Comparison of cstring, String, char * (1)

(1) Overview

String and cstring are both string template classes. string is a string class defined by the standard template class (STL) and has been incorporated into the C ++ standard;

Cstring (typedef cstringt <tchar, strtraitmfc <tchar> cstring) is the most common string class in Visual C ++. It inherits from the csimplestringt class and is mainly used in MFC and ATL programming, the main data types include char (used in ANSI), wchar_t (UNICODE), and tchar (both ANSI and Unicode );

Char * is the most commonly used string pointer in C programming. It generally ends with '\ 0;

(2) Construction

String is convenient and can be constructed from almost all strings, including cstring and char *;

Followed by cstring, which can be constructed from some basic string variables, including char;

Char * has no constructor and can only be assigned a value;

Example:

Char * psz = "joise ";

Cstring CSTR (psz );

String STR (CSTR );

(3) Operator Overloading

A) operator =

String is the most convenient, and almost all strings can be assigned directly, including cstring and char *;

Followed by cstring. You can directly assign values using some basic strings, including char;

Char * can only be assigned values by pointers, which is extremely dangerous. We recommend that you use strcpy or memcpy. In addition, if the initial value is not assigned to char *, we recommend that you set it to null first, to avoid wild pointers and drive you crazy;

Example:

Char * psz = NULL;

Psz = new char [10]; // Of course, the above is directly written as char * psz = new char [10 ];

Memset (psz, 0, 10 );

Strcpy (psz, "joise ");

Cstring CSTR;

CSTR = psz;

String STR;

STR = psz;

STR = CSTR;

Delete [] psz;

B) operator +

String is similar to cstring. It can be added directly to char *, but the + operator cannot be used with each other. That is, string STR = STR + CSTR is invalid and must be converted to char *;

Char * has no + operation. Only two pointers can be connected using strcat;

Example:

Char * psz = "joise ";

Cstring CSTR = psz;

CSTR = CSTR + psz;

String STR = psz;

STR = STR + psz;

Strcat (psz, psz );

Strcat (psz, CSTR); // valid

Strcat (psz, STR); // invalid. Therefore, cstring can be automatically converted to const char *, but string cannot.

C) operator ++ =

String is the most powerful and can be used with almost all string variables + =, including cstring and char *;

Followed by cstring, which can be + = with some basic string variables, including char;

Char * has no + = Operator and can only use strcat to connect two pointers;

D) operator []

The cstring is the best. When a cross-border request is made, an asserted exception is thrown;

The results of the out-of-bounds string and char * subscripts are undefined;

Example:

Char * psz = "joise ";

Cstring CSTR = psz;

Cout <CSTR [8];

String STR = psz;

Cout <STR [8];

Cout <psz [8];

E) operator =, Operator! =, Operator>, operator <, operator> =, perator <=

Cstring and string cannot be compared, but both can be compared with char * and compared with the value rather than the address;

Cout <(psz = CSTR );

Cout <(psz = Str );

Cout <(STR = psz );

Cout <(CSTR = psz); // aboveCodeReturns 1

(4) CommonAlgorithm

A) Search

Function	Char *	String	Cstring
Search for a specified value	Strchr Strstr Strrstr Strspns	Find	Find
The first matched Value		Fild_first_of	Findoneof
Start searching later			Reservefind
Matching Method		Find_if

Note: In find_if, values in the range are substituted into the matching function one by one until true is returned.

B) Comparison

Function	Char *	String	Cstring
Search for a specified value (case sensitive)	Strcmp Strncmp Strcoll _ Strncoll	Operator < Operator> Operator <= Operator> = Operator = Operator! =	Collate Compare
Search for the specified value (Case Insensitive)	_ Stricmp _ Strnicmp _ Stricoll _ Strnicoll		Collatenocase Comparenocas

Note: If the return value is <0, the previous value is smaller than the subsequent value, and vice versa.

C) replace

Function	Char *	String	Cstring
Search for a specified value	_ Strset _ Strnset	Replace Replace_copy Replace_copy_if Replace_if	Replace

D) insert

Function	Char *	String	Cstring
Search for a specified value		Insert	Insert