git.distorted.org.uk Git - u/mdw/putty/blob - unix/uxsel.c

   1 /*
   2  * uxsel.c
   3  *
   4  * This module is a sort of all-purpose interchange for file
   5  * descriptors. At one end it talks to uxnet.c and pty.c and
   6  * anything else which might have one or more fds that need
   7  * select()-type things doing to them during an extended program
   8  * run; at the other end it talks to pterm.c or uxplink.c or
   9  * anything else which might have its own means of actually doing
  10  * those select()-type things.
  11  */
  12
  13 #include <assert.h>
  14
  15 #include "putty.h"
  16 #include "tree234.h"
  17
  18 struct fd {
  19     int fd;
  20     int rwx;                           /* 4=except 2=write 1=read */
  21     uxsel_callback_fn callback;
  22     int id;                            /* for uxsel_input_remove */
  23 };
  24
  25 static tree234 *fds;
  26
  27 static int uxsel_fd_cmp(void *av, void *bv)
  28 {
  29     struct fd *a = (struct fd *)av;
  30     struct fd *b = (struct fd *)bv;
  31     if (a->fd < b->fd)
  32         return -1;
  33     if (a->fd > b->fd)
  34         return +1;
  35     return 0;
  36 }
  37 static int uxsel_fd_findcmp(void *av, void *bv)
  38 {
  39     int *a = (int *)av;
  40     struct fd *b = (struct fd *)bv;
  41     if (*a < b->fd)
  42         return -1;
  43     if (*a > b->fd)
  44         return +1;
  45     return 0;
  46 }
  47
  48 void uxsel_init(void)
  49 {
  50     fds = newtree234(uxsel_fd_cmp);
  51 }
  52
  53 /*
  54  * Here is the interface to fd-supplying modules. They supply an
  55  * fd, a set of read/write/execute states, and a callback function
  56  * for when the fd satisfies one of those states. Repeated calls to
  57  * uxsel_set on the same fd are perfectly legal and serve to change
  58  * the rwx state (typically you only want to select an fd for
  59  * writing when you actually have pending data you want to write to
  60  * it!).
  61  */
  62
  63 void uxsel_set(int fd, int rwx, uxsel_callback_fn callback)
  64 {
  65     struct fd *newfd = snew(struct fd);
  66     struct fd *oldfd;
  67
  68     newfd->fd = fd;
  69     newfd->rwx = rwx;
  70     newfd->callback = callback;
  71
  72     oldfd = find234(fds, newfd, NULL);
  73     if (oldfd) {
  74         uxsel_input_remove(oldfd->id);
  75         del234(fds, oldfd);
  76         sfree(oldfd);
  77     }
  78
  79     add234(fds, newfd);
  80     newfd->id = uxsel_input_add(fd, rwx);
  81 }
  82
  83 void uxsel_del(int fd)
  84 {
  85     struct fd *oldfd = find234(fds, &fd, uxsel_fd_findcmp);
  86     if (oldfd) {
  87         uxsel_input_remove(oldfd->id);
  88         del234(fds, oldfd);
  89         sfree(oldfd);
  90     }
  91 }
  92
  93 /*
  94  * And here is the interface to select-functionality-supplying
  95  * modules.
  96  */
  97
  98 int next_fd(int *state, int *rwx)
  99 {
 100     struct fd *fd;
 101     fd = index234(fds, (*state)++);
 102     if (fd) {
 103         *rwx = fd->rwx;
 104         return fd->fd;
 105     } else
 106         return -1;
 107 }
 108
 109 int first_fd(int *state, int *rwx)
 110 {
 111     *state = 0;
 112     return next_fd(state, rwx);
 113 }
 114
 115 int select_result(int fd, int event)
 116 {
 117     struct fd *fdstruct = find234(fds, &fd, uxsel_fd_findcmp);
 118     /*
 119      * Apparently this can sometimes be NULL. Can't see how, but I
 120      * assume it means I need to ignore the event since it's on an
 121      * fd I've stopped being interested in. Sigh.
 122      */
 123     if (fdstruct)
 124         return fdstruct->callback(fd, event);
 125     else
 126         return 1;
 127 }