Unit BoolPos; {$Define Test} { Once debugging is complete, remove the above line to turn off debug mode. } { Version 1.3.5.P. Requires Borland Turbo Pascal version 6.0 or later to compile. Author: Bruce J. Lackore. Created Friday, July 23, 1993. Copyright (c) 1993 Bruce J. Lackore. ALL RIGHTS RESERVED. } {$IFDEF Test} {$A+,B-,D+,F-,G-,I+,L+,O-,R+,S+,V-,X+} {$ELSE} {$A+,B-,D-,F-,G-,I-,L-,O-,R-,S-,V-,X+} {$ENDIF} { This unit comprises a function capable of searching a string for multiple occurences of substrings using Boolean operators. In the search string, Boolean operators And and Or are defined as follows: & - And | - Or Parentheses are supported for doing multiple searches. Search strings are submitted as follows: i.e. In the source string "The quick brown fox jumped over the lazy dog" and the search is for the word blue and the words quick or fox, the search string is entered as follows: (blue&(quick|fox)) The way the function is currently written, And (&) and Or (|) have the same precedence level hence the above search string without parentheses would be interpretted to be (blue&quick|fox): blue And quick would be searched for first, the result Or'd with the results of the search for fox. Notice the difference in that (blue&(quick|fox)) is a False statement whilst (blue&quick|fox) is True. The function will automatically scan for () pairs, adding the necessary ) at the end of the search string or ( at the beginning if required. The function will also search for (|, |), (& and &) symbols, these being illegal. It should also be noted that although excess parens will not cause the function to fail, they DO cause the function to loop unnecessarily through the token search (once for each set of parens) while bringing the final answer out of the final set of parens. } { Bug fixes: 07/04/1994: Thought the 06/01 fix did the job. It didn't. This time, I went back into the token processor and found that it was missing a left paren when the tokenized search string was in the form of (b@b...)@(b@b...) where b is a boolean designator (T or F) and @ is a boolean operator (| or &). Thanx to Michael Jarmulowicz for pointing this out. The fix was to go into the Process_token_str function and ensure that a multi-pass required token string has sufficient parens so as to not confuse the token processor. Also defined BPos return value should the Fixup_srch_str function fail. The default is False (as set in the first line of the BPos function itself) and is triggered by Fixup_srch_str returning a null string. Removed the "fix" that was suggested in the 06/01 bug fix and replaced it with code that scans the first and last letters of the Srch_str to ensure that they are parens, if not, add a pair. 06/01/1994: After returning from WestPac, I received a couple of emails telling me that if the function was called with NO parentheses, it would fail. The fix is simply to add a set of parens in the Fixup_srch_str function just before the function returns if the first character of the Srch_str is NOT a left paren equivalent. I have had one report of the unit not working in protected mode. As I don't yet know much about protected mode programming, I am still working on that particular bug but I WILL fix it if the error is in here. I also tightened up one of the assembly replacement functions, see the docs for the change. 10/04/1993: Noticed that length of Src_str in function Next_CPos was incorrectly calculated because of positioning of INC DI. INC DI precedes the MOV CL,[ES:DI] causing the function to consider the first character of Src_str to represent the length rather than the actual length byte. Fix is to move the INC DI to the line following the MOV CL,[ES:DI]. } Interface Function BPos(Srch_str, Src_str: String; Ignore_case: Boolean): Boolean; { This function accepts a source string and a search string as described above and returns a Boolean value based on whether or not the parsed search string was found. } { ************************************************************************** } Implementation Const Lt_pn: Char = '('; Rt_pn: Char = ')'; Function Cnt_ch(Scan_char: Char; In_str: String): Byte; Assembler; { This function will scan a string for occurences of a particular character. The function will return the number of occurences. } Asm { Function Cnt_ch } XOR AX,AX { 0 AX } MOV BL,Scan_char { Put char to count in BL } LES SI,In_str { Set ES:SI to point to start of string } XOR CX,CX { 0 CX } MOV CL,[ES:SI] { Move string length to CX } ADD SI,CX { Set ES:SI to point to END of string } @LOOK: CMP BL,[ES:SI] { Start Loop, compare current char and BL } JNE @NEXT { If not equal, jump to end of loop } INC AX { If equal, Inc char cnt (AX) } @NEXT: DEC SI { Set ES:SI back one character } LOOP @LOOK { Decrement CX and jump to start of loop } End; { Function Cnt_ch } Function Fill_str(Dupe_ch: Char; How_many: Byte): String; Assembler; { This function returns How_many of Dupe_char. } Asm { Function Fill_str } LES DI, @Result { Set ES:DI to function result area } CLD { Clear direction flag } XOR CH,CH { 0 CH } MOV CL,How_many { Length in CX } MOV AX,CX { and in AX } STOSB { Store length byte } MOV AL,Dupe_ch { Put char to dupe in AL } REP STOSB { Fill string with char } End; { Function Fill_str } Function PosC(Srch_ch: Char; Src_str: String): Boolean; Assembler; { This function is similar to the Pos function of Pascal except that it accepts only a single character to search for. This function returns a True if a Srch_ch is encountered, a False if not. } Asm { Function PosC } XOR BX,BX { 0 BX } MOV AL,Srch_ch { Put char to look for in AL } LES DI,Src_str { Set ES:DI to start of Src_str } XOR CX,CX { 0 CX } MOV CL,[ES:DI] { Store length of Src_str in CL } ADD DI,CX { Set ES:DI to end of string } STD { Set direction flag } @LOOK: REPNZ SCASB { Look for AL in Src_str } JNZ @DONE { If not found, jump to end (BX = 0) } INC BX { If Found, Inc Bx to 1 = Pascal True } @DONE: MOV AX,BX { Move BX to AX (return result) } End; { Function PosC } Function Last_Cpos(Srch_ch: Char; Src_str: String): Byte; Assembler; { This function performs the same function as the Pascal POS function except that it works only with a single character and rather than returning the first position the character is found in, it returns the LAST position that the search character is found in. } Asm { Function Last_Cpos } MOV AL,Srch_ch { Put char to look for in AL } LES DI,Src_str { Set ES:DI to start of Src_str } XOR CX,CX { 0 CX } MOV CL,[ES:DI] { Move length of Src_str to CL } ADD DI,CX { Set ES:DI to end of Src_str } INC CX { Add one to CX (correct for string length } STD { Set direction flag } REPNZ SCASB { Look for character in string } MOV AX,CX { If found CX indicates position, else 0 } End; { Function Last_Cpos } Function Next_CPos (Srch_ch: Char; Src_str: String; Strt_at: Byte): Byte; Assembler; { This function searches for the next occurence of Srch_ch in Src_str AFTER position Strt_at. The function returns the offset from the beginning of the string, NOT the offset from Strt_at. } Asm { Function Next_CPos } XOR AX,AX { 0 AX } MOV AL,Strt_at { Move position to start at to AL } LES DI,Src_str { Set ES:DI to start of Src_str } XOR CX,CX { 0 CX } MOV CL,[ES:DI] { Store length of Src_str in CL } INC DI { Set ES:DI to first char of Src_str } MOV BX,CX { Move CX to BX } SUB CX,AX { Set CX to length of string after Strt_at } ADD DI,AX { Set ES:DI to char at Strt_at in Src_str } MOV AL,Srch_ch { Move Srch_ch to AL } CLD { Clear direction flag } REPNZ SCASB { Look for character following Strt_at } JNZ @NOTFND { If not found, jump to end of procedure } SUB BX,CX { Set BX to position char found in } JMP @DONE { Jump to end of procedure } @NOTFND: XOR BX,BX { Srch_ch not found, set BX to 0 } @DONE: MOV AX,BX { Move position found at (BX) to AX } End; { Function Next_CPos } {$F+} Function Up_cs(In_str: String): String; { This function converts In_str to all upper case characters. } Begin { Function Up_cs } Inline( $1E/ { PUSH DS } $C4/$7E/$0A/ { LES DI,[BP+$0A] } $C5/$76/$06/ { LDS SI,[BP+$06] } $30/$E4/ { XOR AH,AH } $AC/ { LODSB } $AA/ { STOSB } $89/$C1/ { MOV CX,AX } $E3/$0F/ { JCXZ DONE } $FC/ { CLD } $AC/ {DOCHAR: LODSB } $3C/$61/ { CMP AL,'a' } $72/$06/ { JB NEXTCH } $3C/$7A/ { CMP AL,'z' } $77/$02/ { JA NEXTCH } $24/$DF/ { AND AL,$DF } $AA/ {NEXTCH: STOSB } $E2/$F2/ { LOOP DOCHAR } $1F) {DONE: POP DS } End; { Function Up_cs } {$F-} Function Fixup_srch_str(Srch_str: String): String; { This functions sole purpose in life is to count the number of parantheses pairs and correct for a deficient number of either by adding the appropriate character either at the beginning or the end of the search string. This may not yield the correct result as the searcher intended but is a requirement of the algorithm (it searches for paran pairs). Note that the function will add one set of parantheses if none are found. This function also looks for illegal character pairs (&, &), (| and |), these pairs indicate an illegal Boolean search. The function returns the corrected Srch_str if all is well, an empty string if not. } Var Left_para, Right_para, How_many: Integer; Begin { Function Fixup_srch_str } If (Srch_str[Length(Srch_str)] <> Rt_pn) Or (Srch_str[1] <> Lt_pn) Then Srch_str := Lt_pn + Srch_str + Rt_pn; Left_para := Cnt_ch(Lt_pn, Srch_str); { Count the parens } Right_para := Cnt_ch(Rt_pn, Srch_str); How_many := Abs(Left_para - Right_para); { Get the difference } If How_many > 0 Then If Right_para < Left_para Then Srch_str := Srch_str + Fill_str(Rt_pn, How_many) Else Srch_str := Fill_str(Lt_pn, How_many) + Srch_str; If (Pos(Lt_pn + '&', Srch_str) <> 0) Or { Illegal call? } (Pos('&' + Rt_pn, Srch_str) <> 0) Or (Pos(Lt_pn + '|', Srch_str) <> 0) Or (Pos('|' + Rt_pn, Srch_str) <> 0) Then Fixup_srch_str := '' Else Fixup_srch_str := Srch_str { All is well } End; { Function Fixup_srch_str } Function Parse_srch_str(Srch_str, Src_str: String): String; { This function simply extracts each string to search for, tests to see if it exists in the original string and replaces the extracted substring with the appropriate token. It should be noted that each substring is determined solely by the characters used for parantheses and operators. Any other characters are assumed to be part of the search string. Each substring is searched for in the original Search_str and its presense or absense noted with a T or F respectively. } Var Rtn_str, Token_str: String; End_token: Boolean; Begin { Function Parse_srch_str } Token_str := ''; Rtn_str := ''; While Srch_str <> '' Do Begin If (Srch_str[1] In [Lt_pn, Rt_pn, '&', '|']) Then { Token starts? } Begin End_token := (Token_str <> ''); { End of token? If not } If Not(End_token) Then { then start one. } Rtn_str := Rtn_str + Srch_str[1] End Else Begin Token_str := Token_str + Srch_str[1]; { Add a char to substring } End_token := False End; If End_token Then { If complete token, look } Begin { for it in the source str } If Pos(Token_str, Src_str) <> 0 Then Rtn_str := Rtn_str + 'T' { If found, return T } Else Rtn_str := Rtn_str + 'F'; { If not, return F } Rtn_str := Rtn_str + Srch_str[1]; Token_str := ''; { Reset to look for more } End_token := False End; { If End_token } Delete(Srch_str, 1, 1) { Delete the char just processed and start again } End; { While Srch_str <> '' } Parse_srch_str := Rtn_str End; { Function Parse_srch_str } Function Process_token_str(Token_str: String): Char; Var One_token: String; One_token_len, Left_para: Byte; Function Process_one_token_str(The_token: String): Char; Var Lcv: Byte; Curr_answer, Do_and: Boolean; Begin { Function Process_one_token_str } Curr_answer := (The_token[1] = 'T'); { Establish current answer by checking first token. } For Lcv := 2 to Length(The_token) Do { Look at the rest of the token str. } Case The_token[Lcv] of { Boolean op is And } '&': Do_and := True; { Boolean op is Or } '|': Do_and := False; 'T': If Do_and Then Curr_answer := Curr_answer And True { If And } Else Curr_answer := True; { If Or } 'F': If Do_and Then { If And (Or stays T) } Curr_answer := False; End; { Case } If Curr_answer Then { Final result } Process_one_token_str := 'T' Else Process_one_token_str := 'F' End; { Function Process_one_token_str } Begin { Function Process_token_str } { Are parens present? If so process as tokenized phrase, if not, final result has been received or can be processed in a single pass. } If PosC(Lt_pn, Token_str) Then Begin While Length(Token_str) > 1 Do Begin { Ensure that the token has enough parens to not confuse the token string processor. One need only check for a left paren since the Fixup_srch_str function ensures that an equal number of paren PAIRS exists. } If Not(PosC(Lt_pn, Token_str)) Then Token_str := Lt_pn + Token_str + Rt_pn; { Find leftmost left paren } Left_para := Last_Cpos(Lt_pn, Token_str); { Find first right paren after leftmost left paren } One_token_len := Succ(Next_CPos(Rt_pn, Token_str, Left_para) - Left_para); { Copy everything between the two } One_token := Copy(Token_str, Left_para, One_token_len); { Remove the parens } Dec(One_token[0]); Delete(One_token, 1, 1); { Remove the original substring from the phrase } Delete(Token_str, Left_para, One_token_len); { Insert the resultant single character in place of the old substring. } Insert(Process_one_token_str(One_token), Token_str, Left_para) End; { While Length(Token_str) > 1 } Process_token_str := Token_str[1] End Else Process_token_str := Process_one_token_str(One_token) End; { Function Process_token_str } Function BPos; Begin { Function BPos } BPos := False; If Ignore_case Then Begin Srch_str := Up_cs(Srch_str); Src_str := Up_cs(Src_str) End; { If Ignore_case } { Is this a Boolean expression? If so process with this function, else process with Pascal POS function. } If PosC('|', Srch_str) Or PosC('&', Srch_str) Then Begin Srch_str := Parse_srch_str(Fixup_srch_str(Srch_str), Src_str); If Srch_str <> '' Then BPos := (Process_token_str(Srch_str) = 'T') End Else BPos := Pos(Srch_str, Src_str) <> 0 End; { Function BPos } End. { Unit BoolPos } Program Test; {$Define test} { Version 1.0.0.T Requires Borland Turbo Pascal version 6.0 or later to compile. Author: Bruce J. Lackore. Created Monday, June 13, 1994. Copyright (c) 1994 Bruce J. Lackore. ALL RIGHTS RESERVED. } {$IFDEF Test} {$A+,B-,D+,E+,F-,G-,I+,L+,N-,R+,S+,V-,X+} {$ELSE} {$A+,B-,D-,E+,F-,G-,I-,L-,N-,R-,S-,V-,X+} {$ENDIF} {$M 16384, 0, 655360} { This is a quick and really dirty test program for the Boolpos unit. Just tinker with the search phrase in line 3 of the code and enjoy! } Uses Boolpos; Var BResult: Boolean; Src_str: String; Procedure Start_program; Begin { Procedure Start_program } BResult := False; Src_str := 'Now is the time for all good programmers to switch to OS/2'; BResult := BPos('(Now&then)|(time&bad)', Src_str, False) End; { Procedure Start_program } Begin { Program: Test } Start_program; End. { Program: Test }