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/* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <ansidecl.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <sys/uio.h>
#pragma weak writev = __writev
/* Write data pointed by the buffers described by VECTOR, which
is a vector of COUNT `struct iovec's, to file descriptor FD.
The data is written in the order specified.
Operates just like `write' (see <unistd.h>) except that the data
are taken from VECTOR instead of a contiguous buffer. */
int
DEFUN(__writev, (fd, vector, count),
int fd AND CONST struct iovec *vector AND size_t count)
{
char *buffer;
register char *bp;
size_t bytes, to_copy;
register size_t i;
int bytes_write;
/* We try the system call first. */
#define min(a, b) ((a) > (b) ? (b) : (a))
#ifdef MAX_IOVEC
for (i = 0, bytes = 0; i < count; i += MAX_IOVEC, bytes += bytes_write) {
bytes_write = __syscall_writev (fd, vector+i, min(count-i,MAX_IOVEC));
if (bytes_write < 0) {
if (errno != ENOSYS) return bytes_write;
else goto nonsyscall; /* probably shouldn't happen */
}
}
return bytes;
#else /* this probably means syscall doesn't exist, but just in case... */
bytes_write = __syscall_writev (fd, vector, count);
if (bytes_write >= 0 || (bytes_write < 0 && errno != ENOSYS))
{
return bytes_write;
}
#endif
nonsyscall:
errno = 0;
/* Find the total number of bytes to be written. */
bytes = 0;
for (i = 0; i < count; ++i)
bytes += vector[i].iov_len;
if (bytes == 0)
return 0;
/* Allocate a temporary buffer to hold the data. */
buffer = (char *) __alloca(bytes);
/* Copy the data into BUFFER. */
to_copy = bytes;
bp = buffer;
for (i = 0; i < count; ++i)
{
size_t copy = min(vector[i].iov_len, to_copy);
(void) memcpy((PTR) bp, (PTR) vector[i].iov_base, copy);
bp += copy;
to_copy -= copy;
if (to_copy == 0)
break;
}
return write(fd, buffer, bytes);
}
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