210 lines
2.9 KiB
Plaintext
210 lines
2.9 KiB
Plaintext
;Read a string ending in a null of at most AL characters to DI until a
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;return.
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readstr:
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;Store the initial registers in the stack
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push ax
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push bx
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push cx
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push dx
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push di
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;Setup
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;Store the input length in the stack
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mov ah, 0
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push ax
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;Initialise the destination with spaces
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mov cx, ax
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mov al, 0x20
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rep stosb
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pop ax
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push ax
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sub di, ax
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;Store the last column number
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mov ah, 0xf
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int 0x10
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dec ah
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mov [.lastcolumn], ah
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;Initialise the cursor pointer in BL and clear BH
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mov bx, 0x1
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.loop:
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;Read a keypress
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mov ah, 0x0
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int 0x16
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;Check for special keys and non-printing characters
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;Check for return
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cmp al, 0xd
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je .return
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;Check for backspace
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cmp al, 0x8
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je .backspace
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;Check for input end
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pop dx
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push dx
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cmp bl, dl
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je .loop
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;Check for space
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cmp al, 0x20
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je .space
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;Check for erase
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cmp al, 0x9
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je .erase
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;Check for non-printing characters
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cmp al, 0x1f
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jle .loop
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cmp al, 0x7f
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je .loop
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;Store and print a character
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.character:
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;Store
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stosb
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;Print
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mov ah, 0xe
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int 0x10
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;Move the cursor pointer
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inc bl
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jmp .loop
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;Replace the cursor position with a space
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.erase:
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mov al, 0x20
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jmp .character
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;Move the cursor forward
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.space:
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call .nextchar
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inc di
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inc bl
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jmp .loop
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;Move the cursor backward
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.backspace:
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;Check for the input beginning
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cmp bl, 0x1
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je .loop
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;Move
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call .prevchar
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dec di
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dec bl
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jmp .loop
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;Finish reading the string
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.return:
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;Check for and remove trailing spaces
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;Go to the end of the input
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pop ax
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mov bh, 0x0
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sub ax, bx
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push di
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add di, ax
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.findtrailing:
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;Check
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cmp byte [di], 0x20
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je .deltrailing
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jmp .end
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.deltrailing:
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;Remove
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mov al, 0x0
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stosb
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sub di, 0x2
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jmp .findtrailing
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;Move the cursor to the end of the input string
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.end:
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pop di
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.findend:
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cmp byte [di], 0x0
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jne .notend
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jmp .done
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.notend:
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call .nextchar
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inc di
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inc bl
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jmp .findend
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.done:
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;Load the initial registers from the stack
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pop di
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pop dx
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pop cx
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pop bx
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pop ax
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iret
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;Data
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.lastcolumn db 0x0
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;Move the cursor forward within a line
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.nextchar:
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;Get the cursor position
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mov ah, 0x3
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int 0x10
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;Check for the end of the line
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cmp dl, [.lastcolumn]
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je .nextln
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;Move
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inc dl
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mov ah, 0x2
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int 0x10
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ret
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;Move the cursor to the beginning of the next line
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.nextln:
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;Check if the current line is the last on screen
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cmp dh, 0x18
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je .scroll
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;Move
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mov ah, 0x2
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inc dh
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mov dl, 0x0
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int 0x10
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ret
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;Scroll the screen up by one line
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.scroll:
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;Scroll
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mov ah, 0x6
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mov al, 0x1
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mov bh, 0x7
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mov ch, 0x0
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mov cl, 0x0
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mov dh, 0x18
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mov dl, [.lastcolumn]
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int 0x10
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;Move to the beginning of the new line
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mov ah, 0x2
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mov bh, 0x0
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mov dl, 0x0
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int 0x10
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ret
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;Move the cursor backward within a line
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.prevchar:
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;Get the cursor position
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mov ah, 0x3
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int 0x10
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;Check for the beginning of the line
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cmp dl, 0x0
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je .prevln
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;Move
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dec dl
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mov ah, 0x2
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int 0x10
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ret
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;Move the cursor to the end of the previous line
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.prevln:
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mov ah, 0x2
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dec dh
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mov dl, [.lastcolumn]
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int 0x10
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ret
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