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72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
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/* readv supports all Linux kernels >= 2.0.
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Copyright (C) 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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read to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <errno.h>
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#include <stddef.h>
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#include <sys/param.h>
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#include <sys/uio.h>
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extern ssize_t __syscall_readv __P ((int, __const struct iovec *, int));
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/* Not all versions of the kernel support the large number of records. */
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#undef MAX_IOVEC
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#ifdef UIO_FASTIOV
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# define MAX_IOVEC UIO_FASTIOV
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#else
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# define MAX_IOVEC 8 /* 8 is a safe number. */
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#endif
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/* We should deal with kernel which have a smaller UIO_MAXIOV as well
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as a very big count. */
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ssize_t
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readv (fd, vector, count)
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int fd;
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const struct iovec *vector;
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int count;
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{
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int errno_saved = errno;
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ssize_t bytes_read;
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bytes_read = __syscall_readv (fd, vector, count);
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if (bytes_read < 0 && errno == EINVAL && count > MAX_IOVEC)
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{
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int i;
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/* Restore the old error value as if nothing happened. */
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__set_errno (errno_saved);
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bytes_read = 0;
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for (i = 0; i < count; i += MAX_IOVEC)
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{
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ssize_t bytes = __syscall_readv (fd, vector + i,
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MIN (count - i, MAX_IOVEC));
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if (bytes < 0)
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return bytes;
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bytes_read += bytes;
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}
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}
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return bytes_read;
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}
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