iconv/strtab.c

   1 /* C string table handling.
   2    Copyright (C) 2000-2017 Free Software Foundation, Inc.
   3    Written by Ulrich Drepper <drepper@redhat.com>, 2000.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #ifdef HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <assert.h>
  23 #include <inttypes.h>
  24 #include <stddef.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <sys/cdefs.h>
  29 #include <sys/param.h>
  30
  31
  32 struct Strent
  33 {
  34   const char *string;
  35   size_t len;
  36   struct Strent *next;
  37   struct Strent *left;
  38   struct Strent *right;
  39   size_t offset;
  40   char reverse[0];
  41 };
  42
  43
  44 struct memoryblock
  45 {
  46   struct memoryblock *next;
  47   char memory[0];
  48 };
  49
  50
  51 struct Strtab
  52 {
  53   struct Strent *root;
  54   struct memoryblock *memory;
  55   char *backp;
  56   size_t left;
  57   size_t total;
  58
  59   struct Strent null;
  60 };
  61
  62
  63 /* Cache for the pagesize.  We correct this value a bit so that `malloc'
  64    is not allocating more than a page.  */
  65 static size_t ps;
  66
  67
  68 #include <programs/xmalloc.h>
  69
  70 /* Prototypes for our functions that are used from iconvconfig.c.  If
  71    you change these, change also iconvconfig.c.  */
  72 /* Create new C string table object in memory.  */
  73 extern struct Strtab *strtabinit (void);
  74
  75 /* Free resources allocated for C string table ST.  */
  76 extern void strtabfree (struct Strtab *st);
  77
  78 /* Add string STR (length LEN is != 0) to C string table ST.  */
  79 extern struct Strent *strtabadd (struct Strtab *st, const char *str,
  80                                  size_t len);
  81
  82 /* Finalize string table ST and store size in *SIZE and return a pointer.  */
  83 extern void *strtabfinalize (struct Strtab *st, size_t *size);
  84
  85 /* Get offset in string table for string associated with SE.  */
  86 extern size_t strtaboffset (struct Strent *se);
  87
  88
  89 struct Strtab *
  90 strtabinit (void)
  91 {
  92   struct Strtab *ret;
  93
  94   if (ps == 0)
  95     {
  96       ps = sysconf (_SC_PAGESIZE) - 2 * sizeof (void *);
  97       assert (sizeof (struct memoryblock) < ps);
  98     }
  99
 100   ret = (struct Strtab *) calloc (1, sizeof (struct Strtab));
 101   if (ret != NULL)
 102     {
 103       ret->null.len = 1;
 104       ret->null.string = "";
 105     }
 106   return ret;
 107 }
 108
 109
 110 static void
 111 morememory (struct Strtab *st, size_t len)
 112 {
 113   struct memoryblock *newmem;
 114
 115   if (len < ps)
 116     len = ps;
 117   newmem = (struct memoryblock *) malloc (len);
 118   if (newmem == NULL)
 119     abort ();
 120
 121   newmem->next = st->memory;
 122   st->memory = newmem;
 123   st->backp = newmem->memory;
 124   st->left = len - offsetof (struct memoryblock, memory);
 125 }
 126
 127
 128 void
 129 strtabfree (struct Strtab *st)
 130 {
 131   struct memoryblock *mb = st->memory;
 132
 133   while (mb != NULL)
 134     {
 135       void *old = mb;
 136       mb = mb->next;
 137       free (old);
 138     }
 139
 140   free (st);
 141 }
 142
 143
 144 static struct Strent *
 145 newstring (struct Strtab *st, const char *str, size_t len)
 146 {
 147   struct Strent *newstr;
 148   size_t align;
 149   int i;
 150
 151   /* Compute the amount of padding needed to make the structure aligned.  */
 152   align = ((__alignof__ (struct Strent)
 153             - (((uintptr_t) st->backp)
 154                & (__alignof__ (struct Strent) - 1)))
 155            & (__alignof__ (struct Strent) - 1));
 156
 157   /* Make sure there is enough room in the memory block.  */
 158   if (st->left < align + sizeof (struct Strent) + len)
 159     {
 160       morememory (st, sizeof (struct Strent) + len);
 161       align = 0;
 162     }
 163
 164   /* Create the reserved string.  */
 165   newstr = (struct Strent *) (st->backp + align);
 166   newstr->string = str;
 167   newstr->len = len;
 168   newstr->next = NULL;
 169   newstr->left = NULL;
 170   newstr->right = NULL;
 171   newstr->offset = 0;
 172   for (i = len - 2; i >= 0; --i)
 173     newstr->reverse[i] = str[len - 2 - i];
 174   newstr->reverse[len - 1] = '\0';
 175   st->backp += align + sizeof (struct Strent) + len;
 176   st->left -= align + sizeof (struct Strent) + len;
 177
 178   return newstr;
 179 }
 180
 181
 182 /* XXX This function should definitely be rewritten to use a balancing
 183    tree algorithm (AVL, red-black trees).  For now a simple, correct
 184    implementation is enough.  */
 185 static struct Strent **
 186 searchstring (struct Strent **sep, struct Strent *newstr)
 187 {
 188   int cmpres;
 189
 190   /* More strings?  */
 191   if (*sep == NULL)
 192     {
 193       *sep = newstr;
 194       return sep;
 195     }
 196
 197   /* Compare the strings.  */
 198   cmpres = memcmp ((*sep)->reverse, newstr->reverse,
 199                    MIN ((*sep)->len, newstr->len) - 1);
 200   if (cmpres == 0)
 201     /* We found a matching string.  */
 202     return sep;
 203   else if (cmpres > 0)
 204     return searchstring (&(*sep)->left, newstr);
 205   else
 206     return searchstring (&(*sep)->right, newstr);
 207 }
 208
 209
 210 /* Add new string.  The actual string is assumed to be permanent.  */
 211 struct Strent *
 212 strtabadd (struct Strtab *st, const char *str, size_t len)
 213 {
 214   struct Strent *newstr;
 215   struct Strent **sep;
 216
 217   /* Compute the string length if the caller doesn't know it.  */
 218   if (len == 0)
 219     len = strlen (str) + 1;
 220
 221   /* Make sure all "" strings get offset 0.  */
 222   if (len == 1)
 223     return &st->null;
 224
 225   /* Allocate memory for the new string and its associated information.  */
 226   newstr = newstring (st, str, len);
 227
 228   /* Search in the array for the place to insert the string.  If there
 229      is no string with matching prefix and no string with matching
 230      leading substring, create a new entry.  */
 231   sep = searchstring (&st->root, newstr);
 232   if (*sep != newstr)
 233     {
 234       /* This is not the same entry.  This means we have a prefix match.  */
 235       if ((*sep)->len > newstr->len)
 236         {
 237           struct Strent *subs;
 238
 239           for (subs = (*sep)->next; subs; subs = subs->next)
 240             if (subs->len == newstr->len)
 241               {
 242                 /* We have an exact match with a substring.  Free the memory
 243                    we allocated.  */
 244                 st->left += st->backp - (char *) newstr;
 245                 st->backp = (char *) newstr;
 246
 247                 return subs;
 248               }
 249
 250           /* We have a new substring.  This means we don't need the reverse
 251              string of this entry anymore.  */
 252           st->backp -= newstr->len;
 253           st->left += newstr->len;
 254
 255           newstr->next = (*sep)->next;
 256           (*sep)->next = newstr;
 257         }
 258       else if ((*sep)->len != newstr->len)
 259         {
 260           /* When we get here it means that the string we are about to
 261              add has a common prefix with a string we already have but
 262              it is longer.  In this case we have to put it first.  */
 263           st->total += newstr->len - (*sep)->len;
 264           newstr->next = *sep;
 265           newstr->left = (*sep)->left;
 266           newstr->right = (*sep)->right;
 267           *sep = newstr;
 268         }
 269       else
 270         {
 271           /* We have an exact match.  Free the memory we allocated.  */
 272           st->left += st->backp - (char *) newstr;
 273           st->backp = (char *) newstr;
 274
 275           newstr = *sep;
 276         }
 277     }
 278   else
 279     st->total += newstr->len;
 280
 281   return newstr;
 282 }
 283
 284
 285 static void
 286 copystrings (struct Strent *nodep, char **freep, size_t *offsetp)
 287 {
 288   struct Strent *subs;
 289
 290   if (nodep->left != NULL)
 291     copystrings (nodep->left, freep, offsetp);
 292
 293   /* Process the current node.  */
 294   nodep->offset = *offsetp;
 295   *freep = (char *) mempcpy (*freep, nodep->string, nodep->len);
 296   *offsetp += nodep->len;
 297
 298   for (subs = nodep->next; subs != NULL; subs = subs->next)
 299     {
 300       assert (subs->len < nodep->len);
 301       subs->offset = nodep->offset + nodep->len - subs->len;
 302     }
 303
 304   if (nodep->right != NULL)
 305     copystrings (nodep->right, freep, offsetp);
 306 }
 307
 308
 309 void *
 310 strtabfinalize (struct Strtab *st, size_t *size)
 311 {
 312   size_t copylen;
 313   char *endp;
 314   char *retval;
 315
 316   /* Fill in the information.  */
 317   endp = retval = (char *) xmalloc (st->total + 1);
 318
 319   /* Always put an empty string at the beginning so that a zero offset
 320      can mean error.  */
 321   *endp++ = '\0';
 322
 323   /* Now run through the tree and add all the string while also updating
 324      the offset members of the elfstrent records.  */
 325   copylen = 1;
 326   copystrings (st->root, &endp, &copylen);
 327   assert (copylen == st->total + 1);
 328   assert (endp == retval + st->total + 1);
 329   *size = copylen;
 330
 331   return retval;
 332 }
 333
 334
 335 size_t
 336 strtaboffset (struct Strent *se)
 337 {
 338   return se->offset;
 339 }