Implementing String in Metal for use on GPU

The C++ String class implemented in Metal (MSL).

Definitions:

Type Conversion:

int stoi(const char str[])

long stol(const char str[])

unsigned int stoul(const char str[])

float stof(const char str[])

Capacity:

size_t length(const char str[])

size_t size(const char str[])

size_t max_size(const char str[])

void clear(char str[])

bool empty(char str[])

Element access:

char at(const char str[], size_t pos)

char back(const char str[])

char front(const char str[])

Modifiers:

void append(char dest[], const char src[])

void push_back(char str[], char c)

void assign(char dest[], const char src[])

void assign(char dest[], const char src[], size_t subpos, size_t sublen)

void assign(char dest[], const char src[], size_t sublen)

void assign(char str[], size_t n, char c)

void insert(char dest[], size_t pos, const char src[])

void insert(char dest[], size_t pos, const char src[], size_t subpos, size_t sublen)

void insert(char dest[], size_t pos, const char src[], size_t sublen)

void insert(char dest[], size_t pos, size_t n, const char src[], size_t sublen)

void erase(char str[], size_t pos, size_t len)

void replace(char dest[], size_t pos, size_t len, const char src[])

void replace(char dest[], size_t pos, size_t len, const char src[], size_t subpos, size_t sublen)

void replace(char dest[], size_t pos, size_t len, const char src[], size_t sublen)

void replace(char dest[], size_t pos, size_t len, char c)

void swap(char swap1[], char swap2[])

void pop_back(char str[])

String operations:

void copy(char dest[], const char src[], size_t len, size_t pos)

size_t find(const char full_str[], const char search_substr[])

size_t find(const char full_str[], const char search_substr[], size_t pos)

size_t find(const char str[], char c)

size_t find(const char str[], char c, size_t pos)

size_t rfind(const char full_str[], const char search_substr[])

size_t rfind(const char full_str[], const char search_substr[], size_t pos)

size_t rfind(const char str[], char c)

size_t rfind(const char str[], char c, size_t pos)

size_t find_first_of (const char str[], const char chars[])

size_t find_first_of (const char str[], const char chars[], size_t pos)

size_t find_first_of (const char str[], char c)

size_t find_first_of (const char str[], char c, size_t pos)

size_t find_last_of(const char str[], const char chars[])

size_t find_last_of(const char str[], const char chars[], size_t pos)

size_t find_last_of(const char str[], char c)

size_t find_last_of(const char str[], char c, size_t pos)

size_t find_first_not_of(const char str[], const char chars[])

size_t find_first_not_of(const char str[], const char chars[], size_t pos)

size_t find_first_not_of(const char str[], const char c)

size_t find_first_not_of(const char str[], const char c, size_t pos)

size_t find_last_not_of(const char str[], const char chars[])

size_t find_last_not_of(const char str[], const char chars[], size_t pos)

size_t find_last_not_of(const char str[], char c)

size_t find_last_not_of(const char str[], char c, size_t pos)

void substr(char dest[], const char src[], size_t pos, size_t len)

int compare(const char str[], const char compare_str[])

int compare(const char str[], size_t compare_str_pos, size_t compare_str_len, const char compare_str[])

Performance

Find

string len	substr len	find runtime
5	1	0.797 ms
10	1	0.806 ms
10	5	0.832 ms
25	1	0.846 ms
25	5	0.834 ms
25	10	0.831 ms
50	1	0.861 ms
50	5	0.869 ms
50	10	0.867 ms
50	25	0.878 ms
100	1	0.926 ms
100	5	0.933 ms
100	10	0.940 ms
100	25	0.945 ms
100	50	0.954 ms

(averaged for 1,000 runs where substr wasn't in string)

Replace

string len	substr len	replace runtime
5	1	0.819 ms
10	1	0.835 ms
10	5	0.846 ms
25	1	0.848 ms
25	5	0.853 ms
25	10	0.853 ms
50	1	0.864 ms
50	5	0.871 ms
50	10	0.915 ms
50	25	0.905 ms
100	1	0.919 ms
100	5	0.930 ms
100	10	0.934 ms
100	25	0.958 ms
100	50	0.978 ms

(averaged for 1,000 runs)

References

https://cplusplus.com/reference/string/string/
https://developer.apple.com/metal/