bin/ksh/alloc.c

   1 /*      $OpenBSD: alloc.c,v 1.19 2018/01/16 22:52:32 jca Exp $  */
   2
   3 /* Public domain, like most of the rest of ksh */
   4
   5 /*
   6  * area-based allocation built on malloc/free
   7  */
   8
   9 #include <stdint.h>
  10 #include <stdlib.h>
  11
  12 #include "sh.h"
  13
  14 struct link {
  15         struct link *prev;
  16         struct link *next;
  17 };
  18
  19 Area *
  20 ainit(Area *ap)
  21 {
  22         ap->freelist = NULL;
  23         return ap;
  24 }
  25
  26 void
  27 afreeall(Area *ap)
  28 {
  29         struct link *l, *l2;
  30
  31         for (l = ap->freelist; l != NULL; l = l2) {
  32                 l2 = l->next;
  33                 free(l);
  34         }
  35         ap->freelist = NULL;
  36 }
  37
  38 #define L2P(l)  ( (void *)(((char *)(l)) + sizeof(struct link)) )
  39 #define P2L(p)  ( (struct link *)(((char *)(p)) - sizeof(struct link)) )
  40
  41 void *
  42 alloc(size_t size, Area *ap)
  43 {
  44         struct link *l;
  45
  46         /* ensure that we don't overflow by allocating space for link */
  47         if (size > SIZE_MAX - sizeof(struct link))
  48                 internal_errorf("unable to allocate memory");
  49
  50         l = malloc(sizeof(struct link) + size);
  51         if (l == NULL)
  52                 internal_errorf("unable to allocate memory");
  53         l->next = ap->freelist;
  54         l->prev = NULL;
  55         if (ap->freelist)
  56                 ap->freelist->prev = l;
  57         ap->freelist = l;
  58
  59         return L2P(l);
  60 }
  61
  62 /*
  63  * Copied from calloc().
  64  *
  65  * This is sqrt(SIZE_MAX+1), as s1*s2 <= SIZE_MAX
  66  * if both s1 < MUL_NO_OVERFLOW and s2 < MUL_NO_OVERFLOW
  67  */
  68 #define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
  69
  70 void *
  71 areallocarray(void *ptr, size_t nmemb, size_t size, Area *ap)
  72 {
  73         /* condition logic cloned from calloc() */
  74         if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) &&
  75             nmemb > 0 && SIZE_MAX / nmemb < size) {
  76                 internal_errorf("unable to allocate memory");
  77         }
  78
  79         return aresize(ptr, nmemb * size, ap);
  80 }
  81
  82 void *
  83 aresize(void *ptr, size_t size, Area *ap)
  84 {
  85         struct link *l, *l2, *lprev, *lnext;
  86
  87         if (ptr == NULL)
  88                 return alloc(size, ap);
  89
  90         /* ensure that we don't overflow by allocating space for link */
  91         if (size > SIZE_MAX - sizeof(struct link))
  92                 internal_errorf("unable to allocate memory");
  93
  94         l = P2L(ptr);
  95         lprev = l->prev;
  96         lnext = l->next;
  97
  98         l2 = realloc(l, sizeof(struct link) + size);
  99         if (l2 == NULL)
 100                 internal_errorf("unable to allocate memory");
 101         if (lprev)
 102                 lprev->next = l2;
 103         else
 104                 ap->freelist = l2;
 105         if (lnext)
 106                 lnext->prev = l2;
 107
 108         return L2P(l2);
 109 }
 110
 111 void
 112 afree(void *ptr, Area *ap)
 113 {
 114         struct link *l;
 115
 116         if (!ptr)
 117                 return;
 118
 119         l = P2L(ptr);
 120         if (l->prev)
 121                 l->prev->next = l->next;
 122         else
 123                 ap->freelist = l->next;
 124         if (l->next)
 125                 l->next->prev = l->prev;
 126
 127         free(l);
 128 }