There are many ways to turn a &str
into a String
in Rust and therefore many ways to concatenate two &str
s.
Here I benchmark several different ways to concatenate the strings "2014-11-28"
, "T"
and "12:00:09Z"
into "2014-11-28T12:00:09Z"
.
Thanks to all the comments on and discussion on reddit where I posted these originally only 7 benchmarks. Some go into the details of what is going on in the background of these operations.
- benchmarks:
cargo +nightly bench
- tests:
cargo +nightly test --benches
$ cargo +nightly bench
running 36 tests
test array_concat_test ... ignored
test array_join_long_test ... ignored
test array_join_test ... ignored
test collect_from_array_to_string_test ... ignored
test collect_from_vec_to_string_test ... ignored
test format_macro_implicit_args_test ... ignored
test format_macro_test ... ignored
test from_bytes_test ... ignored
test mut_string_push_str_test ... ignored
test mut_string_push_string_test ... ignored
test mut_string_with_capacity_push_str_char_test ... ignored
test mut_string_with_capacity_push_str_test ... ignored
test mut_string_with_too_little_capacity_push_str_test ... ignored
test mut_string_with_too_much_capacity_push_str_test ... ignored
test string_from_all_test ... ignored
test string_from_plus_op_test ... ignored
test to_owned_plus_op_test ... ignored
test to_string_plus_op_test ... ignored
test array_concat ... bench: 30 ns/iter (+/- 2)
test array_join ... bench: 22 ns/iter (+/- 0)
test array_join_long ... bench: 24 ns/iter (+/- 1)
test collect_from_array_to_string ... bench: 32 ns/iter (+/- 2)
test collect_from_vec_to_string ... bench: 35 ns/iter (+/- 24)
test format_macro ... bench: 67 ns/iter (+/- 1)
test format_macro_implicit_args ... bench: 67 ns/iter (+/- 1)
test from_bytes ... bench: 0 ns/iter (+/- 0)
test mut_string_push_str ... bench: 24 ns/iter (+/- 0)
test mut_string_push_string ... bench: 69 ns/iter (+/- 1)
test mut_string_with_capacity_push_str ... bench: 10 ns/iter (+/- 0)
test mut_string_with_capacity_push_str_char ... bench: 10 ns/iter (+/- 0)
test mut_string_with_too_little_capacity_push_str ... bench: 39 ns/iter (+/- 0)
test mut_string_with_too_much_capacity_push_str ... bench: 11 ns/iter (+/- 0)
test string_from_all ... bench: 43 ns/iter (+/- 0)
test string_from_plus_op ... bench: 34 ns/iter (+/- 26)
test to_owned_plus_op ... bench: 29 ns/iter (+/- 4)
test to_string_plus_op ... bench: 27 ns/iter (+/- 0)
test result: ok. 0 passed; 0 failed; 18 ignored; 18 measured; 0 filtered out; finished in 31.34s
0 ns/iter (+/- 0) from_bytes
10 ns/iter (+/- 0) mut_string_with_capacity_push_str
10 ns/iter (+/- 0) mut_string_with_capacity_push_str_char
11 ns/iter (+/- 0) mut_string_with_too_much_capacity_push_str
22 ns/iter (+/- 0) array_join
24 ns/iter (+/- 0) mut_string_push_str
24 ns/iter (+/- 1) array_join_long
27 ns/iter (+/- 0) to_string_plus_op
29 ns/iter (+/- 4) to_owned_plus_op
30 ns/iter (+/- 2) array_concat
32 ns/iter (+/- 2) collect_from_array_to_string
34 ns/iter (+/- 26) string_from_plus_op
35 ns/iter (+/- 24) collect_from_vec_to_string
39 ns/iter (+/- 0) mut_string_with_too_little_capacity_push_str
43 ns/iter (+/- 0) string_from_all
67 ns/iter (+/- 1) format_macro
67 ns/iter (+/- 1) format_macro_implicit_args
69 ns/iter (+/- 1) mut_string_push_string
let datetime = &[DATE, T, TIME].concat();
let datetime = &[DATE, TIME].join(T);
let datetime = &[DATE, T, TIME].join("");
let list = [DATE, T, TIME];
let datetime: String = list.iter().map(|x| *x).collect();
let list = vec![DATE, T, TIME];
let datetime: String = list.iter().map(|x| *x).collect();
let datetime = &format!("{}{}{}", DATE, T, TIME);
let datetime = &format!("{DATE}{T}{TIME}");
use std::ffi::OsStr;
use std::os::unix::ffi::OsStrExt;
use std::slice;
let bytes = unsafe { slice::from_raw_parts(DATE.as_ptr(), 20) };
let datetime = OsStr::from_bytes(bytes);
let mut datetime = String::new();
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);
let mut datetime = Vec::<String>::new();
datetime.push(String::from(DATE));
datetime.push(String::from(T));
datetime.push(String::from(TIME));
let datetime = datetime.join("");
let mut datetime = String::with_capacity(20);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);
let mut datetime = String::with_capacity(20);
datetime.push_str(DATE);
datetime.push('T');
datetime.push_str(TIME);
let mut datetime = String::with_capacity(2);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);
let mut datetime = String::with_capacity(200);
datetime.push_str(DATE);
datetime.push_str(T);
datetime.push_str(TIME);
let datetime = &(String::from(DATE) + &String::from(T) + &String::from(TIME));
let datetime = &(String::from(DATE) + T + TIME);
let datetime = &(DATE.to_owned() + T + TIME);
let datetime = &(DATE.to_string() + T + TIME);