6/lib/libc_r/uthread/uthread_writev.c

   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  * $FreeBSD$
  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 #include <pthread.h>
  43 #include "pthread_private.h"
  44
  45 __weak_reference(__writev, writev);
  46
  47 ssize_t
  48 _writev(int fd, const struct iovec * iov, int iovcnt)
  49 {
  50         struct pthread  *curthread = _get_curthread();
  51         int     blocking;
  52         int     idx = 0;
  53         int     type;
  54         ssize_t cnt;
  55         ssize_t n;
  56         ssize_t num = 0;
  57         ssize_t ret;
  58         struct iovec liov[20];
  59         struct iovec *p_iov = liov;
  60
  61         /* Check if the array size exceeds to compiled in size: */
  62         if (iovcnt > (sizeof(liov) / sizeof(struct iovec))) {
  63                 /* Allocate memory for the local array: */
  64                 if ((p_iov = (struct iovec *)
  65                     malloc(iovcnt * sizeof(struct iovec))) == NULL) {
  66                         /* Insufficient memory: */
  67                         errno = ENOMEM;
  68                         return (-1);
  69                 }
  70         }
  71
  72         /* Copy the caller's array so that it can be modified locally: */
  73         memcpy(p_iov,iov,iovcnt * sizeof(struct iovec));
  74
  75         /* Lock the file descriptor for write: */
  76         if ((ret = _FD_LOCK(fd, FD_WRITE, NULL)) == 0) {
  77                 /* Get the read/write mode type: */
  78                 type = _thread_fd_getflags(fd) & O_ACCMODE;
  79
  80                 /* Check if the file is not open for write: */
  81                 if (type != O_WRONLY && type != O_RDWR) {
  82                         /* File is not open for write: */
  83                         errno = EBADF;
  84                         _FD_UNLOCK(fd, FD_WRITE);
  85                         return (-1);
  86                 }
  87
  88                 /* Check if file operations are to block */
  89                 blocking = ((_thread_fd_getflags(fd) & O_NONBLOCK) == 0);
  90
  91                 /*
  92                  * Loop while no error occurs and until the expected number
  93                  * of bytes are written if performing a blocking write:
  94                  */
  95                 while (ret == 0) {
  96                         /* Perform a non-blocking write syscall: */
  97                         n = __sys_writev(fd, &p_iov[idx], iovcnt - idx);
  98
  99                         /* Check if one or more bytes were written: */
 100                         if (n > 0) {
 101                                 /*
 102                                  * Keep a count of the number of bytes
 103                                  * written:
 104                                  */
 105                                 num += n;
 106
 107                                 /*
 108                                  * Enter a loop to check if a short write
 109                                  * occurred and move the index to the
 110                                  * array entry where the short write
 111                                  * ended:
 112                                  */
 113                                 cnt = n;
 114                                 while (cnt > 0 && idx < iovcnt) {
 115                                         /*
 116                                          * If the residual count exceeds
 117                                          * the size of this vector, then
 118                                          * it was completely written:
 119                                          */
 120                                         if (cnt >= p_iov[idx].iov_len)
 121                                                 /*
 122                                                  * Decrement the residual
 123                                                  * count and increment the
 124                                                  * index to the next array
 125                                                  * entry:
 126                                                  */
 127                                                 cnt -= p_iov[idx++].iov_len;
 128                                         else {
 129                                                 /*
 130                                                  * This entry was only
 131                                                  * partially written, so
 132                                                  * adjust it's length
 133                                                  * and base pointer ready
 134                                                  * for the next write:
 135                                                  */
 136                                                 p_iov[idx].iov_len -= cnt;
 137                                                 p_iov[idx].iov_base =
 138                                                     (char *)p_iov[idx].iov_base
 139                                                     + cnt;
 140                                                 cnt = 0;
 141                                         }
 142                                 }
 143                         } else if (n == 0) {
 144                                 /*
 145                                  * Avoid an infinite loop if the last iov_len is
 146                                  * 0.
 147                                  */
 148                                 while (idx < iovcnt && p_iov[idx].iov_len == 0)
 149                                         idx++;
 150
 151                                 if (idx == iovcnt) {
 152                                         ret = num;
 153                                         break;
 154                                 }
 155                         }
 156
 157                         /*
 158                          * If performing a blocking write, check if the
 159                          * write would have blocked or if some bytes
 160                          * were written but there are still more to
 161                          * write:
 162                          */
 163                         if (blocking && ((n < 0 && (errno == EWOULDBLOCK ||
 164                             errno == EAGAIN)) || (n >= 0 && idx < iovcnt))) {
 165                                 curthread->data.fd.fd = fd;
 166                                 _thread_kern_set_timeout(NULL);
 167
 168                                 /* Reset the interrupted operation flag: */
 169                                 curthread->interrupted = 0;
 170
 171                                 _thread_kern_sched_state(PS_FDW_WAIT,
 172                                     __FILE__, __LINE__);
 173
 174                                 /*
 175                                  * Check if the operation was
 176                                  * interrupted by a signal
 177                                  */
 178                                 if (curthread->interrupted) {
 179                                         if (num > 0) {
 180                                                 /* Return partial success: */
 181                                                 ret = num;
 182                                         } else {
 183                                                 /* Return an error: */
 184                                                 errno = EINTR;
 185                                                 ret = -1;
 186                                         }
 187                                 }
 188
 189                         /*
 190                          * If performing a non-blocking write,
 191                          * just return whatever the write syscall did:
 192                          */
 193                         } else if (!blocking) {
 194                                 /* A non-blocking call might return zero: */
 195                                 ret = n;
 196                                 break;
 197
 198                         /*
 199                          * If there was an error, return partial success
 200                          * (if any bytes were written) or else the error:
 201                          */
 202                         } else if (n < 0) {
 203                                 if (num > 0)
 204                                         ret = num;
 205                                 else
 206                                         ret = n;
 207
 208                         /* Check if the write has completed: */
 209                         } else if (idx == iovcnt)
 210                                 /* Return the number of bytes written: */
 211                                 ret = num;
 212                 }
 213                 _FD_UNLOCK(fd, FD_RDWR);
 214         }
 215
 216         /* If memory was allocated for the array, free it: */
 217         if (p_iov != liov)
 218                 free(p_iov);
 219
 220         return (ret);
 221 }
 222
 223 ssize_t
 224 __writev(int fd, const struct iovec *iov, int iovcnt)
 225 {
 226         ssize_t ret;
 227
 228         _thread_enter_cancellation_point();
 229         ret = _writev(fd, iov, iovcnt);
 230         _thread_leave_cancellation_point();
 231
 232         return ret;
 233 }