |
132 | /* No space in the buffer. Make it bigger. */ | |
133 | ||
134 | sz *= 2; | |
135 | val newout = ByteBuffer.allocate(sz); | |
136 | out.flip(); newout.put(out); | |
137 | out = newout; | |
138 | } else if (r.isUnderflow) { | |
139 | /* All done. Check that there are no unexpected zero bytes -- so | |
140 | * this will indeed be a valid C string -- and convert into a byte | |
141 | * array that the C code will be able to pick apart. | |
142 | */ | |
143 | ||
144 | out.flip(); val n = out.limit; val u = out.array; | |
145 | if ({val z = u.indexOf(0); 0 <= z && z < n}) | |
146 | throw new InvalidCStringException("null byte in encoding"); | |
147 | val v = new Array[Byte](n + 1); | |
148 | out.array.copyToArray(v, 0, n); | |
149 | v(n) = 0; | |
150 | return v; | |
151 | } | |
152 | } | |
153 | ||
154 | /* Placate the type checker. */ | |
155 | unreachable("unreachable"); | |
156 | } | |
157 | } | |
158 | ||
159 | implicit class ConvertCStringToJString(v: CString) { | |
160 | /* Magic to convert a C string into a `proper' string. */ | |
161 | ||
162 | def toJString: String = { | |
163 | /* Convert the receiver to a C string. | |
164 | * | |
165 | * We do this by hand, rather than relying on the JNI's built-in | |
166 | * conversions, because we use the default encoding taken from the | |
167 | * locale settings, rather than the ridiculous `modified UTF-8' which | |
168 | * is (a) insensitive to the user's chosen locale and (b) not actually | |
169 | * UTF-8 either. | |
170 | */ | |
171 | ||
172 | val inlen = v.indexOf(0) match { | |
173 | case -1 => v.length | |
174 | case n => n | |
175 | } | |
176 | val dec = Charset.defaultCharset.newDecoder; | |
177 | val in = ByteBuffer.wrap(v, 0, inlen); | |
178 | dec.decode(in).toString | |
179 | } | |
180 | } | |
181 | } | |
182 | ||
183 | /*----- Cleanup assistant -------------------------------------------------*/ | |
184 | ||
185 | class Cleaner { | |
186 | /* A helper class for avoiding deep nests of `try'/`finally'. | |
187 | * | |
188 | * Make a `Cleaner' instance CL at the start of your operation. Apply it | |
189 | * to blocks of code -- as CL { ACTION } -- as you proceed, to accumulate | |
190 | * cleanup actions. Finally, call CL.cleanup() to invoke the accumulated | |
191 | * actions, in reverse order. | |
192 | */ | |
193 | ||
194 | var cleanups: List[() => Unit] = Nil; | |
195 | def apply(cleanup: => Unit) { cleanups +:= { () => cleanup; } } | |
196 | def cleanup() { cleanups foreach { _() } } | |
197 | } | |
198 | ||
199 | def withCleaner[T](body: Cleaner => T): T = { | |
200 | /* An easier way to use the `Cleaner' class. Just | |
201 | * | |
202 | * withCleaner { CL => BODY } | |
203 | * | |
204 | * The BODY can attach cleanup actions to the cleaner CL by saying | |
205 | * CL { ACTION } as usual. When the BODY exits, normally or otherwise, the | |
206 | * cleanup actions are invoked in reverse order. | |
207 | */ | |
208 | ||
209 | val cleaner = new Cleaner; | |
210 | try { body(cleaner) } | |
211 | finally { cleaner.cleanup(); } | |
212 | } | |
213 | ||
214 | def closing[T, U <: Closeable](thing: U)(body: U => T): T = | |
215 | try { body(thing) } | |
216 | finally { thing.close(); } | |
217 | ||
218 | /*----- A gadget for fetching URLs ----------------------------------------*/ | |
219 | ||
220 | class URLFetchException(msg: String) extends Exception(msg); | |
221 | ||
222 | trait URLFetchCallbacks { | |
223 | def preflight(conn: URLConnection) { } | |
224 | def write(buf: Array[Byte], n: Int, len: Int): Unit; | |
225 | def done(win: Boolean) { } | |
226 | } | |
227 | ||
228 | def fetchURL(url: URL, cb: URLFetchCallbacks) { | |
229 | /* Fetch the URL, feeding the data through the callbacks CB. */ | |
230 | ||
231 | withCleaner { clean => | |
232 | var win: Boolean = false; | |
233 | clean { cb.done(win); } | |
234 | ||
235 | /* Set up the connection, and run a preflight check. */ | |
236 | val c = url.openConnection(); | |
237 | cb.preflight(c); | |
238 | ||
239 | /* Start fetching data. */ | |
240 | val in = c.getInputStream; clean { in.close(); } | |
241 | val explen = c.getContentLength(); | |
242 | ||
243 | /* Read a buffer at a time, and give it to the callback. Maintain a | |
244 | * running total. | |
245 | */ | |
246 | val buf = new Array[Byte](4096); | |
247 | var n = 0; | |
248 | var len = 0; | |
249 | while ({n = in.read(buf); n >= 0 && (explen == -1 || len <= explen)}) { | |
250 | cb.write(buf, n, len); | |
251 | len += n; | |
252 | } | |
253 | ||
254 | /* I can't find it documented anywhere that the existing machinery | |
255 | * checks the received stream against the advertised content length. | |
256 | * It doesn't hurt to check again, anyway. | |
257 | */ | |
258 | if (explen != -1 && explen != len) { | |
259 | throw new URLFetchException( | |
260 | s"received $len /= $explen bytes from `$url'"); | |
261 | } | |
262 | ||
263 | /* Glorious success is ours. */ | |
264 | win = true; | |
265 | } | |
266 | } | |
267 | ||
268 | /*----- Running processes -------------------------------------------------*/ | |
269 | ||
270 | //def runProgram( | |
271 | ||
272 | /*----- Threading things --------------------------------------------------*/ | |
273 | ||
274 | def thread[T](name: String, run: Boolean = true, daemon: Boolean = true) | |
275 | (f: => T): Thread = { | |
276 | /* Make a thread with a given name, and maybe start running it. */ | |
277 | ||
278 | val t = new Thread(new Runnable { def run() { f; } }, name); | |
279 | if (daemon) t.setDaemon(true); | |
280 | if (run) t.start(); | |
281 | t | |
282 | } | |
283 | ||
284 | /*----- Quoting and parsing tokens ----------------------------------------*/ | |
285 | ||
286 | def quoteTokens(v: Seq[String]): String = { | |
287 | /* Return a string representing the token sequence V. | |
288 | * | |
289 | * The tokens are quoted as necessary. | |
290 | */ | |
291 | ||
292 | val b = new StringBuilder; | |
293 | var sep = false; | |
294 | for (s <- v) { | |
295 | ||
296 | /* If this isn't the first word, then write a separating space. */ | |
297 | if (!sep) sep = true; | |
298 | else b += ' '; | |
299 | ||
300 | /* Decide how to handle this token. */ | |
301 | if (s.length > 0 && | |
302 | (s forall { ch => (ch != ''' && ch != '"' && ch != '\\' && | |
303 | !ch.isWhitespace) })) { | |
304 | /* If this word is nonempty and contains no problematic characters, | |
305 | * we can write it literally. | |
306 | */ | |
307 | ||
308 | b ++= s; | |
309 | } else { | |
310 | /* Otherwise, we shall have to do this the hard way. We could be | |
311 | * cleverer about this, but it's not worth the effort. | |
312 | */ | |
313 | ||
314 | b += '"'; | |
315 | s foreach { ch => | |
316 | if (ch == '"' || ch == '\\') b += '\\'; | |
317 | b += ch; | |
318 | } | |
319 | b += '"'; | |
320 | } | |
321 | } | |
322 | b.result | |
323 | } | |
324 | ||
325 | class InvalidQuotingException(msg: String) extends Exception(msg); | |
326 | ||
327 | def nextToken(s: String, pos: Int = 0): Option[(String, Int)] = { | |
328 | /* Parse the next token from a string S. | |
329 | * | |
330 | * If there is a token in S starting at or after index POS, then return | |
331 | * it, and the index for the following token; otherwise return `None'. | |
332 | */ | |
333 | ||
334 | val b = new StringBuilder; | |
335 | val n = s.length; | |
336 | var i = pos; | |
337 | var q = 0; | |
338 | ||
339 | /* Skip whitespace while we find the next token. */ | |
340 | while (i < n && s(i).isWhitespace) i += 1; | |
341 | ||
342 | /* Maybe there just isn't anything to find. */ | |
343 | if (i >= n) return None; | |
344 | ||
345 | /* There is something there. Unpick the quoting and escaping. */ | |
346 | while (i < n && (q != 0 || !s(i).isWhitespace)) { | |
347 | s(i) match { | |
348 | case '\\' => | |
349 | if (i + 1 >= n) throw new InvalidQuotingException("trailing `\\'"); | |
350 | b += s(i + 1); i += 2; | |
351 | case ch@('"' | ''') => | |
352 | if (q == 0) q = ch; | |
353 | else if (q == ch) q = 0; | |
354 | else b += ch; | |
355 | i += 1; | |
356 | case ch => | |
357 | b += ch; | |
358 | i += 1; | |
359 | } | |
360 | } | |
361 | ||
362 | /* Check that the quoting was valid. */ | |
363 | if (q != 0) throw new InvalidQuotingException(s"unmatched `$q'"); | |
364 | ||
365 | /* Skip whitespace before the next token. */ | |
366 | while (i < n && s(i).isWhitespace) i += 1; | |
367 | ||
368 | /* We're done. */ | |
369 | Some((b.result, i)) | |
370 | } | |
371 | ||
372 | def splitTokens(s: String, pos: Int = 0): Seq[String] = { | |
373 | /* Return all of the tokens in string S into tokens, starting at POS. */ | |
374 | ||
375 | val b = List.newBuilder[String]; | |
376 | var i = pos; | |
377 | ||
378 | while (nextToken(s, i) match { | |
379 | case Some((w, j)) => b += w; i = j; true | |
380 | case None => false | |
381 | }) (); | |
382 | b.result | |
383 | } | |
384 | ||
385 | trait LookaheadIterator[T] extends BufferedIterator[T] { | |
386 | private[this] var st: Option[T] = None; | |
387 | protected def fetch(): Option[T]; | |
388 | private[this] def peek() { | |
389 | if (st == None) fetch() match { | |
390 | case None => st = null; | |
391 | case x@Some(_) => st = x; | |
392 | } | |
393 | } | |
394 | override def hasNext: Boolean = { peek(); st != null } | |
395 | override def head(): T = | |
396 | { peek(); if (st == null) throw new NoSuchElementException; st.get } | |
397 | override def next(): T = { val it = head(); st = None; it } | |
398 | } | |
399 | ||
400 | def lines(r: Reader) = new LookaheadIterator[String] { | |
401 | /* Iterates over the lines of text in a `Reader' object. */ | |
402 | ||
403 | private[this] val in = r match { | |
404 | case br: BufferedReader => br; | |
405 | case _ => new BufferedReader(r); | |
406 | } | |
407 | protected override def fetch(): Option[String] = Option(in.readLine); | |
408 | } | |
409 | ||
410 | /*----- That's all, folks -------------------------------------------------*/ | |
411 | ||
412 | } |