contrib/gdb-6.2.1/gdb/event-loop.h

   1 /* Definitions used by the GDB event loop.
   2    Copyright 1999, 2000 Free Software Foundation, Inc.
   3    Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 /* An event loop listens for events from multiple event sources. When
  23    an event arrives, it is queued and processed by calling the
  24    appropriate event handler. The event loop then continues to listen
  25    for more events. An event loop completes when there are no event
  26    sources to listen on.  External event sources can be plugged into
  27    the loop.
  28
  29    There are 3 main components:
  30    - a list of file descriptors to be monitored, GDB_NOTIFIER.
  31    - a list of events that have occurred, EVENT_QUEUE.
  32    - a list of signal handling functions, SIGHANDLER_LIST.
  33
  34    GDB_NOTIFIER keeps track of the event sources. Event sources for
  35    gdb are currently the UI and the target.  Gdb communicates with the
  36    command line user interface via the readline library and usually
  37    communicates with remote targets via a serial port. Serial ports
  38    are represented in GDB as file descriptors and select/poll calls.
  39    For native targets instead, the communication consists of calls to
  40    ptrace and waits (via signals) or calls to poll/select (via file
  41    descriptors). In the current gdb, the code handling events related
  42    to the target resides in the wait_for_inferior function and in
  43    various target specific files (*-tdep.c).
  44
  45    EVENT_QUEUE keeps track of the events that have happened during the
  46    last iteration of the event loop, and need to be processed.  An
  47    event is represented by a procedure to be invoked in order to
  48    process the event.  The queue is scanned head to tail.  If the
  49    event of interest is a change of state in a file descriptor, then a
  50    call to poll or select will be made to detect it.
  51
  52    If the events generate signals, they are also queued by special
  53    functions that are invoked through traditional signal handlers.
  54    The actions to be taken is response to such events will be executed
  55    when the SIGHANDLER_LIST is scanned, the next time through the
  56    infinite loop.
  57
  58    Corollary tasks are the creation and deletion of event sources. */
  59
  60 typedef void *gdb_client_data;
  61 struct async_signal_handler;
  62 typedef void (handler_func) (int, gdb_client_data);
  63 typedef void (sig_handler_func) (gdb_client_data);
  64 typedef void (timer_handler_func) (gdb_client_data);
  65
  66 /* Where to add an event onto the event queue, by queue_event. */
  67 typedef enum
  68   {
  69     /* Add at tail of queue. It will be processed in first in first
  70        out order. */
  71     TAIL,
  72     /* Add at head of queue. It will be processed in last in first out
  73        order. */
  74     HEAD
  75   }
  76 queue_position;
  77
  78 /* Tell create_file_handler what events we are interested in.
  79    This is used by the select version of the event loop. */
  80
  81 #define GDB_READABLE    (1<<1)
  82 #define GDB_WRITABLE    (1<<2)
  83 #define GDB_EXCEPTION   (1<<3)
  84
  85 /* Exported functions from event-loop.c */
  86
  87 extern void start_event_loop (void);
  88 extern int gdb_do_one_event (void *data);
  89 extern void delete_file_handler (int fd);
  90 extern void add_file_handler (int fd, handler_func * proc, gdb_client_data client_data);
  91 extern void mark_async_signal_handler (struct async_signal_handler *async_handler_ptr);
  92 extern struct async_signal_handler *
  93   create_async_signal_handler (sig_handler_func * proc, gdb_client_data client_data);
  94 extern void delete_async_signal_handler (struct async_signal_handler **async_handler_ptr);
  95 extern int create_timer (int milliseconds, timer_handler_func * proc, gdb_client_data client_data);
  96 extern void delete_timer (int id);