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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); | |
8eabb4ff | 48 | |
25c35469 | 49 | object Implicits { |
8eabb4ff MW |
50 | |
51 | /* --- Syntactic sugar for locks --- */ | |
52 | ||
53 | implicit class LockOps(lk: Lock) { | |
54 | /* LK withLock { BODY } | |
55 | * LK.withLock(INTERRUPT) { BODY } | |
25c35469 MW |
56 | * LK.withLock(DUR, [INTERRUPT]) { BODY } orElse { ALT } |
57 | * LK.withLock(DL, [INTERRUPT]) { BODY } orElse { ALT } | |
8eabb4ff MW |
58 | * |
59 | * Acquire a lock while executing a BODY. If a duration or deadline is | |
60 | * given then wait so long for the lock, and then give up and run ALT | |
61 | * instead. | |
62 | */ | |
63 | ||
64 | def withLock[T](dur: Duration, interrupt: Boolean) | |
65 | (body: => T): PendingLock[T] = | |
66 | new PendingLock(lk, if (dur > Duration.Zero) dur else Duration.Zero, | |
67 | interrupt, body); | |
68 | def withLock[T](dur: Duration)(body: => T): PendingLock[T] = | |
69 | withLock(dur, true)(body); | |
70 | def withLock[T](dl: Deadline, interrupt: Boolean) | |
71 | (body: => T): PendingLock[T] = | |
72 | new PendingLock(lk, dl.timeLeft, interrupt, body); | |
73 | def withLock[T](dl: Deadline)(body: => T): PendingLock[T] = | |
74 | withLock(dl, true)(body); | |
75 | def withLock[T](interrupt: Boolean)(body: => T): T = { | |
76 | if (interrupt) lk.lockInterruptibly(); | |
77 | else lk.lock(); | |
78 | try { body; } finally lk.unlock(); | |
79 | } | |
80 | def withLock[T](body: => T): T = withLock(true)(body); | |
81 | } | |
82 | ||
25c35469 | 83 | class PendingLock[T] private[Implicits] |
8eabb4ff MW |
84 | (val lk: Lock, val dur: Duration, |
85 | val interrupt: Boolean, body: => T) { | |
25c35469 | 86 | /* An auxiliary class for LockOps; provides the `orElse' qualifier. */ |
8eabb4ff | 87 | |
25c35469 | 88 | def orElse(alt: => T): T = { |
8eabb4ff MW |
89 | val locked = (dur, interrupt) match { |
90 | case (Duration.Inf, true) => lk.lockInterruptibly(); true | |
91 | case (Duration.Inf, false) => lk.lock(); true | |
92 | case (Duration.Zero, false) => lk.tryLock() | |
93 | case (_, true) => lk.tryLock(dur.length, dur.unit) | |
94 | case _ => unreachable("timed wait is always interruptible"); | |
95 | } | |
96 | if (!locked) alt; | |
97 | else try { body; } finally lk.unlock(); | |
98 | } | |
99 | } | |
8eabb4ff MW |
100 | } |
101 | ||
102 | /*----- Cleanup assistant -------------------------------------------------*/ | |
103 | ||
104 | class Cleaner { | |
105 | /* A helper class for avoiding deep nests of `try'/`finally'. | |
106 | * | |
107 | * Make a `Cleaner' instance CL at the start of your operation. Apply it | |
108 | * to blocks of code -- as CL { ACTION } -- as you proceed, to accumulate | |
109 | * cleanup actions. Finally, call CL.cleanup() to invoke the accumulated | |
110 | * actions, in reverse order. | |
111 | */ | |
112 | ||
113 | var cleanups: List[() => Unit] = Nil; | |
114 | def apply(cleanup: => Unit) { cleanups +:= { () => cleanup; } } | |
115 | def cleanup() { cleanups foreach { _() } } | |
116 | } | |
117 | ||
118 | def withCleaner[T](body: Cleaner => T): T = { | |
119 | /* An easier way to use the `Cleaner' class. Just | |
120 | * | |
121 | * withCleaner { CL => BODY } | |
122 | * | |
123 | * The BODY can attach cleanup actions to the cleaner CL by saying | |
124 | * CL { ACTION } as usual. When the BODY exits, normally or otherwise, the | |
125 | * cleanup actions are invoked in reverse order. | |
126 | */ | |
127 | ||
128 | val cleaner = new Cleaner; | |
129 | try { body(cleaner) } | |
130 | finally { cleaner.cleanup(); } | |
131 | } | |
132 | ||
133 | def closing[T, U <: Closeable](thing: U)(body: U => T): T = | |
134 | try { body(thing) } | |
135 | finally { thing.close(); } | |
136 | ||
137 | /*----- A gadget for fetching URLs ----------------------------------------*/ | |
138 | ||
139 | class URLFetchException(msg: String) extends Exception(msg); | |
140 | ||
141 | trait URLFetchCallbacks { | |
142 | def preflight(conn: URLConnection) { } | |
143 | def write(buf: Array[Byte], n: Int, len: Int): Unit; | |
144 | def done(win: Boolean) { } | |
145 | } | |
146 | ||
147 | def fetchURL(url: URL, cb: URLFetchCallbacks) { | |
148 | /* Fetch the URL, feeding the data through the callbacks CB. */ | |
149 | ||
150 | withCleaner { clean => | |
151 | var win: Boolean = false; | |
152 | clean { cb.done(win); } | |
153 | ||
154 | /* Set up the connection, and run a preflight check. */ | |
155 | val c = url.openConnection(); | |
156 | cb.preflight(c); | |
157 | ||
158 | /* Start fetching data. */ | |
159 | val in = c.getInputStream; clean { in.close(); } | |
160 | val explen = c.getContentLength(); | |
161 | ||
162 | /* Read a buffer at a time, and give it to the callback. Maintain a | |
163 | * running total. | |
164 | */ | |
165 | val buf = new Array[Byte](4096); | |
166 | var n = 0; | |
167 | var len = 0; | |
168 | while ({n = in.read(buf); n >= 0 && (explen == -1 || len <= explen)}) { | |
169 | cb.write(buf, n, len); | |
170 | len += n; | |
171 | } | |
172 | ||
173 | /* I can't find it documented anywhere that the existing machinery | |
174 | * checks the received stream against the advertised content length. | |
175 | * It doesn't hurt to check again, anyway. | |
176 | */ | |
177 | if (explen != -1 && explen != len) { | |
178 | throw new URLFetchException( | |
179 | s"received $len /= $explen bytes from `$url'"); | |
180 | } | |
181 | ||
182 | /* Glorious success is ours. */ | |
183 | win = true; | |
184 | } | |
185 | } | |
186 | ||
187 | /*----- Running processes -------------------------------------------------*/ | |
188 | ||
189 | //def runProgram( | |
190 | ||
191 | /*----- Threading things --------------------------------------------------*/ | |
192 | ||
193 | def thread[T](name: String, run: Boolean = true, daemon: Boolean = true) | |
194 | (f: => T): Thread = { | |
195 | /* Make a thread with a given name, and maybe start running it. */ | |
196 | ||
197 | val t = new Thread(new Runnable { def run() { f; } }, name); | |
198 | if (daemon) t.setDaemon(true); | |
199 | if (run) t.start(); | |
200 | t | |
201 | } | |
202 | ||
203 | /*----- Quoting and parsing tokens ----------------------------------------*/ | |
204 | ||
205 | def quoteTokens(v: Seq[String]): String = { | |
206 | /* Return a string representing the token sequence V. | |
207 | * | |
208 | * The tokens are quoted as necessary. | |
209 | */ | |
210 | ||
211 | val b = new StringBuilder; | |
212 | var sep = false; | |
213 | for (s <- v) { | |
214 | ||
215 | /* If this isn't the first word, then write a separating space. */ | |
216 | if (!sep) sep = true; | |
217 | else b += ' '; | |
218 | ||
219 | /* Decide how to handle this token. */ | |
220 | if (s.length > 0 && | |
221 | (s forall { ch => (ch != ''' && ch != '"' && ch != '\\' && | |
222 | !ch.isWhitespace) })) { | |
223 | /* If this word is nonempty and contains no problematic characters, | |
224 | * we can write it literally. | |
225 | */ | |
226 | ||
227 | b ++= s; | |
228 | } else { | |
229 | /* Otherwise, we shall have to do this the hard way. We could be | |
230 | * cleverer about this, but it's not worth the effort. | |
231 | */ | |
232 | ||
233 | b += '"'; | |
234 | s foreach { ch => | |
235 | if (ch == '"' || ch == '\\') b += '\\'; | |
236 | b += ch; | |
237 | } | |
238 | b += '"'; | |
239 | } | |
240 | } | |
241 | b.result | |
242 | } | |
243 | ||
244 | class InvalidQuotingException(msg: String) extends Exception(msg); | |
245 | ||
246 | def nextToken(s: String, pos: Int = 0): Option[(String, Int)] = { | |
247 | /* Parse the next token from a string S. | |
248 | * | |
249 | * If there is a token in S starting at or after index POS, then return | |
250 | * it, and the index for the following token; otherwise return `None'. | |
251 | */ | |
252 | ||
253 | val b = new StringBuilder; | |
254 | val n = s.length; | |
255 | var i = pos; | |
256 | var q = 0; | |
257 | ||
258 | /* Skip whitespace while we find the next token. */ | |
259 | while (i < n && s(i).isWhitespace) i += 1; | |
260 | ||
261 | /* Maybe there just isn't anything to find. */ | |
262 | if (i >= n) return None; | |
263 | ||
264 | /* There is something there. Unpick the quoting and escaping. */ | |
265 | while (i < n && (q != 0 || !s(i).isWhitespace)) { | |
266 | s(i) match { | |
267 | case '\\' => | |
268 | if (i + 1 >= n) throw new InvalidQuotingException("trailing `\\'"); | |
269 | b += s(i + 1); i += 2; | |
270 | case ch@('"' | ''') => | |
271 | if (q == 0) q = ch; | |
272 | else if (q == ch) q = 0; | |
273 | else b += ch; | |
274 | i += 1; | |
275 | case ch => | |
276 | b += ch; | |
277 | i += 1; | |
278 | } | |
279 | } | |
280 | ||
281 | /* Check that the quoting was valid. */ | |
282 | if (q != 0) throw new InvalidQuotingException(s"unmatched `$q'"); | |
283 | ||
284 | /* Skip whitespace before the next token. */ | |
285 | while (i < n && s(i).isWhitespace) i += 1; | |
286 | ||
287 | /* We're done. */ | |
288 | Some((b.result, i)) | |
289 | } | |
290 | ||
291 | def splitTokens(s: String, pos: Int = 0): Seq[String] = { | |
292 | /* Return all of the tokens in string S into tokens, starting at POS. */ | |
293 | ||
294 | val b = List.newBuilder[String]; | |
295 | var i = pos; | |
296 | ||
297 | while (nextToken(s, i) match { | |
298 | case Some((w, j)) => b += w; i = j; true | |
299 | case None => false | |
300 | }) (); | |
301 | b.result | |
302 | } | |
303 | ||
304 | trait LookaheadIterator[T] extends BufferedIterator[T] { | |
305 | private[this] var st: Option[T] = None; | |
306 | protected def fetch(): Option[T]; | |
307 | private[this] def peek() { | |
308 | if (st == None) fetch() match { | |
309 | case None => st = null; | |
310 | case x@Some(_) => st = x; | |
311 | } | |
312 | } | |
313 | override def hasNext: Boolean = { peek(); st != null } | |
314 | override def head(): T = | |
315 | { peek(); if (st == null) throw new NoSuchElementException; st.get } | |
316 | override def next(): T = { val it = head(); st = None; it } | |
317 | } | |
318 | ||
319 | def lines(r: Reader) = new LookaheadIterator[String] { | |
320 | /* Iterates over the lines of text in a `Reader' object. */ | |
321 | ||
322 | private[this] val in = r match { | |
323 | case br: BufferedReader => br; | |
324 | case _ => new BufferedReader(r); | |
325 | } | |
326 | protected override def fetch(): Option[String] = Option(in.readLine); | |
327 | } | |
328 | ||
329 | /*----- That's all, folks -------------------------------------------------*/ | |
330 | ||
331 | } |