Add (soft) video abstraction library.

src/video.c

@@ -0,0 +1,28 @@
+#include "video.h"
+
+#include <stdint.h>
+
+static char *const VIDEO_MEMORY = (char *)0xd000;
+static uint16_t offset = 0;
+
+void video_putchar(char c) {
+    if (c == '\n' || c == '\r') {
+        offset += 80 - (offset % 80);
+
+    } else if (c == '\t') {
+        offset += 8 - offset % 8;
+    } else {
+        *(VIDEO_MEMORY + offset++) = c;
+    }
+
+    offset = offset % 2000;
+}
+
+void video_put(uint8_t x, uint8_t y, char c) {
+    if (x >= 80)
+        return;
+    if (y >= 25)
+        return;
+
+    *(VIDEO_MEMORY + x + y * 80) = c;
+}

src/video.h

@@ -0,0 +1,10 @@
+#ifndef CEDA_PRINT_H
+#define CEDA_PRINT_H
+
+#include <stdint.h>
+
+void video_cls(void);
+void video_put(uint8_t x, uint8_t y, char c);
+void video_putchar(char c);
+
+#endif // CEDA_PRINT_H

src/video_a.asm

@@ -0,0 +1,26 @@
+SECTION code
+PUBLIC _video_cls
+
+_video_cls:
+    push    af
+    push    bc
+    push    de
+    push    hl
+
+    ld      hl,$d000
+    ld      de,2000
+    ld      c,$20
+_video_cls_loop:
+    ld      (hl),c
+    inc     hl
+    dec     de
+    ld      a,d
+    or      e
+    jp      nz,_video_cls_loop
+
+    pop     hl
+    pop     de
+    pop     bc
+    pop     af
+
+    ret