mdw@git.distorted.org.uk Git - fwd/blob - chan.c

   1 /* -*-c-*-
   2  *
   3  * $Id: chan.c,v 1.5 2000/07/19 17:55:43 mdw Exp $
   4  *
   5  * Channel management
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of the `fw' port forwarder.
  13  *
  14  * `fw' is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * `fw' is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with `fw'; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: chan.c,v $
  32  * Revision 1.5  2000/07/19 17:55:43  mdw
  33  * (writechan): Pointless tweak: when the buffer is empty, reset the start
  34  * pointer to the beginning.  This saves doing slightly trickier
  35  * @writev(2)@ calls when loading is light.
  36  *
  37  * Revision 1.4  1999/08/31 17:42:49  mdw
  38  * Use `sel_force' to avoid a `select' call between reads and writes.
  39  *
  40  * Revision 1.3  1999/07/27 18:30:53  mdw
  41  * Various minor portability fixes.
  42  *
  43  * Revision 1.2  1999/07/26 23:27:52  mdw
  44  * Minor modifications for new design.
  45  *
  46  * Revision 1.1.1.1  1999/07/01 08:56:23  mdw
  47  * Initial revision.
  48  *
  49  */
  50
  51 /*----- Header files ------------------------------------------------------*/
  52
  53 #include "config.h"
  54
  55 #include <errno.h>
  56 #include <stdio.h>
  57 #include <stdlib.h>
  58 #include <string.h>
  59
  60 #include <sys/types.h>
  61 #include <sys/time.h>
  62 #include <unistd.h>
  63 #include <sys/uio.h>
  64
  65 #include <mLib/alloc.h>
  66 #include <mLib/conn.h>
  67 #include <mLib/sel.h>
  68
  69 #include "chan.h"
  70 #include "fw.h"
  71
  72 /*----- Main code ---------------------------------------------------------*/
  73
  74 /* --- @writechan@ --- *
  75  *
  76  * Arguments:   @int fd@ = file descriptor to write to
  77  *              @unsigned mode@ = what the descriptor is ready for
  78  *              @void *vp@ = pointer to channel block
  79  *
  80  * Returns:     ---
  81  *
  82  * Use:         Writes to a channel.
  83  */
  84
  85 static void writechan(int fd, unsigned mode, void *vp)
  86 {
  87   chan *c = vp;
  88   int w;
  89   unsigned base = c->base;
  90   unsigned len = c->len;
  91
  92   /* --- Write data from my buffer --- */
  93
  94   if (len) {
  95
  96     /* --- Do the write --- */
  97
  98     if (base + len <= CHAN_BUFSZ)
  99       w = write(fd, c->buf + base, len);
 100     else {
 101       struct iovec iov[2];
 102       iov[0].iov_base = c->buf + base;
 103       iov[0].iov_len = CHAN_BUFSZ - base;
 104       iov[1].iov_base = c->buf;
 105       iov[1].iov_len = len - iov[0].iov_len;
 106       w = writev(fd, iov, 2);
 107     }
 108
 109     /* --- Sift through the results --- */
 110
 111     if (w < 0) {
 112       if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
 113         return;
 114       goto close;
 115     }
 116     else if (w == 0)
 117       goto close;
 118     else if (c->len == CHAN_BUFSZ && !(c->f & CHANF_CLOSE))
 119       sel_addfile(&c->r);
 120     c->len -= w;
 121   }
 122   if (c->len == 0)
 123     sel_rmfile(&c->w);
 124
 125   /* --- Close the output end if necessary --- */
 126
 127   if (c->len == 0) {
 128     c->base = 0;
 129     if (c->f & CHANF_CLOSE)
 130       c->func(c->p);
 131   }
 132   return;
 133
 134   /* --- Force a close if an error occurred --- */
 135
 136 close:
 137   chan_close(c);
 138   c->func(c->p);
 139 }
 140
 141 /* --- @readchan@ --- *
 142  *
 143  * Arguments:   @int fd@ = file descriptor to read from
 144  *              @unsigned mode@ = what the descriptor is ready for
 145  *              @void *vp@ = pointer to channel block
 146  *
 147  * Returns:     ---
 148  *
 149  * Use:         Reads from a channel.
 150  */
 151
 152 static void readchan(int fd, unsigned mode, void *vp)
 153 {
 154   chan *c = vp;
 155   int r;
 156   unsigned base = (c->base + c->len) & (CHAN_BUFSZ - 1);
 157   unsigned len = CHAN_BUFSZ - c->len;
 158
 159   /* --- Do the read --- */
 160
 161   if (base + len <= CHAN_BUFSZ)
 162     r = read(fd, c->buf + base, len);
 163   else {
 164     struct iovec iov[2];
 165     iov[0].iov_base = c->buf + base;
 166     iov[0].iov_len = CHAN_BUFSZ - base;
 167     iov[1].iov_base = c->buf;
 168     iov[1].iov_len = len - iov[0].iov_len;
 169     r = readv(fd, iov, 2);
 170   }
 171
 172   /* --- Sift through the results --- */
 173
 174   if (r < 0) {
 175     if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
 176       return;
 177     goto close;
 178   }
 179   else if (r == 0)
 180     goto close;
 181   else if (c->len == 0 && (c->f & CHANF_READY)) {
 182     sel_addfile(&c->w);
 183     sel_force(&c->w);
 184   }
 185   c->len += r;
 186   if (c->len == CHAN_BUFSZ)
 187     sel_rmfile(&c->r);
 188   return;
 189
 190   /* --- Close the read end of the channel --- */
 191
 192 close:
 193   c->f |= CHANF_CLOSE;
 194   if (!c->len && (c->f & CHANF_READY)) {
 195     sel_addfile(&c->w);
 196     sel_force(&c->w);
 197   }
 198   sel_rmfile(&c->r);
 199 }
 200
 201 /* --- @chan_close@ --- *
 202  *
 203  * Arguments:   @chan *c@ = pointer to channel
 204  *
 205  * Returns:     ---
 206  *
 207  * Use:         Closes down a channel prematurely.
 208  */
 209
 210 void chan_close(chan *c)
 211 {
 212   if (!(c->f & CHANF_CLOSE) && c->len != CHAN_BUFSZ)
 213     sel_rmfile(&c->r);
 214   if ((c->f & CHANF_READY) && c->len != 0)
 215     sel_rmfile(&c->w);
 216 }
 217
 218 /* --- @chan_dest@ --- *
 219  *
 220  * Arguments:   @chan *c@ = pointer to channel
 221  *              @int fd@ = destination file descriptor for channel
 222  *
 223  * Returns:     ---
 224  *
 225  * Use:         Sets the channel's destination so it knows where to put
 226  *              data.
 227  */
 228
 229 void chan_dest(chan *c, int fd)
 230 {
 231   if (c->f & CHANF_READY)
 232     return;
 233   sel_initfile(sel, &c->w, fd, SEL_WRITE, writechan, c);
 234   if (c->len || (c->f & CHANF_CLOSE)) {
 235     sel_addfile(&c->w);
 236     sel_force(&c->w);
 237   }
 238   c->f |= CHANF_READY;
 239 }
 240
 241 /* --- @chan_open@ --- *
 242  *
 243  * Arguments:   @chan *c@ = pointer to channel to open
 244  *              @int from, to@ = source and destination file descriptors
 245  *              @void (*func)(void *p)@ = function to call on closure
 246  *              @void *p@ = argument to pass to function
 247  *
 248  * Returns:     ---
 249  *
 250  * Use:         Opens a channel.  Data is copied from the source to the
 251  *              destination.  The @to@ argument may be @-1@ if the file
 252  *              descriptor isn't known yet.
 253  */
 254
 255 void chan_open(chan *c, int from, int to,
 256                void (*func)(void */*p*/), void *p)
 257 {
 258   c->func = func;
 259   c->p = p;
 260
 261   c->base = 0;
 262   c->len = 0;
 263   c->f = 0;
 264
 265   sel_initfile(sel, &c->r, from, SEL_READ, readchan, c);
 266   sel_addfile(&c->r);
 267
 268   if (to != -1)
 269     chan_dest(c, to);
 270 }
 271
 272 /*----- That's all, folks -------------------------------------------------*/