[PATCH 12/17] Add server.h and server.c

[David Malcolm <dmalcolm at redhat dot com>]

This patch adds a "server" abstract base class for listening
on a port, for use by the later patches to implement an LSP server.

It's largely adapted from examples in glibc's docs.  I suspect that
I've introduced platform-specific assumptions (and that it may need some
extra configure tests for the extra functionality), but this part of
the kit is just a proof-of-concept.

gcc/ChangeLog:
	* Makefile.in (OBJS): Add server.o.
	* server.c: New file.
	* server.h: New file.
---
 gcc/Makefile.in |   1 +
 gcc/server.c    | 152 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gcc/server.h    |  46 +++++++++++++++++
 3 files changed, 199 insertions(+)
 create mode 100644 gcc/server.c
 create mode 100644 gcc/server.h

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 77ecbd6..4e60bc0 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1454,6 +1454,7 @@ OBJS = \
 	sel-sched.o \
 	selftest-rtl.o \
 	selftest-run-tests.o \
+	server.o \
 	sese.o \
 	shrink-wrap.o \
 	simplify-rtx.o \
diff --git a/gcc/server.c b/gcc/server.c
new file mode 100644
index 0000000..871a95f
--- /dev/null
+++ b/gcc/server.c
@@ -0,0 +1,152 @@
+/* Abstract server implementation.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC 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 3, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "server.h"
+
+/* adapted from GNU libc docs.  */
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+
+#define MAXMSG  512
+
+static int
+make_socket (uint16_t port)
+{
+  int sock;
+  struct sockaddr_in name;
+
+  /* Create the socket. */
+  sock = socket (PF_INET, SOCK_STREAM, 0);
+  if (sock < 0)
+    {
+      perror ("socket");
+      exit (EXIT_FAILURE);
+    }
+
+  /* Give the socket a name. */
+  name.sin_family = AF_INET;
+  name.sin_port = htons (port);
+  name.sin_addr.s_addr = htonl (INADDR_ANY);
+  if (bind (sock, (struct sockaddr *) &name, sizeof (name)) < 0)
+    {
+      perror ("bind");
+      exit (EXIT_FAILURE);
+    }
+
+  return sock;
+}
+
+/* Serve on PORT.  */
+
+void
+server::serve (int port)
+{
+  int sock;
+  fd_set active_fd_set, read_fd_set;
+  int i;
+  struct sockaddr_in clientname;
+  socklen_t size;
+
+  /* Create the socket and set it up to accept connections. */
+  sock = make_socket (port);
+  if (listen (sock, 1) < 0)
+    {
+      perror ("listen");
+      exit (EXIT_FAILURE);
+    }
+
+  /* Initialize the set of active sockets. */
+  FD_ZERO (&active_fd_set);
+  FD_SET (sock, &active_fd_set);
+
+  while (1)
+    {
+      /* Block until input arrives on one or more active sockets. */
+      read_fd_set = active_fd_set;
+      if (select (FD_SETSIZE, &read_fd_set, NULL, NULL, NULL) < 0)
+	{
+	  perror ("select");
+	  exit (EXIT_FAILURE);
+	}
+
+      /* Service all the sockets with input pending. */
+      for (i = 0; i < FD_SETSIZE; ++i)
+	if (FD_ISSET (i, &read_fd_set))
+	  {
+	    if (i == sock)
+	      {
+		/* Connection request on original socket. */
+		int new_;
+		size = sizeof (clientname);
+		new_ = accept (sock,
+			       (struct sockaddr *) &clientname,
+			       &size);
+		if (new_ < 0)
+		  {
+		    perror ("accept");
+		    exit (EXIT_FAILURE);
+		  }
+		fprintf (stderr,
+			 "Server: connect from host %s, port %hd.\n",
+			 inet_ntoa (clientname.sin_addr),
+			 ntohs (clientname.sin_port));
+		FD_SET (new_, &active_fd_set);
+	      }
+	    else
+	      {
+		/* Data arriving on an already-connected socket. */
+		if (read_from_client (file_descriptor (i)) < 0)
+		  {
+		    close (i);
+		    FD_CLR (i, &active_fd_set);
+		  }
+	      }
+	  }
+    }
+}
+
+int
+server::read_from_client (file_descriptor fd)
+{
+  char buffer[MAXMSG];
+  int nbytes;
+
+  nbytes = read (fd.m_fd, buffer, MAXMSG);
+  if (nbytes < 0)
+    {
+      /* Read error. */
+      perror ("read");
+      exit (EXIT_FAILURE);
+    }
+  else if (nbytes == 0)
+    /* End-of-file. */
+    return -1;
+  else
+    {
+      /* Data read. */
+      on_read (fd, nbytes, buffer);
+      return 0;
+    }
+}
diff --git a/gcc/server.h b/gcc/server.h
new file mode 100644
index 0000000..3bcf9f6e
--- /dev/null
+++ b/gcc/server.h
@@ -0,0 +1,46 @@
+/* Abstract server implementation.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC 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 3, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_SERVER_H
+#define GCC_SERVER_H
+
+/* Wrapper aroung "int" for file descriptors.  */
+
+struct file_descriptor
+{
+  explicit file_descriptor (int fd) : m_fd (fd) {}
+
+  int m_fd;
+};
+
+/* Abstract base class for implementing a server.  */
+
+class server
+{
+ public:
+  virtual ~server () {}
+  void serve (int port);
+
+  virtual void on_read (file_descriptor fd, size_t length, const char *buf) = 0;
+
+ private:
+  int read_from_client (file_descriptor fd);
+};
+
+#endif  /* GCC_SERVER_H  */
-- 
1.8.5.3