Question

part8.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

/* In part8.c, you will implement a function, called string_token, that
* splits a string into a sequence of tokens according to
* a specific delimiter character.
*
* On the first call, the string to be parsed is given in the "str" argument. The "saveptr"
* argument is ignored. The function returns "saveptr", which is to be used internally by string_token() in
* subsequent calls that parse the same string in order to maintain context.
*
* On a subsequent call to parse the same string, the caller is expected to set the
* "str" argument to be NULL, and set "saveptr" to be the returned saveptr value of
* the previous string_token invocation.
*
* Each call to string_token returns a pointer to a null-terminated string containing the next token.
* This string does not include the delimiting byte. More concretely, the next token is determined by
* scanning forward (from either "savedptr" or from "str" depending on whether it's the first or subsequent string_token call)
* for the next * non-delimiter character. If no such character is found, the function returns NULL.
*
* Here's an example usage of the function string_token:
*
* char str[100] = "aaa;;bbb;ccc"
* char *savedptr;
*
* while (1) {
*    token = * string_token(str, ';', &savedptr);
*    if (token == NULL) {
*       break;
*    }
*    printf("%s\n"); str = NULL; // set str to be NULL for subsequent string_token call
* }
*
* The above code snippet should print out 3 lines:
* aaa
* bbb
* ccc
*
*
* Note: The string_token function is supposed to modify the buffer holding the
* argument "str". It should not perform any memory allocation (e.g. using
* malloc).
*
*
* Note: This function is similar but not identical to the standard C library's
* strtok_r(...) function.
*/

char *
string_token(char *str, char delim, char **saveptr)
{
   //TODO: Your code here
}

part8.h

#pragma once

char *string_token(char *str, char delim, char **saveptr);

Answer 1

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

char* string_token(char *str, char delim, char **saveptr)
{
char *remaining;

if (str == NULL)
str = *saveptr;

if (str == NULL)
{
*saveptr = str;
return NULL;
}

char *delim_ptr = strchr(str, delim);

if(delim_ptr == NULL)
{
remaining = NULL;
}
else
{
remaining = delim_ptr + 1; //contains the string after the first occurrence of delimiter
*delim_ptr = '\0'; //Now str will contain string before delimiter
}

if ( remaining == NULL || *remaining == '\0' )
{
*saveptr = remaining;
return str;
}

*saveptr = remaining; //saveptr contains the remaining part
return str;
}

int main()
{
char p[100] = "aaa;;bbb;ccc";
char *str = p;
char *savedptr;
while (1) {
char *token = string_token(str, ';', &savedptr);
if (token == NULL) {
break;
}
printf("%s\n", token);
str = NULL; // set str to be NULL for subsequent string_token call
}
}