Commit | Line | Data |
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31cef89c BJ |
1 | /* Copyright (c) 1979 Regents of the University of California */ |
2 | ||
3 | static char sccsid[] = "@(#)malloc.c 4.1 10/10/80"; | |
4 | ||
5 | /* | |
6 | * Patched up version of malloc to do an integrity check | |
7 | * on each allocation or free. | |
8 | */ | |
9 | ||
b202b2da CH |
10 | #ifdef debug |
11 | #define ASSERT(p,t) if(!(p))return(t(TRASHED));else | |
12 | #else | |
13 | #define ASSERT(p,t) | |
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 TRASHED -1 | |
48 | #define testbusy(p) ((INT)(p)&BUSY) | |
49 | #define setbusy(p) (union store *)((INT)(p)|BUSY) | |
50 | #define clearbusy(p) (union store *)((INT)(p)&~BUSY) | |
51 | ||
52 | union store { 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 | static union store *allocp; /*search ptr*/ | |
59 | static union store *alloct; /*arena top*/ | |
b202b2da CH |
60 | char *sbrk(); |
61 | ||
62 | char * | |
63 | malloc(nbytes) | |
31cef89c BJ |
64 | |
65 | unsigned nbytes; | |
b202b2da CH |
66 | { |
67 | register union store *p, *q; | |
68 | register nw; | |
69 | static temp; /*coroutines assume no auto*/ | |
70 | ||
71 | if(allocs[0].ptr==0) { /*first time*/ | |
72 | allocs[0].ptr = setbusy(&allocs[1]); | |
73 | allocs[1].ptr = setbusy(&allocs[0]); | |
74 | alloct = &allocs[1]; | |
75 | allocp = &allocs[0]; | |
76 | } | |
77 | nw = (nbytes+WORD+WORD-1)/WORD; | |
78 | ASSERT(allocp>=allocs && allocp<=alloct,(char *)); | |
79 | ASSERT(allock(),(char *)); | |
80 | for(p=allocp; ; ) { | |
81 | for(temp=0; ; ) { | |
82 | if(!testbusy(p->ptr)) { | |
83 | while(!testbusy((q=p->ptr)->ptr)) { | |
84 | ASSERT(q>p&&q<alloct,(char *)); | |
85 | p->ptr = q->ptr; | |
86 | } | |
87 | if(q>=p+nw && p+nw>=p) | |
88 | goto found; | |
89 | } | |
90 | q = p; | |
91 | p = clearbusy(p->ptr); | |
92 | if(p>q) | |
93 | ASSERT(p<=alloct,(char *)); | |
94 | else if(q!=alloct || p!=allocs) { | |
95 | ASSERT(q==alloct&&p==allocs,(char *)); | |
96 | return(NULL); | |
97 | } else if(++temp>1) | |
98 | break; | |
99 | } | |
100 | temp = ((nw+BLOCK/WORD)/(BLOCK/WORD))*(BLOCK/WORD); | |
101 | q = (union store *)sbrk(0); | |
102 | if(q+temp+GRANULE < q) { | |
103 | return(NULL); | |
104 | } | |
105 | q = (union store *)sbrk(temp*WORD); | |
106 | if((INT)q == -1) { | |
107 | return(NULL); | |
108 | } | |
109 | ASSERT(q>alloct,(char *)); | |
110 | alloct->ptr = q; | |
111 | if(q!=alloct+1) | |
112 | alloct->ptr = setbusy(alloct->ptr); | |
113 | alloct = q->ptr = q+temp-1; | |
114 | alloct->ptr = setbusy(allocs); | |
115 | } | |
116 | found: | |
117 | allocp = p + nw; | |
118 | ASSERT(allocp<=alloct,(char *)); | |
119 | if(q>allocp) { | |
b202b2da CH |
120 | allocp->ptr = p->ptr; |
121 | } | |
122 | p->ptr = setbusy(allocp); | |
123 | return((char *)(p+1)); | |
124 | } | |
125 | ||
31cef89c BJ |
126 | /* |
127 | * freeing strategy tuned for LIFO allocation | |
128 | */ | |
129 | ||
b202b2da | 130 | free(ap) |
31cef89c BJ |
131 | |
132 | register char *ap; | |
b202b2da CH |
133 | { |
134 | register union store *p = (union store *)ap; | |
135 | ||
136 | ASSERT(p != 0,(long)); | |
137 | ASSERT(p>clearbusy(allocs[1].ptr)&&p<=alloct,(long)); | |
138 | ASSERT(allock(),(long)); | |
139 | allocp = --p; | |
140 | ASSERT(testbusy(p->ptr),(long)); | |
141 | p->ptr = clearbusy(p->ptr); | |
142 | ASSERT(p->ptr > allocp && p->ptr <= alloct,(long)); | |
143 | return(NULL); | |
144 | } | |
145 | ||
b202b2da CH |
146 | #ifdef debug |
147 | allock() | |
148 | { | |
149 | #ifdef longdebug | |
150 | register union store *p; | |
151 | int x; | |
152 | x = 0; | |
153 | for(p= &allocs[0]; clearbusy(p->ptr) > p; p=clearbusy(p->ptr)) { | |
154 | if(p==allocp) | |
155 | x++; | |
156 | } | |
157 | ASSERT(p==alloct,(long)); | |
158 | return(x==1|p==allocp); | |
159 | #else | |
160 | return(1); | |
161 | #endif | |
162 | } | |
163 | #endif |