libkern/mkext.c

   1 /*
   2  * Copyright (c) 2000-2016 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include <stdint.h> // For uintptr_t.
  29 #include <string.h>
  30 #include <libkern/mkext.h>
  31
  32
  33 #define BASE 65521L /* largest prime smaller than 65536 */
  34 #define NMAX 5552  // the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
  35
  36 #define DO1(buf, i)  {s1 += buf[i]; s2 += s1;}
  37 #define DO2(buf, i)  DO1(buf,i); DO1(buf,i+1);
  38 #define DO4(buf, i)  DO2(buf,i); DO2(buf,i+2);
  39 #define DO8(buf, i)  DO4(buf,i); DO4(buf,i+4);
  40 #define DO16(buf)   DO8(buf,0); DO8(buf,8);
  41
  42 u_int32_t
  43 mkext_adler32(uint8_t *buf, int32_t len)
  44 {
  45         unsigned long s1 = 1; // adler & 0xffff;
  46         unsigned long s2 = 0; // (adler >> 16) & 0xffff;
  47         int k;
  48
  49
  50         while (len > 0) {
  51                 k = len < NMAX ? len : NMAX;
  52                 len -= k;
  53                 while (k >= 16) {
  54                         DO16(buf);
  55                         buf += 16;
  56                         k -= 16;
  57                 }
  58                 if (k != 0) {
  59                         do {
  60                                 s1 += *buf++;
  61                                 s2 += s1;
  62                         } while (--k);
  63                 }
  64                 s1 %= BASE;
  65                 s2 %= BASE;
  66         }
  67         return (u_int32_t)((s2 << 16) | s1);
  68 }
  69
  70
  71 /**************************************************************
  72 *   LZSS.C -- A Data Compression Program
  73 ***************************************************************
  74 *    4/6/1989 Haruhiko Okumura
  75 *    Use, distribute, and modify this program freely.
  76 *    Please send me your improved versions.
  77 *        PC-VAN      SCIENCE
  78 *        NIFTY-Serve PAF01022
  79 *        CompuServe  74050,1022
  80 *
  81 **************************************************************/
  82
  83 #define N         4096  /* size of ring buffer - must be power of 2 */
  84 #define F         18    /* upper limit for match_length */
  85 #define THRESHOLD 2     /* encode string into position and length
  86                          *  if match_length is greater than this */
  87 #if !KERNEL
  88 #define NIL       N     /* index for root of binary search trees */
  89 #endif
  90
  91 struct encode_state {
  92         /*
  93          * left & right children & parent. These constitute binary search trees.
  94          */
  95         int lchild[N + 1], rchild[N + 257], parent[N + 1];
  96
  97         /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
  98         u_int8_t text_buf[N + F - 1];
  99
 100         /*
 101          * match_length of longest match.
 102          * These are set by the insert_node() procedure.
 103          */
 104         int match_position, match_length;
 105 };
 106
 107
 108 int
 109 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srclen)
 110 {
 111         /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
 112         u_int8_t text_buf[N + F - 1];
 113         u_int8_t *dststart = dst;
 114         u_int8_t *dstend = dst + dstlen;
 115         u_int8_t *srcend = src + srclen;
 116         int  i, j, k, r;
 117         u_int8_t c;
 118         unsigned int flags;
 119
 120         dst = dststart;
 121         srcend = src + srclen;
 122         for (i = 0; i < N - F; i++) {
 123                 text_buf[i] = ' ';
 124         }
 125         r = N - F;
 126         flags = 0;
 127         for (;;) {
 128                 if (((flags >>= 1) & 0x100) == 0) {
 129                         if (src < srcend) {
 130                                 c = *src++;
 131                         } else {
 132                                 break;
 133                         }
 134                         flags = c | 0xFF00; /* uses higher byte cleverly */
 135                 } /* to count eight */
 136                 if (flags & 1) {
 137                         if (src < srcend) {
 138                                 c = *src++;
 139                         } else {
 140                                 break;
 141                         }
 142                         *dst++ = c;
 143                         if (dst >= dstend) {
 144                                 goto finish;
 145                         }
 146                         text_buf[r++] = c;
 147                         r &= (N - 1);
 148                 } else {
 149                         if (src < srcend) {
 150                                 i = *src++;
 151                         } else {
 152                                 break;
 153                         }
 154                         if (src < srcend) {
 155                                 j = *src++;
 156                         } else {
 157                                 break;
 158                         }
 159                         i |= ((j & 0xF0) << 4);
 160                         j  =  (j & 0x0F) + THRESHOLD;
 161                         for (k = 0; k <= j; k++) {
 162                                 c = text_buf[(i + k) & (N - 1)];
 163                                 *dst++ = c;
 164                                 if (dst >= dstend) {
 165                                         goto finish;
 166                                 }
 167                                 text_buf[r++] = c;
 168                                 r &= (N - 1);
 169                         }
 170                 }
 171         }
 172 finish:
 173         return (int)(dst - dststart);
 174 }
 175
 176 #if !KERNEL
 177
 178 /*
 179  * initialize state, mostly the trees
 180  *
 181  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 182  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 183  * is the parent of node i.  These are initialized to NIL (= N), which stands
 184  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 185  * tree for strings that begin with character i.  These are initialized to NIL.
 186  * Note there are 256 trees. */
 187 static void
 188 init_state(struct encode_state *sp)
 189 {
 190         int  i;
 191
 192         bzero(sp, sizeof(*sp));
 193
 194         for (i = 0; i < N - F; i++) {
 195                 sp->text_buf[i] = ' ';
 196         }
 197         for (i = N + 1; i <= N + 256; i++) {
 198                 sp->rchild[i] = NIL;
 199         }
 200         for (i = 0; i < N; i++) {
 201                 sp->parent[i] = NIL;
 202         }
 203 }
 204
 205 /*
 206  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 207  * (text_buf[r]'th tree) and returns the longest-match position and length
 208  * via the global variables match_position and match_length.
 209  * If match_length = F, then removes the old node in favor of the new one,
 210  * because the old one will be deleted sooner. Note r plays double role,
 211  * as tree node and position in buffer.
 212  */
 213 static void
 214 insert_node(struct encode_state *sp, int r)
 215 {
 216         int  i, p, cmp;
 217         u_int8_t  *key;
 218
 219         cmp = 1;
 220         key = &sp->text_buf[r];
 221         p = N + 1 + key[0];
 222         sp->rchild[r] = sp->lchild[r] = NIL;
 223         sp->match_length = 0;
 224         for (;;) {
 225                 if (cmp >= 0) {
 226                         if (sp->rchild[p] != NIL) {
 227                                 p = sp->rchild[p];
 228                         } else {
 229                                 sp->rchild[p] = r;
 230                                 sp->parent[r] = p;
 231                                 return;
 232                         }
 233                 } else {
 234                         if (sp->lchild[p] != NIL) {
 235                                 p = sp->lchild[p];
 236                         } else {
 237                                 sp->lchild[p] = r;
 238                                 sp->parent[r] = p;
 239                                 return;
 240                         }
 241                 }
 242                 for (i = 1; i < F; i++) {
 243                         if ((cmp = key[i] - sp->text_buf[p + i]) != 0) {
 244                                 break;
 245                         }
 246                 }
 247                 if (i > sp->match_length) {
 248                         sp->match_position = p;
 249                         if ((sp->match_length = i) >= F) {
 250                                 break;
 251                         }
 252                 }
 253         }
 254         sp->parent[r] = sp->parent[p];
 255         sp->lchild[r] = sp->lchild[p];
 256         sp->rchild[r] = sp->rchild[p];
 257         sp->parent[sp->lchild[p]] = r;
 258         sp->parent[sp->rchild[p]] = r;
 259         if (sp->rchild[sp->parent[p]] == p) {
 260                 sp->rchild[sp->parent[p]] = r;
 261         } else {
 262                 sp->lchild[sp->parent[p]] = r;
 263         }
 264         sp->parent[p] = NIL; /* remove p */
 265 }
 266
 267 /* deletes node p from tree */
 268 static void
 269 delete_node(struct encode_state *sp, int p)
 270 {
 271         int  q;
 272
 273         if (sp->parent[p] == NIL) {
 274                 return; /* not in tree */
 275         }
 276         if (sp->rchild[p] == NIL) {
 277                 q = sp->lchild[p];
 278         } else if (sp->lchild[p] == NIL) {
 279                 q = sp->rchild[p];
 280         } else {
 281                 q = sp->lchild[p];
 282                 if (sp->rchild[q] != NIL) {
 283                         do {
 284                                 q = sp->rchild[q];
 285                         } while (sp->rchild[q] != NIL);
 286                         sp->rchild[sp->parent[q]] = sp->lchild[q];
 287                         sp->parent[sp->lchild[q]] = sp->parent[q];
 288                         sp->lchild[q] = sp->lchild[p];
 289                         sp->parent[sp->lchild[p]] = q;
 290                 }
 291                 sp->rchild[q] = sp->rchild[p];
 292                 sp->parent[sp->rchild[p]] = q;
 293         }
 294         sp->parent[q] = sp->parent[p];
 295         if (sp->rchild[sp->parent[p]] == p) {
 296                 sp->rchild[sp->parent[p]] = q;
 297         } else {
 298                 sp->lchild[sp->parent[p]] = q;
 299         }
 300         sp->parent[p] = NIL;
 301 }
 302
 303 #endif /* !KERNEL */