thr_writev.c revision 56888 
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 AUTHOR 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 * $FreeBSD: head/lib/libkse/thread/thr_writev.c 56888 2000-01-29 22:53:55Z jasone $
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
47_writev(int fd, const struct iovec * iov, int iovcnt)
48{
49	int	blocking;
50	int	idx = 0;
51	int	type;
52	ssize_t cnt;
53	ssize_t n;
54	ssize_t num = 0;
55	ssize_t	ret;
56	struct iovec liov[20];
57	struct iovec *p_iov = liov;
58
59	/* Check if the array size exceeds to compiled in size: */
60	if (iovcnt > (sizeof(liov) / sizeof(struct iovec))) {
61		/* Allocate memory for the local array: */
62		if ((p_iov = (struct iovec *)
63		    malloc(iovcnt * sizeof(struct iovec))) == NULL) {
64			/* Insufficient memory: */
65			errno = ENOMEM;
66			return (-1);
67		}
68	}
69
70	/* Copy the caller's array so that it can be modified locally: */
71	memcpy(p_iov,iov,iovcnt * sizeof(struct iovec));
72
73	/* Lock the file descriptor for write: */
74	if ((ret = _FD_LOCK(fd, FD_WRITE, NULL)) == 0) {
75		/* Get the read/write mode type: */
76		type = _thread_fd_table[fd]->flags & O_ACCMODE;
77
78		/* Check if the file is not open for write: */
79		if (type != O_WRONLY && type != O_RDWR) {
80			/* File is not open for write: */
81			errno = EBADF;
82			_FD_UNLOCK(fd, FD_WRITE);
83			return (-1);
84		}
85
86		/* Check if file operations are to block */
87		blocking = ((_thread_fd_table[fd]->flags & O_NONBLOCK) == 0);
88
89		/*
90		 * Loop while no error occurs and until the expected number
91		 * of bytes are written if performing a blocking write:
92		 */
93		while (ret == 0) {
94			/* Perform a non-blocking write syscall: */
95			n = _thread_sys_writev(fd, &p_iov[idx], iovcnt - idx);
96
97			/* Check if one or more bytes were written: */
98			if (n > 0) {
99				/*
100				 * Keep a count of the number of bytes
101				 * written:
102				 */
103				num += n;
104
105				/*
106				 * Enter a loop to check if a short write
107				 * occurred and move the index to the
108				 * array entry where the short write
109				 * ended:
110				 */
111				cnt = n;
112				while (cnt > 0 && idx < iovcnt) {
113					/*
114					 * If the residual count exceeds
115					 * the size of this vector, then
116					 * it was completely written:
117					 */
118					if (cnt >= p_iov[idx].iov_len)
119						/*
120						 * Decrement the residual
121						 * count and increment the
122						 * index to the next array
123						 * entry:
124						 */
125						cnt -= p_iov[idx++].iov_len;
126					else {
127						/*
128						 * This entry was only
129						 * partially written, so
130						 * adjust it's length
131						 * and base pointer ready
132						 * for the next write:
133						 */
134						p_iov[idx].iov_len -= cnt;
135						p_iov[idx].iov_base += cnt;
136						cnt = 0;
137					}
138				}
139			} else if (n == 0) {
140				/*
141				 * Avoid an infinite loop if the last iov_len is
142				 * 0.
143				 */
144				while (idx < iovcnt && p_iov[idx].iov_len == 0)
145					idx++;
146
147				if (idx == iovcnt) {
148					ret = num;
149					break;
150				}
151			}
152
153			/*
154			 * If performing a blocking write, check if the
155			 * write would have blocked or if some bytes
156			 * were written but there are still more to
157			 * write:
158			 */
159			if (blocking && ((n < 0 && (errno == EWOULDBLOCK ||
160			    errno == EAGAIN)) || (n >= 0 && idx < iovcnt))) {
161				_thread_run->data.fd.fd = fd;
162				_thread_kern_set_timeout(NULL);
163
164				/* Reset the interrupted operation flag: */
165				_thread_run->interrupted = 0;
166
167				_thread_kern_sched_state(PS_FDW_WAIT,
168				    __FILE__, __LINE__);
169
170				/*
171				 * Check if the operation was
172				 * interrupted by a signal
173				 */
174				if (_thread_run->interrupted) {
175					/* Return an error: */
176					ret = -1;
177				}
178
179			/*
180			 * If performing a non-blocking write or if an
181			 * error occurred, just return whatever the write
182			 * syscall did:
183			 */
184			} else if (!blocking || n < 0) {
185				/* A non-blocking call might return zero: */
186				ret = n;
187				break;
188
189			/* Check if the write has completed: */
190			} else if (idx == iovcnt)
191				/* Return the number of bytes written: */
192				ret = num;
193		}
194		_FD_UNLOCK(fd, FD_RDWR);
195	}
196
197	/* If memory was allocated for the array, free it: */
198	if (p_iov != liov)
199		free(p_iov);
200
201	return (ret);
202}
203
204__strong_reference(_writev, writev);
205#endif
206