Commit | Line | Data |
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7a10d9ad BJ |
1 | /* Copyright (c) 1979 Regents of the University of California */ |
2 | #ifdef debug | |
3 | #define ASSERT(p) if(!(p))botch("p");else | |
4 | botch(s) | |
5 | char *s; | |
6 | { | |
7 | printf("assertion botched: %s\n",s); | |
8 | abort(); | |
9 | } | |
10 | #else | |
11 | #define ASSERT(p) | |
12 | #endif | |
13 | ||
14 | /* avoid break bug */ | |
15 | #ifdef pdp11 | |
16 | #define GRANULE 64 | |
17 | #else | |
18 | #define GRANULE 0 | |
19 | #endif | |
20 | /* C storage allocator | |
21 | * circular first-fit strategy | |
22 | * works with noncontiguous, but monotonically linked, arena | |
23 | * each block is preceded by a ptr to the (pointer of) | |
24 | * the next following block | |
25 | * blocks are exact number of words long | |
26 | * aligned to the data type requirements of ALIGN | |
27 | * pointers to blocks must have BUSY bit 0 | |
28 | * bit in ptr is 1 for busy, 0 for idle | |
29 | * gaps in arena are merely noted as busy blocks | |
30 | * last block of arena (pointed to by alloct) is empty and | |
31 | * has a pointer to first | |
32 | * idle blocks are coalesced during space search | |
33 | * | |
34 | * a different implementation may need to redefine | |
35 | * ALIGN, NALIGN, BLOCK, BUSY, INT | |
36 | * where INT is integer type to which a pointer can be cast | |
37 | */ | |
38 | #define INT int | |
39 | #define ALIGN int | |
40 | #define NALIGN 1 | |
41 | #define WORD sizeof(union store) | |
42 | #define BLOCK 1024 /* a multiple of WORD*/ | |
43 | #define BUSY 1 | |
44 | #define NULL 0 | |
45 | #define testbusy(p) ((INT)(p)&BUSY) | |
46 | #define setbusy(p) (union store *)((INT)(p)|BUSY) | |
47 | #define clearbusy(p) (union store *)((INT)(p)&~BUSY) | |
48 | ||
49 | union store { union store *ptr; | |
50 | ALIGN dummy[NALIGN]; | |
51 | int calloc; /*calloc clears an array of integers*/ | |
52 | }; | |
53 | ||
54 | static union store allocs[2]; /*initial arena*/ | |
55 | static union store *allocp; /*search ptr*/ | |
56 | static union store *alloct; /*arena top*/ | |
57 | static union store *allocx; /*for benefit of realloc*/ | |
58 | char *sbrk(); | |
59 | ||
60 | char * | |
61 | malloc(nbytes) | |
62 | unsigned nbytes; | |
63 | { | |
64 | register union store *p, *q; | |
65 | register nw; | |
66 | static temp; /*coroutines assume no auto*/ | |
67 | ||
68 | if(allocs[0].ptr==0) { /*first time*/ | |
69 | allocs[0].ptr = setbusy(&allocs[1]); | |
70 | allocs[1].ptr = setbusy(&allocs[0]); | |
71 | alloct = &allocs[1]; | |
72 | allocp = &allocs[0]; | |
73 | } | |
74 | nw = (nbytes+WORD+WORD-1)/WORD; | |
75 | ASSERT(allocp>=allocs && allocp<=alloct); | |
76 | ASSERT(allock()); | |
77 | for(p=allocp; ; ) { | |
78 | for(temp=0; ; ) { | |
79 | if(!testbusy(p->ptr)) { | |
80 | while(!testbusy((q=p->ptr)->ptr)) { | |
81 | ASSERT(q>p&&q<alloct); | |
82 | p->ptr = q->ptr; | |
83 | } | |
84 | if(q>=p+nw && p+nw>=p) | |
85 | goto found; | |
86 | } | |
87 | q = p; | |
88 | p = clearbusy(p->ptr); | |
89 | if(p>q) | |
90 | ASSERT(p<=alloct); | |
91 | else if(q!=alloct || p!=allocs) { | |
92 | ASSERT(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 | } | |
102 | q = (union store *)sbrk(temp*WORD); | |
103 | if((INT)q == -1) { | |
104 | return(NULL); | |
105 | } | |
106 | ASSERT(q>alloct); | |
107 | alloct->ptr = q; | |
108 | if(q!=alloct+1) | |
109 | alloct->ptr = setbusy(alloct->ptr); | |
110 | alloct = q->ptr = q+temp-1; | |
111 | alloct->ptr = setbusy(allocs); | |
112 | } | |
113 | found: | |
114 | allocp = p + nw; | |
115 | ASSERT(allocp<=alloct); | |
116 | if(q>allocp) { | |
117 | allocx = allocp->ptr; | |
118 | allocp->ptr = p->ptr; | |
119 | } | |
120 | p->ptr = setbusy(allocp); | |
121 | return((char *)(p+1)); | |
122 | } | |
123 | ||
124 | /* freeing strategy tuned for LIFO allocation | |
125 | */ | |
126 | free(ap) | |
127 | register char *ap; | |
128 | { | |
129 | register union store *p = (union store *)ap; | |
130 | ||
131 | ASSERT(p>clearbusy(allocs[1].ptr)&&p<=alloct); | |
132 | ASSERT(allock()); | |
133 | allocp = --p; | |
134 | ASSERT(testbusy(p->ptr)); | |
135 | p->ptr = clearbusy(p->ptr); | |
136 | ASSERT(p->ptr > allocp && p->ptr <= alloct); | |
137 | } | |
138 | ||
139 | /* realloc(p, nbytes) reallocates a block obtained from malloc() | |
140 | * and freed since last call of malloc() | |
141 | * to have new size nbytes, and old content | |
142 | * returns new location, or 0 on failure | |
143 | */ | |
144 | ||
145 | char * | |
146 | realloc(p, nbytes) | |
147 | register union store *p; | |
148 | unsigned nbytes; | |
149 | { | |
150 | register union store *q; | |
151 | union store *s, *t; | |
152 | register unsigned nw; | |
153 | unsigned onw; | |
154 | ||
155 | if(testbusy(p[-1].ptr)) | |
156 | free((char *)p); | |
157 | onw = p[-1].ptr - p; | |
158 | q = (union store *)malloc(nbytes); | |
159 | if(q==NULL || q==p) | |
160 | return((char *)q); | |
161 | s = p; | |
162 | t = q; | |
163 | nw = (nbytes+WORD-1)/WORD; | |
164 | if(nw<onw) | |
165 | onw = nw; | |
166 | while(onw--!=0) | |
167 | *t++ = *s++; | |
168 | if(q<p && q+nw>=p) | |
169 | (q+(q+nw-p))->ptr = allocx; | |
170 | return((char *)q); | |
171 | } | |
172 | ||
173 | #ifdef debug | |
174 | allock() | |
175 | { | |
176 | #ifdef longdebug | |
177 | register union store *p; | |
178 | int x; | |
179 | x = 0; | |
180 | for(p= &allocs[0]; clearbusy(p->ptr) > p; p=clearbusy(p->ptr)) { | |
181 | if(p==allocp) | |
182 | x++; | |
183 | } | |
184 | ASSERT(p==alloct); | |
185 | return(x==1|p==allocp); | |
186 | #else | |
187 | return(1); | |
188 | #endif | |
189 | } | |
190 | #endif |