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 <string.h>
  29 #include <libkern/mkext.h>
  30
  31 #define BASE 65521L /* largest prime smaller than 65536 */
  32 #define NMAX 5000
  33 // NMAX (was 5521) the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
  34
  35 #define DO1(buf,i)  {s1 += buf[i]; s2 += s1;}
  36 #define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
  37 #define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
  38 #define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
  39 #define DO16(buf)   DO8(buf,0); DO8(buf,8);
  40
  41 u_int32_t
  42 mkext_adler32(uint8_t *buf, int32_t len)
  43 {
  44     unsigned long s1 = 1; // adler & 0xffff;
  45     unsigned long s2 = 0; // (adler >> 16) & 0xffff;
  46     int k;
  47
  48     while (len > 0) {
  49         k = len < NMAX ? len : NMAX;
  50         len -= k;
  51         while (k >= 16) {
  52             DO16(buf);
  53             buf += 16;
  54             k -= 16;
  55         }
  56         if (k != 0) do {
  57             s1 += *buf++;
  58             s2 += s1;
  59         } while (--k);
  60         s1 %= BASE;
  61         s2 %= BASE;
  62     }
  63     return (s2 << 16) | s1;
  64 }
  65
  66
  67 /**************************************************************
  68  LZSS.C -- A Data Compression Program
  69 ***************************************************************
  70     4/6/1989 Haruhiko Okumura
  71     Use, distribute, and modify this program freely.
  72     Please send me your improved versions.
  73         PC-VAN      SCIENCE
  74         NIFTY-Serve PAF01022
  75         CompuServe  74050,1022
  76
  77 **************************************************************/
  78
  79 #define N         4096  /* size of ring buffer - must be power of 2 */
  80 #define F         18    /* upper limit for match_length */
  81 #define THRESHOLD 2     /* encode string into position and length
  82                            if match_length is greater than this */
  83 #define NIL       N     /* index for root of binary search trees */
  84
  85 struct encode_state {
  86     /*
  87      * left & right children & parent. These constitute binary search trees.
  88      */
  89     int lchild[N + 1], rchild[N + 257], parent[N + 1];
  90
  91     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
  92     u_int8_t text_buf[N + F - 1];
  93
  94     /*
  95      * match_length of longest match.
  96      * These are set by the insert_node() procedure.
  97      */
  98     int match_position, match_length;
  99 };
 100
 101
 102 int
 103 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srclen)
 104 {
 105     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
 106     u_int8_t text_buf[N + F - 1];
 107     u_int8_t *dststart = dst;
 108         u_int8_t *dstend = dst + dstlen;
 109     u_int8_t *srcend = src + srclen;
 110     int  i, j, k, r, c;
 111     unsigned int flags;
 112
 113     dst = dststart;
 114     srcend = src + srclen;
 115     for (i = 0; i < N - F; i++)
 116         text_buf[i] = ' ';
 117     r = N - F;
 118     flags = 0;
 119     for ( ; ; ) {
 120         if (((flags >>= 1) & 0x100) == 0) {
 121             if (src < srcend) c = *src++; else break;
 122             flags = c | 0xFF00;  /* uses higher byte cleverly */
 123         }   /* to count eight */
 124         if (flags & 1) {
 125             if (src < srcend) c = *src++; else break;
 126             *dst++ = c;
 127                         if (dst >= dstend) {
 128                                 goto finish;
 129                         }
 130             text_buf[r++] = c;
 131             r &= (N - 1);
 132         } else {
 133             if (src < srcend) i = *src++; else break;
 134             if (src < srcend) j = *src++; else break;
 135             i |= ((j & 0xF0) << 4);
 136             j  =  (j & 0x0F) + THRESHOLD;
 137             for (k = 0; k <= j; k++) {
 138                 c = text_buf[(i + k) & (N - 1)];
 139                 *dst++ = c;
 140                                 if (dst >= dstend) {
 141                                         goto finish;
 142                                 }
 143                 text_buf[r++] = c;
 144                 r &= (N - 1);
 145             }
 146         }
 147     }
 148 finish:
 149     return dst - dststart;
 150 }
 151
 152 #if !KERNEL
 153
 154 /*
 155  * initialize state, mostly the trees
 156  *
 157  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 158  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 159  * is the parent of node i.  These are initialized to NIL (= N), which stands
 160  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 161  * tree for strings that begin with character i.  These are initialized to NIL.
 162  * Note there are 256 trees. */
 163 static void init_state(struct encode_state *sp)
 164 {
 165     int  i;
 166
 167     bzero(sp, sizeof(*sp));
 168
 169     for (i = 0; i < N - F; i++)
 170         sp->text_buf[i] = ' ';
 171     for (i = N + 1; i <= N + 256; i++)
 172         sp->rchild[i] = NIL;
 173     for (i = 0; i < N; i++)
 174         sp->parent[i] = NIL;
 175 }
 176
 177 /*
 178  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 179  * (text_buf[r]'th tree) and returns the longest-match position and length
 180  * via the global variables match_position and match_length.
 181  * If match_length = F, then removes the old node in favor of the new one,
 182  * because the old one will be deleted sooner. Note r plays double role,
 183  * as tree node and position in buffer.
 184  */
 185 static void insert_node(struct encode_state *sp, int r)
 186 {
 187     int  i, p, cmp;
 188     u_int8_t  *key;
 189
 190     cmp = 1;
 191     key = &sp->text_buf[r];
 192     p = N + 1 + key[0];
 193     sp->rchild[r] = sp->lchild[r] = NIL;
 194     sp->match_length = 0;
 195     for ( ; ; ) {
 196         if (cmp >= 0) {
 197             if (sp->rchild[p] != NIL)
 198                 p = sp->rchild[p];
 199             else {
 200                 sp->rchild[p] = r;
 201                 sp->parent[r] = p;
 202                 return;
 203             }
 204         } else {
 205             if (sp->lchild[p] != NIL)
 206                 p = sp->lchild[p];
 207             else {
 208                 sp->lchild[p] = r;
 209                 sp->parent[r] = p;
 210                 return;
 211             }
 212         }
 213         for (i = 1; i < F; i++) {
 214             if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
 215                 break;
 216         }
 217         if (i > sp->match_length) {
 218             sp->match_position = p;
 219             if ((sp->match_length = i) >= F)
 220                 break;
 221         }
 222     }
 223     sp->parent[r] = sp->parent[p];
 224     sp->lchild[r] = sp->lchild[p];
 225     sp->rchild[r] = sp->rchild[p];
 226     sp->parent[sp->lchild[p]] = r;
 227     sp->parent[sp->rchild[p]] = r;
 228     if (sp->rchild[sp->parent[p]] == p)
 229         sp->rchild[sp->parent[p]] = r;
 230     else
 231         sp->lchild[sp->parent[p]] = r;
 232     sp->parent[p] = NIL;  /* remove p */
 233 }
 234
 235 /* deletes node p from tree */
 236 static void delete_node(struct encode_state *sp, int p)
 237 {
 238     int  q;
 239
 240     if (sp->parent[p] == NIL)
 241         return;  /* not in tree */
 242     if (sp->rchild[p] == NIL)
 243         q = sp->lchild[p];
 244     else if (sp->lchild[p] == NIL)
 245         q = sp->rchild[p];
 246     else {
 247         q = sp->lchild[p];
 248         if (sp->rchild[q] != NIL) {
 249             do {
 250                 q = sp->rchild[q];
 251             } while (sp->rchild[q] != NIL);
 252             sp->rchild[sp->parent[q]] = sp->lchild[q];
 253             sp->parent[sp->lchild[q]] = sp->parent[q];
 254             sp->lchild[q] = sp->lchild[p];
 255             sp->parent[sp->lchild[p]] = q;
 256         }
 257         sp->rchild[q] = sp->rchild[p];
 258         sp->parent[sp->rchild[p]] = q;
 259     }
 260     sp->parent[q] = sp->parent[p];
 261     if (sp->rchild[sp->parent[p]] == p)
 262         sp->rchild[sp->parent[p]] = q;
 263     else
 264         sp->lchild[sp->parent[p]] = q;
 265     sp->parent[p] = NIL;
 266 }
 267
 268 #endif /* !KERNEL */
 269