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c906108c SS |
1 | /* Support for sbrk() regions. |
2 | Copyright 1992 Free Software Foundation, Inc. | |
3 | Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com | |
4 | ||
5 | This file is part of the GNU C Library. | |
6 | ||
7 | The GNU C Library is free software; you can redistribute it and/or | |
8 | modify it under the terms of the GNU Library General Public License as | |
9 | published by the Free Software Foundation; either version 2 of the | |
10 | License, or (at your option) any later version. | |
11 | ||
12 | The GNU C Library is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | Library General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU Library General Public | |
18 | License along with the GNU C Library; see the file COPYING.LIB. If | |
19 | not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
20 | Boston, MA 02111-1307, USA. */ | |
21 | ||
22 | #include <string.h> /* Prototypes for memcpy, memmove, memset, etc */ | |
23 | ||
24 | #include "mmprivate.h" | |
25 | ||
26 | static PTR sbrk_morecore PARAMS ((struct mdesc *, int)); | |
27 | extern PTR sbrk PARAMS ((int)); | |
28 | ||
29 | /* The mmalloc() package can use a single implicit malloc descriptor | |
30 | for mmalloc/mrealloc/mfree operations which do not supply an explicit | |
31 | descriptor. For these operations, sbrk() is used to obtain more core | |
32 | from the system, or return core. This allows mmalloc() to provide | |
33 | backwards compatibility with the non-mmap'd version. */ | |
34 | ||
35 | struct mdesc *__mmalloc_default_mdp; | |
36 | ||
37 | /* Use sbrk() to get more core. */ | |
38 | ||
39 | static PTR | |
40 | sbrk_morecore (mdp, size) | |
41 | struct mdesc *mdp; | |
42 | int size; | |
43 | { | |
44 | PTR result; | |
45 | ||
46 | if ((result = sbrk (size)) == (PTR) -1) | |
47 | { | |
48 | result = NULL; | |
49 | } | |
50 | else | |
51 | { | |
52 | mdp -> breakval += size; | |
53 | mdp -> top += size; | |
54 | } | |
55 | return (result); | |
56 | } | |
57 | ||
58 | /* Initialize the default malloc descriptor if this is the first time | |
59 | a request has been made to use the default sbrk'd region. | |
60 | ||
61 | Since no alignment guarantees are made about the initial value returned | |
62 | by sbrk, test the initial value and (if necessary) sbrk enough additional | |
63 | memory to start off with alignment to BLOCKSIZE. We actually only need | |
64 | it aligned to an alignment suitable for any object, so this is overkill. | |
65 | But at most it wastes just part of one BLOCKSIZE chunk of memory and | |
66 | minimizes portability problems by avoiding us having to figure out | |
67 | what the actual minimal alignment is. The rest of the malloc code | |
68 | avoids this as well, by always aligning to the minimum of the requested | |
69 | size rounded up to a power of two, or to BLOCKSIZE. | |
70 | ||
71 | Note that we are going to use some memory starting at this initial sbrk | |
72 | address for the sbrk region malloc descriptor, which is a struct, so the | |
73 | base address must be suitably aligned. */ | |
74 | ||
75 | struct mdesc * | |
76 | __mmalloc_sbrk_init () | |
77 | { | |
78 | PTR base; | |
79 | unsigned int adj; | |
80 | ||
81 | base = sbrk (0); | |
82 | adj = RESIDUAL (base, BLOCKSIZE); | |
83 | if (adj != 0) | |
84 | { | |
85 | sbrk (BLOCKSIZE - adj); | |
86 | base = sbrk (0); | |
87 | } | |
88 | __mmalloc_default_mdp = (struct mdesc *) sbrk (sizeof (struct mdesc)); | |
89 | memset ((char *) __mmalloc_default_mdp, 0, sizeof (struct mdesc)); | |
90 | __mmalloc_default_mdp -> morecore = sbrk_morecore; | |
91 | __mmalloc_default_mdp -> base = base; | |
92 | __mmalloc_default_mdp -> breakval = __mmalloc_default_mdp -> top = sbrk (0); | |
93 | __mmalloc_default_mdp -> fd = -1; | |
94 | return (__mmalloc_default_mdp); | |
95 | } | |
96 | ||
97 |