UNIX 6th Ed. - /usr/source/s4/alloc.s

   1: /	storage allocator for use with C
   2: /
   3: /
   4: /
   5: /	hand-tooled from C compilation to modify save-return
   6: /	so that it can be called from within the C save
   7: /	when running with coroutines
   8: /
   9: /#
  10: //*
  11: / *	C storage allocator
  12: / *	(circular first fit strategy)
  13: / */
  14: /#define BLOK 512
  15: /#define BUSY 01
  16: /
  17: /char *allocs[2] {		/*initial empty arena*/
  18: /	&allocs[1],
  19: /	&allocs[0]
  20: /};
  21: /struct { int word; };
  22: /char **allocp &allocs[1];	/*current search pointer*/
  23: /char **alloct &allocs[1];	/*top of arena (last cell)*/
  24: /
  25: /alloc(nbytes)
  26: /{
  27: /	register int nwords;
  28: /	register char **p, **q;
  29: /	static char **t;
  30: /
  31: /	allocs[0].word =| BUSY;	/*static initialization*/
  32: /	allocs[1].word =| BUSY;
  33: /
  34: /	nwords = (nbytes+(2*sizeof(p)-1))/sizeof(p);
  35: /	for(p=allocp;;) {
  36: /		do {
  37: /			if((p->word&BUSY)==0) {
  38: /				while(((q = *p)->word&BUSY)==0)
  39: /					*p = *q;
  40: /				if(q >= &p[nwords])
  41: /					goto found;
  42: /			}
  43: /			q = p;
  44: /			p = p->word & ~BUSY;
  45: /		} while(q>=allocp || p<allocp);
  46: /		if((*alloct=t=sbrk(BLOK*sizeof(p))) == -1)
  47: /			return(-1);
  48: /		if(t!=alloct+1)
  49: /			alloct->word =| BUSY;
  50: /		alloct = (*t = &t[BLOK]-1);
  51: /		*alloct = allocs;
  52: /		alloct->word =| BUSY;
  53: /	}
  54: /found:
  55: /	allocp = &p[nwords];
  56: /	if(q>allocp)
  57: /		*allocp = *p;
  58: /	*p = allocp.word|BUSY;
  59: /	return(p+1);
  60: /}
  61: /
  62: /free(p)
  63: /char **p;
  64: /{
  65: /	allocp = p-1;
  66: /	allocp->word =& ~BUSY;
  67: /}
  68: .globl  _allocs
  69: .data
  70: _allocs=.
  71: 2+_allocs
  72: _allocs
  73: .globl  _allocp
  74: .data
  75: _allocp=.
  76: 2+_allocs
  77: .globl  _alloct
  78: .data
  79: _alloct=.
  80: 2+_allocs
  81: .globl  _alloc
  82: 
  83: .globl  _sbrk
  84: .text
  85: _alloc:
  86: mov     r5,-(sp)
  87: mov     sp,r5
  88: mov     r4,-(sp)
  89: mov     r3,-(sp)
  90: mov     r2,-(sp)
  91: bis     $1,_allocs
  92: bis     $1,2+_allocs
  93: mov     4(r5),r4
  94: add     $3,r4
  95: asr     r4
  96: mov     _allocp,r3
  97: jbr     L6
  98: L7:mov  r3,r2
  99: mov     (r3),r3
 100: bic     $!177776,r3
 101: cmp     r2,_allocp
 102: jhis    L6
 103: cmp     r3,_allocp
 104: jlo     L6
 105: mov     $2000,-(sp)
 106: jsr     pc,*$_sbrk
 107: tst     (sp)+
 108: mov     r0,t
 109: mov     r0,*_alloct
 110: cmp     $177777,r0
 111: jeq     L11
 112: mov     _alloct,r0
 113: add     $2,r0
 114: cmp     t,r0
 115: jeq     L12
 116: bis     $1,*_alloct
 117: L12:mov t,r0
 118: add     $1776,r0
 119: mov     r0,*t
 120: mov     r0,_alloct
 121: mov     $_allocs,*_alloct
 122: bis     $1,*_alloct
 123: L6:bit  $1,(r3)
 124: jeq     L8
 125: jbr     L7
 126: L20001:mov      (r2),(r3)
 127: L8:mov  (r3),r2
 128: bit     $1,(r2)
 129: jeq     L20001
 130: mov     r4,r0
 131: asl     r0
 132: add     r3,r0
 133: cmp     r2,r0
 134: jlo     L7
 135: mov     r4,r0
 136: asl     r0
 137: add     r3,r0
 138: mov     r0,_allocp
 139: cmp     r2,r0
 140: jlos    L13
 141: mov     (r3),*_allocp
 142: L13:mov _allocp,r0
 143: bis     $1,r0
 144: mov     r0,(r3)
 145: mov     r3,r0
 146: add     $2,r0
 147: L11:
 148: mov     (sp)+,r2
 149: mov     (sp)+,r3
 150: mov     (sp)+,r4
 151: mov     (sp)+,r5
 152: rts     pc
 153: .globl  _free
 154: .text
 155: _free:
 156: mov     r5,-(sp)
 157: mov     sp,r5
 158: mov     4(r5),r0
 159: add     $177776,r0
 160: mov     r0,_allocp
 161: bic     $!177776,*_allocp
 162: mov     (sp)+,r5
 163: rts     pc
 164: .bss
 165: t:      .=.+2

Defined functions

Defined variables