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Text File | 1989-08-28 | 15.0 KB | 356 lines

STRLINK OBJECT Version 1.00 28 August 1989 Rob Rosenberger Barn Owl Software P.O. Box 74 O'Fallon, IL 66269 (618) 632-7345 This Turbo Pascal v5.5 OOP object implements a linked list of strings. You no longer have to read a text file more than one time: you can now let an OOP variable of StrLinkList type read it into memory. You can sort text files based on varying criteria, remove redundant strings, etc. This link list of strings offers an extra added bonus. Each string on the list takes up only as much space as it absolutely requires. This is true even if you change the size of the string after putting it on the list. (You can always inspect the code if you want to see how it was accomplished.) And because it's OOP, you can create a descendent object if you have special needs. If any of the code is ever updated, you can simply upgrade to the version ── you'll never have to change a line of your descendent code. UNIT NAME The name of the main unit is "StrLink". You should put this in any program or unit of your own that needs access to variables of type StrLinkList. CONDITIONAL DIRECTIVES {$IFDEF TPRO5} The StrLink and StrObj units can optionally use TurboPower Software's TPRO5 toolkit. TPRO5 offers some extra efficiency & speed for string link lists. If you do NOT have TPRO5, you must change the '$' to a '.' so the proper code will compile. I encourage you to write or call TurboPower for a brochure about their products. I actually pity you if you aren't using their toolkits. TPRO5 contains 50,000+ lines of source code in over 30 units, and TurboPower is coming out soon with OPRO, the Object Professional Toolkit. You can contact TurboPower at P.O. Box 66747, Scotts Valley, CA 95066, or call (408) 438-8608. Be sure to tell them I said hi. STRLINK OBJECT Page 2 of 7 USES The StrLink unit USES the following units: {$IFDEF TPRO5} TpString, {$ENDIF} Objects, ObjectA, StrObj; The TpString unit is supplied with the TurboPower Software TPRO5 toolkit. Please see the section on conditional compilation directives for more information about this powerful toolkit. The Objects unit is on Turbo Pascal v5.5 disk #3. It imple- ments the foundation of a singly linked list object. The ObjectA unit is included in this file IF this was pulled down from a BBS. If it was pulled down from CompuServe, then you must also download OBJA.ARC from BPROGA forum LIBrary 1. ObjectA builds on the Objects unit by offering a more powerful descendent object for singly linked lists. The StrObj unit is included with StrLink. It implements the foundation for a string object. TYPES SortedOrderType = (ForwardOrder, ReverseOrder, AscendingOrder, DescendingOrder); StrLinkList = OBJECT(LinkList) CurrentStrPtr : StrObjectPtr; UniqueStringsOnly : BOOLEAN; SortedOrder : SortedOrderType; CaseMatters : BOOLEAN; CONSTRUCTOR Init(UniqueStrings : BOOLEAN; SortSpecifier : SortedOrderType; IgnoreCase : BOOLEAN); FUNCTION GetSpecificString(NodePos : LONGINT) : STRING; PROCEDURE DeleteSpecificString(NodePos : LONGINT); FUNCTION ReadStrings(TheFilename : STRING) : BYTE; FUNCTION WriteStrings(TheFilename : STRING; AppendFile : BOOLEAN) : BYTE; PROCEDURE AddString(TheStr : STRING); PROCEDURE DeleteString(TheStr : STRING); STRLINK OBJECT Page 3 of 7 FUNCTION Exists(TheStr : STRING) : BOOLEAN; FUNCTION ExistsSubstring(TheSubStr : STRING) : BOOLEAN; PROCEDURE DeleteStringsWithoutSubstring(TheSubStr : STRING; IgnoreCase : BOOLEAN); PROCEDURE DeleteStringsWithSubstring(TheSubStr : STRING; IgnoreCase : BOOLEAN); PROCEDURE DeleteDuplicates; PROCEDURE DeleteLeadNullStrings; PROCEDURE DeleteNullStrings; PROCEDURE DeleteTrailNullStrings; PROCEDURE InitCurrent; FUNCTION CurrentString : STRING; PROCEDURE ChangeCurrentString(NewStr : STRING); FUNCTION FirstString : STRING; FUNCTION LastString : STRING; PROCEDURE Advance; PROCEDURE Retreat; FUNCTION MoreStrings : BOOLEAN; FUNCTION NoMoreStrings : BOOLEAN END; PROCEDURES & FUNCTIONS CONSTRUCTOR Init(UniqueStrings : BOOLEAN; SortSpecifier : SortedOrderType; IgnoreCase : BOOLEAN); Initializes the StrLinkList instantiation. UniqueStrings dictates if the list should ignore duplicate strings. IgnoreCase dictates if the strings should be viewed as all uppercase, even though they will be stored as upper/lowercase. SortSpecifier dictates how the list is sorted. ForwardOrder means strings will be added to the END of the list. This is the same as reading a regular text file. ReverseOrder means strings will be added to the BEGINNING of the list. This would be like reading a text file backwards. AscendingOrder dictates that the list will be sorted in ascending order. DescendingOrder dictates that the list will be sorted in descending order. The IgnoreCase boolean is important if you choose to sort the list in ascending/descending order. If IgnoreCase is FALSE, "BBBB" will come before "aaaa". When IgnoreCase is TRUE, all strings are viewed as uppercase. But don't worry, they're stored exactly as they are. IgnoreCase is important only during string comparisons. STRLINK OBJECT Page 4 of 7 DESTRUCTOR Done; This destructor is INHERITED from an ancestral object. It completely removes all strings from the list and frees up their associated memory. You must call this destructor/procedure when you're finished with the list. (You can "flush" the list for a new purpose by calling Done, then calling Init once more.) FUNCTION GetSpecificString(NodePos : LONGINT) : STRING; This function returns a string from the StrLinkList based on the position of a particular string in the list. This is useful for people who use TurboPower Software's TPRO5 TpPick unit, for example. The position is represented by NodePos. This function returns a null string if NodePos is <= 0 or if it is > the last node on the list. The CurrentString function will return this string after you use this function. PROCEDURE DeleteSpecificString(NodePos : LONGINT); This procedure deletes a string from the StrLinkList based on the position of the string in the list, represented by NodePos. It does nothing if NodePos is <= 0 or if it is > the last string position on the list. The CurrentString function points to NO string after this call. FUNCTION ReadStrings(TheFilename : STRING) : BYTE; Reads strings from TheFilename and adds them to the list. The IORESULT value is returned as the result of this function. FUNCTION WriteStrings(TheFilename : STRING; AppendFile : BOOLEAN) : BYTE; Writes all strings on the list to TheFilename. The IORESULT value is returned as the result of this function. AppendFile dictates if the strings should be appended to the end of a file if it already exists. NOTE: the file must exist if AppendFile is set to TRUE. PROCEDURE AddString(TheStr : STRING); Adds a string to the list. It does nothing if the string is redundant AND UniqueStrings was TRUE when you called Init. The CurrentString function is undefined after calling this routine. (It may, or may not, point to the newly added string.) PROCEDURE DeleteString(TheStr : STRING); This procedure deletes the given string from the list. It does nothing if the string doesn't exist. The CurrentString function points to NO string after this call. STRLINK OBJECT Page 5 of 7 FUNCTION Exists(TheStr : STRING) : BOOLEAN; Determines if the given string is on the list. FUNCTION ExistsSubstring(TheSubStr : STRING) : BOOLEAN; Similar to the Exists function, this routine determines if a given substring is on the StrLinkList. It searches every string on the list until it either finds the substring inside one of the strings, or it runs out of strings to search. This function is TRUE if TheSubStr is a null string and at least one string exists on the list. If the result is TRUE, CurrentString will return the first string on the list containing the given substring. PROCEDURE DeleteStringsWithoutSubstring(TheSubStr : STRING; IgnoreCase : BOOLEAN); This procedure deletes any string from the list that doesn't contain the given substring. No strings will be deleted if the substring is a null string. The IgnoreCase variable dictates whether upper/lower case is relevant during the search. (This overrides the string comparison check you specified when you called Init.) PROCEDURE DeleteStringsWithSubstring(TheSubStr : STRING; IgnoreCase : BOOLEAN); This procedure deletes any string from the list that DOES contain the given substring. No strings will be deleted if the substring is a null string. The IgnoreCase variable dictates whether upper/lower case is relevant during the search. (This overrides the string comparison check you specified when you called Init.) PROCEDURE DeleteDuplicates; This procedure deletes duplicate strings from the list. It does nothing if you specified unique strings during the call to the Init procedure. PROCEDURE DeleteLeadNullStrings; This procedure deletes leading null strings from the list. It's an easy way to strip out any leading blank lines from a text file. Null strings that exist past the first non-null string in the list are left alone. PROCEDURE DeleteNullStrings; This procedure deletes all null strings from the list. It's an easy way to delete all the blank lines from a text file you just read from disk. STRLINK OBJECT Page 6 of 7 PROCEDURE DeleteTrailNullStrings; This procedure deletes trailing null strings from the list. It's an easy way to delete blank lines from the end of a text file you just read from disk. PROCEDURE InitCurrent; This function initializes the CurrentString so it returns the first first string on the list (assuming there is at least one string on the list). FUNCTION CurrentString : STRING; This function returns the current string pointed to in the list. You must use the InitCurrent procedure to set the current string to the first string in the list. CurrentString returns a null string if it points to no string. (Use the MoreStrings and NoMoreStrings functions to determine if CurrentString points to a string.) PROCEDURE ChangeCurrentString(NewStr : STRING); Changes the current string to the new string. FUNCTION FirstString : STRING; Returns the first String in the list. It returns a null string if there are no strings in the list. The CurrentString function will also return the first string after you call this function. FUNCTION LastString : STRING; Returns the last String in the list. It returns a null string if there are no strings in the list. The CurrentString function will also return the last string after you call this function. PROCEDURE Advance; This procedure simply moves the current string pointer to the next string in the list. You should use the MoreStrings or NoMoreStrings functions to see if there is another string on the list after making this call. PROCEDURE Retreat; This procedure simply moves the current string pointer to the previous string in the list. You should use the MoreStrings or NoMoreStrings functions to see if there is another string on the list after making this call. STRLINK OBJECT Page 7 of 7 FUNCTION MoreStrings : BOOLEAN; Returns TRUE or FALSE, explaining if CurrentString points to a valid string in the list. Should be used with the Advance and Retreat procedures. FUNCTION NoMoreStrings : BOOLEAN; The opposite of the MoreStrings function. See above.