2.9BSD - /usr/src/ucb/csh/alloc.c

   1: static  char *sccsid = "@(#)alloc.c 4.1 10/9/80";
   2: 
   3: #include "sh.local.h"
   4: #ifdef debug
   5: #define ASSERT(p) if(!(p))botch("p");else
   6: botch(s)
   7: char *s;
   8: {
   9:     printf("assertion botched: %s\n",s);
  10:     abort();
  11: }
  12: #else
  13: #define ASSERT(p)
  14: #endif
  15: 
  16: /*	avoid break bug */
  17: #ifdef pdp11
  18: #define GRANULE 64
  19: #else
  20: #define GRANULE 0
  21: #endif
  22: /*	C storage allocator
  23:  *	circular first-fit strategy
  24:  *	works with noncontiguous, but monotonically linked, arena
  25:  *	each block is preceded by a ptr to the (pointer of)
  26:  *	the next following block
  27:  *	blocks are exact number of words long
  28:  *	aligned to the data type requirements of ALIGN
  29:  *	pointers to blocks must have BUSY bit 0
  30:  *	bit in ptr is 1 for busy, 0 for idle
  31:  *	gaps in arena are merely noted as busy blocks
  32:  *	last block of arena (pointed to by alloct) is empty and
  33:  *	has a pointer to first
  34:  *	idle blocks are coalesced during space search
  35:  *
  36:  *	a different implementation may need to redefine
  37:  *	ALIGN, NALIGN, BLOCK, BUSY, INT
  38:  *	where INT is integer type to which a pointer can be cast
  39: */
  40: #define INT int
  41: #define ALIGN int
  42: #define NALIGN 1
  43: #define WORD sizeof(union store)
  44: #define BLOCK 1024  /* a multiple of WORD*/
  45: #define BUSY 1
  46: #define NULL 0
  47: #define testbusy(p) ((INT)(p)&BUSY)
  48: #define setbusy(p) (union store *)((INT)(p)|BUSY)
  49: #define clearbusy(p) (union store *)((INT)(p)&~BUSY)
  50: 
  51: union store { union store *ptr;
  52:           ALIGN dummy[NALIGN];
  53:           int calloc;   /*calloc clears an array of integers*/
  54: };
  55: 
  56: static  union store allocs[2];  /*initial arena*/
  57: static  union store *allocp;    /*search ptr*/
  58: static  union store *alloct;    /*arena top*/
  59: static  union store *allocx;    /*for benefit of realloc*/
  60: char    *sbrk();
  61: 
  62: char *
  63: malloc(nbytes)
  64: unsigned nbytes;
  65: {
  66:     register union store *p, *q;
  67:     register nw;
  68:     static temp;    /*coroutines assume no auto*/
  69: 
  70:     if(allocs[0].ptr==0) {  /*first time*/
  71:         allocs[0].ptr = setbusy(&allocs[1]);
  72:         allocs[1].ptr = setbusy(&allocs[0]);
  73:         alloct = &allocs[1];
  74:         allocp = &allocs[0];
  75:     }
  76:     nw = (nbytes+WORD+WORD-1)/WORD;
  77:     ASSERT(allocp>=allocs && allocp<=alloct);
  78:     ASSERT(allock());
  79:     for(p=allocp; ; ) {
  80:         for(temp=0; ; ) {
  81:             if(!testbusy(p->ptr)) {
  82:                 while(!testbusy((q=p->ptr)->ptr)) {
  83:                     ASSERT(q>p&&q<alloct);
  84:                     p->ptr = q->ptr;
  85:                 }
  86:                 if(q>=p+nw && p+nw>=p)
  87:                     goto found;
  88:             }
  89:             q = p;
  90:             p = clearbusy(p->ptr);
  91:             if(p>q)
  92:                 ASSERT(p<=alloct);
  93:             else if(q!=alloct || p!=allocs) {
  94:                 ASSERT(q==alloct&&p==allocs);
  95:                 return(NULL);
  96:             } else if(++temp>1)
  97:                 break;
  98:         }
  99:         temp = ((nw+BLOCK/WORD)/(BLOCK/WORD))*(BLOCK/WORD);
 100:         q = (union store *)sbrk(0);
 101:         if(q+temp+GRANULE < q) {
 102:             return(NULL);
 103:         }
 104:         q = (union store *)sbrk(temp*WORD);
 105:         if((INT)q == -1) {
 106:             return(NULL);
 107:         }
 108:         ASSERT(q>alloct);
 109:         alloct->ptr = q;
 110:         if(q!=alloct+1)
 111:             alloct->ptr = setbusy(alloct->ptr);
 112:         alloct = q->ptr = q+temp-1;
 113:         alloct->ptr = setbusy(allocs);
 114:     }
 115: found:
 116:     allocp = p + nw;
 117:     ASSERT(allocp<=alloct);
 118:     if(q>allocp) {
 119:         allocx = allocp->ptr;
 120:         allocp->ptr = p->ptr;
 121:     }
 122:     p->ptr = setbusy(allocp);
 123:     return((char *)(p+1));
 124: }
 125: 
 126: /*	freeing strategy tuned for LIFO allocation
 127: */
 128: free(ap)
 129: register char *ap;
 130: {
 131:     register union store *p = (union store *)ap;
 132: 
 133:     ASSERT(p>clearbusy(allocs[1].ptr)&&p<=alloct);
 134:     ASSERT(allock());
 135:     allocp = --p;
 136: /* 	ASSERT(testbusy(p->ptr)); */
 137:     p->ptr = clearbusy(p->ptr);
 138:     ASSERT(p->ptr > allocp && p->ptr <= alloct);
 139: }
 140: 
 141: /*	realloc(p, nbytes) reallocates a block obtained from malloc()
 142:  *	and freed since last call of malloc()
 143:  *	to have new size nbytes, and old content
 144:  *	returns new location, or 0 on failure
 145: */
 146: 
 147: char *
 148: realloc(p, nbytes)
 149: register union store *p;
 150: unsigned nbytes;
 151: {
 152:     register union store *q;
 153:     union store *s, *t;
 154:     register unsigned nw;
 155:     unsigned onw;
 156: 
 157:     if(testbusy(p[-1].ptr))
 158:         free((char *)p);
 159:     onw = p[-1].ptr - p;
 160:     q = (union store *)malloc(nbytes);
 161:     if(q==NULL || q==p)
 162:         return((char *)q);
 163:     s = p;
 164:     t = q;
 165:     nw = (nbytes+WORD-1)/WORD;
 166:     if(nw<onw)
 167:         onw = nw;
 168:     while(onw--!=0)
 169: #ifdef  V6
 170:         copy(t++, s++, sizeof (*t));
 171: #else
 172:         *t++ = *s++;
 173: #endif
 174:     if(q<p && q+nw>=p)
 175:         (q+(q+nw-p))->ptr = allocx;
 176:     return((char *)q);
 177: }
 178: 
 179: #ifdef debug
 180: allock()
 181: {
 182: #ifdef longdebug
 183:     register union store *p;
 184:     int x;
 185:     x = 0;
 186:     for(p= &allocs[0]; clearbusy(p->ptr) > p; p=clearbusy(p->ptr)) {
 187:         if(p==allocp)
 188:             x++;
 189:     }
 190:     ASSERT(p==alloct);
 191:     return(x==1|p==allocp);
 192: #else
 193:     return(1);
 194: #endif
 195: }
 196: #endif
 197: 
 198: #ifdef debug
 199: showall(v)
 200:     char **v;
 201: {
 202:     register union store *p, *q;
 203:     int used = 0, free = 0, i;
 204: 
 205:     for (p = clearbusy(allocs[1].ptr); p != alloct; p = q) {
 206:         q = clearbusy(p->ptr);
 207:         if (v[1])
 208:         printf("%6o %5d %s\n", p,
 209:             ((unsigned) q - (unsigned) p),
 210:             testbusy(p->ptr) ? "BUSY" : "FREE");
 211:         i = ((unsigned) q - (unsigned) p);
 212:         if (testbusy(p->ptr)) used += i; else free += i;
 213:     }
 214:     printf("%d used, %d free, %l end\n", used, free, clearbusy(alloct));
 215: }
 216: #endif

Defined functions

Defined variables

Defined union's

Defined macros