Launcher feature

.gitignore

@@ -1,3 +1,5 @@
 *.[Ee][Xx][Ee]
 *.[Oo][Bb][Jj]
 *.[Cc][Oo][Mm]
+*.[Mm][Aa][Pp]
+*.[Ll][Ss][Tt]

README.md

@@ -5,4 +5,6 @@ It is written in C to compile with Borland Turbo C++ 3.0.
 
 You can probably get it to work with other MS-DOS C compilers without too much trouble.
 
+It also contains an assembly language component compiled with NASM (LAUNCHER.COM). This attempts to reduce memory consumption to maximise the amount of conventional memory available to programs run from the menu. Without LAUNCHER.COM, DOSMENU.COM will consume 66KB of conventional memory, whereas using LAUNCHER.COM the consumption is reduced to only 4KB. Note that LAUNCHER.COM is optional, and DOSMENU.COM will still work without it being present, just at the cost of more memory consumption.
+
 ![Screenshot](./screenshot.png?raw=true "Screenshot")

compile.bat

@@ -1,3 +1,4 @@
 @echo off
 cls
-tcc -mt -lt dosmenu.c
+nasm -fbin -o launcher.com -l launcher.lst launcher.asm
+tcc -mt -lt -M dosmenu.c

dosmenu.c

@@ -9,6 +9,8 @@
 #define true 1
 #define false 0
 
+#define LAUNCHER_VECTOR 0x88
+
 void abortMsg(char *msg);
 
 void * xmalloc(size_t size) {
@@ -18,6 +20,71 @@ void * xmalloc(size_t size) {
         return r;
 }
 
+char * xstrdup(char *str) {
+	char *copy = xmalloc(strlen(str)+1);
+	strcpy(copy,str);
+	return copy;
+}
+
+char * xstrcat(char *a, char *b) {
+	int na, nb;
+	char *r;
+
+	na = strlen(a);
+	nb = strlen(b);
+	r = xmalloc(na+nb+1);
+	r[0] = 0;
+	strcat(r, a);
+	strcat(r, b);
+	return r;
+}
+
+int fileExistenceCheck(char *fname) {
+	FILE *fh = fopen(fname,"r");
+	if (fh == NULL)
+		return false;
+	fclose(fh);
+	return true;
+}
+
+int checkLauncherInstalled() {
+	return getvect(LAUNCHER_VECTOR) != 0;
+}
+
+int callLauncher(char *exec, char *args, int pause) {
+	union REGS in;
+	memset(&in,0,sizeof(union REGS));
+	in.x.ax = 0x1369;
+	in.x.bx = (int)exec;
+	in.x.cx = pause;
+	in.x.si = (int)args;
+	return int86(LAUNCHER_VECTOR, &in, &in);
+}
+
+// Split cmd into command line and argument
+void launcherSystem(char *line, int pause) {
+	char *comspec, *arg;
+	int rc;
+
+	comspec = getenv("COMSPEC");
+	if (comspec == NULL || strlen(comspec) == 0)
+		abortMsg("COMSPEC not set");
+	if (!fileExistenceCheck(comspec))
+		abortMsg("Command interpreter (COMSPEC) not found");
+
+	arg = xstrcat("/C ",line);
+	if (strlen(arg) > 126) {
+		free(arg);
+		abortMsg("Command line too long");
+	}
+
+	rc = callLauncher(comspec,arg,pause);
+	free(arg);
+	if (rc != 0)
+		abortMsg("Launcher invocation failed");
+	exit(0);
+}
+
 void resetVideo(void) {
         textmode(C80);
         textcolor(LIGHTGRAY);
@@ -46,17 +113,16 @@ struct section {
 
 struct section * newSection(char *name) {
         struct section * s = (struct section*) xmalloc(sizeof(struct section));
-        s->name = strdup(name);
+        s->name = xstrdup(name);
         s->settings = NULL;
         s->next = NULL;
         return s;
 }
 
-
 struct setting * newSetting(char *name, char* value) {
         struct setting * s = (struct setting*) xmalloc(sizeof(struct setting));
-        s->name = strdup(name);
-        s->value = strdup(value);
+        s->name = xstrdup(name);
+        s->value = xstrdup(value);
         s->next = NULL;
         return s;
 }
@@ -329,6 +395,16 @@ int main(int argc, char**argv) {
         saveCWD = xmalloc(256);
         getcwd(saveCWD, 256);
 
+	// The launcher is an assembly language program used to reduce
+	// memory consumption. If we find it run it instead of ourselves.
+	if (fileExistenceCheck("DOSMENU.COM") &&
+		!checkLauncherInstalled() &&
+		fileExistenceCheck("LAUNCHER.COM")) {
+			execl("LAUNCHER.COM","LAUNCHER.COM",NULL);
+			// If we get to here, launcher failed
+	}
+
+	drainInput();
         resetVideo();
         _setcursortype(_NOCURSOR);
         sections = loadConfig();
@@ -392,9 +468,20 @@ int main(int argc, char**argv) {
                         struct section * nth = getSectionByIndex(sections, selected);
                         char *dir = getSettingInSection(nth, "dir");
                         char *run = getSettingInSection(nth, "run");
+			char *pause = getSettingInSection(nth, "pause");
+
                         if (dir != NULL)
                                 chdir(dir);
-                        system(run);
+			if (checkLauncherInstalled())
+				launcherSystem(run, strcmp(pause,"1")==0);
+			else
+				system(run);
+			if (strcmp(pause,"1")==0) {
+				drainInput();
+				printf("Press any key to continue...");
+				readScanCode();
+				printf("\n");
+			}
                         chdir(saveCWD);
                         resetVideo();
                         _setcursortype(_NOCURSOR);

dosmenu.cfg

@@ -17,3 +17,13 @@ run=KEEN2.EXE
 [Keen 3]
 dir=C:\GAMES\KEEN3
 run=KEEN3.EXE
+[TEST]
+run=Z:\COMMAND.COM
+[TEST2]
+run=c:\zutl\dumpargs.com foo
+pause=1
+[DEBUG]
+run=c:\debug.exe
+[MEM]
+run=c:\dos\mem.exe
+pause=1