libsa/mkext.c

   1 /*
   2  * Copyright (c) 2000-2004 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 <string.h>
  29 #if KERNEL
  30 #include <libsa/mkext.h>
  31 #include <libsa/stdlib.h>
  32 #else
  33 #include <Kernel/libsa/mkext.h>
  34 #include <stdlib.h>
  35 #endif /* KERNEL */
  36
  37 #define BASE 65521L /* largest prime smaller than 65536 */
  38 #define NMAX 5000
  39 // NMAX (was 5521) the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
  40
  41 #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
  42 #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
  43 #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
  44 #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
  45 #define DO16(buf)   DO8(buf,0); DO8(buf,8);
  46
  47 __private_extern__ u_int32_t
  48 adler32(uint8_t *buf, int32_t len)
  49 {
  50     unsigned long s1 = 1; // adler & 0xffff;
  51     unsigned long s2 = 0; // (adler >> 16) & 0xffff;
  52     int k;
  53
  54     while (len > 0) {
  55         k = len < NMAX ? len : NMAX;
  56         len -= k;
  57         while (k >= 16) {
  58             DO16(buf);
  59             buf += 16;
  60             k -= 16;
  61         }
  62         if (k != 0) do {
  63             s1 += *buf++;
  64             s2 += s1;
  65         } while (--k);
  66         s1 %= BASE;
  67         s2 %= BASE;
  68     }
  69     return (s2 << 16) | s1;
  70 }
  71
  72
  73 /**************************************************************
  74  LZSS.C -- A Data Compression Program
  75 ***************************************************************
  76     4/6/1989 Haruhiko Okumura
  77     Use, distribute, and modify this program freely.
  78     Please send me your improved versions.
  79         PC-VAN      SCIENCE
  80         NIFTY-Serve PAF01022
  81         CompuServe  74050,1022
  82
  83 **************************************************************/
  84
  85 #define N         4096  /* size of ring buffer - must be power of 2 */
  86 #define F         18    /* upper limit for match_length */
  87 #define THRESHOLD 2     /* encode string into position and length
  88                            if match_length is greater than this */
  89 #define NIL       N     /* index for root of binary search trees */
  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 __private_extern__ int
 109 decompress_lzss(u_int8_t *dst, 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 *srcend = src + srclen;
 115     int  i, j, k, r, c;
 116     unsigned int flags;
 117
 118     dst = dststart;
 119     srcend = src + srclen;
 120     for (i = 0; i < N - F; i++)
 121         text_buf[i] = ' ';
 122     r = N - F;
 123     flags = 0;
 124     for ( ; ; ) {
 125         if (((flags >>= 1) & 0x100) == 0) {
 126             if (src < srcend) c = *src++; else break;
 127             flags = c | 0xFF00;  /* uses higher byte cleverly */
 128         }   /* to count eight */
 129         if (flags & 1) {
 130             if (src < srcend) c = *src++; else break;
 131             *dst++ = c;
 132             text_buf[r++] = c;
 133             r &= (N - 1);
 134         } else {
 135             if (src < srcend) i = *src++; else break;
 136             if (src < srcend) j = *src++; else break;
 137             i |= ((j & 0xF0) << 4);
 138             j  =  (j & 0x0F) + THRESHOLD;
 139             for (k = 0; k <= j; k++) {
 140                 c = text_buf[(i + k) & (N - 1)];
 141                 *dst++ = c;
 142                 text_buf[r++] = c;
 143                 r &= (N - 1);
 144             }
 145         }
 146     }
 147
 148     return dst - dststart;
 149 }
 150
 151 #if !KERNEL
 152
 153 /*
 154  * initialize state, mostly the trees
 155  *
 156  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 157  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 158  * is the parent of node i.  These are initialized to NIL (= N), which stands
 159  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 160  * tree for strings that begin with character i.  These are initialized to NIL.
 161  * Note there are 256 trees. */
 162 static void init_state(struct encode_state *sp)
 163 {
 164     int  i;
 165
 166     bzero(sp, sizeof(*sp));
 167
 168     for (i = 0; i < N - F; i++)
 169         sp->text_buf[i] = ' ';
 170     for (i = N + 1; i <= N + 256; i++)
 171         sp->rchild[i] = NIL;
 172     for (i = 0; i < N; i++)
 173         sp->parent[i] = NIL;
 174 }
 175
 176 /*
 177  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 178  * (text_buf[r]'th tree) and returns the longest-match position and length
 179  * via the global variables match_position and match_length.
 180  * If match_length = F, then removes the old node in favor of the new one,
 181  * because the old one will be deleted sooner. Note r plays double role,
 182  * as tree node and position in buffer.
 183  */
 184 static void insert_node(struct encode_state *sp, int r)
 185 {
 186     int  i, p, cmp;
 187     u_int8_t  *key;
 188
 189     cmp = 1;
 190     key = &sp->text_buf[r];
 191     p = N + 1 + key[0];
 192     sp->rchild[r] = sp->lchild[r] = NIL;
 193     sp->match_length = 0;
 194     for ( ; ; ) {
 195         if (cmp >= 0) {
 196             if (sp->rchild[p] != NIL)
 197                 p = sp->rchild[p];
 198             else {
 199                 sp->rchild[p] = r;
 200                 sp->parent[r] = p;
 201                 return;
 202             }
 203         } else {
 204             if (sp->lchild[p] != NIL)
 205                 p = sp->lchild[p];
 206             else {
 207                 sp->lchild[p] = r;
 208                 sp->parent[r] = p;
 209                 return;
 210             }
 211         }
 212         for (i = 1; i < F; i++) {
 213             if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
 214                 break;
 215         }
 216         if (i > sp->match_length) {
 217             sp->match_position = p;
 218             if ((sp->match_length = i) >= F)
 219                 break;
 220         }
 221     }
 222     sp->parent[r] = sp->parent[p];
 223     sp->lchild[r] = sp->lchild[p];
 224     sp->rchild[r] = sp->rchild[p];
 225     sp->parent[sp->lchild[p]] = r;
 226     sp->parent[sp->rchild[p]] = r;
 227     if (sp->rchild[sp->parent[p]] == p)
 228         sp->rchild[sp->parent[p]] = r;
 229     else
 230         sp->lchild[sp->parent[p]] = r;
 231     sp->parent[p] = NIL;  /* remove p */
 232 }
 233
 234 /* deletes node p from tree */
 235 static void delete_node(struct encode_state *sp, int p)
 236 {
 237     int  q;
 238
 239     if (sp->parent[p] == NIL)
 240         return;  /* not in tree */
 241     if (sp->rchild[p] == NIL)
 242         q = sp->lchild[p];
 243     else if (sp->lchild[p] == NIL)
 244         q = sp->rchild[p];
 245     else {
 246         q = sp->lchild[p];
 247         if (sp->rchild[q] != NIL) {
 248             do {
 249                 q = sp->rchild[q];
 250             } while (sp->rchild[q] != NIL);
 251             sp->rchild[sp->parent[q]] = sp->lchild[q];
 252             sp->parent[sp->lchild[q]] = sp->parent[q];
 253             sp->lchild[q] = sp->lchild[p];
 254             sp->parent[sp->lchild[p]] = q;
 255         }
 256         sp->rchild[q] = sp->rchild[p];
 257         sp->parent[sp->rchild[p]] = q;
 258     }
 259     sp->parent[q] = sp->parent[p];
 260     if (sp->rchild[sp->parent[p]] == p)
 261         sp->rchild[sp->parent[p]] = q;
 262     else
 263         sp->lchild[sp->parent[p]] = q;
 264     sp->parent[p] = NIL;
 265 }
 266
 267 __private_extern__ u_int8_t *
 268 compress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srcLen)
 269 {
 270     /* Encoding state, mostly tree but some current match stuff */
 271     struct encode_state *sp;
 272
 273     int  i, c, len, r, s, last_match_length, code_buf_ptr;
 274     u_int8_t code_buf[17], mask;
 275     u_int8_t *srcend = src + srcLen;
 276     u_int8_t *dstend = dst + dstlen;
 277
 278     /* initialize trees */
 279     sp = (struct encode_state *) malloc(sizeof(*sp));
 280     init_state(sp);
 281
 282     /*
 283      * code_buf[1..16] saves eight units of code, and code_buf[0] works
 284      * as eight flags, "1" representing that the unit is an unencoded
 285      * letter (1 byte), "0" a position-and-length pair (2 bytes).
 286      * Thus, eight units require at most 16 bytes of code.
 287      */
 288     code_buf[0] = 0;
 289     code_buf_ptr = mask = 1;
 290
 291     /* Clear the buffer with any character that will appear often. */
 292     s = 0;  r = N - F;
 293
 294     /* Read F bytes into the last F bytes of the buffer */
 295     for (len = 0; len < F && src < srcend; len++)
 296         sp->text_buf[r + len] = *src++;
 297     if (!len)
 298         return (void *) 0;  /* text of size zero */
 299
 300     /*
 301      * Insert the F strings, each of which begins with one or more
 302      * 'space' characters.  Note the order in which these strings are
 303      * inserted.  This way, degenerate trees will be less likely to occur.
 304      */
 305     for (i = 1; i <= F; i++)
 306         insert_node(sp, r - i);
 307
 308     /*
 309      * Finally, insert the whole string just read.
 310      * The global variables match_length and match_position are set.
 311      */
 312     insert_node(sp, r);
 313     do {
 314         /* match_length may be spuriously long near the end of text. */
 315         if (sp->match_length > len)
 316             sp->match_length = len;
 317         if (sp->match_length <= THRESHOLD) {
 318             sp->match_length = 1;  /* Not long enough match.  Send one byte. */
 319             code_buf[0] |= mask;  /* 'send one byte' flag */
 320             code_buf[code_buf_ptr++] = sp->text_buf[r];  /* Send uncoded. */
 321         } else {
 322             /* Send position and length pair. Note match_length > THRESHOLD. */
 323             code_buf[code_buf_ptr++] = (u_int8_t) sp->match_position;
 324             code_buf[code_buf_ptr++] = (u_int8_t)
 325                 ( ((sp->match_position >> 4) & 0xF0)
 326                 |  (sp->match_length - (THRESHOLD + 1)) );
 327         }
 328         if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */
 329                 /* Send at most 8 units of code together */
 330             for (i = 0; i < code_buf_ptr; i++)
 331                 if (dst < dstend)
 332                     *dst++ = code_buf[i];
 333                 else
 334                     return (void *) 0;
 335             code_buf[0] = 0;
 336             code_buf_ptr = mask = 1;
 337         }
 338         last_match_length = sp->match_length;
 339         for (i = 0; i < last_match_length && src < srcend; i++) {
 340             delete_node(sp, s);    /* Delete old strings and */
 341             c = *src++;
 342             sp->text_buf[s] = c;    /* read new bytes */
 343
 344             /*
 345              * If the position is near the end of buffer, extend the buffer
 346              * to make string comparison easier.
 347              */
 348             if (s < F - 1)
 349                 sp->text_buf[s + N] = c;
 350
 351             /* Since this is a ring buffer, increment the position modulo N. */
 352             s = (s + 1) & (N - 1);
 353             r = (r + 1) & (N - 1);
 354
 355             /* Register the string in text_buf[r..r+F-1] */
 356             insert_node(sp, r);
 357         }
 358         while (i++ < last_match_length) {
 359         delete_node(sp, s);
 360
 361             /* After the end of text, no need to read, */
 362             s = (s + 1) & (N - 1);
 363             r = (r + 1) & (N - 1);
 364             /* but buffer may not be empty. */
 365             if (--len)
 366                 insert_node(sp, r);
 367         }
 368     } while (len > 0);   /* until length of string to be processed is zero */
 369
 370     if (code_buf_ptr > 1) {    /* Send remaining code. */
 371         for (i = 0; i < code_buf_ptr; i++)
 372             if (dst < dstend)
 373                 *dst++ = code_buf[i];
 374             else
 375                 return (void *) 0;
 376     }
 377
 378     return dst;
 379 }
 380
 381 #endif /* !KERNEL */
 382