mdw@git.distorted.org.uk Git - sgt/putty/blob - contrib/cygtermd/sel.h

   1 /*
   2  * sel.h: subsystem to manage the grubby details of a select loop,
   3  * buffering data to write, and performing the actual writes and
   4  * reads.
   5  */
   6
   7 #ifndef FIXME_SEL_H
   8 #define FIXME_SEL_H
   9
  10 typedef struct sel sel;
  11 typedef struct sel_wfd sel_wfd;
  12 typedef struct sel_rfd sel_rfd;
  13
  14 /*
  15  * Callback called when some data is written to a wfd. "bufsize"
  16  * is the remaining quantity of data buffered in that wfd.
  17  */
  18 typedef void (*sel_written_fn_t)(sel_wfd *wfd, size_t bufsize);
  19
  20 /*
  21  * Callback called when an error occurs on a wfd, preventing
  22  * further writing to it. "error" is the errno value.
  23  */
  24 typedef void (*sel_writeerr_fn_t)(sel_wfd *wfd, int error);
  25
  26 /*
  27  * Callback called when some data is read from an rfd. On EOF,
  28  * this will be called with len==0.
  29  */
  30 typedef void (*sel_readdata_fn_t)(sel_rfd *rfd, void *data, size_t len);
  31
  32 /*
  33  * Callback called when an error occurs on an rfd, preventing
  34  * further reading from it. "error" is the errno value.
  35  */
  36 typedef void (*sel_readerr_fn_t)(sel_rfd *rfd, int error);
  37
  38 /*
  39  * Create a sel structure, which will oversee a select loop.
  40  *
  41  * "ctx" is user-supplied data stored in the sel structure; it can
  42  * be read and written with sel_get_ctx() and sel_set_ctx().
  43  */
  44 sel *sel_new(void *ctx);
  45
  46 /*
  47  * Add a new fd for writing. Returns a sel_wfd which identifies
  48  * that fd in the sel structure, e.g. for putting data into its
  49  * output buffer.
  50  *
  51  * "ctx" is user-supplied data stored in the sel structure; it can
  52  * be read and written with sel_wfd_get_ctx() and sel_wfd_set_ctx().
  53  *
  54  * "written" and "writeerr" are called from the event loop when
  55  * things happen.
  56  *
  57  * The fd passed in can be -1, in which case it will be assumed to
  58  * be unwritable at all times. An actual fd can be passed in later
  59  * using sel_wfd_setfd.
  60  */
  61 sel_wfd *sel_wfd_add(sel *sel, int fd,
  62                      sel_written_fn_t written, sel_writeerr_fn_t writeerr,
  63                      void *ctx);
  64
  65 /*
  66  * Add a new fd for reading. Returns a sel_rfd which identifies
  67  * that fd in the sel structure.
  68  *
  69  * "ctx" is user-supplied data stored in the sel structure; it can
  70  * be read and written with sel_rfd_get_ctx() and sel_rfd_set_ctx().
  71  *
  72  * "readdata" and "readerr" are called from the event loop when
  73  * things happen. "ctx" is passed to both of them.
  74  */
  75 sel_rfd *sel_rfd_add(sel *sel, int fd,
  76                      sel_readdata_fn_t readdata, sel_readerr_fn_t readerr,
  77                      void *ctx);
  78
  79 /*
  80  * Write data into the output buffer of a wfd. Returns the new
  81  * size of the output buffer. (You can call it with len==0 if you
  82  * just want to know the buffer size; in that situation data==NULL
  83  * is also safe.)
  84  */
  85 size_t sel_write(sel_wfd *wfd, const void *data, size_t len);
  86
  87 /*
  88  * Freeze and unfreeze an rfd. When frozen, sel will temporarily
  89  * not attempt to read from it, but all its state is retained so
  90  * it can be conveniently unfrozen later. (You might use this
  91  * facility, for instance, if what you were doing with the
  92  * incoming data could only accept it at a certain rate: freeze
  93  * the rfd when you've got lots of backlog, and unfreeze it again
  94  * when things get calmer.)
  95  */
  96 void sel_rfd_freeze(sel_rfd *rfd);
  97 void sel_rfd_unfreeze(sel_rfd *rfd);
  98
  99 /*
 100  * Delete a wfd structure from its containing sel. Returns the
 101  * underlying fd, which the client may now consider itself to own
 102  * once more.
 103  */
 104 int sel_wfd_delete(sel_wfd *wfd);
 105
 106 /*
 107  * Delete an rfd structure from its containing sel. Returns the
 108  * underlying fd, which the client may now consider itself to own
 109  * once more.
 110  */
 111 int sel_rfd_delete(sel_rfd *rfd);
 112
 113 /*
 114  * NOT IMPLEMENTED YET: useful functions here might be ones which
 115  * enumerated all the wfds/rfds in a sel structure in some
 116  * fashion, so you could go through them and remove them all while
 117  * doing sensible things to them. Or, at the very least, just
 118  * return an arbitrary one of the wfds/rfds.
 119  */
 120
 121 /*
 122  * Free a sel structure and all its remaining wfds and rfds.
 123  */
 124 void sel_free(sel *sel);
 125
 126 /*
 127  * Read and write the ctx parameters in sel, sel_wfd and sel_rfd.
 128  */
 129 void *sel_get_ctx(sel *sel);
 130 void sel_set_ctx(sel *sel, void *ctx);
 131 void *sel_wfd_get_ctx(sel_wfd *wfd);
 132 void sel_wfd_set_ctx(sel_wfd *wfd, void *ctx);
 133 void *sel_rfd_get_ctx(sel_rfd *rfd);
 134 void sel_rfd_set_ctx(sel_rfd *rfd, void *ctx);
 135
 136 /*
 137  * Run one iteration of the sel event loop, calling callbacks as
 138  * necessary. Returns zero on success; in the event of a fatal
 139  * error, returns the errno value.
 140  *
 141  * "timeout" is a value in microseconds to limit the length of the
 142  * select call. Less than zero means to wait indefinitely.
 143  */
 144 int sel_iterate(sel *sel, long timeout);
 145
 146 /*
 147  * Change the underlying fd in a wfd. If set to -1, no write
 148  * attempts will take place and the wfd's buffer will simply store
 149  * everything passed to sel_write(). If later set to something
 150  * other than -1, all that buffered data will become eligible for
 151  * real writing.
 152  */
 153 void sel_wfd_setfd(sel_wfd *wfd, int fd);
 154
 155 /*
 156  * Change the underlying fd in a rfd. If set to -1, no read
 157  * attempts will take place.
 158  */
 159 void sel_rfd_setfd(sel_rfd *rfd, int fd);
 160
 161 #endif /* FIXME_SEL_H */