include/ocache.h

   1 /* ocache.h -- a minimal object caching implementation. */
   2
   3 /* Copyright (C) 2002 Free Software Foundation, Inc.
   4
   5    This file is part of GNU Bash, the Bourne Again SHell.
   6
   7    Bash is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation, either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    Bash is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with Bash.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #if !defined (_OCACHE_H_)
  22 #define _OCACHE_H_ 1
  23
  24 #ifndef PTR_T
  25
  26 #if defined (__STDC__)
  27 #  define PTR_T void *
  28 #else
  29 #  define PTR_T char *
  30 #endif
  31
  32 #endif /* PTR_T */
  33
  34 #define OC_MEMSET(memp, xch, nbytes)                                    \
  35 do {                                                                    \
  36   if ((nbytes) <= 32) {                                                 \
  37     register char * mzp = (char *)(memp);                               \
  38     unsigned long mctmp = (nbytes);                                     \
  39     register long mcn;                                                  \
  40     if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp &= 7; }     \
  41     switch (mctmp) {                                                    \
  42       case 0: for(;;) { *mzp++ = xch;                                   \
  43       case 7:      *mzp++ = xch;                                        \
  44       case 6:      *mzp++ = xch;                                        \
  45       case 5:      *mzp++ = xch;                                        \
  46       case 4:      *mzp++ = xch;                                        \
  47       case 3:      *mzp++ = xch;                                        \
  48       case 2:      *mzp++ = xch;                                        \
  49       case 1:      *mzp++ = xch; if(mcn <= 0) break; mcn--; }           \
  50     }                                                                   \
  51   } else                                                                \
  52     memset ((memp), (xch), (nbytes));                                   \
  53 } while(0)
  54
  55 typedef struct objcache {
  56         PTR_T   data;
  57         int     cs;             /* cache size, number of objects */
  58         int     nc;             /* number of cache entries */
  59 } sh_obj_cache_t;
  60
  61 /* Create an object cache C of N pointers to OTYPE. */
  62 #define ocache_create(c, otype, n) \
  63         do { \
  64                 (c).data = xmalloc((n) * sizeof (otype *)); \
  65                 (c).cs = (n); \
  66                 (c).nc = 0; \
  67         } while (0)
  68
  69 /* Destroy an object cache C. */
  70 #define ocache_destroy(c) \
  71         do { \
  72                 if ((c).data) \
  73                         xfree ((c).data); \
  74                 (c).data = 0; \
  75                 (c).cs = (c).nc = 0; \
  76         } while (0)
  77
  78 /* Free all cached items, which are pointers to OTYPE, in object cache C. */
  79 #define ocache_flush(c, otype) \
  80         do { \
  81                 while ((c).nc > 0) \
  82                         xfree (((otype **)((c).data))[--(c).nc]); \
  83         } while (0)
  84
  85 /*
  86  * Allocate a new item of type pointer to OTYPE, using data from object
  87  * cache C if any cached items exist, otherwise calling xmalloc.  Return
  88  * the object in R.
  89  */
  90 #define ocache_alloc(c, otype, r) \
  91         do { \
  92                 if ((c).nc > 0) { \
  93                         (r) = (otype *)((otype **)((c).data))[--(c).nc]; \
  94                 } else \
  95                         (r) = (otype *)xmalloc (sizeof (otype)); \
  96         } while (0)
  97
  98 /*
  99  * Free an item R of type pointer to OTYPE, adding to object cache C if
 100  * there is room and calling xfree if the cache is full.  If R is added
 101  * to the object cache, the contents are scrambled.
 102  */
 103 #define ocache_free(c, otype, r) \
 104         do { \
 105                 if ((c).nc < (c).cs) { \
 106                         OC_MEMSET ((r), 0xdf, sizeof(otype)); \
 107                         ((otype **)((c).data))[(c).nc++] = (r); \
 108                 } else \
 109                         xfree (r); \
 110         } while (0)
 111
 112 /*
 113  * One may declare and use an object cache as (for instance):
 114  *
 115  *      sh_obj_cache_t wdcache = {0, 0, 0};
 116  *      sh_obj_cache_t wlcache = {0, 0, 0};
 117  *
 118  *      ocache_create(wdcache, WORD_DESC, 30);
 119  *      ocache_create(wlcache, WORD_LIST, 30);
 120  *
 121  *      WORD_DESC *wd;
 122  *      ocache_alloc (wdcache, WORD_DESC, wd);
 123  *
 124  *      WORD_LIST *wl;
 125  *      ocache_alloc (wlcache, WORD_LIST, wl);
 126  *
 127  *      ocache_free(wdcache, WORD_DESC, wd);
 128  *      ocache_free(wlcache, WORD_LIST, wl);
 129  *
 130  * The use is almost arbitrary.
 131  */
 132
 133 #endif /* _OCACHE_H  */