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) 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 #if !KERNEL
  86 #define NIL       N     /* index for root of binary search trees */
  87 #endif
  88
  89 struct encode_state {
  90     /*
  91      * left & right children & parent. These constitute binary search trees.
  92      */
  93     int lchild[N + 1], rchild[N + 257], parent[N + 1];
  94
  95     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
  96     u_int8_t text_buf[N + F - 1];
  97
  98     /*
  99      * match_length of longest match.
 100      * These are set by the insert_node() procedure.
 101      */
 102     int match_position, match_length;
 103 };
 104
 105
 106 int
 107 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srclen)
 108 {
 109     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
 110     u_int8_t text_buf[N + F - 1];
 111     u_int8_t *dststart = dst;
 112         u_int8_t *dstend = dst + dstlen;
 113     u_int8_t *srcend = src + srclen;
 114     int  i, j, k, r, c;
 115     unsigned int flags;
 116
 117     dst = dststart;
 118     srcend = src + srclen;
 119     for (i = 0; i < N - F; i++)
 120         text_buf[i] = ' ';
 121     r = N - F;
 122     flags = 0;
 123     for ( ; ; ) {
 124         if (((flags >>= 1) & 0x100) == 0) {
 125             if (src < srcend) c = *src++; else break;
 126             flags = c | 0xFF00;  /* uses higher byte cleverly */
 127         }   /* to count eight */
 128         if (flags & 1) {
 129             if (src < srcend) c = *src++; else break;
 130             *dst++ = c;
 131                         if (dst >= dstend) {
 132                                 goto finish;
 133                         }
 134             text_buf[r++] = c;
 135             r &= (N - 1);
 136         } else {
 137             if (src < srcend) i = *src++; else break;
 138             if (src < srcend) j = *src++; else break;
 139             i |= ((j & 0xF0) << 4);
 140             j  =  (j & 0x0F) + THRESHOLD;
 141             for (k = 0; k <= j; k++) {
 142                 c = text_buf[(i + k) & (N - 1)];
 143                 *dst++ = c;
 144                                 if (dst >= dstend) {
 145                                         goto finish;
 146                                 }
 147                 text_buf[r++] = c;
 148                 r &= (N - 1);
 149             }
 150         }
 151     }
 152 finish:
 153     return dst - dststart;
 154 }
 155
 156 #if !KERNEL
 157
 158 /*
 159  * initialize state, mostly the trees
 160  *
 161  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 162  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 163  * is the parent of node i.  These are initialized to NIL (= N), which stands
 164  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 165  * tree for strings that begin with character i.  These are initialized to NIL.
 166  * Note there are 256 trees. */
 167 static void init_state(struct encode_state *sp)
 168 {
 169     int  i;
 170
 171     bzero(sp, sizeof(*sp));
 172
 173     for (i = 0; i < N - F; i++)
 174         sp->text_buf[i] = ' ';
 175     for (i = N + 1; i <= N + 256; i++)
 176         sp->rchild[i] = NIL;
 177     for (i = 0; i < N; i++)
 178         sp->parent[i] = NIL;
 179 }
 180
 181 /*
 182  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 183  * (text_buf[r]'th tree) and returns the longest-match position and length
 184  * via the global variables match_position and match_length.
 185  * If match_length = F, then removes the old node in favor of the new one,
 186  * because the old one will be deleted sooner. Note r plays double role,
 187  * as tree node and position in buffer.
 188  */
 189 static void insert_node(struct encode_state *sp, int r)
 190 {
 191     int  i, p, cmp;
 192     u_int8_t  *key;
 193
 194     cmp = 1;
 195     key = &sp->text_buf[r];
 196     p = N + 1 + key[0];
 197     sp->rchild[r] = sp->lchild[r] = NIL;
 198     sp->match_length = 0;
 199     for ( ; ; ) {
 200         if (cmp >= 0) {
 201             if (sp->rchild[p] != NIL)
 202                 p = sp->rchild[p];
 203             else {
 204                 sp->rchild[p] = r;
 205                 sp->parent[r] = p;
 206                 return;
 207             }
 208         } else {
 209             if (sp->lchild[p] != NIL)
 210                 p = sp->lchild[p];
 211             else {
 212                 sp->lchild[p] = r;
 213                 sp->parent[r] = p;
 214                 return;
 215             }
 216         }
 217         for (i = 1; i < F; i++) {
 218             if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
 219                 break;
 220         }
 221         if (i > sp->match_length) {
 222             sp->match_position = p;
 223             if ((sp->match_length = i) >= F)
 224                 break;
 225         }
 226     }
 227     sp->parent[r] = sp->parent[p];
 228     sp->lchild[r] = sp->lchild[p];
 229     sp->rchild[r] = sp->rchild[p];
 230     sp->parent[sp->lchild[p]] = r;
 231     sp->parent[sp->rchild[p]] = r;
 232     if (sp->rchild[sp->parent[p]] == p)
 233         sp->rchild[sp->parent[p]] = r;
 234     else
 235         sp->lchild[sp->parent[p]] = r;
 236     sp->parent[p] = NIL;  /* remove p */
 237 }
 238
 239 /* deletes node p from tree */
 240 static void delete_node(struct encode_state *sp, int p)
 241 {
 242     int  q;
 243
 244     if (sp->parent[p] == NIL)
 245         return;  /* not in tree */
 246     if (sp->rchild[p] == NIL)
 247         q = sp->lchild[p];
 248     else if (sp->lchild[p] == NIL)
 249         q = sp->rchild[p];
 250     else {
 251         q = sp->lchild[p];
 252         if (sp->rchild[q] != NIL) {
 253             do {
 254                 q = sp->rchild[q];
 255             } while (sp->rchild[q] != NIL);
 256             sp->rchild[sp->parent[q]] = sp->lchild[q];
 257             sp->parent[sp->lchild[q]] = sp->parent[q];
 258             sp->lchild[q] = sp->lchild[p];
 259             sp->parent[sp->lchild[p]] = q;
 260         }
 261         sp->rchild[q] = sp->rchild[p];
 262         sp->parent[sp->rchild[p]] = q;
 263     }
 264     sp->parent[q] = sp->parent[p];
 265     if (sp->rchild[sp->parent[p]] == p)
 266         sp->rchild[sp->parent[p]] = q;
 267     else
 268         sp->lchild[sp->parent[p]] = q;
 269     sp->parent[p] = NIL;
 270 }
 271
 272 #endif /* !KERNEL */
 273