Copyright (C) 2001 Günter Woigk
kio@little-bat.de
This file is free software
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Kio's final° String Library version 0.92 last modified 2001-11-17
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°) up to now, all my string libraries (~5 to 10 of them) were final <:-]
Description
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o No tags before or behind the text
=> full substring capability
=> Assignments to substrings possible; e.g.: a$[10..15] = "anton"
o Max. text length = 0x7FFFFFFE characters
o All character codes [0...255] allowed
o Text sharing for fast passing of text values to/from functions
o Ad-hoc string descriptors for const. text literals for fast passing of text values
Quirks
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o Due to text sharing and ad-hoc string descriptors, strings can be 'shared' or 'dirty'.
Then the contents of the text must not me modified. => use String::MakeWritable()
This only applies to writing to the text as in a$[123]="x" oder a$[10..15] = "anton"
It does not apply to overwriting the string itself as in a$="anton"; a$=b$; or a$=LeftString(b$,n).
o Ad-hoc string descriptors do not protect their text contents, which still can be modified from
'outside' easily:
char b[]="anton";
String a(b); // => a = "anton"
b[0]="X"; // => a = "Xnton"
Member Functions - Overview (simplified)
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o String Creators
String ( ) empty String
String ( void*, length ) String from arbitrary data
String ( length ) String of given length, not cleared
String ( length, fillchar ) String of given length, cleared
o Automatic Type Conversion Creators
String ( char* ) String from c-style string
String ( uchar* ) String from Pascal-style string
String ( char ) String from char
o Operators
String& operator= ( text ) Assignment; text = string, c-string, int, char, etc.
String operator+ ( text ) Text concatenation; text = string, c-string, int, char, etc.
String& operator+= ( text )
String operator* ( times ) Text repetition
String operator*= ( times )
bool operator== ( text ) Comparison; also: <, >, <=, >=, !=
o Functions
String SubString ( long a, long e ) Substring; indexes start with 0
String MidString ( long a, long n ) n characters from the middle
String MidString ( long a ) trailing string starting at position a
String LeftString ( long n ) n characters from the left
String RightString ( long n ) n characters from the right
String NumString ( number ) String from integer or float
String HexString ( number, digits )
String SpaceString ( length, fillchar )
long Len ( )
uchar& operator[] ( index ) note: indexes start with 0
bool IsWritable ( ) test, whether text is writable; that is: not shared and not dirty
void MakeWritable( ) make text writable
void ToUpper ( )
void ToLower ( )
void Replace ( oldchar, newchar )
uchar* PString ( ) get Pascal-style string from String
char* CString ( ) get C-style string from String
long Find ( searchstring, startidx ) search for text starting at startidx; returns -1 if not found
long RFind ( searchstring, startidx ) search backwards
long Find ( searchchar, startidx ) search for single character
long RFind ( searchchar, startidx ) search backwards
Global Function Redefinitions for Convenience - Overview (simplified)
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String emptyString global constant
String SpaceString ( length, fillchar )
String CharString ( char )
uchar* PString ( String )
char* CString ( String )
String SubString ( String, long a, long e )
String MidString ( String, long a, long n )
String MidString ( String, long a )
String LeftString ( String, long n )
String RightString ( String, long n )
String HexString ( number, digits )
String NumString ( number )
String UpperString ( String )
String LowerString ( String )
String ReplaceString(String, oldchar, newchar )
long FindString ( targetstring, searchstring, startidx )
long RFindString ( targetstring, searchstring, startidx )
long FindChar ( targetstring, searchchar, startidx )
long RFindChar ( targetstring, searchchar, startidx )
String Using ( Formatstring, ... );
Technical Details
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o Strings consist of 3 components:
o uchar* text a pointer to the text
o long len length of text
o StrMem* strmem NULL or address of an administration block for dynamically allocated memory
o Strings may have one of three states:
o 'dirty' strmem==NULL && len>0.
The referenced text lies somewhere outside the control of the String class.
o 'shared' strmem!=NULL und strmem.count!=1.
The referenced text is dynamically allocated and shared between multiple Strings.
o 'writable' strmem!=NULL und strmem.count==1.
The referenced text is dynamically allocated and is exclusively used.
o Most String operators create 'dirty' strings for the sake of speed.
e.g.: String("abcde") creates a descriptor which directly points to the text constant "abcde" itself.
Before you can overwrite some characters within this text you must use MakeWritable().
o The copy creator does not create a copy of the source text but shares the source text between source and copy.
The copy of a 'dirty' String is itself 'dirty'.
After copying a 'writable' String both (!) become 'shared'.
Before you can overwrite some characters within this text you must use MakeWritable().
o The assignment operator creates a new, 'writable' String from a 'dirty' source.
This prevents storing a reference to short-lived text in a long-living String.
After assigning a 'writable' String both (!) source and target become 'shared'.
Before you can overwrite some characters within this text you must use MakeWritable().
o Before you can overwrite some characters within a String's text you must make shure that it is 'writable'.
This is what the Functions IsWritable() and of course MakeWritable() are for.
Changes
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2001-11-09 kio: mod: changed behaviour of RightString(a) to SubString(a,len)
2001-11-17 kio: mod: changed behaviour of RightString(n) back to SubString(len-n,len)