RLE blitter, plus RLE encoding and decoding tools

[bootsplash] / bootsplash.asm

diff --git a/bootsplash.asm b/bootsplash.asm
index 26f557a..a6a552a 100644 (file)
--- a/bootsplash.asm
+++ b/bootsplash.asm
@@ -37,9 +37,9 @@ start:
 
        ; expects string ptr in ax
 printstr:
-       mov bx, ax
-.loop: mov al, [bx]
-       inc bx
+       mov si, ax
+.loop: mov al, [si]
+       inc si
        test al, al
        jz .done
        mov ah, 0eh
@@ -49,7 +49,7 @@ printstr:
 .done: ret
 
 str_load_fail db "Failed to load second stage!",0
-str_foo db "Loaded 2nd stage boot loader",0
+str_booting db "Booting ...",0
 
 
        times 510-($-$$) db 0
@@ -57,30 +57,66 @@ str_foo db "Loaded 2nd stage boot loader",0
 
        ; start of the second stage
 stage2_start:
+       call splash
+
+       xor ax, ax
+       mov es, ax
+       mov ds, ax
+
+       mov ax, str_booting
+       call printstr
+
+       cli
+.hang: hlt
+       jmp .hang
+
+       ; splash screen effect
+splash:
        mov ax, 13h
        int 10h
 
        mov ax, 0a000h
        mov es, ax
        xor di, di
-       mov cx, 32000
-       mov ax, 0505h
-       rep stosw
+
+       mov ax, pic
+       shr ax, 4
+       mov ds, ax
+       xor si, si
+
+       mov cx, 64000
+       call decode_rle
 
        call waitkey
 
        mov ax, 3
        int 10h
+       ret
 
-       xor ax, ax
-       mov es, ax
-
-       mov ax, str_foo
-       call printstr
-
-.hang: cli
-       hlt
-       jmp .hang
+       ; decode RLE from ds:si to es:di, cx: number of decoded bytes (0 means 65536)
+       ; - high bit set for the repetition count, followed by a value byte to
+       ;   be repeated N times
+       ; - high bit not set for raw data that should be copied directly
+decode_rle:
+       mov al, [si]
+       inc si
+       mov bl, 1       ; default to "copy once" for raw values
+       test al, 0x80   ; test the high bit to see if it's a count or a raw value
+       jz .copy
+       ; it's a count, clear the high bit, and read the next byte for the value
+       and al, 0x7f
+       mov bl, al
+       mov al, [si]
+       inc si
+.copy: mov [es:di], al
+       inc di
+       dec cx          ; decrement decoded bytes counter
+       jz .end         ; as soon as it reaches 0, bail
+       dec bl
+       jnz .copy
+       jmp decode_rle
+.end:  ret
+       
 
 waitkey:
        in al, 64h
@@ -89,6 +125,10 @@ waitkey:
        in al, 60h
        ret
 
+       ; data
+       align 16
+pic:   incbin "nuclear.rle"
+
 stage2_end:
 
 ; vi:set ft=nasm: