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1 | /*******************************************************************************. |
2 | * Copyright (c) 2011-2012 Ericsson, Ecole Polytechnique de Montreal and others | |
3 | * | |
4 | * All rights reserved. This program and the accompanying materials are made | |
5 | * available under the terms of the Eclipse Public License v1.0 which | |
6 | * accompanies this distribution, and is available at | |
7 | * http://www.eclipse.org/legal/epl-v10.html | |
8 | * | |
9 | * Contributors: Matthew Khouzam - Initial Design and implementation | |
10 | * Contributors: Francis Giraldeau - Initial API and implementation | |
11 | * Contributors: Philippe Proulx - Some refinement and optimization | |
12 | *******************************************************************************/ | |
13 | ||
14 | package org.eclipse.linuxtools.ctf.core.event.io; | |
15 | ||
16 | import java.nio.BufferOverflowException; | |
17 | import java.nio.ByteBuffer; | |
18 | import java.nio.ByteOrder; | |
19 | ||
20 | /** | |
21 | * <b><u>BitBuffer</u></b> | |
22 | * <p> | |
23 | * A bitwise buffer capable of accessing fields with bit offsets. | |
24 | * @since 2.0 | |
25 | */ | |
26 | public class BitBuffer { | |
27 | ||
28 | // ------------------------------------------------------------------------ | |
29 | // Constants | |
30 | // ------------------------------------------------------------------------ | |
31 | ||
32 | /* default bit width */ | |
33 | /** 8 bits to a char */ | |
34 | public static final int BIT_CHAR = 8; | |
35 | /** 16 bits to a short */ | |
36 | public static final int BIT_SHORT = 16; | |
37 | /** 32 bits to an int */ | |
38 | public static final int BIT_INT = 32; | |
39 | /** 32 bits to a float */ | |
40 | public static final int BIT_FLOAT = 32; | |
41 | /** 64 bits to a long */ | |
42 | public static final int BIT_LONG = 64; | |
43 | ||
44 | // ------------------------------------------------------------------------ | |
45 | // Attributes | |
46 | // ------------------------------------------------------------------------ | |
47 | ||
48 | private ByteBuffer buf; | |
49 | private int pos; | |
50 | private ByteOrder byteOrder; | |
51 | ||
52 | // ------------------------------------------------------------------------ | |
53 | // Constructors | |
54 | // ------------------------------------------------------------------------ | |
55 | /** | |
56 | * Default constructor, makes a bigendian buffer | |
57 | */ | |
58 | public BitBuffer() { | |
59 | this(null, ByteOrder.BIG_ENDIAN); | |
60 | } | |
61 | ||
62 | /** | |
63 | * Constructor, makes a bigendian buffer | |
64 | * | |
65 | * @param buf | |
66 | * the bytebuffer to read | |
67 | */ | |
68 | public BitBuffer(ByteBuffer buf) { | |
69 | this(buf, ByteOrder.BIG_ENDIAN); | |
70 | } | |
71 | ||
72 | /** | |
73 | * Constructor that is fully parametrisable | |
74 | * | |
75 | * @param buf | |
76 | * the buffer to read | |
77 | * @param order | |
78 | * the byte order (big endian, little endian, network?) | |
79 | */ | |
80 | public BitBuffer(ByteBuffer buf, ByteOrder order) { | |
81 | setByteBuffer(buf); | |
82 | setByteOrder(order); | |
83 | position(0); | |
84 | } | |
85 | ||
86 | // ------------------------------------------------------------------------ | |
87 | // 'Get' operations on buffer | |
88 | // ------------------------------------------------------------------------ | |
89 | ||
90 | /** | |
91 | * Relative <i>get</i> method for reading 32-bit integer. | |
92 | * | |
93 | * Reads next four bytes from the current bit position according to current | |
94 | * byte order. | |
95 | * | |
96 | * @return The int value read from the buffer | |
97 | */ | |
98 | public int getInt() { | |
99 | int val = getInt(BIT_INT, true); | |
100 | return val; | |
101 | } | |
102 | ||
103 | /** | |
104 | * Relative <i>get</i> method for reading integer of <i>length</i> bits. | |
105 | * | |
106 | * Reads <i>length</i> bits starting at the current position. The result is | |
107 | * signed extended if <i>signed</i> is true. The current position is | |
108 | * increased of <i>length</i> bits. | |
109 | * | |
110 | * @param length | |
111 | * The length in bits of this integer | |
112 | * @param signed | |
113 | * The sign extended flag | |
114 | * @return The int value read from the buffer | |
115 | */ | |
116 | public int getInt(int length, boolean signed) { | |
117 | int val = 0; | |
118 | if (!canRead(length)) { | |
119 | throw new BufferOverflowException(); | |
120 | } | |
121 | if (length == 0) { | |
122 | return 0; | |
123 | } | |
124 | boolean gotIt = false; | |
125 | ||
126 | // Fall back to fast ByteBuffer reader if we want to read byte-aligned bytes | |
127 | if (this.pos % BitBuffer.BIT_CHAR == 0) { | |
128 | switch (length) { | |
129 | case BitBuffer.BIT_CHAR: | |
130 | // Byte | |
131 | if (signed) { | |
132 | val = this.buf.get(this.pos / 8); | |
133 | } else { | |
134 | val = (this.buf.get(this.pos / 8)) & 0xff; | |
135 | } | |
136 | gotIt = true; | |
137 | break; | |
138 | ||
139 | case BitBuffer.BIT_SHORT: | |
140 | // Word | |
141 | if (signed) { | |
142 | val = this.buf.getShort(this.pos / 8); | |
143 | } else { | |
144 | short a = this.buf.getShort(this.pos / 8); | |
145 | val = a & 0xffff; | |
146 | } | |
147 | gotIt = true; | |
148 | break; | |
149 | ||
150 | case BitBuffer.BIT_INT: | |
151 | // Double word | |
152 | val = this.buf.getInt(this.pos / 8); | |
153 | gotIt = true; | |
154 | break; | |
155 | ||
156 | default: | |
157 | break; | |
158 | } | |
159 | } | |
160 | if (!gotIt) { | |
161 | // Nothing read yet: use longer methods | |
162 | if (this.byteOrder == ByteOrder.LITTLE_ENDIAN) { | |
163 | val = getIntLE(this.pos, length, signed); | |
164 | } else { | |
165 | val = getIntBE(this.pos, length, signed); | |
166 | } | |
167 | } | |
168 | this.pos += length; | |
169 | ||
170 | return val; | |
171 | } | |
172 | ||
173 | private int getIntBE(int index, int length, boolean signed) { | |
174 | assert ((length > 0) && (length <= BIT_INT)); | |
175 | int end = index + length; | |
176 | int startByte = index / BIT_CHAR; | |
177 | int endByte = (end + (BIT_CHAR - 1)) / BIT_CHAR; | |
178 | int currByte, lshift, cshift, mask, cmask, cache; | |
179 | int value = 0; | |
180 | ||
181 | currByte = startByte; | |
182 | cache = this.buf.get(currByte) & 0xFF; | |
183 | boolean isNeg = (cache & (1 << (BIT_CHAR - (index % BIT_CHAR) - 1))) != 0; | |
184 | if (signed && isNeg) { | |
185 | value = ~0; | |
186 | } | |
187 | if (startByte == (endByte - 1)) { | |
188 | cmask = cache >>> ((BIT_CHAR - (end % BIT_CHAR)) % BIT_CHAR); | |
189 | if (((length) % BIT_CHAR) > 0) { | |
190 | mask = ~((~0) << length); | |
191 | cmask &= mask; | |
192 | } | |
193 | value <<= length; | |
194 | value |= cmask; | |
195 | return value; | |
196 | } | |
197 | cshift = index % BIT_CHAR; | |
198 | if (cshift > 0) { | |
199 | mask = ~((~0) << (BIT_CHAR - cshift)); | |
200 | cmask = cache & mask; | |
201 | lshift = BIT_CHAR - cshift; | |
202 | value <<= lshift; | |
203 | value |= cmask; | |
204 | // index += lshift; | |
205 | currByte++; | |
206 | } | |
207 | for (; currByte < (endByte - 1); currByte++) { | |
208 | value <<= BIT_CHAR; | |
209 | value |= this.buf.get(currByte) & 0xFF; | |
210 | } | |
211 | lshift = end % BIT_CHAR; | |
212 | if (lshift > 0) { | |
213 | mask = ~((~0) << lshift); | |
214 | cmask = this.buf.get(currByte) & 0xFF; | |
215 | cmask >>>= BIT_CHAR - lshift; | |
216 | cmask &= mask; | |
217 | value <<= lshift; | |
218 | value |= cmask; | |
219 | } else { | |
220 | value <<= BIT_CHAR; | |
221 | value |= this.buf.get(currByte) & 0xFF; | |
222 | } | |
223 | return value; | |
224 | } | |
225 | ||
226 | private int getIntLE(int index, int length, boolean signed) { | |
227 | assert ((length > 0) && (length <= BIT_INT)); | |
228 | int end = index + length; | |
229 | int startByte = index / BIT_CHAR; | |
230 | int endByte = (end + (BIT_CHAR - 1)) / BIT_CHAR; | |
231 | int currByte, lshift, cshift, mask, cmask, cache, mod; | |
232 | int value = 0; | |
233 | ||
234 | currByte = endByte - 1; | |
235 | cache = buf.get(currByte) & 0xFF; | |
236 | mod = end % BIT_CHAR; | |
237 | lshift = (mod > 0) ? mod : BIT_CHAR; | |
238 | boolean isNeg = (cache & (1 << (lshift - 1))) != 0; | |
239 | if (signed && isNeg) { | |
240 | value = ~0; | |
241 | } | |
242 | if (startByte == (endByte - 1)) { | |
243 | cmask = cache >>> (index % BIT_CHAR); | |
244 | if (((length) % BIT_CHAR) > 0) { | |
245 | mask = ~((~0) << length); | |
246 | cmask &= mask; | |
247 | } | |
248 | value <<= length; | |
249 | value |= cmask; | |
250 | return value; | |
251 | } | |
252 | cshift = end % BIT_CHAR; | |
253 | if (cshift > 0) { | |
254 | mask = ~((~0) << cshift); | |
255 | cmask = cache & mask; | |
256 | value <<= cshift; | |
257 | value |= cmask; | |
258 | // end -= cshift; | |
259 | currByte--; | |
260 | } | |
261 | for (; currByte >= (startByte + 1); currByte--) { | |
262 | value <<= BIT_CHAR; | |
263 | value |= buf.get(currByte) & 0xFF; | |
264 | } | |
265 | lshift = index % BIT_CHAR; | |
266 | if (lshift > 0) { | |
267 | mask = ~((~0) << (BIT_CHAR - lshift)); | |
268 | cmask = buf.get(currByte) & 0xFF; | |
269 | cmask >>>= lshift; | |
270 | cmask &= mask; | |
271 | value <<= (BIT_CHAR - lshift); | |
272 | value |= cmask; | |
273 | } else { | |
274 | value <<= BIT_CHAR; | |
275 | value |= buf.get(currByte) & 0xFF; | |
276 | } | |
277 | return value; | |
278 | } | |
279 | ||
280 | // ------------------------------------------------------------------------ | |
281 | // 'Put' operations on buffer | |
282 | // ------------------------------------------------------------------------ | |
283 | ||
284 | /** | |
285 | * Relative <i>put</i> method to write signed 32-bit integer. | |
286 | * | |
287 | * Write four bytes starting from current bit position in the buffer | |
288 | * according to the current byte order. The current position is increased of | |
289 | * <i>length</i> bits. | |
290 | * | |
291 | * @param value | |
292 | * The int value to write | |
293 | */ | |
294 | public void putInt(int value) { | |
295 | putInt(BIT_INT, value); | |
296 | } | |
297 | ||
298 | /** | |
299 | * Relative <i>put</i> method to write <i>length</i> bits integer. | |
300 | * | |
301 | * Writes <i>length</i> lower-order bits from the provided <i>value</i>, | |
302 | * starting from current bit position in the buffer. Sequential bytes are | |
303 | * written according to the current byte order. The sign bit is carried to | |
304 | * the MSB if signed is true. The sign bit is included in <i>length</i>. The | |
305 | * current position is increased of <i>length</i>. | |
306 | * | |
307 | * @param length | |
308 | * The number of bits to write | |
309 | * @param value | |
310 | * The value to write | |
311 | */ | |
312 | public void putInt(int length, int value) { | |
313 | final int curPos = this.pos; | |
314 | ||
315 | if (!canRead(length)) { | |
316 | throw new BufferOverflowException(); | |
317 | } | |
318 | if (length == 0) { | |
319 | return; | |
320 | } | |
321 | if (this.byteOrder == ByteOrder.LITTLE_ENDIAN) { | |
322 | putIntLE(curPos, length, value); | |
323 | } else { | |
324 | putIntBE(curPos, length, value); | |
325 | } | |
326 | this.pos += length; | |
327 | } | |
328 | ||
329 | private void putIntBE(int index, int length, int value) { | |
330 | assert ((length > 0) && (length <= BIT_INT)); | |
331 | int end = index + length; | |
332 | int startByte = index / BIT_CHAR; | |
333 | int endByte = (end + (BIT_CHAR - 1)) / BIT_CHAR; | |
334 | int currByte, lshift, cshift, mask, cmask; | |
335 | int correctedValue = value; | |
336 | ||
337 | /* | |
338 | * mask v high bits. Works for unsigned and two complement signed | |
339 | * numbers which value do not overflow on length bits. | |
340 | */ | |
341 | ||
342 | if (length < BIT_INT) { | |
343 | correctedValue &= ~(~0 << length); | |
344 | } | |
345 | ||
346 | /* sub byte */ | |
347 | if (startByte == (endByte - 1)) { | |
348 | lshift = (BIT_CHAR - (end % BIT_CHAR)) % BIT_CHAR; | |
349 | mask = ~((~0) << lshift); | |
350 | if ((index % BIT_CHAR) > 0) { | |
351 | mask |= (~(0)) << (BIT_CHAR - (index % BIT_CHAR)); | |
352 | } | |
353 | cmask = correctedValue << lshift; | |
354 | /* | |
355 | * low bits are cleared because of lshift and high bits are already | |
356 | * cleared | |
357 | */ | |
358 | cmask &= ~mask; | |
359 | int b = this.buf.get(startByte) & 0xFF; | |
360 | this.buf.put(startByte, (byte) ((b & mask) | cmask)); | |
361 | return; | |
362 | } | |
363 | ||
364 | /* head byte contains MSB */ | |
365 | currByte = endByte - 1; | |
366 | cshift = end % BIT_CHAR; | |
367 | if (cshift > 0) { | |
368 | lshift = BIT_CHAR - cshift; | |
369 | mask = ~((~0) << lshift); | |
370 | cmask = correctedValue << lshift; | |
371 | cmask &= ~mask; | |
372 | int b = this.buf.get(currByte) & 0xFF; | |
373 | this.buf.put(currByte, (byte) ((b & mask) | cmask)); | |
374 | correctedValue >>>= cshift; | |
375 | // end -= cshift; | |
376 | currByte--; | |
377 | } | |
378 | ||
379 | /* middle byte(s) */ | |
380 | for (; currByte >= (startByte + 1); currByte--) { | |
381 | this.buf.put(currByte, (byte) correctedValue); | |
382 | correctedValue >>>= BIT_CHAR; | |
383 | } | |
384 | /* end byte contains LSB */ | |
385 | if ((index % BIT_CHAR) > 0) { | |
386 | mask = (~0) << (BIT_CHAR - (index % BIT_CHAR)); | |
387 | cmask = correctedValue & ~mask; | |
388 | int b = this.buf.get(currByte) & 0xFF; | |
389 | this.buf.put(currByte, (byte) ((b & mask) | cmask)); | |
390 | } else { | |
391 | this.buf.put(currByte, (byte) correctedValue); | |
392 | } | |
393 | } | |
394 | ||
395 | private void putIntLE(int index, int length, int value) { | |
396 | assert ((length > 0) && (length <= BIT_INT)); | |
397 | int end = index + length; | |
398 | int startByte = index / BIT_CHAR; | |
399 | int endByte = (end + (BIT_CHAR - 1)) / BIT_CHAR; | |
400 | int currByte, lshift, cshift, mask, cmask; | |
401 | int correctedValue = value; | |
402 | ||
403 | /* | |
404 | * mask v high bits. Works for unsigned and two complement signed | |
405 | * numbers which value do not overflow on length bits. | |
406 | */ | |
407 | ||
408 | if (length < BIT_INT) { | |
409 | correctedValue &= ~(~0 << length); | |
410 | } | |
411 | ||
412 | /* sub byte */ | |
413 | if (startByte == (endByte - 1)) { | |
414 | lshift = index % BIT_CHAR; | |
415 | mask = ~((~0) << lshift); | |
416 | if ((end % BIT_CHAR) > 0) { | |
417 | mask |= (~(0)) << (end % BIT_CHAR); | |
418 | } | |
419 | cmask = correctedValue << lshift; | |
420 | /* | |
421 | * low bits are cleared because of lshift and high bits are already | |
422 | * cleared | |
423 | */ | |
424 | cmask &= ~mask; | |
425 | int b = this.buf.get(startByte) & 0xFF; | |
426 | this.buf.put(startByte, (byte) ((b & mask) | cmask)); | |
427 | return; | |
428 | } | |
429 | ||
430 | /* head byte */ | |
431 | currByte = startByte; | |
432 | cshift = index % BIT_CHAR; | |
433 | if (cshift > 0) { | |
434 | mask = ~((~0) << cshift); | |
435 | cmask = correctedValue << cshift; | |
436 | cmask &= ~mask; | |
437 | int b = this.buf.get(currByte) & 0xFF; | |
438 | this.buf.put(currByte, (byte) ((b & mask) | cmask)); | |
439 | correctedValue >>>= BIT_CHAR - cshift; | |
440 | // index += BIT_CHAR - cshift; | |
441 | currByte++; | |
442 | } | |
443 | ||
444 | /* middle byte(s) */ | |
445 | for (; currByte < (endByte - 1); currByte++) { | |
446 | this.buf.put(currByte, (byte) correctedValue); | |
447 | correctedValue >>>= BIT_CHAR; | |
448 | } | |
449 | /* end byte */ | |
450 | if ((end % BIT_CHAR) > 0) { | |
451 | mask = (~0) << (end % BIT_CHAR); | |
452 | cmask = correctedValue & ~mask; | |
453 | int b = this.buf.get(currByte) & 0xFF; | |
454 | this.buf.put(currByte, (byte) ((b & mask) | cmask)); | |
455 | } else { | |
456 | this.buf.put(currByte, (byte) correctedValue); | |
457 | } | |
458 | } | |
459 | ||
460 | // ------------------------------------------------------------------------ | |
461 | // Buffer attributes handling | |
462 | // ------------------------------------------------------------------------ | |
463 | ||
464 | /** | |
465 | * Can this buffer be read for thus amount of bits? | |
466 | * | |
467 | * @param length | |
468 | * the length in bits to read | |
469 | * @return does the buffer have enough room to read the next "length" | |
470 | */ | |
471 | public boolean canRead(int length) { | |
472 | if (this.buf == null) { | |
473 | return false; | |
474 | } | |
475 | ||
476 | if ((this.pos + length) > (this.buf.capacity() * BIT_CHAR)) { | |
477 | return false; | |
478 | } | |
479 | return true; | |
480 | } | |
481 | ||
482 | /** | |
483 | * Sets the order of the buffer. | |
484 | * | |
485 | * @param order | |
486 | * The order of the buffer. | |
487 | */ | |
488 | public void setByteOrder(ByteOrder order) { | |
489 | this.byteOrder = order; | |
490 | if (this.buf != null) { | |
491 | this.buf.order(order); | |
492 | } | |
493 | } | |
494 | ||
495 | /** | |
496 | * Sets the order of the buffer. | |
497 | * | |
498 | * @return The order of the buffer. | |
499 | */ | |
500 | public ByteOrder getByteOrder() { | |
501 | return this.byteOrder; | |
502 | } | |
503 | ||
504 | /** | |
505 | * Sets the position in the buffer. | |
506 | * | |
507 | * @param newPosition | |
508 | * The new position of the buffer. | |
509 | */ | |
510 | public void position(int newPosition) { | |
511 | this.pos = newPosition; | |
512 | } | |
513 | ||
514 | /** | |
515 | * | |
516 | * Sets the position in the buffer. | |
517 | * | |
518 | * @return order The position of the buffer. | |
519 | */ | |
520 | public int position() { | |
521 | return this.pos; | |
522 | } | |
523 | ||
524 | /** | |
525 | * Sets the byte buffer | |
526 | * | |
527 | * @param buf | |
528 | * the byte buffer | |
529 | */ | |
530 | public void setByteBuffer(ByteBuffer buf) { | |
531 | this.buf = buf; | |
532 | if (buf != null) { | |
533 | this.buf.order(this.byteOrder); | |
534 | } | |
535 | clear(); | |
536 | } | |
537 | ||
538 | /** | |
539 | * Gets the byte buffer | |
540 | * | |
541 | * @return The byte buffer | |
542 | */ | |
543 | public ByteBuffer getByteBuffer() { | |
544 | return this.buf; | |
545 | } | |
546 | ||
547 | /** | |
548 | * resets the bitbuffer. | |
549 | */ | |
550 | public void clear() { | |
551 | position(0); | |
552 | ||
553 | if (this.buf == null) { | |
554 | return; | |
555 | } | |
556 | this.buf.clear(); | |
557 | } | |
558 | ||
559 | } |