mkext.c

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    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) {
   59                         do {
   60                                 s1 += *buf++;
   61                                 s2 += s1;
   62                         } while (--k);
   63                 }
   64                 s1 %= BASE;
   65                 s2 %= BASE;
   66         }
   67         return (u_int32_t)((s2 << 16) | s1);
   68 }
   69 
   70 
   71 /**************************************************************
   72 *   LZSS.C -- A Data Compression Program
   73 ***************************************************************
   74 *    4/6/1989 Haruhiko Okumura
   75 *    Use, distribute, and modify this program freely.
   76 *    Please send me your improved versions.
   77 *        PC-VAN      SCIENCE
   78 *        NIFTY-Serve PAF01022
   79 *        CompuServe  74050,1022
   80 *
   81 **************************************************************/
   82 
   83 #define N         4096  /* size of ring buffer - must be power of 2 */
   84 #define F         18    /* upper limit for match_length */
   85 #define THRESHOLD 2     /* encode string into position and length
   86                          *  if match_length is greater than this */
   87 #if !KERNEL
   88 #define NIL       N     /* index for root of binary search trees */
   89 #endif
   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 int
  109 decompress_lzss(u_int8_t *dst, u_int32_t dstlen, 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 *dstend = dst + dstlen;
  115         u_int8_t *srcend = src + srclen;
  116         int  i, j, k, r;
  117         u_int8_t c;
  118         unsigned int flags;
  119 
  120         dst = dststart;
  121         srcend = src + srclen;
  122         for (i = 0; i < N - F; i++) {
  123                 text_buf[i] = ' ';
  124         }
  125         r = N - F;
  126         flags = 0;
  127         for (;;) {
  128                 if (((flags >>= 1) & 0x100) == 0) {
  129                         if (src < srcend) {
  130                                 c = *src++;
  131                         } else {
  132                                 break;
  133                         }
  134                         flags = c | 0xFF00; /* uses higher byte cleverly */
  135                 } /* to count eight */
  136                 if (flags & 1) {
  137                         if (src < srcend) {
  138                                 c = *src++;
  139                         } else {
  140                                 break;
  141                         }
  142                         *dst++ = c;
  143                         if (dst >= dstend) {
  144                                 goto finish;
  145                         }
  146                         text_buf[r++] = c;
  147                         r &= (N - 1);
  148                 } else {
  149                         if (src < srcend) {
  150                                 i = *src++;
  151                         } else {
  152                                 break;
  153                         }
  154                         if (src < srcend) {
  155                                 j = *src++;
  156                         } else {
  157                                 break;
  158                         }
  159                         i |= ((j & 0xF0) << 4);
  160                         j  =  (j & 0x0F) + THRESHOLD;
  161                         for (k = 0; k <= j; k++) {
  162                                 c = text_buf[(i + k) & (N - 1)];
  163                                 *dst++ = c;
  164                                 if (dst >= dstend) {
  165                                         goto finish;
  166                                 }
  167                                 text_buf[r++] = c;
  168                                 r &= (N - 1);
  169                         }
  170                 }
  171         }
  172 finish:
  173         return (int)(dst - dststart);
  174 }
  175 
  176 #if !KERNEL
  177 
  178 /*
  179  * initialize state, mostly the trees
  180  *
  181  * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
  182  * children of node i.  These nodes need not be initialized.  Also, parent[i]
  183  * is the parent of node i.  These are initialized to NIL (= N), which stands
  184  * for 'not used.'  For i = 0 to 255, rchild[N + i + 1] is the root of the
  185  * tree for strings that begin with character i.  These are initialized to NIL.
  186  * Note there are 256 trees. */
  187 static void
  188 init_state(struct encode_state *sp)
  189 {
  190         int  i;
  191 
  192         bzero(sp, sizeof(*sp));
  193 
  194         for (i = 0; i < N - F; i++) {
  195                 sp->text_buf[i] = ' ';
  196         }
  197         for (i = N + 1; i <= N + 256; i++) {
  198                 sp->rchild[i] = NIL;
  199         }
  200         for (i = 0; i < N; i++) {
  201                 sp->parent[i] = NIL;
  202         }
  203 }
  204 
  205 /*
  206  * Inserts string of length F, text_buf[r..r+F-1], into one of the trees
  207  * (text_buf[r]'th tree) and returns the longest-match position and length
  208  * via the global variables match_position and match_length.
  209  * If match_length = F, then removes the old node in favor of the new one,
  210  * because the old one will be deleted sooner. Note r plays double role,
  211  * as tree node and position in buffer.
  212  */
  213 static void
  214 insert_node(struct encode_state *sp, int r)
  215 {
  216         int  i, p, cmp;
  217         u_int8_t  *key;
  218 
  219         cmp = 1;
  220         key = &sp->text_buf[r];
  221         p = N + 1 + key[0];
  222         sp->rchild[r] = sp->lchild[r] = NIL;
  223         sp->match_length = 0;
  224         for (;;) {
  225                 if (cmp >= 0) {
  226                         if (sp->rchild[p] != NIL) {
  227                                 p = sp->rchild[p];
  228                         } else {
  229                                 sp->rchild[p] = r;
  230                                 sp->parent[r] = p;
  231                                 return;
  232                         }
  233                 } else {
  234                         if (sp->lchild[p] != NIL) {
  235                                 p = sp->lchild[p];
  236                         } else {
  237                                 sp->lchild[p] = r;
  238                                 sp->parent[r] = p;
  239                                 return;
  240                         }
  241                 }
  242                 for (i = 1; i < F; i++) {
  243                         if ((cmp = key[i] - sp->text_buf[p + i]) != 0) {
  244                                 break;
  245                         }
  246                 }
  247                 if (i > sp->match_length) {
  248                         sp->match_position = p;
  249                         if ((sp->match_length = i) >= F) {
  250                                 break;
  251                         }
  252                 }
  253         }
  254         sp->parent[r] = sp->parent[p];
  255         sp->lchild[r] = sp->lchild[p];
  256         sp->rchild[r] = sp->rchild[p];
  257         sp->parent[sp->lchild[p]] = r;
  258         sp->parent[sp->rchild[p]] = r;
  259         if (sp->rchild[sp->parent[p]] == p) {
  260                 sp->rchild[sp->parent[p]] = r;
  261         } else {
  262                 sp->lchild[sp->parent[p]] = r;
  263         }
  264         sp->parent[p] = NIL; /* remove p */
  265 }
  266 
  267 /* deletes node p from tree */
  268 static void
  269 delete_node(struct encode_state *sp, int p)
  270 {
  271         int  q;
  272 
  273         if (sp->parent[p] == NIL) {
  274                 return; /* not in tree */
  275         }
  276         if (sp->rchild[p] == NIL) {
  277                 q = sp->lchild[p];
  278         } else if (sp->lchild[p] == NIL) {
  279                 q = sp->rchild[p];
  280         } else {
  281                 q = sp->lchild[p];
  282                 if (sp->rchild[q] != NIL) {
  283                         do {
  284                                 q = sp->rchild[q];
  285                         } while (sp->rchild[q] != NIL);
  286                         sp->rchild[sp->parent[q]] = sp->lchild[q];
  287                         sp->parent[sp->lchild[q]] = sp->parent[q];
  288                         sp->lchild[q] = sp->lchild[p];
  289                         sp->parent[sp->lchild[p]] = q;
  290                 }
  291                 sp->rchild[q] = sp->rchild[p];
  292                 sp->parent[sp->rchild[p]] = q;
  293         }
  294         sp->parent[q] = sp->parent[p];
  295         if (sp->rchild[sp->parent[p]] == p) {
  296                 sp->rchild[sp->parent[p]] = q;
  297         } else {
  298                 sp->lchild[sp->parent[p]] = q;
  299         }
  300         sp->parent[p] = NIL;
  301 }
  302 
  303 #endif /* !KERNEL */
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FreeBSD/Linux Kernel Cross Reference sys/libkern/mkext.c

FreeBSD/Linux Kernel Cross Reference
sys/libkern/mkext.c
