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Assembly Source File | 1986-05-08 | 9.0 KB | 344 lines

COMMENT ~ STRINGS.ASM -- String Manipulation Procedures From `BLUEBOOK of ASSEMBLY ROUTINES for the IBM PC & XT' by Christopher L. Morgan Copyright (C) 1984 by The Waite Group, Inc. Purpose: These routines manipulate strings. Contents: --------- COMPARE -- Compare two strings LEXINSERT -- Lexigraphically insert LEXSEARCH -- Search a lexigraphically ordered list LOWERCASE -- Convert to lower case SORTB -- Bubble sort a string array STRINSERT -- Insert one string in another STRSEARCH -- Search for one string within another SWITCH -- Switch two strings UPPERCASE -- Convert to upper case _____________________________________________________________________________ ~ DATAS SEGMENT PUBLIC DUMMY DB 5 DUP(?) DATAS ENDS ;_____________________________________________________________________________ CODES SEGMENT PUBLIC LOWERCASE,UPPERCASE,STRSEARCH,STRINSERT PUBLIC LEXSEARCH,LEXINSERT,COMPARE,SWITCH,SORTB ASSUME CS:CODES,DS:DATAS ;____________________________I/O ROUTINES_____________________________________ ;Routine to convert string to lower case LOWERCASE PROC FAR PUSH BX ;Save registers PUSH CX PUSH AX ; ;Get the length MOV CX,[BX] ;First two bytes contain length INC BX ;Point to beginning of text INC BX ; ;Loop through the bytes of the string LOWERCASE1: MOV AL,[BX] ;Get the character CMP AL,'A' ;Below the upper case chars? JB LOWERCASE2 ;If so, skip CMP AL,'Z' ;Above the upper case chars? JA LOWERCASE2 ;If so, skip OR AL,20H ;OR bit 5 into the byte LOWERCASE2: MOV [BX],AL ;Store the character INC BX ;Point to next character LOOP LOWERCASE1 POP AX ;Restore registers POP CX POP BX RET LOWERCASE ENDP ;------------------------------------------------------------------------------ ;Routine to convert string to uppercase ; UPPERCASE PROC FAR PUSH BX ;Save registers PUSH CX PUSH AX ; ;Get the length MOV CX,[BX] ;First two bytes contain length INC BX ;Point to beginning of text INC BX ; ;Loop through the bytes of the string UPPERCASE1: MOV AL,[BX] ;Get the character CMP AL,'a' ;Below the lower case chars? JB UPPERCASE2 ;If so, skip CMP AL,'z' ;Above the lower case chars? JA UPPERCASE2 ;If so, skip AND AL,5FH ;Mask out bit number 5 UPPERCASE2: MOV [BX],AL ;Store the character INC BX ;Point to next character LOOP UPPERCASE1 POP AX ;Restore registers POP CX POP BX RET UPPERCASE ENDP ;------------------------------------------------------------------------------ ;Routine to search for one string within another ; STRSEARCH PROC FAR PUSH SI ;Save registers PUSH DI PUSH CX ; ;Get length of destination and point to first byte MOV SI,DX ;Use source index LODSW ;Get the length of destination MOV CX,AX ;Use the length as a count MOV DX,SI ;Text begins here STRSEARCH1: ; ;Point indices to beginning of source and destination MOV SI,BX ;Load source index MOV DI,DX ;Load destination index ; ;Scan for a match MOV AL,[SI+2] ;Get the first character CLD ;Point forward REPNZ SCASB ;Scan for match JCXZ STRSEARCH2 ;If no match, quit ; ;Got a match of first characters -- now check the entire string MOV DX,DI ;Save current dest location DEC DI ;Beginning of word LODSW ;Get source length XCHG CX,AX ;Use sourc cnt & save dest cnt REPZ CMPSB ;Compare two strings JCXZ STRSEARCH3 ;It`s a match if no more source ; ;Continue the scan XCHG CX,AX ;Use destination count JMP STRSEARCH1 ;Back for more scanning of dest ; ;No match is possible STRSEARCH2: MOV AL,0 ;Unsuccessful outcome JMP STRSEARCHXIT ; ;Found a match STRSEARCH3: DEC DX ;Point to beginning of match MOV AL,0FFH ;Successful outcome JMP STRSEARCHXIT STRSEARCHXIT: POP CX ;Restore registers POP DI POP SI RET STRSEARCH ENDP ;------------------------------------------------------------------------------ ;Routine to insert one string within another ; STRINSERT PROC FAR PUSH SI ;Save registers PUSH DI PUSH CX PUSH AX ; ;Find current end of destination string MOV SI,BP ;Start of string ADD SI,ES:[SI] ;Point to next to last byte INC SI ;Adjust for length information ; ;Find new end of destination string and update length MOV DI,SI ;Get old end of destination MOV AX,[BX] ;Get length of source ADD DI,DX ;New end of destination ADD ES:[BP],AX ;New length of destination ; ;Move tail of destination string out of the way MOV CX,SI ;SI + DX + 1 is the count SUB CX,DX INC CX STD ;Backward direction REP MOVS BYTE PTR[DI],ES:[SI] ;Move the tail ; ;Move source string into place MOV DI,DX ;Destination of move MOV SI,BX ;Source of movw CLD ;Forward direction LODSW ;Length of source MOV CX,AX ;The count REP MOVSB ;Make the string move STRINSERTXIT: POP AX ;Restore registers POP CX POP DI POP SI RET STRINSERT ENDP ;------------------------------------------------------------------------------ ;Routine to search for a word in an ordered list of words ; LEXSEARCH PROC FAR ; PUSH SI ;Save register PUSH DI PUSH CX ; ;Point to beginning of list and get its length MOV DI,BP ;Beginning of list MOV CX,[DI] ;Get length INC DI INC DI ; ;Compare source word with words in the list LEXSEARCH1: MOV DX,DI ;Save beginning of dest word CLD ;Forward direction MOV SI,BX ;Point to beginning of source INC SI INC SI ; ;Compare source word with a word of the list LEXSEARCH2: ; ;Check for end of the list JCXZ LEXSEARCH5 ;End of list -- insert it ; ;Set up <CR> as scan character MOV AL,13 ;ASCII <CR> ; ;Check for end of source word CMP [SI],AL ;Source byte = <CR>? JE LEXSEARCH4 ;Found end of source word ; ;Check for end of destination word CMP ES:[DI],AL ;Destination byte = <CR>? JE LEXSEARCH3 ;No match -- go to next word ; ;Compare character by character DEC CX CMPSB ;Check for match JE LEXSEARCH2 ;Matched -- check next char JB LEXSEARCH5 ;Too high -- this is the place ; ;Scan for next <CR> LEXSEARCH3: REPNZ SCASB ;Scan until <CR> JMP LEXSEARCH1 ;Next word ; ;End of source word was found LEXSEARCH4: CMP [DI],AL ;Dest character = <CR>? JE LEXSEARCH6 ;End of destination word? ; ;Found a spot to insert the word LEXSEARCH5: MOV AL,0FFH ;Success JMP LEXSEARCHXIT ; ;Word already present LEXSEARCH6: MOV AL,00H ;Already there JMP LEXSEARCHXIT LEXSEARCHXIT: POP CX ;Restore registers POP DI POP SI RET LEXSEARCH ENDP ;------------------------------------------------------------------------------ ;Routine to insert a word in an ordered list of words ; LEXINSERT PROC FAR PUSH AX ;Save register CALL LEXSEARCH ;Search for match CMP AL,0 ;Already there? JE LEXINSERTXIT ;Skip, if so CALL STRINSERT ;Insert the new word LEXINSERTXIT: POP AX ;Restore register RET LEXINSERT ENDP ;------------------------------------------------------------------------------ ;Routine to compare two strings ; COMPARE PROC FAR PUSH SI ;Save registers PUSH DI PUSH CX REPZ CMPSB ;One compare does it ! POP CX ;Restore registers POP DI POP SI COMPARE ENDP ;------------------------------------------------------------------------------ ;Routine to switch two strings ; SWITCH PROC FAR PUSH SI ;Save registers PUSH DI PUSH CX PUSH AX CLD ;Forward direction SWITCH1: MOV AL,[DI] ;Get byte from destination MOVSB ;Move from source to dest MOV ES:[SI-1],AL ;Put byte in source LOOP SWITCH1 ;Loop back for more POP AX ;Restore registers POP CX POP DI POP SI RET SWITCH ENDP ;------------------------------------------------------------------------------ ;Routine to sort a string array ; SORTB PROC FAR PUSH SI ;Save registers PUSH DI PUSH CX PUSH AX ; ;Adjust count for one less than number of items DEC CX ;Adjust the count ; ;Outer loop -- for SI = 1 to N-1 SORTB1: PUSH CX ;Save the count MOV DI,SI ;Destination points to source ; ;Inner loop -- for DI = SI+1 to N SORTB2: PUSH CX ;Save the count ADD DI,DX ;Point to next destination MOV CX,DX ;Entry length CALL COMPARE ;Compare the strings JLE SORTB3 ;Skip if source <= destination CALL SWITCH ;Switch if not SORTB3: POP CX ;Restore the count LOOP SORTB2 ADD SI,DX ;Point to next source POP CX ;Restore the count LOOP SORTB1 SORTBXIT: POP AX ;Restore registers POP CX POP DI POP SI RET SORTB ENDP ;----------------------------------------------------------------------------- CODES ENDS ; END ;_____________________________________________________________________________ ;>>>>> Physical EOF STRINGS.ASM <<<<<