172 lines
4.4 KiB
NASM
172 lines
4.4 KiB
NASM
; Copyright (C) 2025 Elaina Claus
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <https://www.gnu.org/licenses/>.
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%ifndef __INC_VIDEO
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; Sets output to 80x25 16 color text mode via BIOS call
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; also clears screen
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; void SetTextMode(void)
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ALIGN 4, db 0x90
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SetTextMode:
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.prolog:
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__CDECL16_ENTRY
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pushf
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.func:
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xor ah, ah ; Set Video mode BIOS function
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mov al, 0x03 ; 16 color 80x25 Text mode
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int 0x10 ; Call video interrupt
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mov ah, 0x05 ; Select active display page BIOS function
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xor al, al ; page 0
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int 0x10 ; call video interrupt
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.endp:
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popf
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__CDECL16_EXIT
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ret
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; disables blinking text mode cursor via crtc pokes
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; 0x3D4/0x3D5 for color, mono at 0x3B4/0x3B5
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ALIGN 4, db 0x90
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disable_cursor_crtc:
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__CDECL16_ENTRY
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.func:
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mov dx, 0x3D4
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mov al, 0xA ; low cursor shape register
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out dx, al
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inc dx
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mov al, 0x20 ; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
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out dx, al
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.endp:
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__CDECL16_EXIT
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ret
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; disables blinking text mode cursor via BIOS int 10h, ah = 01
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ALIGN 4, db 0x90
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disable_cursor_bios:
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__CDECL16_ENTRY
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.func:
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push bx
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mov ah, 03h ; read cursor pos & shape
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xor bh, bh
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int 10h ; CH=top scanline, CL=bottom
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or ch, 20h ; set bit 5 = disable
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mov ah, 01h ; set leaf 01h
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int 10h
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pop bx
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.endp:
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__CDECL16_EXIT
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ret
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; Prints a C-Style string (null terminated) using BIOS vga teletype call
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; void PrintString(char* buf)
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ALIGN 4, db 0x90
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PrintString:
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__CDECL16_ENTRY
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mov di, [bp + 4] ; first arg is char[]
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.str_len:
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xor cx, cx ; ECX = 0
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not cx ; ECX = -1 == 0xFFFF
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xor ax, ax ; search for al = 0x0
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cld
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repne scasb ; deincrement cx while searching for al
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not cx ; the inverse of a neg number = abs(x) - 1
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dec cx ; CX contains the length of the string - nul byte at end
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.print:
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mov si, [bp + 4] ; source string
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.print_L0:
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movzx ax, byte [si]
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push ax
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call PrintCharacter
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add sp, 0x2
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inc si
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dec cx
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jcxz PrintString.endp
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jmp PrintString.print_L0 ; Fetch next character from string
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.endp:
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__CDECL16_EXIT
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ret ; Return from procedure
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; Prints a single character
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; void PrintCharacter(char c);
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ALIGN 4, db 0x90
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PrintCharacter:
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__CDECL16_ENTRY
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.func:
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movzx ax, byte [bp + 4] ; AL = character c
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mov ah, 0x0E ; INT 0x10, AH=0x0E call
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mov bx, 0x0007 ; BH = page no. BL =Text attribute 0x07 is lightgrey font on black background
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int 0x10 ; call video interrupt
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; TODO: check for carry and clear carry before call
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.endp:
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__CDECL16_EXIT
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ret
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; TODO: fix the prolog, epilog and stack usage to confirm with cdecl16
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; prints the hex representation of of val
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; void PrintDWORD(uint32_t val);
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ALIGN 4, db 0x90
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PrintDWORD:
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__CDECL16_ENTRY
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.func:
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mov si, IntToHex_table
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mov ebx, 16 ; base-16
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mov eax, dword [bp + 4] ;val
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xor edx, edx
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xor cx, cx
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.next_digit:
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div ebx ; dividend in edx:eax -> quotient in eax, remainder in edx
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push dx ; save remainder
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inc cx
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xor dx, dx
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test eax, eax
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jnz PrintDWORD.next_digit
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.zero_pad:
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cmp cx, 0x0008
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je PrintDWORD.print_stack
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xor ax, ax
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push ax
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inc cx
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jmp PrintDWORD.zero_pad
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.print_stack:
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pop bx
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dec cx
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push cx
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movzx ax, byte [bx+si+0] ; bx = index into Hex lookup table
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push ax
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call PrintCharacter
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add sp, 0x2
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pop cx
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jcxz PrintDWORD.endp
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jmp PrintDWORD.print_stack
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.endp:
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__CDECL16_EXIT
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ret
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%endif
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%define __INC_VIDEO |