string

C string helpers

Finds the indicies of all locations of the given needle in the haystack. substrings is an array of size_t indicies that the substring is found at. This function allocates the memory for substrings and memory cleanup is managed by the user. num_substrings is a pointer to a pre-allocated size_t that will be modified to contain the number of found substrings and subsequently the size of substrings.

If no substrings are found, substrings will not be allocated and left set to NULL, num_substrings will be 0, and the function will return 0.

Returns 0 if the function is successful. Returns a non-zero value if there is an error.

int find_substrings(const char* haystack, const char* needle, size_t *num_substrings, size_t **substrings);
 
/* Usage */
const char* haystack = "One two three two";
const char* needle = "two";
 
size_t subs_sz = 0;
size_t *subs = NULL;
size_t *subs = find_substrings(haystack, needle, &subs_sz, &subs);
// subs: [ 4, 14 ]
// subs_sz: 2
 
free(subs);

Extracts a substring at a specific index and length. This function returns a copy of the substring in a heap allocated buffer that the user is responsible for freeing. Returns NULL if there is an error.

const char* substr(const char* str, size_t idx, size_t len);
 
/* Usage */
const char *s = substr("One two three", 4, 3);
assert(strcmp(s, "two") == 0);
free(s);