libkern/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 <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) do {
  59             s1 += *buf++;
  60             s2 += s1;
  61         } while (--k);
  62         s1 %= BASE;
  63         s2 %= BASE;
  64     }
  65     return (s2 << 16) | s1;
  66 }
  67
  68
  69 /**************************************************************
  70  LZSS.C -- A Data Compression Program
  71 ***************************************************************
  72     4/6/1989 Haruhiko Okumura
  73     Use, distribute, and modify this program freely.
  74     Please send me your improved versions.
  75         PC-VAN      SCIENCE
  76         NIFTY-Serve PAF01022
  77         CompuServe  74050,1022
  78
  79 **************************************************************/
  80
  81 #define N         4096  /* size of ring buffer - must be power of 2 */
  82 #define F         18    /* upper limit for match_length */
  83 #define THRESHOLD 2     /* encode string into position and length
  84                            if match_length is greater than this */
  85 #define NIL       N     /* index for root of binary search trees */
  86
  87 struct encode_state {
  88     /*
  89      * left & right children & parent. These constitute binary search trees.
  90      */
  91     int lchild[N + 1], rchild[N + 257], parent[N + 1];
  92
  93     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
  94     u_int8_t text_buf[N + F - 1];
  95
  96     /*
  97      * match_length of longest match.
  98      * These are set by the insert_node() procedure.
  99      */
 100     int match_position, match_length;
 101 };
 102
 103
 104 int
 105 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srclen)
 106 {
 107     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
 108     u_int8_t text_buf[N + F - 1];
 109     u_int8_t *dststart = dst;
 110         u_int8_t *dstend = dst + dstlen;
 111     u_int8_t *srcend = src + srclen;
 112     int  i, j, k, r, c;
 113     unsigned int flags;
 114
 115     dst = dststart;
 116     srcend = src + srclen;
 117     for (i = 0; i < N - F; i++)
 118         text_buf[i] = ' ';
 119     r = N - F;
 120     flags = 0;
 121     for ( ; ; ) {
 122         if (((flags >>= 1) & 0x100) == 0) {
 123             if (src < srcend) c = *src++; else break;
 124             flags = c | 0xFF00;  /* uses higher byte cleverly */
 125         }   /* to count eight */
 126         if (flags & 1) {
 127             if (src < srcend) c = *src++; else break;
 128             *dst++ = c;
 129                         if (dst >= dstend) {
 130                                 goto finish;
 131                         }
 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                                 if (dst >= dstend) {
 143                                         goto finish;
 144                                 }
 145                 text_buf[r++] = c;
 146                 r &= (N - 1);
 147             }
 148         }
 149     }
 150 finish:
 151     return dst - dststart;
 152 }
 153
 154 #if !KERNEL
 155
 156 /*
 157  * initialize state, mostly the trees
 158  *
 159  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 160  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 161  * is the parent of node i.  These are initialized to NIL (= N), which stands
 162  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 163  * tree for strings that begin with character i.  These are initialized to NIL.
 164  * Note there are 256 trees. */
 165 static void init_state(struct encode_state *sp)
 166 {
 167     int  i;
 168
 169     bzero(sp, sizeof(*sp));
 170
 171     for (i = 0; i < N - F; i++)
 172         sp->text_buf[i] = ' ';
 173     for (i = N + 1; i <= N + 256; i++)
 174         sp->rchild[i] = NIL;
 175     for (i = 0; i < N; i++)
 176         sp->parent[i] = NIL;
 177 }
 178
 179 /*
 180  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 181  * (text_buf[r]'th tree) and returns the longest-match position and length
 182  * via the global variables match_position and match_length.
 183  * If match_length = F, then removes the old node in favor of the new one,
 184  * because the old one will be deleted sooner. Note r plays double role,
 185  * as tree node and position in buffer.
 186  */
 187 static void insert_node(struct encode_state *sp, int r)
 188 {
 189     int  i, p, cmp;
 190     u_int8_t  *key;
 191
 192     cmp = 1;
 193     key = &sp->text_buf[r];
 194     p = N + 1 + key[0];
 195     sp->rchild[r] = sp->lchild[r] = NIL;
 196     sp->match_length = 0;
 197     for ( ; ; ) {
 198         if (cmp >= 0) {
 199             if (sp->rchild[p] != NIL)
 200                 p = sp->rchild[p];
 201             else {
 202                 sp->rchild[p] = r;
 203                 sp->parent[r] = p;
 204                 return;
 205             }
 206         } else {
 207             if (sp->lchild[p] != NIL)
 208                 p = sp->lchild[p];
 209             else {
 210                 sp->lchild[p] = r;
 211                 sp->parent[r] = p;
 212                 return;
 213             }
 214         }
 215         for (i = 1; i < F; i++) {
 216             if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
 217                 break;
 218         }
 219         if (i > sp->match_length) {
 220             sp->match_position = p;
 221             if ((sp->match_length = i) >= F)
 222                 break;
 223         }
 224     }
 225     sp->parent[r] = sp->parent[p];
 226     sp->lchild[r] = sp->lchild[p];
 227     sp->rchild[r] = sp->rchild[p];
 228     sp->parent[sp->lchild[p]] = r;
 229     sp->parent[sp->rchild[p]] = r;
 230     if (sp->rchild[sp->parent[p]] == p)
 231         sp->rchild[sp->parent[p]] = r;
 232     else
 233         sp->lchild[sp->parent[p]] = r;
 234     sp->parent[p] = NIL;  /* remove p */
 235 }
 236
 237 /* deletes node p from tree */
 238 static void delete_node(struct encode_state *sp, int p)
 239 {
 240     int  q;
 241
 242     if (sp->parent[p] == NIL)
 243         return;  /* not in tree */
 244     if (sp->rchild[p] == NIL)
 245         q = sp->lchild[p];
 246     else if (sp->lchild[p] == NIL)
 247         q = sp->rchild[p];
 248     else {
 249         q = sp->lchild[p];
 250         if (sp->rchild[q] != NIL) {
 251             do {
 252                 q = sp->rchild[q];
 253             } while (sp->rchild[q] != NIL);
 254             sp->rchild[sp->parent[q]] = sp->lchild[q];
 255             sp->parent[sp->lchild[q]] = sp->parent[q];
 256             sp->lchild[q] = sp->lchild[p];
 257             sp->parent[sp->lchild[p]] = q;
 258         }
 259         sp->rchild[q] = sp->rchild[p];
 260         sp->parent[sp->rchild[p]] = q;
 261     }
 262     sp->parent[q] = sp->parent[p];
 263     if (sp->rchild[sp->parent[p]] == p)
 264         sp->rchild[sp->parent[p]] = q;
 265     else
 266         sp->lchild[sp->parent[p]] = q;
 267     sp->parent[p] = NIL;
 268 }
 269
 270 #endif /* !KERNEL */
 271