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