[vga] a few more vga character writing functions

.gitignore

@@ -2,3 +2,4 @@ kernel
 *.o
 bootdisk.img
 initrd
+*.swp

core/vga.c

@@ -66,6 +66,43 @@ cls() {
 	move_csr();
 }
 
+/*
+ * placech
+ * Put a character in a particular cell with the given attributes.
+ */
+void
+placech(
+		unsigned char c,
+		int x,
+		int y,
+		int attr
+	   ) {
+	unsigned short *where;
+	unsigned att = attr << 8;
+	where = textmemptr + (y * 80 + x);
+	*where = c | att;
+}
+
+/*
+ * writechf
+ * Force write the given character.
+ */
+void
+writechf(
+		unsigned char c
+		) {
+	placech(c, csr_x, csr_y, attrib);
+	csr_x++;
+	if (csr_x >= 80) {
+		csr_x = 0;
+		++csr_y;
+	}
+	scroll();
+	move_csr();
+}
+
+
+
 /*
  * writech
  * Write a character to the screen.

include/system.h

@@ -48,6 +48,8 @@ extern void puts(char *str);
 extern void settextcolor(unsigned char forecolor, unsigned char backcolor);
 extern void resettextcolor();
 extern void init_video();
+extern void placech(unsigned char c, int x, int y, int attr);
+extern void writechf(unsigned char c);
 extern void writech(unsigned char c);
 
 /* GDT */