String parse in C - c

Question

Is there a better of parsing the below string instead of doing a strtok() to get each field.
"subject=what&cc=bose#yahoo.com&server=smtp.yahoo.com:8000"
Basically I want to retrieve the value for each field into another char buf's.
Here is my code. Just wanted to know if there is any other better way of doing it (any better string parsing algos)
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#define SUBJECT "subject="
#define CC_LIST "cc="
#define SERVER "server="
static void
get_value (const char *tok, char **rval_buf, size_t field_len)
{
size_t val_size = 0;
if (!tok || !rval_buf)
return;
val_size = strlen(tok + field_len) + 1;
*rval_buf = calloc(1, val_size);
if (*rval_buf) {
strlcpy(*rval_buf, tok + field_len, val_size);
}
}
int
main (int argc, char **argv)
{
/* hard coded buf for testing */
char buf[] = "subject=what&cc=bose#yahoo.com&server=smtp.yahoo.com:8000";
char *subject_text = NULL;
char *cc_list = NULL;
char *server_addr = NULL;
char *tok = NULL;
int field_len = 0;
int val_len = 0;
tok = strtok(buf, "&");
while(tok) {
/*
* Handle the token
*/
/* check if it is subject */
if (strstr(tok, SUBJECT)) {
get_value(tok, &subject_text, strlen(SUBJECT));
} else if (strstr(tok, CC_LIST)) { /* check if it is CC */
get_value(tok, &cc_list, strlen(CC_LIST));
} else if (strstr(tok, SERVER)) { /* check if it is server */
get_value(tok, &server_addr, strlen(SERVER));
}
tok = strtok(NULL, "&");
}
/* dump data */
fprintf(stdout, "\nSUBJECT: \"%s\"\nCC_LIST: \"%s\"\nSERVER: \"%s\" \n\n",
subject_text, cc_list, server_addr);
return EXIT_SUCCESS;
}

Answer 1

strstr searches for one string ("the needle") inside another ("the haystack"), but you really only want to know whether the needle is the beginning of the haystack.
Here's a small suggestion: (requires #include <stdbool> or change the booleans to ints. I like bools.)
static bool
getval(const char* haystack, const char** res, const char* needle, size_t len) {
if (haystack && 0 == strncmp(haystack, needle, len)) {
*res = strdup(haystack + len);
return true;
}
return false;
}
and later:
for (tok = strtok(buf, "&"); tok; tok = strtok(NULL, "&")) {
getval(tok, &subject_text, SUBJECT, strlen(SUBJECT)) ||
getval(tok, &cc_list, CC_LIST, strlen(CC_LIST)) ||
getval(tok, &server_addr, SERVER, strlen(SERVER));
}
You can actually get away with doing the strlen inside of getval, which cuts down a lot on the noise, because most modern compilers are clever enough to inline getval and constant-fold the length of a constant string.

Answer 2

Use strtok()
char *strtok(char *str, const char *delim)
You can put '&' as a delimeter

Answer 3

I wrote a quick-n-dirty splitter for you:
int split(char* input, char delim, char*** parts)
{
int count = 1;
char** result;
char* t = input;
while(*t != '\0')
{
if (*t++ == delim)
{
count++;
}
}
result = (char**)malloc(count * sizeof(char*));
t = input;
int i = 0;
result[i] = input;
while(*t != '\0')
{
if (*t == delim)
{
*t = '\0';
result[++i] = ++t;
}
else
{
t++;
}
}
*parts = result;
return count;
}
int main()
{
char raw[] = "subject=\"some text\"&cc=abcd&server=acd.com";
char* str = _strdup(raw);
char** parts;
char** keyval;
int cnt = split(str, '&', &parts);
for(int i=0; i<cnt; ++i)
{
split(parts[i], '=', &keyval);
printf("[%d]: %s <--> %s\n", i, keyval[0], keyval[1]);
free(keyval);
}
free(parts);
getchar();
return 0;
}
Output
[0]: subject <--> "some text"
[1]: cc <--> abcd
[2]: server <--> acd.com