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69 lines
3.1 KiB
C
69 lines
3.1 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2021 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/intrin/lockcmpxchg.h"
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#include "libc/log/check.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/x/x.h"
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#include "third_party/zlib/zlib.h"
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/**
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* Inflates data once atomically, e.g.
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*
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* void *GetData(void) {
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* static char once;
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* static void *ptr;
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* static const unsigned char rodata[] = {...};
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* if (once) return ptr;
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* return xload(&once, &ptr, rodata, 112, 1024);
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* }
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*
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* The above is an example of how this helper may be used to have lazy
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* loading of big infrequently accessed image data.
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*
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* @param o points to your static init guard
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* @param t points to your static pointer holder
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* @param p is read-only data compressed using raw deflate
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* @param n is byte length of deflated data
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* @param m is byte length of inflated data
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* @return pointer to inflated data
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* @threadsafe
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*/
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void *xload(bool *o, void **t, const void *p, size_t n, size_t m) {
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void *q;
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z_stream zs;
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q = malloc(m);
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zs.zfree = 0;
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zs.zalloc = 0;
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zs.next_in = p;
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zs.avail_in = n;
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zs.total_in = n;
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zs.avail_out = m;
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zs.total_out = m;
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zs.next_out = (void *)q;
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inflateInit2(&zs, -MAX_WBITS);
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inflate(&zs, Z_NO_FLUSH);
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if (_lockcmpxchg(t, 0, q)) {
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__cxa_atexit(free, q, 0);
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} else {
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free(q);
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}
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*o = true;
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return *t;
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}
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