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1 | /* $RCSfile: malloc.c,v $$Revision: 4.0.1.2 $$Date: 91/06/07 11:20:45 $ |
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2 | * |
3 | * $Log: malloc.c,v $ |
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4 | * Revision 4.0.1.2 91/06/07 11:20:45 lwall |
5 | * patch4: many, many itty-bitty portability fixes |
6 | * |
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7 | * Revision 4.0.1.1 91/04/11 17:48:31 lwall |
8 | * patch1: Configure now figures out malloc ptr type |
9 | * |
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10 | * Revision 4.0 91/03/20 01:28:52 lwall |
11 | * 4.0 baseline. |
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12 | * |
13 | */ |
14 | |
15 | #ifndef lint |
16 | static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83"; |
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17 | |
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18 | #ifdef DEBUGGING |
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19 | #define RCHECK |
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20 | #endif |
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21 | /* |
22 | * malloc.c (Caltech) 2/21/82 |
23 | * Chris Kingsley, kingsley@cit-20. |
24 | * |
25 | * This is a very fast storage allocator. It allocates blocks of a small |
26 | * number of different sizes, and keeps free lists of each size. Blocks that |
27 | * don't exactly fit are passed up to the next larger size. In this |
28 | * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long. |
29 | * This is designed for use in a program that uses vast quantities of memory, |
30 | * but bombs when it runs out. |
31 | */ |
32 | |
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33 | #include "EXTERN.h" |
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34 | #include "perl.h" |
35 | |
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36 | static findbucket(), morecore(); |
37 | |
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38 | /* I don't much care whether these are defined in sys/types.h--LAW */ |
39 | |
40 | #define u_char unsigned char |
41 | #define u_int unsigned int |
42 | #define u_short unsigned short |
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43 | |
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44 | /* |
45 | * The overhead on a block is at least 4 bytes. When free, this space |
46 | * contains a pointer to the next free block, and the bottom two bits must |
47 | * be zero. When in use, the first byte is set to MAGIC, and the second |
48 | * byte is the size index. The remaining bytes are for alignment. |
49 | * If range checking is enabled and the size of the block fits |
50 | * in two bytes, then the top two bytes hold the size of the requested block |
51 | * plus the range checking words, and the header word MINUS ONE. |
52 | */ |
53 | union overhead { |
54 | union overhead *ov_next; /* when free */ |
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55 | #if ALIGNBYTES > 4 |
56 | double strut; /* alignment problems */ |
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57 | #endif |
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58 | struct { |
59 | u_char ovu_magic; /* magic number */ |
60 | u_char ovu_index; /* bucket # */ |
61 | #ifdef RCHECK |
62 | u_short ovu_size; /* actual block size */ |
63 | u_int ovu_rmagic; /* range magic number */ |
64 | #endif |
65 | } ovu; |
66 | #define ov_magic ovu.ovu_magic |
67 | #define ov_index ovu.ovu_index |
68 | #define ov_size ovu.ovu_size |
69 | #define ov_rmagic ovu.ovu_rmagic |
70 | }; |
71 | |
72 | #define MAGIC 0xff /* magic # on accounting info */ |
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73 | #define OLDMAGIC 0x7f /* same after a free() */ |
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74 | #define RMAGIC 0x55555555 /* magic # on range info */ |
75 | #ifdef RCHECK |
76 | #define RSLOP sizeof (u_int) |
77 | #else |
78 | #define RSLOP 0 |
79 | #endif |
80 | |
81 | /* |
82 | * nextf[i] is the pointer to the next free block of size 2^(i+3). The |
83 | * smallest allocatable block is 8 bytes. The overhead information |
84 | * precedes the data area returned to the user. |
85 | */ |
86 | #define NBUCKETS 30 |
87 | static union overhead *nextf[NBUCKETS]; |
88 | extern char *sbrk(); |
89 | |
90 | #ifdef MSTATS |
91 | /* |
92 | * nmalloc[i] is the difference between the number of mallocs and frees |
93 | * for a given block size. |
94 | */ |
95 | static u_int nmalloc[NBUCKETS]; |
96 | #include <stdio.h> |
97 | #endif |
98 | |
99 | #ifdef debug |
100 | #define ASSERT(p) if (!(p)) botch("p"); else |
101 | static |
102 | botch(s) |
103 | char *s; |
104 | { |
105 | |
106 | printf("assertion botched: %s\n", s); |
107 | abort(); |
108 | } |
109 | #else |
110 | #define ASSERT(p) |
111 | #endif |
112 | |
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113 | MALLOCPTRTYPE * |
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114 | malloc(nbytes) |
115 | register unsigned nbytes; |
116 | { |
117 | register union overhead *p; |
118 | register int bucket = 0; |
119 | register unsigned shiftr; |
120 | |
121 | /* |
122 | * Convert amount of memory requested into |
123 | * closest block size stored in hash buckets |
124 | * which satisfies request. Account for |
125 | * space used per block for accounting. |
126 | */ |
127 | nbytes += sizeof (union overhead) + RSLOP; |
128 | nbytes = (nbytes + 3) &~ 3; |
129 | shiftr = (nbytes - 1) >> 2; |
130 | /* apart from this loop, this is O(1) */ |
131 | while (shiftr >>= 1) |
132 | bucket++; |
133 | /* |
134 | * If nothing in hash bucket right now, |
135 | * request more memory from the system. |
136 | */ |
137 | if (nextf[bucket] == NULL) |
138 | morecore(bucket); |
139 | if ((p = (union overhead *)nextf[bucket]) == NULL) |
140 | return (NULL); |
141 | /* remove from linked list */ |
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142 | #ifdef RCHECK |
143 | if (*((int*)p) & (sizeof(union overhead) - 1)) |
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144 | #ifndef I286 |
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145 | fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p); |
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146 | #else |
147 | fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p); |
148 | #endif |
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149 | #endif |
150 | nextf[bucket] = p->ov_next; |
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151 | p->ov_magic = MAGIC; |
152 | p->ov_index= bucket; |
153 | #ifdef MSTATS |
154 | nmalloc[bucket]++; |
155 | #endif |
156 | #ifdef RCHECK |
157 | /* |
158 | * Record allocated size of block and |
159 | * bound space with magic numbers. |
160 | */ |
161 | if (nbytes <= 0x10000) |
162 | p->ov_size = nbytes - 1; |
163 | p->ov_rmagic = RMAGIC; |
164 | *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC; |
165 | #endif |
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166 | return ((MALLOCPTRTYPE *)(p + 1)); |
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167 | } |
168 | |
169 | /* |
170 | * Allocate more memory to the indicated bucket. |
171 | */ |
172 | static |
173 | morecore(bucket) |
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174 | register int bucket; |
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175 | { |
176 | register union overhead *op; |
177 | register int rnu; /* 2^rnu bytes will be requested */ |
178 | register int nblks; /* become nblks blocks of the desired size */ |
179 | register int siz; |
180 | |
181 | if (nextf[bucket]) |
182 | return; |
183 | /* |
184 | * Insure memory is allocated |
185 | * on a page boundary. Should |
186 | * make getpageize call? |
187 | */ |
188 | op = (union overhead *)sbrk(0); |
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189 | #ifndef I286 |
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190 | if ((int)op & 0x3ff) |
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191 | (void)sbrk(1024 - ((int)op & 0x3ff)); |
192 | #else |
193 | /* The sbrk(0) call on the I286 always returns the next segment */ |
194 | #endif |
195 | |
196 | #ifndef I286 |
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197 | /* take 2k unless the block is bigger than that */ |
198 | rnu = (bucket <= 8) ? 11 : bucket + 3; |
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199 | #else |
200 | /* take 16k unless the block is bigger than that |
201 | (80286s like large segments!) */ |
202 | rnu = (bucket <= 11) ? 14 : bucket + 3; |
203 | #endif |
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204 | nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */ |
205 | if (rnu < bucket) |
206 | rnu = bucket; |
207 | op = (union overhead *)sbrk(1 << rnu); |
208 | /* no more room! */ |
209 | if ((int)op == -1) |
210 | return; |
211 | /* |
212 | * Round up to minimum allocation size boundary |
213 | * and deduct from block count to reflect. |
214 | */ |
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215 | #ifndef I286 |
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216 | if ((int)op & 7) { |
217 | op = (union overhead *)(((int)op + 8) &~ 7); |
218 | nblks--; |
219 | } |
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220 | #else |
221 | /* Again, this should always be ok on an 80286 */ |
222 | #endif |
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223 | /* |
224 | * Add new memory allocated to that on |
225 | * free list for this hash bucket. |
226 | */ |
227 | nextf[bucket] = op; |
228 | siz = 1 << (bucket + 3); |
229 | while (--nblks > 0) { |
230 | op->ov_next = (union overhead *)((caddr_t)op + siz); |
231 | op = (union overhead *)((caddr_t)op + siz); |
232 | } |
233 | } |
234 | |
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235 | void |
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236 | free(mp) |
237 | MALLOCPTRTYPE *mp; |
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238 | { |
239 | register int size; |
240 | register union overhead *op; |
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241 | char *cp = (char*)mp; |
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242 | |
243 | if (cp == NULL) |
244 | return; |
245 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
246 | #ifdef debug |
247 | ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ |
248 | #else |
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249 | if (op->ov_magic != MAGIC) { |
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250 | warn("%s free() ignored", |
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251 | op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad"); |
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252 | return; /* sanity */ |
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253 | } |
254 | op->ov_magic = OLDMAGIC; |
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255 | #endif |
256 | #ifdef RCHECK |
257 | ASSERT(op->ov_rmagic == RMAGIC); |
258 | if (op->ov_index <= 13) |
259 | ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC); |
260 | #endif |
261 | ASSERT(op->ov_index < NBUCKETS); |
262 | size = op->ov_index; |
263 | op->ov_next = nextf[size]; |
264 | nextf[size] = op; |
265 | #ifdef MSTATS |
266 | nmalloc[size]--; |
267 | #endif |
268 | } |
269 | |
270 | /* |
271 | * When a program attempts "storage compaction" as mentioned in the |
272 | * old malloc man page, it realloc's an already freed block. Usually |
273 | * this is the last block it freed; occasionally it might be farther |
274 | * back. We have to search all the free lists for the block in order |
275 | * to determine its bucket: 1st we make one pass thru the lists |
276 | * checking only the first block in each; if that fails we search |
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277 | * ``reall_srchlen'' blocks in each list for a match (the variable |
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278 | * is extern so the caller can modify it). If that fails we just copy |
279 | * however many bytes was given to realloc() and hope it's not huge. |
280 | */ |
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281 | int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ |
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282 | |
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283 | MALLOCPTRTYPE * |
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284 | realloc(mp, nbytes) |
285 | MALLOCPTRTYPE *mp; |
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286 | unsigned nbytes; |
287 | { |
288 | register u_int onb; |
289 | union overhead *op; |
290 | char *res; |
291 | register int i; |
292 | int was_alloced = 0; |
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293 | char *cp = (char*)mp; |
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294 | |
295 | if (cp == NULL) |
296 | return (malloc(nbytes)); |
297 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
298 | if (op->ov_magic == MAGIC) { |
299 | was_alloced++; |
300 | i = op->ov_index; |
301 | } else { |
302 | /* |
303 | * Already free, doing "compaction". |
304 | * |
305 | * Search for the old block of memory on the |
306 | * free list. First, check the most common |
307 | * case (last element free'd), then (this failing) |
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308 | * the last ``reall_srchlen'' items free'd. |
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309 | * If all lookups fail, then assume the size of |
310 | * the memory block being realloc'd is the |
311 | * smallest possible. |
312 | */ |
313 | if ((i = findbucket(op, 1)) < 0 && |
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314 | (i = findbucket(op, reall_srchlen)) < 0) |
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315 | i = 0; |
316 | } |
317 | onb = (1 << (i + 3)) - sizeof (*op) - RSLOP; |
318 | /* avoid the copy if same size block */ |
319 | if (was_alloced && |
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320 | nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) { |
321 | #ifdef RCHECK |
322 | /* |
323 | * Record new allocated size of block and |
324 | * bound space with magic numbers. |
325 | */ |
326 | if (op->ov_index <= 13) { |
327 | /* |
328 | * Convert amount of memory requested into |
329 | * closest block size stored in hash buckets |
330 | * which satisfies request. Account for |
331 | * space used per block for accounting. |
332 | */ |
333 | nbytes += sizeof (union overhead) + RSLOP; |
334 | nbytes = (nbytes + 3) &~ 3; |
335 | op->ov_size = nbytes - 1; |
336 | *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC; |
337 | } |
338 | #endif |
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339 | return((MALLOCPTRTYPE*)cp); |
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340 | } |
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341 | if ((res = (char*)malloc(nbytes)) == NULL) |
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342 | return (NULL); |
343 | if (cp != res) /* common optimization */ |
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344 | (void)bcopy(cp, res, (int)((nbytes < onb) ? nbytes : onb)); |
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345 | if (was_alloced) |
346 | free(cp); |
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347 | return ((MALLOCPTRTYPE*)res); |
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348 | } |
349 | |
350 | /* |
351 | * Search ``srchlen'' elements of each free list for a block whose |
352 | * header starts at ``freep''. If srchlen is -1 search the whole list. |
353 | * Return bucket number, or -1 if not found. |
354 | */ |
355 | static |
356 | findbucket(freep, srchlen) |
357 | union overhead *freep; |
358 | int srchlen; |
359 | { |
360 | register union overhead *p; |
361 | register int i, j; |
362 | |
363 | for (i = 0; i < NBUCKETS; i++) { |
364 | j = 0; |
365 | for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { |
366 | if (p == freep) |
367 | return (i); |
368 | j++; |
369 | } |
370 | } |
371 | return (-1); |
372 | } |
373 | |
374 | #ifdef MSTATS |
375 | /* |
376 | * mstats - print out statistics about malloc |
377 | * |
378 | * Prints two lines of numbers, one showing the length of the free list |
379 | * for each size category, the second showing the number of mallocs - |
380 | * frees for each size category. |
381 | */ |
382 | mstats(s) |
383 | char *s; |
384 | { |
385 | register int i, j; |
386 | register union overhead *p; |
387 | int totfree = 0, |
388 | totused = 0; |
389 | |
390 | fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); |
391 | for (i = 0; i < NBUCKETS; i++) { |
392 | for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) |
393 | ; |
394 | fprintf(stderr, " %d", j); |
395 | totfree += j * (1 << (i + 3)); |
396 | } |
397 | fprintf(stderr, "\nused:\t"); |
398 | for (i = 0; i < NBUCKETS; i++) { |
399 | fprintf(stderr, " %d", nmalloc[i]); |
400 | totused += nmalloc[i] * (1 << (i + 3)); |
401 | } |
402 | fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", |
403 | totused, totfree); |
404 | } |
405 | #endif |
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406 | #endif /* lint */ |