Rewrite much of client's playing phase code:

(EOF_COOKIE, INTR_COOKIE, input_fd, send_intr, recv_output)
(recv_input, intr, play): New playing phase code.  No native Windows
support yet.  Sends just one EOF cookie on EOF on standard input
instead of up to three.  Old servers (before recvclient.c rev. 1.16)
fail to terminate the session when they receive an EOF cookie at an
argument prompt.  The session then hangs; use SIGINT to get out.  No
longer blocks on sending input, which could deadlock the session.
Closes #827090.  Fixes error handling for select().  Fixes race
condition that could cause server output to be discarded on EOF on
standard input.
(main): Replace old playing phase code by a call to play().
(intr, sock, interrupt, handleintr): Replaced by play(), remove.
[_WIN32] (hStdIn): Ditto.
(auxfp): New.
(servercmd, prompt, doexecute): Remove parameter auxfi, use auxfp.
(eight_bit_clean): Move to servcmd.c.
(servercmd): Work on a single non-C_DATA line instead of getting lines
from an ioqueue.
(servercmd, output, screen, outch): Deal with all ids in servercmd()
rather than some there and some in output().  Don't treat C_NOECHO,
C_ABORT, C_CMDERR, C_BADCMD specially.  Fix C_FLASH and C_EXIT to
ignore redirections; they used to ignore them only for some parts.
Replace output() by outch(), fold screen into outch().
(servercmd): Truncate long prompts and telegram infos to prevent
buffer overflow.
(prompt): Use new parameters code, prompt, teles instead of global
variables mode, the_prompt, num_teles.
(num_teles, the_prompt, mode, nbtu, nmin): Remove.
(prompt): Don't write an empty line before argument prompts to auxfp.
(servercmd): Don't strip newline from redirections and execute,
doredir(), dopipe() and doexecute() need it now.
(doredir, dopipe, doexecute): Use new seen_input() instead of gettag().
(doexecute): Set input_fd and leave reading the script file to play().
(serverio, termio, sendeof): Replaced by play(), remove.
(LBUF_LEN_MAX, lbuf, lbuf_init, lbuf_len, lbuf_full, lbuf_line)
(lbuf_putc): New.
(RING_SIZE, ring, ring_init, ring_len, ring_space, ring_peek)
(ring_getc, ring_putc, ring_putm, ring_discard, ring_search)
(ring_from_file, ring_to_file): New.
(clear_recent_input, save_input, seen_input): New.
(MAX): New.
(ioqueue, io, ioq_init, ioq_dequeue, ioq_read, ioq_write, ioq_qsize)
(ioq_drain, ioq_gets, ioqtobuf, enqueuecc, dequeuecc): Unused, remove.
(QEMPTY, qelem, insque, remque, initque): Unused, remove.
(tagstruct, taglist, io_init, gettag): Unused, remove.

src/client/ringbuf.h

@@ -0,0 +1,67 @@
+/*
+ *  Empire - A multi-player, client/server Internet based war game.
+ *  Copyright (C) 1986-2007, Dave Pare, Jeff Bailey, Thomas Ruschak,
+ *                           Ken Stevens, Steve McClure
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *  ---
+ *
+ *  See files README, COPYING and CREDITS in the root of the source
+ *  tree for related information and legal notices.  It is expected
+ *  that future projects/authors will amend these files as needed.
+ *
+ *  ---
+ *
+ *  ringbuf.h: Simple ring buffer
+ * 
+ *  Known contributors to this file:
+ *     Markus Armbruster, 2007
+ */
+
+#ifndef RINGBUF_H
+#define RINGBUF_H
+
+#include <stddef.h>
+
+#define RING_SIZE 4096
+
+/* Ring buffer, consumer reads, producer writes */
+struct ring {
+    /* All members are private! */
+    /*
+     * Consumer reads from buf[cons % RING_SIZE], incrementing cons
+     * Produces writes to buf[prod % RING_SIZE], incrementing prod
+     * prod == cons: empty
+     * prod == cons + RING_SIZE: full
+     * invariant: prod - cons <= RING_SIZE
+     */
+    unsigned cons, prod;
+    unsigned char buf[RING_SIZE];
+};
+
+extern void ring_init(struct ring *);
+extern int ring_len(struct ring *);
+extern int ring_space(struct ring *);
+extern int ring_peek(struct ring *, int);
+extern int ring_getc(struct ring *);
+extern int ring_putc(struct ring *, unsigned char);
+extern int ring_putm(struct ring *, void *, size_t);
+extern void ring_discard(struct ring *, int);
+extern int ring_search(struct ring *, char *);
+extern int ring_from_file(struct ring *, int fd);
+extern int ring_to_file(struct ring *, int fd);
+
+#endif