thr_writev.c revision 36830 
1/*
2 * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by John Birrell.
16 * 4. Neither the name of the author nor the names of any co-contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $Id: uthread_writev.c,v 1.7 1998/05/27 00:44:58 jb Exp $
33 *
34 */
35#include <sys/types.h>
36#include <sys/fcntl.h>
37#include <sys/uio.h>
38#include <errno.h>
39#include <stdlib.h>
40#include <string.h>
41#include <unistd.h>
42#ifdef _THREAD_SAFE
43#include <pthread.h>
44#include "pthread_private.h"
45
46ssize_t
47writev(int fd, const struct iovec * iov, int iovcnt)
48{
49	int	blocking;
50	int	idx = 0;
51	ssize_t cnt;
52	ssize_t n;
53	ssize_t num = 0;
54	ssize_t	ret;
55	struct iovec liov[20];
56	struct iovec *p_iov = liov;
57
58	/* Check if the array size exceeds to compiled in size: */
59	if (iovcnt > (sizeof(liov) / sizeof(struct iovec))) {
60		/* Allocate memory for the local array: */
61		if ((p_iov = (struct iovec *)
62		    malloc(iovcnt * sizeof(struct iovec))) == NULL) {
63			/* Insufficient memory: */
64			errno = ENOMEM;
65			return (-1);
66		}
67	}
68
69	/* Copy the caller's array so that it can be modified locally: */
70	memcpy(p_iov,iov,iovcnt * sizeof(struct iovec));
71
72	/* Lock the file descriptor for write: */
73	if ((ret = _FD_LOCK(fd, FD_WRITE, NULL)) == 0) {
74		/* Check if file operations are to block */
75		blocking = ((_thread_fd_table[fd]->flags & O_NONBLOCK) == 0);
76
77		/*
78		 * Loop while no error occurs and until the expected number
79		 * of bytes are written if performing a blocking write:
80		 */
81		while (ret == 0) {
82			/* Perform a non-blocking write syscall: */
83			n = _thread_sys_writev(fd, &p_iov[idx], iovcnt - idx);
84
85			/* Check if one or more bytes were written: */
86			if (n > 0) {
87				/*
88				 * Keep a count of the number of bytes
89				 * written:
90				 */
91				num += n;
92
93				/*
94				 * Enter a loop to check if a short write
95				 * occurred and move the index to the
96				 * array entry where the short write
97				 * ended:
98				 */
99				cnt = n;
100				while (cnt > 0 && idx < iovcnt) {
101					/*
102					 * If the residual count exceeds
103					 * the size of this vector, then
104					 * it was completely written:
105					 */
106					if (cnt >= p_iov[idx].iov_len)
107						/*
108						 * Decrement the residual
109						 * count and increment the
110						 * index to the next array
111						 * entry:
112						 */
113						cnt -= p_iov[idx++].iov_len;
114					else {
115						/*
116						 * This entry was only
117						 * partially written, so
118						 * adjust it's length
119						 * and base pointer ready
120						 * for the next write:
121						 */
122						p_iov[idx].iov_len -= cnt;
123						p_iov[idx].iov_base += cnt;
124						cnt = 0;
125					}
126				}
127			}
128
129			/*
130			 * If performing a blocking write, check if the
131			 * write would have blocked or if some bytes
132			 * were written but there are still more to
133			 * write:
134			 */
135			if (blocking && ((n < 0 && (errno == EWOULDBLOCK ||
136			    errno == EAGAIN)) || idx < iovcnt)) {
137				_thread_run->data.fd.fd = fd;
138				_thread_kern_set_timeout(NULL);
139
140				/* Reset the interrupted operation flag: */
141				_thread_run->interrupted = 0;
142
143				_thread_kern_sched_state(PS_FDW_WAIT,
144				    __FILE__, __LINE__);
145
146				/*
147				 * Check if the operation was
148				 * interrupted by a signal
149				 */
150				if (_thread_run->interrupted) {
151					/* Return an error: */
152					ret = -1;
153				}
154
155			/*
156			 * If performing a non-blocking write or if an
157			 * error occurred, just return whatever the write
158			 * syscall did:
159			 */
160			} else if (!blocking || n < 0) {
161				/* A non-blocking call might return zero: */
162				ret = n;
163				break;
164
165			/* Check if the write has completed: */
166			} else if (idx == iovcnt)
167				/* Return the number of bytes written: */
168				ret = num;
169		}
170		_FD_UNLOCK(fd, FD_RDWR);
171	}
172
173	/* If memory was allocated for the array, free it: */
174	if (p_iov != liov)
175		free(p_iov);
176
177	return (ret);
178}
179#endif
180