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 #if defined _ARM_ARCH_6
  50
  51         /* align buf to 16-byte boundary */
  52     while ((((uintptr_t)buf)&15)&&(len>0)) { /* not on a 16-byte boundary */
  53         len--;
  54         s1 += *buf++;
  55         s2 += s1;
  56         if (s1 >= BASE) s1 -= BASE;
  57     }
  58         s2 %= BASE;
  59
  60         if (len>=16) {
  61                 return adler32_vec(s1, s2, buf, len);
  62         }
  63
  64 #endif
  65
  66     while (len > 0) {
  67         k = len < NMAX ? len : NMAX;
  68         len -= k;
  69         while (k >= 16) {
  70             DO16(buf);
  71             buf += 16;
  72             k -= 16;
  73         }
  74         if (k != 0) do {
  75             s1 += *buf++;
  76             s2 += s1;
  77         } while (--k);
  78         s1 %= BASE;
  79         s2 %= BASE;
  80     }
  81     return (s2 << 16) | s1;
  82 }
  83
  84
  85 /**************************************************************
  86  LZSS.C -- A Data Compression Program
  87 ***************************************************************
  88     4/6/1989 Haruhiko Okumura
  89     Use, distribute, and modify this program freely.
  90     Please send me your improved versions.
  91         PC-VAN      SCIENCE
  92         NIFTY-Serve PAF01022
  93         CompuServe  74050,1022
  94
  95 **************************************************************/
  96
  97 #define N         4096  /* size of ring buffer - must be power of 2 */
  98 #define F         18    /* upper limit for match_length */
  99 #define THRESHOLD 2     /* encode string into position and length
 100                            if match_length is greater than this */
 101 #define NIL       N     /* index for root of binary search trees */
 102
 103 struct encode_state {
 104     /*
 105      * left & right children & parent. These constitute binary search trees.
 106      */
 107     int lchild[N + 1], rchild[N + 257], parent[N + 1];
 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
 112     /*
 113      * match_length of longest match.
 114      * These are set by the insert_node() procedure.
 115      */
 116     int match_position, match_length;
 117 };
 118
 119
 120 int
 121 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srclen)
 122 {
 123     /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
 124     u_int8_t text_buf[N + F - 1];
 125     u_int8_t *dststart = dst;
 126         u_int8_t *dstend = dst + dstlen;
 127     u_int8_t *srcend = src + srclen;
 128     int  i, j, k, r, c;
 129     unsigned int flags;
 130
 131     dst = dststart;
 132     srcend = src + srclen;
 133     for (i = 0; i < N - F; i++)
 134         text_buf[i] = ' ';
 135     r = N - F;
 136     flags = 0;
 137     for ( ; ; ) {
 138         if (((flags >>= 1) & 0x100) == 0) {
 139             if (src < srcend) c = *src++; else break;
 140             flags = c | 0xFF00;  /* uses higher byte cleverly */
 141         }   /* to count eight */
 142         if (flags & 1) {
 143             if (src < srcend) c = *src++; else break;
 144             *dst++ = c;
 145                         if (dst >= dstend) {
 146                                 goto finish;
 147                         }
 148             text_buf[r++] = c;
 149             r &= (N - 1);
 150         } else {
 151             if (src < srcend) i = *src++; else break;
 152             if (src < srcend) j = *src++; else break;
 153             i |= ((j & 0xF0) << 4);
 154             j  =  (j & 0x0F) + THRESHOLD;
 155             for (k = 0; k <= j; k++) {
 156                 c = text_buf[(i + k) & (N - 1)];
 157                 *dst++ = c;
 158                                 if (dst >= dstend) {
 159                                         goto finish;
 160                                 }
 161                 text_buf[r++] = c;
 162                 r &= (N - 1);
 163             }
 164         }
 165     }
 166 finish:
 167     return dst - dststart;
 168 }
 169
 170 #if !KERNEL
 171
 172 /*
 173  * initialize state, mostly the trees
 174  *
 175  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
 176  * children of node i.  These nodes need not be initialized.  Also, parent[i]
 177  * is the parent of node i.  These are initialized to NIL (= N), which stands
 178  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
 179  * tree for strings that begin with character i.  These are initialized to NIL.
 180  * Note there are 256 trees. */
 181 static void init_state(struct encode_state *sp)
 182 {
 183     int  i;
 184
 185     bzero(sp, sizeof(*sp));
 186
 187     for (i = 0; i < N - F; i++)
 188         sp->text_buf[i] = ' ';
 189     for (i = N + 1; i <= N + 256; i++)
 190         sp->rchild[i] = NIL;
 191     for (i = 0; i < N; i++)
 192         sp->parent[i] = NIL;
 193 }
 194
 195 /*
 196  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
 197  * (text_buf[r]'th tree) and returns the longest-match position and length
 198  * via the global variables match_position and match_length.
 199  * If match_length = F, then removes the old node in favor of the new one,
 200  * because the old one will be deleted sooner. Note r plays double role,
 201  * as tree node and position in buffer.
 202  */
 203 static void insert_node(struct encode_state *sp, int r)
 204 {
 205     int  i, p, cmp;
 206     u_int8_t  *key;
 207
 208     cmp = 1;
 209     key = &sp->text_buf[r];
 210     p = N + 1 + key[0];
 211     sp->rchild[r] = sp->lchild[r] = NIL;
 212     sp->match_length = 0;
 213     for ( ; ; ) {
 214         if (cmp >= 0) {
 215             if (sp->rchild[p] != NIL)
 216                 p = sp->rchild[p];
 217             else {
 218                 sp->rchild[p] = r;
 219                 sp->parent[r] = p;
 220                 return;
 221             }
 222         } else {
 223             if (sp->lchild[p] != NIL)
 224                 p = sp->lchild[p];
 225             else {
 226                 sp->lchild[p] = r;
 227                 sp->parent[r] = p;
 228                 return;
 229             }
 230         }
 231         for (i = 1; i < F; i++) {
 232             if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
 233                 break;
 234         }
 235         if (i > sp->match_length) {
 236             sp->match_position = p;
 237             if ((sp->match_length = i) >= F)
 238                 break;
 239         }
 240     }
 241     sp->parent[r] = sp->parent[p];
 242     sp->lchild[r] = sp->lchild[p];
 243     sp->rchild[r] = sp->rchild[p];
 244     sp->parent[sp->lchild[p]] = r;
 245     sp->parent[sp->rchild[p]] = r;
 246     if (sp->rchild[sp->parent[p]] == p)
 247         sp->rchild[sp->parent[p]] = r;
 248     else
 249         sp->lchild[sp->parent[p]] = r;
 250     sp->parent[p] = NIL;  /* remove p */
 251 }
 252
 253 /* deletes node p from tree */
 254 static void delete_node(struct encode_state *sp, int p)
 255 {
 256     int  q;
 257
 258     if (sp->parent[p] == NIL)
 259         return;  /* not in tree */
 260     if (sp->rchild[p] == NIL)
 261         q = sp->lchild[p];
 262     else if (sp->lchild[p] == NIL)
 263         q = sp->rchild[p];
 264     else {
 265         q = sp->lchild[p];
 266         if (sp->rchild[q] != NIL) {
 267             do {
 268                 q = sp->rchild[q];
 269             } while (sp->rchild[q] != NIL);
 270             sp->rchild[sp->parent[q]] = sp->lchild[q];
 271             sp->parent[sp->lchild[q]] = sp->parent[q];
 272             sp->lchild[q] = sp->lchild[p];
 273             sp->parent[sp->lchild[p]] = q;
 274         }
 275         sp->rchild[q] = sp->rchild[p];
 276         sp->parent[sp->rchild[p]] = q;
 277     }
 278     sp->parent[q] = sp->parent[p];
 279     if (sp->rchild[sp->parent[p]] == p)
 280         sp->rchild[sp->parent[p]] = q;
 281     else
 282         sp->lchild[sp->parent[p]] = q;
 283     sp->parent[p] = NIL;
 284 }
 285
 286 #endif /* !KERNEL */
 287