75 lines
3.6 KiB
C
75 lines
3.6 KiB
C
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/*-*- 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 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/calls/calls.h"
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#include "libc/dce.h"
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#include "libc/limits.h"
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#include "libc/macros.h"
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#include "libc/runtime/ring.h"
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#include "libc/str/str.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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/**
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* Allocates ring buffer.
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*
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* Reads/writes wrap around on overflow.
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*
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* ┌────────────┐
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* │ 𝑓₀..𝑓ₙ₋₁ │
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* └┬┬──────────┘
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* │└────────────┐
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* ┌┴────────────┬┴────────────┐
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* │ 𝑣₀..𝑣ₙ₋₁ │ 𝑣ₙ..𝑣ₙ*₂₋₁ │
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* └─────────────┴─────────────┘
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*
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* @param r is metadata object owned by caller, initialized to zero
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* @param n is byte length
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* @return r->p, or NULL w/ errno
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* @see ringfree(), balloc()
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*/
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void *ringalloc(struct RingBuffer *r, size_t n) {
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void *a2;
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int fd, rc;
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size_t grain;
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assert(!r->p);
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assert(n > 0);
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assert(n <= (INT_MAX - FRAMESIZE + 1) / 2);
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if ((fd = openanon("ring", 0)) != -1) {
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grain = ROUNDUP(n, FRAMESIZE);
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rc = ftruncate(fd, grain * 2);
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assert(rc != -1);
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r->_size = grain * 2;
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r->_addr = mmap(NULL, grain, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (r->_addr != MAP_FAILED) {
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a2 = mmap(r->_addr + grain, grain, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_FIXED, fd, grain - n);
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assert(a2 != MAP_FAILED);
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r->p = r->_addr + grain - n;
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if (IsWindows()) {
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memset(r->p, 0, n); /* @see ftruncate() */
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}
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}
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}
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rc = close(fd);
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assert(rc != -1);
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return r->p;
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}
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