Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
/*
 * LZ4 HC - High Compression Mode of LZ4
 * Copyright (C) 2011-2012, Yann Collet.
 * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * You can contact the author at :
 * - LZ4 homepage : http://fastcompression.blogspot.com/p/lz4.html
 * - LZ4 source repository : http://code.google.com/p/lz4/
 *
 *  Changed for kernel use by:
 *  Chanho Min <chanho.min@lge.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/lz4.h>
#include <asm/unaligned.h>
#include "lz4defs.h"

struct lz4hc_data {
	const u8 *base;
	HTYPE hashtable[HASHTABLESIZE];
	u16 chaintable[MAXD];
	const u8 *nexttoupdate;
} __attribute__((__packed__));

static inline int lz4hc_init(struct lz4hc_data *hc4, const u8 *base)
{
	memset((void *)hc4->hashtable, 0, sizeof(hc4->hashtable));
	memset(hc4->chaintable, 0xFF, sizeof(hc4->chaintable));

#if LZ4_ARCH64
	hc4->nexttoupdate = base + 1;
#else
	hc4->nexttoupdate = base;
#endif
	hc4->base = base;
	return 1;
}

/* Update chains up to ip (excluded) */
static inline void lz4hc_insert(struct lz4hc_data *hc4, const u8 *ip)
{
	u16 *chaintable = hc4->chaintable;
	HTYPE *hashtable  = hc4->hashtable;
#if LZ4_ARCH64
	const BYTE * const base = hc4->base;
#else
	const int base = 0;
#endif

	while (hc4->nexttoupdate < ip) {
		const u8 *p = hc4->nexttoupdate;
		size_t delta = p - (hashtable[HASH_VALUE(p)] + base);
		if (delta > MAX_DISTANCE)
			delta = MAX_DISTANCE;
		chaintable[(size_t)(p) & MAXD_MASK] = (u16)delta;
		hashtable[HASH_VALUE(p)] = (p) - base;
		hc4->nexttoupdate++;
	}
}

static inline size_t lz4hc_commonlength(const u8 *p1, const u8 *p2,
		const u8 *const matchlimit)
{
	const u8 *p1t = p1;

	while (p1t < matchlimit - (STEPSIZE - 1)) {
#if LZ4_ARCH64
		u64 diff = A64(p2) ^ A64(p1t);
#else
		u32 diff = A32(p2) ^ A32(p1t);
#endif
		if (!diff) {
			p1t += STEPSIZE;
			p2 += STEPSIZE;
			continue;
		}
		p1t += LZ4_NBCOMMONBYTES(diff);
		return p1t - p1;
	}
#if LZ4_ARCH64
	if ((p1t < (matchlimit-3)) && (A32(p2) == A32(p1t))) {
		p1t += 4;
		p2 += 4;
	}
#endif

	if ((p1t < (matchlimit - 1)) && (A16(p2) == A16(p1t))) {
		p1t += 2;
		p2 += 2;
	}
	if ((p1t < matchlimit) && (*p2 == *p1t))
		p1t++;
	return p1t - p1;
}

static inline int lz4hc_insertandfindbestmatch(struct lz4hc_data *hc4,
		const u8 *ip, const u8 *const matchlimit, const u8 **matchpos)
{
	u16 *const chaintable = hc4->chaintable;
	HTYPE *const hashtable = hc4->hashtable;
	const u8 *ref;
#if LZ4_ARCH64
	const BYTE * const base = hc4->base;
#else
	const int base = 0;
#endif
	int nbattempts = MAX_NB_ATTEMPTS;
	size_t repl = 0, ml = 0;
	u16 delta;

	/* HC4 match finder */
	lz4hc_insert(hc4, ip);
	ref = hashtable[HASH_VALUE(ip)] + base;

	/* potential repetition */
	if (ref >= ip-4) {
		/* confirmed */
		if (A32(ref) == A32(ip)) {
			delta = (u16)(ip-ref);
			repl = ml  = lz4hc_commonlength(ip + MINMATCH,
					ref + MINMATCH, matchlimit) + MINMATCH;
			*matchpos = ref;
		}
		ref -= (size_t)chaintable[(size_t)(ref) & MAXD_MASK];
	}

	while ((ref >= ip - MAX_DISTANCE) && nbattempts) {
		nbattempts--;
		if (*(ref + ml) == *(ip + ml)) {
			if (A32(ref) == A32(ip)) {
				size_t mlt =
					lz4hc_commonlength(ip + MINMATCH,
					ref + MINMATCH, matchlimit) + MINMATCH;
				if (mlt > ml) {
					ml = mlt;
					*matchpos = ref;
				}
			}
		}
		ref -= (size_t)chaintable[(size_t)(ref) & MAXD_MASK];
	}

	/* Complete table */
	if (repl) {
		const BYTE *ptr = ip;
		const BYTE *end;
		end = ip + repl - (MINMATCH-1);
		/* Pre-Load */
		while (ptr < end - delta) {
			chaintable[(size_t)(ptr) & MAXD_MASK] = delta;
			ptr++;
		}
		do {
			chaintable[(size_t)(ptr) & MAXD_MASK] = delta;
			/* Head of chain */
			hashtable[HASH_VALUE(ptr)] = (ptr) - base;
			ptr++;
		} while (ptr < end);
		hc4->nexttoupdate = end;
	}

	return (int)ml;
}

static inline int lz4hc_insertandgetwidermatch(struct lz4hc_data *hc4,
	const u8 *ip, const u8 *startlimit, const u8 *matchlimit, int longest,
	const u8 **matchpos, const u8 **startpos)
{
	u16 *const chaintable = hc4->chaintable;
	HTYPE *const hashtable = hc4->hashtable;
#if LZ4_ARCH64
	const BYTE * const base = hc4->base;
#else
	const int base = 0;
#endif
	const u8 *ref;
	int nbattempts = MAX_NB_ATTEMPTS;
	int delta = (int)(ip - startlimit);

	/* First Match */
	lz4hc_insert(hc4, ip);
	ref = hashtable[HASH_VALUE(ip)] + base;

	while ((ref >= ip - MAX_DISTANCE) && (ref >= hc4->base)
		&& (nbattempts)) {
		nbattempts--;
		if (*(startlimit + longest) == *(ref - delta + longest)) {
			if (A32(ref) == A32(ip)) {
				const u8 *reft = ref + MINMATCH;
				const u8 *ipt = ip + MINMATCH;
				const u8 *startt = ip;

				while (ipt < matchlimit-(STEPSIZE - 1)) {
					#if LZ4_ARCH64
					u64 diff = A64(reft) ^ A64(ipt);
					#else
					u32 diff = A32(reft) ^ A32(ipt);
					#endif

					if (!diff) {
						ipt += STEPSIZE;
						reft += STEPSIZE;
						continue;
					}
					ipt += LZ4_NBCOMMONBYTES(diff);
					goto _endcount;
				}
				#if LZ4_ARCH64
				if ((ipt < (matchlimit - 3))
					&& (A32(reft) == A32(ipt))) {
					ipt += 4;
					reft += 4;
				}
				ipt += 2;
				#endif
				if ((ipt < (matchlimit - 1))
					&& (A16(reft) == A16(ipt))) {
					reft += 2;
				}
				if ((ipt < matchlimit) && (*reft == *ipt))
					ipt++;
_endcount:
				reft = ref;

				while ((startt > startlimit)
					&& (reft > hc4->base)
					&& (startt[-1] == reft[-1])) {
					startt--;
					reft--;
				}

				if ((ipt - startt) > longest) {
					longest = (int)(ipt - startt);
					*matchpos = reft;
					*startpos = startt;
				}
			}
		}
		ref -= (size_t)chaintable[(size_t)(ref) & MAXD_MASK];
	}
	return longest;
}

static inline int lz4_encodesequence(const u8 **ip, u8 **op, const u8 **anchor,
		int ml, const u8 *ref)
{
	int length, len;
	u8 *token;

	/* Encode Literal length */
	length = (int)(*ip - *anchor);
	token = (*op)++;
	if (length >= (int)RUN_MASK) {
		*token = (RUN_MASK << ML_BITS);
		len = length - RUN_MASK;
		for (; len > 254 ; len -= 255)
			*(*op)++ = 255;
		*(*op)++ = (u8)len;
	} else
		*token = (length << ML_BITS);

	/* Copy Literals */
	LZ4_BLINDCOPY(*anchor, *op, length);

	/* Encode Offset */
	LZ4_WRITE_LITTLEENDIAN_16(*op, (u16)(*ip - ref));

	/* Encode MatchLength */
	len = (int)(ml - MINMATCH);
	if (len >= (int)ML_MASK) {
		*token += ML_MASK;
		len -= ML_MASK;
		for (; len > 509 ; len -= 510) {
			*(*op)++ = 255;
			*(*op)++ = 255;
		}
		if (len > 254) {
			len -= 255;
			*(*op)++ = 255;
		}
		*(*op)++ = (u8)len;
	} else
		*token += len;

	/* Prepare next loop */
	*ip += ml;
	*anchor = *ip;

	return 0;
}

static int lz4_compresshcctx(struct lz4hc_data *ctx,
		const char *source,
		char *dest,
		int isize)
{
	const u8 *ip = (const u8 *)source;
	const u8 *anchor = ip;
	const u8 *const iend = ip + isize;
	const u8 *const mflimit = iend - MFLIMIT;
	const u8 *const matchlimit = (iend - LASTLITERALS);

	u8 *op = (u8 *)dest;

	int ml, ml2, ml3, ml0;
	const u8 *ref = NULL;
	const u8 *start2 = NULL;
	const u8 *ref2 = NULL;
	const u8 *start3 = NULL;
	const u8 *ref3 = NULL;
	const u8 *start0;
	const u8 *ref0;
	int lastrun;

	ip++;

	/* Main Loop */
	while (ip < mflimit) {
		ml = lz4hc_insertandfindbestmatch(ctx, ip, matchlimit, (&ref));
		if (!ml) {
			ip++;
			continue;
		}

		/* saved, in case we would skip too much */
		start0 = ip;
		ref0 = ref;
		ml0 = ml;
_search2:
		if (ip+ml < mflimit)
			ml2 = lz4hc_insertandgetwidermatch(ctx, ip + ml - 2,
				ip + 1, matchlimit, ml, &ref2, &start2);
		else
			ml2 = ml;
		/* No better match */
		if (ml2 == ml) {
			lz4_encodesequence(&ip, &op, &anchor, ml, ref);
			continue;
		}

		if (start0 < ip) {
			/* empirical */
			if (start2 < ip + ml0) {
				ip = start0;
				ref = ref0;
				ml = ml0;
			}
		}
		/*
		 * Here, start0==ip
		 * First Match too small : removed
		 */
		if ((start2 - ip) < 3) {
			ml = ml2;
			ip = start2;
			ref = ref2;
			goto _search2;
		}

_search3:
		/*
		 * Currently we have :
		 * ml2 > ml1, and
		 * ip1+3 <= ip2 (usually < ip1+ml1)
		 */
		if ((start2 - ip) < OPTIMAL_ML) {
			int correction;
			int new_ml = ml;
			if (new_ml > OPTIMAL_ML)
				new_ml = OPTIMAL_ML;
			if (ip + new_ml > start2 + ml2 - MINMATCH)
				new_ml = (int)(start2 - ip) + ml2 - MINMATCH;
			correction = new_ml - (int)(start2 - ip);
			if (correction > 0) {
				start2 += correction;
				ref2 += correction;
				ml2 -= correction;
			}
		}
		/*
		 * Now, we have start2 = ip+new_ml,
		 * with new_ml=min(ml, OPTIMAL_ML=18)
		 */
		if (start2 + ml2 < mflimit)
			ml3 = lz4hc_insertandgetwidermatch(ctx,
				start2 + ml2 - 3, start2, matchlimit,
				ml2, &ref3, &start3);
		else
			ml3 = ml2;

		/* No better match : 2 sequences to encode */
		if (ml3 == ml2) {
			/* ip & ref are known; Now for ml */
			if (start2 < ip+ml)
				ml = (int)(start2 - ip);

			/* Now, encode 2 sequences */
			lz4_encodesequence(&ip, &op, &anchor, ml, ref);
			ip = start2;
			lz4_encodesequence(&ip, &op, &anchor, ml2, ref2);
			continue;
		}

		/* Not enough space for match 2 : remove it */
		if (start3 < ip + ml + 3) {
			/*
			 * can write Seq1 immediately ==> Seq2 is removed,
			 * so Seq3 becomes Seq1
			 */
			if (start3 >= (ip + ml)) {
				if (start2 < ip + ml) {
					int correction =
						(int)(ip + ml - start2);
					start2 += correction;
					ref2 += correction;
					ml2 -= correction;
					if (ml2 < MINMATCH) {
						start2 = start3;
						ref2 = ref3;
						ml2 = ml3;
					}
				}

				lz4_encodesequence(&ip, &op, &anchor, ml, ref);
				ip  = start3;
				ref = ref3;
				ml  = ml3;

				start0 = start2;
				ref0 = ref2;
				ml0 = ml2;
				goto _search2;
			}

			start2 = start3;
			ref2 = ref3;
			ml2 = ml3;
			goto _search3;
		}

		/*
		 * OK, now we have 3 ascending matches; let's write at least
		 * the first one ip & ref are known; Now for ml
		 */
		if (start2 < ip + ml) {
			if ((start2 - ip) < (int)ML_MASK) {
				int correction;
				if (ml > OPTIMAL_ML)
					ml = OPTIMAL_ML;
				if (ip + ml > start2 + ml2 - MINMATCH)
					ml = (int)(start2 - ip) + ml2
						- MINMATCH;
				correction = ml - (int)(start2 - ip);
				if (correction > 0) {
					start2 += correction;
					ref2 += correction;
					ml2 -= correction;
				}
			} else
				ml = (int)(start2 - ip);
		}
		lz4_encodesequence(&ip, &op, &anchor, ml, ref);

		ip = start2;
		ref = ref2;
		ml = ml2;

		start2 = start3;
		ref2 = ref3;
		ml2 = ml3;

		goto _search3;
	}

	/* Encode Last Literals */
	lastrun = (int)(iend - anchor);
	if (lastrun >= (int)RUN_MASK) {
		*op++ = (RUN_MASK << ML_BITS);
		lastrun -= RUN_MASK;
		for (; lastrun > 254 ; lastrun -= 255)
			*op++ = 255;
		*op++ = (u8) lastrun;
	} else
		*op++ = (lastrun << ML_BITS);
	memcpy(op, anchor, iend - anchor);
	op += iend - anchor;
	/* End */
	return (int) (((char *)op) - dest);
}

int lz4hc_compress(const unsigned char *src, size_t src_len,
			unsigned char *dst, size_t *dst_len, void *wrkmem)
{
	int ret = -1;
	int out_len = 0;

	struct lz4hc_data *hc4 = (struct lz4hc_data *)wrkmem;
	lz4hc_init(hc4, (const u8 *)src);
	out_len = lz4_compresshcctx((struct lz4hc_data *)hc4, (const u8 *)src,
		(char *)dst, (int)src_len);

	if (out_len < 0)
		goto exit;

	*dst_len = out_len;
	return 0;

exit:
	return ret;
}
EXPORT_SYMBOL(lz4hc_compress);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("LZ4HC compressor");