projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 394a1d25 C |
1 | /************************************************************************* |
| 2 | * This program is copyright (C) 1985, 1986 by Jonathan Payne. It is * | |
| 3 | * provided to you without charge for use only on a licensed Unix * | |
| 4 | * system. You may copy JOVE provided that this notice is included with * | |
| 5 | * the copy. You may not sell copies of this program or versions * | |
| 6 | * modified for use on microcomputer systems, unless the copies are * | |
| 7 | * included with a Unix system distribution and the source is provided. * | |
| 8 | *************************************************************************/ | |
| 9 | ||
| 10 | #include "tune.h" | |
| 11 | ||
| 12 | #ifdef MY_MALLOC | |
| 13 | ||
| 14 | /* avoid break bug */ | |
| 15 | #ifdef pdp11 | |
| 16 | # define GRANULE 64 | |
| 17 | #else | |
| 18 | # define GRANULE 0 | |
| 19 | #endif | |
| 20 | ||
| 21 | /* C storage allocator | |
| 22 | * circular first-fit strategy | |
| 23 | * works with noncontiguous, but monotonically linked, arena | |
| 24 | * each block is preceded by a ptr to the (pointer of) | |
| 25 | * the next following block | |
| 26 | * blocks are exact number of words long | |
| 27 | * aligned to the data type requirements of ALIGN | |
| 28 | * pointers to blocks must have BUSY bit 0 | |
| 29 | * bit in ptr is 1 for busy, 0 for idle | |
| 30 | * gaps in arena are merely noted as busy blocks | |
| 31 | * last block of arena (pointed to by alloct) is empty and | |
| 32 | * has a pointer to first | |
| 33 | * idle blocks are coalesced during space search | |
| 34 | * | |
| 35 | * a different implementation may need to redefine | |
| 36 | * ALIGN, NALIGN, BLOCK, BUSY, INT | |
| 37 | * where INT is integer type to which a pointer can be cast | |
| 38 | */ | |
| 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 { | |
| 52 | union store *ptr; | |
| 53 | ALIGN dummy[NALIGN]; | |
| 54 | int calloc; /*calloc clears an array of integers*/ | |
| 55 | }; | |
| 56 | ||
| 57 | static union store allocs[2], /*initial arena*/ | |
| 58 | *allocp, /*search ptr*/ | |
| 59 | *alloct, /*arena top*/ | |
| 60 | *allocx; /*for benefit of realloc*/ | |
| 61 | ||
| 62 | char *sbrk(); | |
| 63 | ||
| 64 | char * | |
| 65 | malloc(nbytes) | |
| 66 | unsigned int nbytes; | |
| 67 | { | |
| 68 | register union store *p, | |
| 69 | *q; | |
| 70 | register int nw; | |
| 71 | static int temp; /* coroutines assume no auto */ | |
| 72 | ||
| 73 | if (allocs[0].ptr == 0) { /* first time */ | |
| 74 | allocs[0].ptr = setbusy(&allocs[1]); | |
| 75 | allocs[1].ptr = setbusy(&allocs[0]); | |
| 76 | alloct = &allocs[1]; | |
| 77 | allocp = &allocs[0]; | |
| 78 | } | |
| 79 | nw = (nbytes + WORD + WORD - 1) / WORD; | |
| 80 | for (p = allocp; ; ) { | |
| 81 | for (temp = 0; ; ) { | |
| 82 | if (!testbusy(p->ptr)) { | |
| 83 | while (!testbusy((q = p->ptr)->ptr)) | |
| 84 | p->ptr = q->ptr; | |
| 85 | if(q >= p + nw && p + nw >= p) | |
| 86 | goto found; | |
| 87 | } | |
| 88 | q = p; | |
| 89 | p = clearbusy(p->ptr); | |
| 90 | if (p > q) | |
| 91 | ; | |
| 92 | else if (q != alloct || p != allocs) | |
| 93 | return NULL; | |
| 94 | else if (++temp > 1) | |
| 95 | break; | |
| 96 | } | |
| 97 | temp = ((nw + BLOCK/WORD) / (BLOCK/WORD)) * (BLOCK/WORD); | |
| 98 | q = (union store *) sbrk(0); | |
| 99 | if (q + temp + GRANULE < q) | |
| 100 | return NULL; | |
| 101 | q = (union store *) sbrk(temp * WORD); | |
| 102 | if ((INT) q == -1) | |
| 103 | return NULL; | |
| 104 | alloct->ptr = q; | |
| 105 | if (q != alloct+1) | |
| 106 | alloct->ptr = setbusy(alloct->ptr); | |
| 107 | alloct = q->ptr = q + temp - 1; | |
| 108 | alloct->ptr = setbusy(allocs); | |
| 109 | } | |
| 110 | found: | |
| 111 | allocp = p + nw; | |
| 112 | if (q > allocp) { | |
| 113 | allocx = allocp->ptr; | |
| 114 | allocp->ptr = p->ptr; | |
| 115 | } | |
| 116 | p->ptr = setbusy(allocp); | |
| 117 | return (char *) (p + 1); | |
| 118 | } | |
| 119 | ||
| 120 | /* freeing strategy tuned for LIFO allocation */ | |
| 121 | ||
| 122 | free(ap) | |
| 123 | register char *ap; | |
| 124 | { | |
| 125 | register union store *p = (union store *) ap; | |
| 126 | ||
| 127 | allocp = --p; | |
| 128 | p->ptr = clearbusy(p->ptr); | |
| 129 | } | |
| 130 | ||
| 131 | /* realloc(p, nbytes) reallocates a block obtained from malloc() | |
| 132 | * and freed since last call of malloc() | |
| 133 | * to have new size nbytes, and old content | |
| 134 | * returns new location, or 0 on failure | |
| 135 | */ | |
| 136 | ||
| 137 | char * | |
| 138 | realloc(obj, nbytes) | |
| 139 | char *obj; | |
| 140 | unsigned int nbytes; | |
| 141 | { | |
| 142 | register union store *q, | |
| 143 | *p = (union store *) obj; | |
| 144 | union store *s, | |
| 145 | *t; | |
| 146 | register unsigned int nw; | |
| 147 | unsigned int onw; | |
| 148 | ||
| 149 | if (testbusy(p[-1].ptr)) | |
| 150 | free((char *) p); | |
| 151 | onw = p[-1].ptr - p; | |
| 152 | q = (union store *) malloc(nbytes); | |
| 153 | if(q == NULL || q == p) | |
| 154 | return((char *) q); | |
| 155 | s = p; | |
| 156 | t = q; | |
| 157 | nw = (nbytes + WORD - 1)/WORD; | |
| 158 | if (nw < onw) | |
| 159 | onw = nw; | |
| 160 | while (onw-- != 0) | |
| 161 | *t++ = *s++; | |
| 162 | if(q < p && q + nw >= p) | |
| 163 | (q + (q+nw-p))->ptr = allocx; | |
| 164 | return (char *) q; | |
| 165 | } | |
| 166 | ||
| 167 | #endif MY_MALLOC |