Implementation of C string processing functions

1. strlen (), calculate the string length

Int strlen (const char string)

{

Int I = 0;

While (string [I]) I ++;

Return I;

}

2. strcpy (), copy the string.

 

Char * strcpy (char * destination, const char * source)

{

While (* destinaton ++ = * source ++ );

Return (destination-1 );

}

3. strcat (), string connection.

 

Char * strcat (char * target, const char * source)

{

Char * original = target;

While (* target) target ++; // Find the end of the string

While (* target ++ = * source ++ );

Return (original );

}

4. streql () to determine whether two strings are equal.

 

Int streql (char * str1, char * str2)

{

While (* str1 = * str2) & (* str1 ))

{

Str1 ++;

Str2 ++;

}

Return (* str1 = NULL) & (* str2 = NULL ));

}

5. strchr (): searches for a character in the string.

 

Char * strchr (const char * string, int letter)

{

While (* string! = Letter) & (* string ))

String ++;

Return (string );

}

6. chrcnt () is used to calculate the number of times a character appears in a string.

Int chrcnt (const char * string, int letter)

{

Int count = 0;

While (* string)

If (* string = letter) count ++;

Return count;

}

7. strcmp () to determine whether two strings are equal.

Int strcmp (const char * str1, const char * str2)

{

While (* str1 = * str2) & (* str1 ))

{

Str1 ++;

Str2 ++;

}

If (* str1 = * str2 )&&(! * Str1) // Same strings

Return o;

Else if (* str1 )&&(! * Str2) // Same but str1 longer

Return-1;

Else if (* str2 )&&(! * Str1) // Same but str2 longer

Else

Return (* str1> * str2 )? -1:1 );

}