Use the C language to implement string processing library functions and extend

1. Implement the basic C language library functions:

int Mystrlen (const char* str);//Gets the length of the string based on the first address of the incoming string; The return value is length

int Mystrlen (const char* STR)

{

if (str = = NULL)

return 0;

int length=0;

while (*str! = ')

{

length++;

str++;

}

return length;

}

void* mystrcpy (char* des, const char* source);//copy Source to des

void* mystrcpy (char* des, const char* source)
{
if (des = = NULL | | source = = NULL)
return NULL;
char *desbak = des;
while (((*des++) = (*source++))! = ' + ');
*des = ' + ';
return desbak;
}

void * MYSTRCAT (char* des, const char *source);//Add source to the end of Des

void * MYSTRCAT (char* des, const char *source)
{
if (Source = = NULL | | | des = = NULL)
return NULL;
if (Mystrlen (source) = = 0)
Return des;
Des = (char*) realloc (DES, Mystrlen (des) + mystrlen (source) + 1);

int i = Mystrlen (DES);
while (*source! = ')
{
* (des + i) = *source;
i++;
source++;
}
* (des + i) = ' + ';
Return des;
}

char* mystrrev (const char* str); String reversal

char* mystrrev (const char* STR)
{
int i = 0;
int len = Mystrlen (str);
char* res = (char*) calloc (len+1,sizeof (char));
* (res + len) = ' + ';
for (i = len-1; I >= 0; I--, str++)
{
* (res + i) = *str;
}
return res;
}

int str2int (const char* str);//convert integer string to integer; return value is result integer, failure returns-1

int str2int (const char* STR)
{
if (str = = NULL)
return-1;
char* strbak = str;
int res = 0;
while (*str! = ')
{
if (*str< ' 0 ' | | | *str> ' 9 ')
{
return-1;
}
str++;
}
str = Strbak;
while (*str! = ')
{
Res *= 10;
int temp = *str-48;
res + = temp;
str++;
}
return res;
}

char* int2str (int num);//Converts a positive integer to a string, returning the first address of the string

char* int2str (unsigned int num)
{
int numbak = num;
int n=0;//computes the number of int digits
while (num! = 0)
{
n++;
Num/= 10;
}
char* res = (char*) calloc (n+1,sizeof (char));
char* Resbak=res;
num = Numbak;
while (num! = 0)
{
*res = num% 10 + 48;
res++;
Num/= 10;
}
*res = ' + ';
Resbak = Mystrrev (Resbak);
return resbak;
}

2. According to the library functions written above, some extended functions are implemented:

typedef struct _MYSTRING//defines the string structure, including the string and its length

{

Char *p;

int length;

} myString;

int initstring (myString *string, char* str);//Initialize string

int initstring (myString *string, char* str)
{
if (str = = NULL)
return-1;
int length = Mystrlen (str);

String->p = (char*) calloc (length + 1,sizeof (char));
mystrcpy (STRING->P,STR);
string->length = length;
return 1;
}

void * Findchar (const myString *string, const char FINDCH);//Find a specific character and return to the first address

void * Findchar (const myString *string, char findch)
{
char* s = string->p;
while (*s! = ')
{
if (*s== findch)
return s;
s++;
}
return NULL;
}

void * findString (const myString *string,const char* FINDSTR);//Find String, return first address, cannot find return null

void * findString (const myString *string,const char* findStr)
{
if (NULL = = findStr)
return NULL;
if (Mystrlen (FINDSTR) > Mystrlen (string->p))
return NULL;

char* s = string->p;
CHAR*SP = NULL;

int i = 0,j=0;
for (i = 0; i < string->length-1; i++)
{
char* fs = FINDSTR;
if (* (s + i) = = * (FS))
{
SP = s + i;
for (j = 0; J < Mystrlen (FINDSTR)-1; j + +)
{
sp++;
fs++;
if (*sp! = *fs)
Break
}
if (J ==mystrlen (FINDSTR)-1)
return s + i;
}
}
return NULL;
}

int Addchar (myString *string, Char addch, char* POS),//pos null is added after string, otherwise a character is added at the specified position; Return 1 means the operation failed

int Addchar (myString *string, Char addch, char* POS)//pos to null means to add after string
{
if (pos = = NULL)
{
String->p = (char *) realloc (string->p, string->length + 2);
Mystrcat (String->p, &ADDCH);
String->length + = 1;
return 1;
}

if (pos<string->p | | pos>string->p + string->length)
return-1;

int i = string->length, addlength = pos-string->p;
String->p = (char *) realloc (string->p,string->length+2);
Char *s = string->p;
* (s + i + 1) = ' + ';

for (i = string->length; i > addlength; i--)
{
* (s + i) = * (s+i-1);
}
* (s + i) = ADDCH;
String->length + = 1;
return 1;
}

int addstring (myString *string, const char* ADDSTR, char* pos),//pos null is added after string, otherwise a string is added at the specified position; Return 1 means the operation failed

int addstring (myString *string, const char* ADDSTR, char* POS)
{
if (pos = = NULL)
{
Mystrcat (String->p, ADDSTR);
String->length + = Mystrlen (ADDSTR);
return 1;
}

if (pos<string->p | | pos>string->p + string->length| | Addstr==null)
return-1;

String->length + = Mystrlen (ADDSTR);

int i = String->length+mystrlen (addstr), addlength = pos-string->p;
String->p = (char *) realloc (string->p, String->length +mystrlen (ADDSTR) +1);
Char *s = string->p;
* (s + i) = ' + ';

for (i = String->length+mystrlen (addstr)-1; i > addlength; i--)
{
* (s + i) = * (S + i-mystrlen (ADDSTR));
}
while (*addstr! = ')
{
* (s + i) = *addstr;
i++;
addstr++;
}

return 1;
}

void Deletechar (myString *string,char deletech,int tag),//tag is 1, all specified characters are deleted, otherwise, only the first

void Deletechar (myString *string, char deletech,int tag)
{
char * pos = (char*) Findchar (string, Deletech);
if (pos = = NULL)
return;

while (*pos! = ')
{
*pos = * (pos+ 1);
pos++;
}
String->length-= 1;
if (tag = = 1)
{
while (Findchar (string, Deletech)! = NULL)
Deletechar (string, deletech,1);
}
}

void DeleteString (myString *string,const char *deletestr,int tag),//tag is 1, all specified characters are deleted; otherwise, only the first one is deleted;

void DeleteString (myString *string, const char *deletestr,int tag)
{
char * pos = (char*) findString (string, deletestr);
if (pos = = NULL)
Return

while (* (Pos+mystrlen (DELETESTR)-1)! = ' + ')
{
*pos = * (pos + mystrlen (DELETESTR));
pos++;
}
String->length-= Mystrlen (DELETESTR);
if (tag ==1)
{
while (FindString (string, deletestr)! = NULL)
DeleteString (string, deletestr,1);
}
}

void Updatechar (myString *string,char oldch,char newch);//Update one character

void Updatechar (myString *string, Char Oldch, char newch)
{
char* POS;
if (pos = Findchar (String, oldch) = = = NULL)
Return
*pos = Newch;
while (Findchar (string, OLDCH)! = NULL)
Updatechar (STRING,OLDCH,NEWCH);
}

void Updatestring (myString *string, char* oldstr, const char* NEWSTR);//Update string

void Updatestring (myString *string, char* oldstr, const char* NEWSTR)
{
if (newstr = = NULL)
Return
char* POS;
if (pos = findString (String, oldstr) = = = NULL)
Return
DeleteString (string,oldstr,0);
AddString (String,newstr,pos);
while (FindString (string, oldstr)! = NULL)
{
Updatestring (STRING,OLDSTR,NEWSTR);
}
}

Use the C language to implement string processing library functions and extend