New feature: poll external file for console commands

The commit adds "-refreshfile" and "-refreshinterval" command-line
arguments. Every refreshinterval tics (or once a second if not
specified) a refreshfile is read and is evaluated if exists and not
empty. Then it is truncated.

This feature provides a facility for an external program to control
the game.

src/common/console/c_console.cpp

@@ -65,6 +65,7 @@
 #include "g_input.h"
 #include "c_commandbuffer.h"
 #include "vm.h"
+#include "m_argv.h"
 
 #define LEFTMARGIN 8
 #define RIGHTMARGIN 8
@@ -110,6 +111,9 @@ static int TopLine, InsertLine;
 
 static void ClearConsole ();
 
+static const char *RefreshFile = NULL;
+static int RefreshInterval = 0;
+
 struct GameAtExit
 {
 	GameAtExit(FString str) : Command(str) {}
@@ -235,6 +239,7 @@ void C_InitConback(FTextureID fallback, bool tile, double brightness)
 void C_InitConsole (int width, int height, bool ingame)
 {
 	int cwidth, cheight;
+	const char *v;
 
 	vidactive = ingame;
 	if (CurrentConsoleFont != NULL)
@@ -250,6 +255,18 @@ void C_InitConsole (int width, int height, bool ingame)
 	CmdLine.ConCols = ConWidth / cwidth;
 
 	if (conbuffer == NULL) conbuffer = new FConsoleBuffer;
+
+	v = Args->CheckValue ("-refreshfile");
+	if (v != NULL)
+	{
+		RefreshFile = v;
+		RefreshInterval = TICRATE;
+		v = Args->CheckValue ("-refreshinterval");
+		if (v != NULL && (atoi(v) != 0))
+		{
+			RefreshInterval = atoi(v);
+		}
+	}
 }
 
 //==========================================================================
@@ -534,9 +551,45 @@ void C_NewModeAdjust ()
 int consoletic = 0;
 void C_Ticker()
 {
+	FILE *refresh;
+	static char refresh_cmd[PATH_MAX + 6];
 	static int lasttic = 0;
+	long filesize = 1;
 	consoletic++;
 
+	if (RefreshInterval > 0 && (consoletic % RefreshInterval) == 0)
+	{
+		refresh = fopen (RefreshFile, "r");
+		if (refresh != NULL)
+		{
+			if (fseek (refresh, 0, SEEK_END) == 0)
+			{
+				filesize = ftell (refresh);
+			}
+			else
+			{
+				filesize = 1;
+			}
+			fclose (refresh);
+
+			if (!strlen (refresh_cmd)) {
+				strcpy (refresh_cmd, "exec ");
+				strcat (refresh_cmd, RefreshFile);
+			}
+
+			if (filesize > 0)
+			{
+				C_DoCommand (refresh_cmd);
+
+				// Truncate the file
+				refresh = fopen (RefreshFile, "w");
+				if (refresh != NULL) {
+					fclose (refresh);
+				}
+			}
+		}
+	}
+
 	if (lasttic == 0)
 		lasttic = consoletic - 1;