From 2941ac6b8ecc1fd96b886219795f5d7e55bb85d8 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 29 May 2023 23:32:41 +0100
Subject: Initial import

---
 src/Makefile | 25 +++++++++++++++++++++++++
 src/main.c   | 33 +++++++++++++++++++++++++++++++++
 src/vga.c    | 24 ++++++++++++++++++++++++
 src/vga.h    |  9 +++++++++
 4 files changed, 91 insertions(+)
 create mode 100644 src/Makefile
 create mode 100644 src/main.c
 create mode 100644 src/vga.c
 create mode 100644 src/vga.h

(limited to 'src')

diff --git a/src/Makefile b/src/Makefile
new file mode 100644
index 0000000..94b83eb
--- /dev/null
+++ b/src/Makefile
@@ -0,0 +1,25 @@
+BIN	:= ../game.exe
+CC	:= i586-pc-msdosdjgpp-gcc
+CFLAGS	:= -I. -c -Wall -pedantic -O2 -march=i386
+LDFLAGS := -s
+
+SRCS	:= $(wildcard *.c)
+OBJS	:= $(SRCS:.c=.o)
+
+all: $(BIN)
+
+$(BIN): $(OBJS)
+	$(CC) $(LDFLAGS) $(OBJS) $(LIBS) -o $@
+
+.c.o:
+	$(CC) $(CFLAGS) $< -o $@
+
+clean:
+	rm -f $(BIN) *.o Makefile.deps
+
+Makefile.deps: $(SRCS)
+	$(CC) $(CFLAGS) -MM *.[ch] > Makefile.deps
+
+.PHONY: all clean
+
+include Makefile.deps
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..5b315df
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,33 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <conio.h>
+
+#include "vga.h"
+
+int main(int argc, char *argv[])
+{
+    /* set VGA 320x200, 256 col */
+    set_mode(0x13);
+
+    uint8_t *screen = open_framebuffer();
+    if (!screen)
+    {
+        fprintf(stderr, "ERROR: failed to open the framebuffer\n");
+        return 1;
+    }
+
+    for (int i = 0; i < 320 * 200 * 10; i++)
+        screen[rand() % (320 * 200)] = rand() % 255;
+
+    printf("Hello DOS!\n");
+
+    getch();
+
+    set_mode(3);
+    close_framebuffer();
+
+    return 0;
+}
diff --git a/src/vga.c b/src/vga.c
new file mode 100644
index 0000000..5badd82
--- /dev/null
+++ b/src/vga.c
@@ -0,0 +1,24 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <dpmi.h>
+#include <sys/nearptr.h>
+
+uint8_t *open_framebuffer()
+{
+    if (__djgpp_nearptr_enable() == 0)
+        return NULL;
+
+    return (uint8_t *)(0xa0000 + __djgpp_conventional_base);
+}
+
+void close_framebuffer()
+{
+    __djgpp_nearptr_disable();
+}
+
+void set_mode(uint8_t mode)
+{
+    __dpmi_regs regs = { 0 };
+    regs.x.ax = mode;
+    __dpmi_int(0x10, &regs);
+}
diff --git a/src/vga.h b/src/vga.h
new file mode 100644
index 0000000..f35e6dd
--- /dev/null
+++ b/src/vga.h
@@ -0,0 +1,9 @@
+#ifndef _VGA_H
+#define _VGA_H
+
+uint8_t *open_framebuffer();
+void close_framebuffer();
+
+void set_mode(uint8_t mode);
+
+#endif // _VGA_H
-- 
cgit v1.2.3