source: xtideuniversalbios/trunk/Assembly_Library/Src/Menu/Dialog/LineSplitter.asm @ 51

; File name     :   Line Splitter.asm
; Project name  :   Assembly Library
; Created date  :   8.8.2010
; Last update   :   1.10.2010
; Author        :   Tomi Tilli
; Description   :   Splits long strings to multiple lines.

struc LINE_SPLITTER
    .pLastWord          resb    2
    .wMaxLineLength     resb    2
    .wLines             resb    2
endstruc


; Section containing code
SECTION .text

;--------------------------------------------------------------------
; LineSplitter_SplitStringFromDSSIwithMaxLineLengthInAXandGetLineCountToAX
;   Parameters:
;       AX:     Maximum allowed length for a line
;       DS:SI:  Ptr to string to split
;   Returns:
;       AX:     Number of lines
;   Corrupts registers:
;       CX, SI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
LineSplitter_SplitStringFromDSSIwithMaxLineLengthInAXandGetLineCountToAX:
    xor     cx, cx
    cmp     [si], cl                        ; String length zero?
    jne     SHORT .PrepareToSplit
    xchg    ax, cx
    ret

ALIGN JUMP_ALIGN
.PrepareToSplit:
    eENTER_STRUCT LINE_SPLITTER_size        ; SS:BP now points to LINE_SPLITTER

    mov     [bp+LINE_SPLITTER.wLines], cx
    call    Memory_SetZFifNullPointerInDSSI
    jz      SHORT .ReturnNumberOfLinesInAX
    call    SplitStringFromDSSIusingLineSplitterInSSBP

.ReturnNumberOfLinesInAX:
    mov     ax, [bp+LINE_SPLITTER.wLines]
    eLEAVE_STRUCT LINE_SPLITTER_size
    ret

;--------------------------------------------------------------------
; SplitStringFromDSSIusingLineSplitterInSSBP
;   Parameters:
;       AX:     Maximum allowed length for a line
;       DS:SI:  Ptr to string to split
;       SS:BP:  Ptr to LINE_SPLITTER
;   Returns:
;       SS:BP:  Ptr to LINE_SPLITTER with number of lines
;   Corrupts registers:
;       AX, CX, SI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SplitStringFromDSSIusingLineSplitterInSSBP:
    mov     [bp+LINE_SPLITTER.pLastWord], si
    mov     [bp+LINE_SPLITTER.wMaxLineLength], ax
    inc     WORD [bp+LINE_SPLITTER.wLines]      ; Always at least one line
    xor     cx, cx                              ; Length of current line
    cld
ALIGN JUMP_ALIGN
.ScanNextCharacter:
    lodsb                   ; Load from [DS:SI] to AL, increment SI
    cmp     al, ' '         ; Control character or space?
    je      SHORT .ProcessSpace
    jb      SHORT .ProcessControlCharacter
.IncrementCharacterCount:
    inc     cx              ; Increment character count
    cmp     cx, [bp+LINE_SPLITTER.wMaxLineLength]
    jbe     SHORT .ScanNextCharacter

    mov     si, [bp+LINE_SPLITTER.pLastWord]    ; Resume to beginning of last word
    mov     BYTE [si-1], STX                    ; STX marks start or new line
    ; Fall to .StartNewLine

;--------------------------------------------------------------------
; .StartNewLine
;   Parameters:
;       CX:     Line length so far
;       DS:SI:  Ptr character that begins new line
;       SS:BP:  Ptr to LINE_SPLITTER
;   Returns:
;       CX:     Zero
;       SS:BP:  LINE_SPLITTER updated for number of lines
;       Jumps to .ScanNextCharacter
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
.StartNewLine:
    inc     WORD [bp+LINE_SPLITTER.wLines]      ; Increment number of lines
    xor     cx, cx                              ; Zero line length
    jmp     SHORT .ScanNextCharacter

;--------------------------------------------------------------------
; .ProcessSpace
;   Parameters:
;       CX:     Line length so far
;       DS:SI:  Ptr first character after space
;       SS:BP:  Ptr to LINE_SPLITTER
;   Returns:
;       SS:BP:  LINE_SPLITTER updated to beginning of next word
;       Jumps to .IncrementCharacterCount
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
.ProcessSpace:
    mov     [bp+LINE_SPLITTER.pLastWord], si
    jmp     SHORT .IncrementCharacterCount

;--------------------------------------------------------------------
; .ProcessControlCharacter
;   Parameters:
;       AL:     Control character
;       CX:     Line length so far
;       DS:SI:  Ptr inside string to split
;       SS:BP:  Ptr to LINE_SPLITTER
;   Returns:
;       SS:BP:  LINE_SPLITTER updated to beginning of next line (LF control character)
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
.ProcessControlCharacter:
    cmp     al, NULL            ; End of string?
    je      SHORT .RemoveEmptyLinesAtTheEndIfAnyExists
    cmp     al, LF              ; Line feed?
    je      SHORT .NewlineCharacter
    cmp     al, SOH             ; Previous newline character?
    je      SHORT .NewlineCharacter

    mov     BYTE [si-1], ' '    ; Replace unhandled control characters with space
    jmp     SHORT .ProcessSpace

ALIGN JUMP_ALIGN
.NewlineCharacter:
    mov     BYTE [si-1], SOH    ; SOH marks previous newline character
    mov     [bp+LINE_SPLITTER.pLastWord], si
    jmp     SHORT .StartNewLine

ALIGN JUMP_ALIGN
.RemoveEmptyLinesAtTheEndIfAnyExists:
    cmp     BYTE [si-2], SOH    ; Character before NULL
    je      SHORT .RemoveEmptyLineAtTheEndOfString
    ret
ALIGN JUMP_ALIGN
.RemoveEmptyLineAtTheEndOfString:
    dec     si
    dec     WORD [bp+LINE_SPLITTER.wLines]
    mov     BYTE [si-1], NULL
    jmp     SHORT .RemoveEmptyLinesAtTheEndIfAnyExists


;--------------------------------------------------------------------
; LineSplitter_PrintLineInCXfromStringInESDI
;   Parameters:
;       CX:     Index of line to print
;       ES:DI:  Ptr to string containing the line
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, BX, SI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
LineSplitter_PrintLineInCXfromStringInESDI:
    push    di
    push    cx

    call    LineSplitter_GetOffsetToSIforLineCXfromStringInESDI
    jnc     SHORT .LineNotFound
    mov     bx, es
    CALL_DISPLAY_LIBRARY PrintCharBufferFromBXSIwithLengthInCX
.LineNotFound:
    pop     cx
    pop     di
    ret


;--------------------------------------------------------------------
; LineSplitter_GetOffsetToSIforLineCXfromStringInESDI
;   Parameters:
;       CX:     Index of line to search for
;       ES:DI:  Ptr to string
;   Returns:
;       CX:     Line length
;       ES:SI:  Ptr to beginning of line
;       CF:     Set if wanted line was found
;   Corrupts registers:
;       AX, DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
LineSplitter_GetOffsetToSIforLineCXfromStringInESDI:
    mov     si, di              ; SI points to start of first line
    mov     al, STX             ; Last control character to scan for
    inc     cx                  ; Increment CX to line count
    cld
ALIGN JUMP_ALIGN
.LineScanLoop:
    scasb                       ; cmp al, [es:di]. Increment DI
    jb      SHORT .LineScanLoop ; Ignore all above STX

    ; NULL, SOH or STX
    dec     cx                  ; Decrement lines to scan through
    jz      SHORT .WantedLineFound
    cmp     BYTE [es:di-1], NULL
    je      SHORT .EndOfString  ; Jump with CF cleared
    mov     si, di              ; SI points to start of new line
    jmp     SHORT .LineScanLoop

ALIGN JUMP_ALIGN
.WantedLineFound:
    stc                         ; Set CF since wanted line was found
.EndOfString:
    lahf                        ; Load FLAGS low to AH
    lea     cx, [di-1]          ; CX = offset to NULL, SOH or STX
    sub     cx, si              ; CX = string length
    sahf                        ; Store AH to FLAGS low
    ret