C Language String processing function source code

Strstr () function source code

/*

Gets the position pointer that contains the S2 string for the first time in S1.

*/

#include <stdlib.h>

char * MY_STRSTR (const char *s1,const char *S2)

{

if (*s1 = = 0)

{

if (*S2)

Return (char *) NULL;

Return (char *) s1;

}

while (*S1)

{

size_t i;

i = 0;

while (1)

{

if (s2[i] = = 0)

{

Return (char *) s1;

}

if (s2[i]! = S1[i])

{

Break

}

i++;

}

s1++;

}

Return (char *) NULL;

}

int main ()

{

Char *str1 = "Ammana_babi";

Char *str2 = "Babi";

Char *p;

if ((p = my_strstr (str1,str2)) = = NULL)

printf ("Can ' t find the string/"%s/"!/n", str2);

Else

printf ("Find the string/"%s/"!/n", p);

STR1 = "ABC";

str2 = "Def";

if ((p = my_strstr (str1,str2)) = = NULL)

printf ("Can ' t find the string/"%s/"!/n", str2);

Else

printf ("Find the string/"%s/"!/n", p);

System ("pause");

return 0;

}

STRPBRK () function source code

/*

Gets the position pointer of the first character in the S1, which is a s2.

*/

#include <stdlib.h>

char * MY_STRPBRK (const char *S1, const char *S2)

{

const char *c = s2;

if (!*S1)

Return (char *) NULL;

while (*S1)

{

for (c = s2; *c; c + +)

{

if (*s1 = = *c)

Break

}

if (*c)

Break

s1++;

}

if (*c = = '/0 ')

S1 = NULL;

Return (char *) s1;

}

int main ()

{

Char *str1 = "Ammana_babi";

Char *str2 = "Babi";

Char *p;

if ((p = my_strpbrk (str1,str2)) = = NULL)

printf ("No same character!/n");

Else

printf ("%c/n", *p);

STR1 = "ABC";

str2 = "Def";

if ((p = my_strpbrk (str1,str2)) = = NULL)

printf ("No same character!/n");

Else

printf ("%c/n", *p);

System ("pause");

return 0;

}

STRCSPN () function source code

/*

Gets the character position of the first character in the S1, which is a s2.

*/

int my_strcspn (const char *S1, const char *S2)

{

const char *s = S1;

const char *p;

while (*S1)

{

for (p = s2; *p; p++)

{

if (*s1 = = *p)

Break

}

if (*p)

Break

s1++;

}

return s1-s;

}

int main ()

{

Char *str1 = "Ammana_babi";

Char *str2 = "Babi";

int offset;

if (offset = my_strcspn (STR1,STR2)) >= strlen (STR1))

printf ("Can ' t find the same character!/n");

Else

printf ("%c/n", * (str1 + offset));

STR1 = "ABC";

str2 = "Def";

if (offset = my_strcspn (STR1,STR2)) >= strlen (STR1))

printf ("Can ' t find the same character!/n");

Else

printf ("%c/n", * (str1 + offset));

System ("pause");

return 0;

}

C Language String processing function source code