Performance

Performance has been tested on MacBook Pro 2017, using Rust 1.38 and tinystr 0.3.2.

All benchmarks use black_box wrapper.

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	1.078 us	31.51 ns	98.67 ns	115.47 ns
8	1.009 us		101.77 ns	119.43 ns
16	1.081 us			122.64 ns

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	1.088 us	20.70 ns	26.93 ns	32.07 ns
8	1.105 us		27.00 ns	31.60 ns
16	1.238 us			31.72 ns

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	1.087 us	20.79 ns	27.36 ns	33.85 ns
8	1.097 us		27.14 ns	33.22 ns
16	1.109 us			33.19 ns

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	1.139 us	23.80 ns	26.90 ns	42.27 ns
8	1.165 us		27.01 ns	42.39 ns
16	1.173 us			42.15 ns

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	42.10 ns	21.45 ns	30.64 ns	34.90 ns
8	52.19 ns		30.66 ns	35.05 ns
16	78.00 us			34.95 ns

Char Limit	String	TinyStr4	TinyStr8	TinyStr16
4	659.48 ns	85.80 ns	86.07 ns	141.57 ns
8	433.12 ns		90.79 ns	146.25 ns
16	380.83 us			147.61 ns

Performance vs. other small string libraries

Crate	Version	Notes
istring	0.1.13	`IString::from` and Rust Nightly has been used
smol_str	0.1.15	`SmolStr::from` has been used
smallstr	0.1.0	`FromStr` with `<[u8; 4/8/16]>` has been used
arraystring	0.3.0	`FromStr` with U4/U8/U16 has been used

Char Limit	SmolStr	smallstr	ArrayString	istring	String	TinyStr4	TinyStr8	TinyStr16
4	318.70 ns	184.02 ns	109.26 ns	130.07 ns	1.078 us	31.51 ns	98.67 ns	115.47 ns
8	309.23 ns	185.24 ns	133.08 ns	131.42 ns	1.009 us		101.77 ns	119.43 ns
16	307.28 ns	248.08 ns	172.67 ns	132.88 ns	1.081 us			122.64 ns

Char Limit	SmolStr	smallstr	ArrayString	istring	String	TinyStr4	TinyStr8	TinyStr16
4	1.584 us	1.053 us	743.74 ns	1.169 us	659.48 ns	85.80 ns	86.07 ns	141.57 ns
8	1.343 us	706.87 ns	498.56 ns	870.97 ns	433.12 ns		90.79 ns	146.25 ns
16	1.190 us	727.96 ns	467.14 ns	724.64 ns	380.83 ns			147.61 ns

For other operations, SmolStr, ArrayString, smallstr and istring have performance comparable to String.