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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 <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/uio.h>
#pragma weak readv = __readv
/* Read data from file descriptor FD, and put the result in the
buffers described by VECTOR, which is a vector of COUNT `struct iovec's.
The buffers are filled in the order specified.
Operates just like `read' (see <unistd.h>) except that data are
put in VECTOR instead of a contiguous buffer. */
int
DEFUN(__readv, (fd, vector, count),
int fd AND CONST struct iovec *vector AND size_t count)
{
char *buffer;
size_t bytes;
int bytes_read;
register size_t i;
/* 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_read) {
bytes_read = __syscall_readv (fd, vector+i, min(count-i,MAX_IOVEC));
if (bytes_read < 0) {
if (errno != ENOSYS) return bytes_read;
else goto nonsyscall; /* probably shouldn't happen */
}
}
return bytes;
#else /* this probably means syscall doesn't exist, but just in case... */
bytes_read = __syscall_readv (fd, vector, count);
if (bytes_read >= 0 || (bytes_read < 0 && errno != ENOSYS))
{
return bytes_read;
}
#endif
nonsyscall:
errno = 0;
/* Find the total number of bytes to be read. */
bytes = 0;
for (i = 0; i < count; ++i)
bytes += vector[i].iov_len;
/* Allocate a temporary buffer to hold the data. */
buffer = (char *) __alloca(bytes);
/* Read the data. */
bytes_read = read(fd, buffer, bytes);
if (bytes_read < 0)
return -1;
if (bytes_read == 0)
return 0;
/* Copy the data from BUFFER into the memory specified by VECTOR. */
bytes = bytes_read;
for (i = 0; i < count; ++i)
{
size_t copy = min(vector[i].iov_len, bytes);
(void) memcpy((PTR) vector[i].iov_base, (PTR) buffer, copy);
buffer += copy;
bytes -= copy;
if (bytes == 0)
break;
}
return bytes_read;
}
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