const-hex
This crate provides a fast conversion of byte arrays to hexadecimal strings, both at compile time, and at run time.
It aims to be a drop-in replacement for the hex crate, as well as extending
the API with const-eval, a const-generics formatting buffer, similar
to itoa's, and more.
Version requirement: rustc 1.64+
Performance
This crate's performance is comparable with faster-hex, but the latter only
provides specialized implementations for x86/x86-64.
This crate is 10 to 50 times faster than hex in encoding and decoding, and
100+ times faster than libstd in formatting.
The following benchmarks were ran on an AMD Ryzen 9 7950X, compiled with
1.78.0-nightly (a4472498d 2024-02-15) on x86_64-unknown-linux-gnu.
You can run these benchmarks with cargo bench --features std on a nightly
compiler.
test decode::const_hex::bench1_32b ... bench: 16 ns/iter (+/- 5)
test decode::const_hex::bench2_256b ... bench: 37 ns/iter (+/- 0)
test decode::const_hex::bench3_2k ... bench: 232 ns/iter (+/- 2)
test decode::const_hex::bench4_16k ... bench: 1,672 ns/iter (+/- 12)
test decode::const_hex::bench5_128k ... bench: 12,979 ns/iter (+/- 91)
test decode::const_hex::bench6_1m ... bench: 104,751 ns/iter (+/- 2,068)
test decode::faster_hex::bench1_32b ... bench: 15 ns/iter (+/- 0)
test decode::faster_hex::bench2_256b ... bench: 54 ns/iter (+/- 1)
test decode::faster_hex::bench3_2k ... bench: 253 ns/iter (+/- 3)
test decode::faster_hex::bench4_16k ... bench: 1,831 ns/iter (+/- 20)
test decode::faster_hex::bench5_128k ... bench: 14,120 ns/iter (+/- 57)
test decode::faster_hex::bench6_1m ... bench: 115,291 ns/iter (+/- 1,325)
test decode::hex::bench1_32b ... bench: 104 ns/iter (+/- 1)
test decode::hex::bench2_256b ... bench: 697 ns/iter (+/- 7)
test decode::hex::bench3_2k ... bench: 5,189 ns/iter (+/- 86)
test decode::hex::bench4_16k ... bench: 42,355 ns/iter (+/- 21,853)
test decode::hex::bench5_128k ... bench: 765,278 ns/iter (+/- 4,091)
test decode::hex::bench6_1m ... bench: 6,161,416 ns/iter (+/- 64,954)
test decode_to_slice::const_hex::bench1_32b ... bench: 5 ns/iter (+/- 0)
test decode_to_slice::const_hex::bench2_256b ... bench: 26 ns/iter (+/- 0)
test decode_to_slice::const_hex::bench3_2k ... bench: 210 ns/iter (+/- 10)
test decode_to_slice::const_hex::bench4_16k ... bench: 1,667 ns/iter (+/- 13)
test decode_to_slice::const_hex::bench5_128k ... bench: 13,043 ns/iter (+/- 19)
test decode_to_slice::const_hex::bench6_1m ... bench: 105,883 ns/iter (+/- 1,427)
test decode_to_slice::faster_hex::bench1_32b ... bench: 6 ns/iter (+/- 0)
test decode_to_slice::faster_hex::bench2_256b ... bench: 28 ns/iter (+/- 0)
test decode_to_slice::faster_hex::bench3_2k ... bench: 214 ns/iter (+/- 2)
test decode_to_slice::faster_hex::bench4_16k ... bench: 1,710 ns/iter (+/- 6)
test decode_to_slice::faster_hex::bench5_128k ... bench: 13,304 ns/iter (+/- 37)
test decode_to_slice::faster_hex::bench6_1m ... bench: 110,276 ns/iter (+/- 3,475)
test decode_to_slice::hex::bench1_32b ... bench: 38 ns/iter (+/- 2)
test decode_to_slice::hex::bench2_256b ... bench: 300 ns/iter (+/- 185)
test decode_to_slice::hex::bench3_2k ... bench: 2,717 ns/iter (+/- 64)
test decode_to_slice::hex::bench4_16k ... bench: 19,257 ns/iter (+/- 530)
test decode_to_slice::hex::bench5_128k ... bench: 624,172 ns/iter (+/- 15,725)
test decode_to_slice::hex::bench6_1m ... bench: 5,333,915 ns/iter (+/- 298,093)
test encode::const_hex::bench1_32b ... bench: 6 ns/iter (+/- 0)
test encode::const_hex::bench2_256b ... bench: 10 ns/iter (+/- 0)
test encode::const_hex::bench3_2k ... bench: 72 ns/iter (+/- 1)
test encode::const_hex::bench4_16k ... bench: 462 ns/iter (+/- 4)
test encode::const_hex::bench5_128k ... bench: 3,600 ns/iter (+/- 28)
test encode::const_hex::bench6_1m ... bench: 29,447 ns/iter (+/- 858)
test encode::faster_hex::bench1_32b ... bench: 17 ns/iter (+/- 0)
test encode::faster_hex::bench2_256b ... bench: 37 ns/iter (+/- 3)
test encode::faster_hex::bench3_2k ... bench: 102 ns/iter (+/- 1)
test encode::faster_hex::bench4_16k ... bench: 614 ns/iter (+/- 6)
test encode::faster_hex::bench5_128k ... bench: 4,764 ns/iter (+/- 12)
test encode::faster_hex::bench6_1m ... bench: 40,894 ns/iter (+/- 1,223)
test encode::hex::bench1_32b ... bench: 112 ns/iter (+/- 0)
test encode::hex::bench2_256b ... bench: 812 ns/iter (+/- 5)
test encode::hex::bench3_2k ... bench: 6,404 ns/iter (+/- 26)
test encode::hex::bench4_16k ... bench: 51,039 ns/iter (+/- 595)
test encode::hex::bench5_128k ... bench: 408,378 ns/iter (+/- 23,022)
test encode::hex::bench6_1m ... bench: 3,571,916 ns/iter (+/- 142,828)
test encode_to_slice::const_hex::bench1_32b ... bench: 1 ns/iter (+/- 0)
test encode_to_slice::const_hex::bench2_256b ... bench: 6 ns/iter (+/- 0)
test encode_to_slice::const_hex::bench3_2k ... bench: 53 ns/iter (+/- 0)
test encode_to_slice::const_hex::bench4_16k ... bench: 452 ns/iter (+/- 3)
test encode_to_slice::const_hex::bench5_128k ... bench: 3,550 ns/iter (+/- 10)
test encode_to_slice::const_hex::bench6_1m ... bench: 29,605 ns/iter (+/- 916)
test encode_to_slice::faster_hex::bench1_32b ... bench: 4 ns/iter (+/- 0)
test encode_to_slice::faster_hex::bench2_256b ... bench: 7 ns/iter (+/- 0)
test encode_to_slice::faster_hex::bench3_2k ... bench: 47 ns/iter (+/- 0)
test encode_to_slice::faster_hex::bench4_16k ... bench: 402 ns/iter (+/- 5)
test encode_to_slice::faster_hex::bench5_128k ... bench: 3,121 ns/iter (+/- 25)
test encode_to_slice::faster_hex::bench6_1m ... bench: 26,171 ns/iter (+/- 573)
test encode_to_slice::hex::bench1_32b ... bench: 11 ns/iter (+/- 0)
test encode_to_slice::hex::bench2_256b ... bench: 118 ns/iter (+/- 0)
test encode_to_slice::hex::bench3_2k ... bench: 994 ns/iter (+/- 4)
test encode_to_slice::hex::bench4_16k ... bench: 8,065 ns/iter (+/- 31)
test encode_to_slice::hex::bench5_128k ... bench: 63,982 ns/iter (+/- 2,026)
test encode_to_slice::hex::bench6_1m ... bench: 515,171 ns/iter (+/- 2,789)
test format::const_hex::bench1_32b ... bench: 9 ns/iter (+/- 0)
test format::const_hex::bench2_256b ... bench: 18 ns/iter (+/- 0)
test format::const_hex::bench3_2k ... bench: 119 ns/iter (+/- 1)
test format::const_hex::bench4_16k ... bench: 1,157 ns/iter (+/- 3)
test format::const_hex::bench5_128k ... bench: 9,560 ns/iter (+/- 443)
test format::const_hex::bench6_1m ... bench: 85,479 ns/iter (+/- 1,498)
test format::std::bench1_32b ... bench: 374 ns/iter (+/- 6)
test format::std::bench2_256b ... bench: 2,952 ns/iter (+/- 10)
test format::std::bench3_2k ... bench: 23,767 ns/iter (+/- 61)
test format::std::bench4_16k ... bench: 183,579 ns/iter (+/- 2,078)
test format::std::bench5_128k ... bench: 1,498,391 ns/iter (+/- 8,445)
test format::std::bench6_1m ... bench: 11,965,082 ns/iter (+/- 43,784)
Acknowledgements
hexfor the initial encoding/decoding implementationsfaster-hexfor thex86/x86-64check and decode implementations- dtolnay/itoa for the initial crate/library API layout