mirror of https://code.videolan.org/videolan/vlc
77 lines
2.2 KiB
C
77 lines
2.2 KiB
C
/*****************************************************************************
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* readv.c: POSIX readv() replacement
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*****************************************************************************
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* Copyright © 2022 Rémi Denis-Courmont
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
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*****************************************************************************/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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ssize_t readv(int fd, const struct iovec *iov, int iovcnt)
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{
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if (iovcnt == 1)
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return read(fd, iov->iov_base, iov->iov_len);
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/*
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* The whole point of readv() is that multiple consecutive reads are *not*
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* generally equivalent to one read of the same total size. We have to read
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* all at once to preserve atomicity and packet boundaries.
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*/
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size_t size = 0;
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for (int i = 0; i < iovcnt; i++) {
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/* TODO: use ckd_add() */
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size += iov[i].iov_len;
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if (iov[i].iov_len > size) {
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errno = EINVAL;
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return -1;
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}
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}
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unsigned char *buf = malloc(size ? size : 1);
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if (buf == NULL) {
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errno = ENOBUFS;
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return -1;
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}
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ssize_t ret = read(fd, buf, size);
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int saved_errno = errno;
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for (ssize_t len = ret; len > 0; iov++) {
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size_t copy = iov->iov_len;
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if (copy > (size_t)len)
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copy = len;
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memcpy(iov->iov_base, buf, copy);
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buf += copy;
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len -= copy;
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}
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free(buf);
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errno = saved_errno;
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return ret;
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}
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