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59 lines
3 KiB
C
59 lines
3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/prot.h"
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#define G __gransize
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/**
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* Extends static allocation.
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*
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* This simple fixed allocator has unusual invariants
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*
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* !(p & 0xffff) && !(((p >> 3) + 0x7fff8000) & 0xffff)
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*
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* which must be the case when selecting a starting address. We also
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* make the assumption that allocations can only grow monotonically.
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* Furthermore allocations shall never be removed or relocated.
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*
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* @param p points to start of memory region
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* @param n specifies how many bytes are needed
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* @param e points to end of memory that's allocated
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* @param h is highest address to which `e` may grow
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* @param f should be `MAP_PRIVATE` or `MAP_SHARED`
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* @return new value for `e` or null w/ errno
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* @raise ENOMEM if we require more vespene gas
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* @asyncsignalsafe
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*/
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void *_extend(void *p, size_t n, void *e, int f, intptr_t h) {
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char *q;
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for (q = e; q < ((char *)p + n); q += 8) {
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if (!((uintptr_t)q & (G - 1))) {
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if (q + G > (char *)h)
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__builtin_trap();
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if (mmap(q, G, PROT_READ | PROT_WRITE, f | MAP_ANONYMOUS | MAP_FIXED, -1,
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0) == MAP_FAILED)
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return 0;
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}
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}
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return q;
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}
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