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1 | /* $Header: malloc.c,v 1.0.1.1 88/01/24 03:53:23 root Exp $ |
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2 | * |
3 | * $Log: malloc.c,v $ |
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4 | * Revision 1.0.1.1 88/01/24 03:53:23 root |
5 | * patch 2: made depend on perl.h. |
6 | * |
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7 | * Revision 1.0 87/12/18 13:05:35 root |
8 | * Initial revision |
9 | * |
10 | */ |
11 | |
12 | #ifndef lint |
13 | static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83"; |
14 | #endif |
15 | #include <stdio.h> |
16 | |
17 | #define RCHECK |
18 | /* |
19 | * malloc.c (Caltech) 2/21/82 |
20 | * Chris Kingsley, kingsley@cit-20. |
21 | * |
22 | * This is a very fast storage allocator. It allocates blocks of a small |
23 | * number of different sizes, and keeps free lists of each size. Blocks that |
24 | * don't exactly fit are passed up to the next larger size. In this |
25 | * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long. |
26 | * This is designed for use in a program that uses vast quantities of memory, |
27 | * but bombs when it runs out. |
28 | */ |
29 | |
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30 | #include "EXTERN.h" |
31 | #include "handy.h" |
32 | #include "search.h" |
33 | #include "perl.h" |
34 | |
35 | /* I don't much care whether these are defined in sys/types.h--LAW */ |
36 | |
37 | #define u_char unsigned char |
38 | #define u_int unsigned int |
39 | #define u_short unsigned short |
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40 | |
41 | #define NULL 0 |
42 | |
43 | /* |
44 | * The overhead on a block is at least 4 bytes. When free, this space |
45 | * contains a pointer to the next free block, and the bottom two bits must |
46 | * be zero. When in use, the first byte is set to MAGIC, and the second |
47 | * byte is the size index. The remaining bytes are for alignment. |
48 | * If range checking is enabled and the size of the block fits |
49 | * in two bytes, then the top two bytes hold the size of the requested block |
50 | * plus the range checking words, and the header word MINUS ONE. |
51 | */ |
52 | union overhead { |
53 | union overhead *ov_next; /* when free */ |
54 | struct { |
55 | u_char ovu_magic; /* magic number */ |
56 | u_char ovu_index; /* bucket # */ |
57 | #ifdef RCHECK |
58 | u_short ovu_size; /* actual block size */ |
59 | u_int ovu_rmagic; /* range magic number */ |
60 | #endif |
61 | } ovu; |
62 | #define ov_magic ovu.ovu_magic |
63 | #define ov_index ovu.ovu_index |
64 | #define ov_size ovu.ovu_size |
65 | #define ov_rmagic ovu.ovu_rmagic |
66 | }; |
67 | |
68 | #define MAGIC 0xff /* magic # on accounting info */ |
69 | #define RMAGIC 0x55555555 /* magic # on range info */ |
70 | #ifdef RCHECK |
71 | #define RSLOP sizeof (u_int) |
72 | #else |
73 | #define RSLOP 0 |
74 | #endif |
75 | |
76 | /* |
77 | * nextf[i] is the pointer to the next free block of size 2^(i+3). The |
78 | * smallest allocatable block is 8 bytes. The overhead information |
79 | * precedes the data area returned to the user. |
80 | */ |
81 | #define NBUCKETS 30 |
82 | static union overhead *nextf[NBUCKETS]; |
83 | extern char *sbrk(); |
84 | |
85 | #ifdef MSTATS |
86 | /* |
87 | * nmalloc[i] is the difference between the number of mallocs and frees |
88 | * for a given block size. |
89 | */ |
90 | static u_int nmalloc[NBUCKETS]; |
91 | #include <stdio.h> |
92 | #endif |
93 | |
94 | #ifdef debug |
95 | #define ASSERT(p) if (!(p)) botch("p"); else |
96 | static |
97 | botch(s) |
98 | char *s; |
99 | { |
100 | |
101 | printf("assertion botched: %s\n", s); |
102 | abort(); |
103 | } |
104 | #else |
105 | #define ASSERT(p) |
106 | #endif |
107 | |
108 | char * |
109 | malloc(nbytes) |
110 | register unsigned nbytes; |
111 | { |
112 | register union overhead *p; |
113 | register int bucket = 0; |
114 | register unsigned shiftr; |
115 | |
116 | /* |
117 | * Convert amount of memory requested into |
118 | * closest block size stored in hash buckets |
119 | * which satisfies request. Account for |
120 | * space used per block for accounting. |
121 | */ |
122 | nbytes += sizeof (union overhead) + RSLOP; |
123 | nbytes = (nbytes + 3) &~ 3; |
124 | shiftr = (nbytes - 1) >> 2; |
125 | /* apart from this loop, this is O(1) */ |
126 | while (shiftr >>= 1) |
127 | bucket++; |
128 | /* |
129 | * If nothing in hash bucket right now, |
130 | * request more memory from the system. |
131 | */ |
132 | if (nextf[bucket] == NULL) |
133 | morecore(bucket); |
134 | if ((p = (union overhead *)nextf[bucket]) == NULL) |
135 | return (NULL); |
136 | /* remove from linked list */ |
137 | if (*((int*)p) > 0x10000000) |
138 | fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p); |
139 | nextf[bucket] = nextf[bucket]->ov_next; |
140 | p->ov_magic = MAGIC; |
141 | p->ov_index= bucket; |
142 | #ifdef MSTATS |
143 | nmalloc[bucket]++; |
144 | #endif |
145 | #ifdef RCHECK |
146 | /* |
147 | * Record allocated size of block and |
148 | * bound space with magic numbers. |
149 | */ |
150 | if (nbytes <= 0x10000) |
151 | p->ov_size = nbytes - 1; |
152 | p->ov_rmagic = RMAGIC; |
153 | *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC; |
154 | #endif |
155 | return ((char *)(p + 1)); |
156 | } |
157 | |
158 | /* |
159 | * Allocate more memory to the indicated bucket. |
160 | */ |
161 | static |
162 | morecore(bucket) |
163 | register bucket; |
164 | { |
165 | register union overhead *op; |
166 | register int rnu; /* 2^rnu bytes will be requested */ |
167 | register int nblks; /* become nblks blocks of the desired size */ |
168 | register int siz; |
169 | |
170 | if (nextf[bucket]) |
171 | return; |
172 | /* |
173 | * Insure memory is allocated |
174 | * on a page boundary. Should |
175 | * make getpageize call? |
176 | */ |
177 | op = (union overhead *)sbrk(0); |
178 | if ((int)op & 0x3ff) |
179 | sbrk(1024 - ((int)op & 0x3ff)); |
180 | /* take 2k unless the block is bigger than that */ |
181 | rnu = (bucket <= 8) ? 11 : bucket + 3; |
182 | nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */ |
183 | if (rnu < bucket) |
184 | rnu = bucket; |
185 | op = (union overhead *)sbrk(1 << rnu); |
186 | /* no more room! */ |
187 | if ((int)op == -1) |
188 | return; |
189 | /* |
190 | * Round up to minimum allocation size boundary |
191 | * and deduct from block count to reflect. |
192 | */ |
193 | if ((int)op & 7) { |
194 | op = (union overhead *)(((int)op + 8) &~ 7); |
195 | nblks--; |
196 | } |
197 | /* |
198 | * Add new memory allocated to that on |
199 | * free list for this hash bucket. |
200 | */ |
201 | nextf[bucket] = op; |
202 | siz = 1 << (bucket + 3); |
203 | while (--nblks > 0) { |
204 | op->ov_next = (union overhead *)((caddr_t)op + siz); |
205 | op = (union overhead *)((caddr_t)op + siz); |
206 | } |
207 | } |
208 | |
209 | free(cp) |
210 | char *cp; |
211 | { |
212 | register int size; |
213 | register union overhead *op; |
214 | |
215 | if (cp == NULL) |
216 | return; |
217 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
218 | #ifdef debug |
219 | ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ |
220 | #else |
221 | if (op->ov_magic != MAGIC) |
222 | return; /* sanity */ |
223 | #endif |
224 | #ifdef RCHECK |
225 | ASSERT(op->ov_rmagic == RMAGIC); |
226 | if (op->ov_index <= 13) |
227 | ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC); |
228 | #endif |
229 | ASSERT(op->ov_index < NBUCKETS); |
230 | size = op->ov_index; |
231 | op->ov_next = nextf[size]; |
232 | nextf[size] = op; |
233 | #ifdef MSTATS |
234 | nmalloc[size]--; |
235 | #endif |
236 | } |
237 | |
238 | /* |
239 | * When a program attempts "storage compaction" as mentioned in the |
240 | * old malloc man page, it realloc's an already freed block. Usually |
241 | * this is the last block it freed; occasionally it might be farther |
242 | * back. We have to search all the free lists for the block in order |
243 | * to determine its bucket: 1st we make one pass thru the lists |
244 | * checking only the first block in each; if that fails we search |
245 | * ``realloc_srchlen'' blocks in each list for a match (the variable |
246 | * is extern so the caller can modify it). If that fails we just copy |
247 | * however many bytes was given to realloc() and hope it's not huge. |
248 | */ |
249 | int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ |
250 | |
251 | char * |
252 | realloc(cp, nbytes) |
253 | char *cp; |
254 | unsigned nbytes; |
255 | { |
256 | register u_int onb; |
257 | union overhead *op; |
258 | char *res; |
259 | register int i; |
260 | int was_alloced = 0; |
261 | |
262 | if (cp == NULL) |
263 | return (malloc(nbytes)); |
264 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
265 | if (op->ov_magic == MAGIC) { |
266 | was_alloced++; |
267 | i = op->ov_index; |
268 | } else { |
269 | /* |
270 | * Already free, doing "compaction". |
271 | * |
272 | * Search for the old block of memory on the |
273 | * free list. First, check the most common |
274 | * case (last element free'd), then (this failing) |
275 | * the last ``realloc_srchlen'' items free'd. |
276 | * If all lookups fail, then assume the size of |
277 | * the memory block being realloc'd is the |
278 | * smallest possible. |
279 | */ |
280 | if ((i = findbucket(op, 1)) < 0 && |
281 | (i = findbucket(op, realloc_srchlen)) < 0) |
282 | i = 0; |
283 | } |
284 | onb = (1 << (i + 3)) - sizeof (*op) - RSLOP; |
285 | /* avoid the copy if same size block */ |
286 | if (was_alloced && |
287 | nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) |
288 | return(cp); |
289 | if ((res = malloc(nbytes)) == NULL) |
290 | return (NULL); |
291 | if (cp != res) /* common optimization */ |
292 | bcopy(cp, res, (nbytes < onb) ? nbytes : onb); |
293 | if (was_alloced) |
294 | free(cp); |
295 | return (res); |
296 | } |
297 | |
298 | /* |
299 | * Search ``srchlen'' elements of each free list for a block whose |
300 | * header starts at ``freep''. If srchlen is -1 search the whole list. |
301 | * Return bucket number, or -1 if not found. |
302 | */ |
303 | static |
304 | findbucket(freep, srchlen) |
305 | union overhead *freep; |
306 | int srchlen; |
307 | { |
308 | register union overhead *p; |
309 | register int i, j; |
310 | |
311 | for (i = 0; i < NBUCKETS; i++) { |
312 | j = 0; |
313 | for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { |
314 | if (p == freep) |
315 | return (i); |
316 | j++; |
317 | } |
318 | } |
319 | return (-1); |
320 | } |
321 | |
322 | #ifdef MSTATS |
323 | /* |
324 | * mstats - print out statistics about malloc |
325 | * |
326 | * Prints two lines of numbers, one showing the length of the free list |
327 | * for each size category, the second showing the number of mallocs - |
328 | * frees for each size category. |
329 | */ |
330 | mstats(s) |
331 | char *s; |
332 | { |
333 | register int i, j; |
334 | register union overhead *p; |
335 | int totfree = 0, |
336 | totused = 0; |
337 | |
338 | fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); |
339 | for (i = 0; i < NBUCKETS; i++) { |
340 | for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) |
341 | ; |
342 | fprintf(stderr, " %d", j); |
343 | totfree += j * (1 << (i + 3)); |
344 | } |
345 | fprintf(stderr, "\nused:\t"); |
346 | for (i = 0; i < NBUCKETS; i++) { |
347 | fprintf(stderr, " %d", nmalloc[i]); |
348 | totused += nmalloc[i] * (1 << (i + 3)); |
349 | } |
350 | fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", |
351 | totused, totfree); |
352 | } |
353 | #endif |