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#7 in Value formatting

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const-hex

github crates.io docs.rs build status

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 1.80.0-nightly (bdbbb6c6a 2024-05-26) on x86_64-unknown-linux-gnu.

You can run these benchmarks with cargo bench --features std on a nightly compiler.

test check::const_hex::bench1_32b             ... bench:           9.79 ns/iter (+/- 2.22)
test check::const_hex::bench2_256b            ... bench:          20.22 ns/iter (+/- 6.41)
test check::const_hex::bench3_2k              ... bench:         124.57 ns/iter (+/- 9.68)
test check::const_hex::bench4_16k             ... bench:         927.53 ns/iter (+/- 81.94)
test check::const_hex::bench5_128k            ... bench:       7,300.16 ns/iter (+/- 153.57)
test check::const_hex::bench6_1m              ... bench:      59,886.62 ns/iter (+/- 1,312.15)
test check::faster_hex::bench1_32b            ... bench:           2.93 ns/iter (+/- 0.20)
test check::faster_hex::bench2_256b           ... bench:          15.54 ns/iter (+/- 0.77)
test check::faster_hex::bench3_2k             ... bench:         121.17 ns/iter (+/- 0.70)
test check::faster_hex::bench4_16k            ... bench:         945.17 ns/iter (+/- 12.48)
test check::faster_hex::bench5_128k           ... bench:       7,632.07 ns/iter (+/- 172.68)
test check::faster_hex::bench6_1m             ... bench:      61,427.03 ns/iter (+/- 732.21)
test check::naive::bench1_32b                 ... bench:          26.15 ns/iter (+/- 1.04)
test check::naive::bench2_256b                ... bench:         225.69 ns/iter (+/- 9.02)
test check::naive::bench3_2k                  ... bench:       1,952.05 ns/iter (+/- 20.46)
test check::naive::bench4_16k                 ... bench:      20,329.63 ns/iter (+/- 455.31)
test check::naive::bench5_128k                ... bench:     503,460.10 ns/iter (+/- 8,930.00)
test check::naive::bench6_1m                  ... bench:   4,252,331.00 ns/iter (+/- 191,519.79)

test decode::const_hex::bench1_32b            ... bench:          19.49 ns/iter (+/- 0.82)
test decode::const_hex::bench2_256b           ... bench:          41.47 ns/iter (+/- 1.45)
test decode::const_hex::bench3_2k             ... bench:         236.69 ns/iter (+/- 2.75)
test decode::const_hex::bench4_16k            ... bench:       1,682.25 ns/iter (+/- 18.07)
test decode::const_hex::bench5_128k           ... bench:      13,096.94 ns/iter (+/- 138.05)
test decode::const_hex::bench6_1m             ... bench:     105,360.67 ns/iter (+/- 2,771.85)
test decode::faster_hex::bench1_32b           ... bench:          16.49 ns/iter (+/- 0.12)
test decode::faster_hex::bench2_256b          ... bench:          54.92 ns/iter (+/- 1.74)
test decode::faster_hex::bench3_2k            ... bench:         246.11 ns/iter (+/- 3.25)
test decode::faster_hex::bench4_16k           ... bench:       1,839.88 ns/iter (+/- 22.36)
test decode::faster_hex::bench5_128k          ... bench:      14,376.52 ns/iter (+/- 203.97)
test decode::faster_hex::bench6_1m            ... bench:     116,345.50 ns/iter (+/- 1,377.06)
test decode::hex::bench1_32b                  ... bench:         101.38 ns/iter (+/- 3.41)
test decode::hex::bench2_256b                 ... bench:         655.85 ns/iter (+/- 17.69)
test decode::hex::bench3_2k                   ... bench:       4,830.90 ns/iter (+/- 73.58)
test decode::hex::bench4_16k                  ... bench:      37,976.46 ns/iter (+/- 443.65)
test decode::hex::bench5_128k                 ... bench:     734,983.30 ns/iter (+/- 4,297.49)
test decode::hex::bench6_1m                   ... bench:   5,901,860.30 ns/iter (+/- 22,806.40)

test decode_to_slice::const_hex::bench1_32b   ... bench:          11.03 ns/iter (+/- 0.50)
test decode_to_slice::const_hex::bench2_256b  ... bench:          28.93 ns/iter (+/- 1.38)
test decode_to_slice::const_hex::bench3_2k    ... bench:         210.49 ns/iter (+/- 5.65)
test decode_to_slice::const_hex::bench4_16k   ... bench:       1,670.55 ns/iter (+/- 17.87)
test decode_to_slice::const_hex::bench5_128k  ... bench:      13,094.65 ns/iter (+/- 115.89)
test decode_to_slice::const_hex::bench6_1m    ... bench:     105,036.12 ns/iter (+/- 1,722.56)
test decode_to_slice::faster_hex::bench1_32b  ... bench:           6.26 ns/iter (+/- 0.10)
test decode_to_slice::faster_hex::bench2_256b ... bench:          28.73 ns/iter (+/- 0.55)
test decode_to_slice::faster_hex::bench3_2k   ... bench:         213.70 ns/iter (+/- 2.83)
test decode_to_slice::faster_hex::bench4_16k  ... bench:       1,718.21 ns/iter (+/- 23.97)
test decode_to_slice::faster_hex::bench5_128k ... bench:      13,530.96 ns/iter (+/- 97.41)
test decode_to_slice::faster_hex::bench6_1m   ... bench:     107,708.79 ns/iter (+/- 1,425.58)
test decode_to_slice::hex::bench1_32b         ... bench:          39.07 ns/iter (+/- 1.85)
test decode_to_slice::hex::bench2_256b        ... bench:         311.73 ns/iter (+/- 10.92)
test decode_to_slice::hex::bench3_2k          ... bench:       2,515.69 ns/iter (+/- 63.09)
test decode_to_slice::hex::bench4_16k         ... bench:      20,899.92 ns/iter (+/- 442.95)
test decode_to_slice::hex::bench5_128k        ... bench:     634,859.00 ns/iter (+/- 6,609.09)
test decode_to_slice::hex::bench6_1m          ... bench:   5,338,354.20 ns/iter (+/- 51,493.30)

test encode::const_hex::bench1_32b            ... bench:           6.92 ns/iter (+/- 0.11)
test encode::const_hex::bench2_256b           ... bench:          11.41 ns/iter (+/- 0.14)
test encode::const_hex::bench3_2k             ... bench:          73.59 ns/iter (+/- 1.52)
test encode::const_hex::bench4_16k            ... bench:         461.00 ns/iter (+/- 5.17)
test encode::const_hex::bench5_128k           ... bench:       3,527.28 ns/iter (+/- 46.86)
test encode::const_hex::bench6_1m             ... bench:      29,402.78 ns/iter (+/- 1,032.91)
test encode::faster_hex::bench1_32b           ... bench:          17.30 ns/iter (+/- 0.30)
test encode::faster_hex::bench2_256b          ... bench:          39.07 ns/iter (+/- 0.73)
test encode::faster_hex::bench3_2k            ... bench:         102.93 ns/iter (+/- 1.92)
test encode::faster_hex::bench4_16k           ... bench:         651.65 ns/iter (+/- 1.55)
test encode::faster_hex::bench5_128k          ... bench:       5,074.50 ns/iter (+/- 22.97)
test encode::faster_hex::bench6_1m            ... bench:      46,227.11 ns/iter (+/- 945.52)
test encode::hex::bench1_32b                  ... bench:         100.46 ns/iter (+/- 0.93)
test encode::hex::bench2_256b                 ... bench:         717.75 ns/iter (+/- 5.91)
test encode::hex::bench3_2k                   ... bench:       5,660.67 ns/iter (+/- 246.73)
test encode::hex::bench4_16k                  ... bench:      44,981.79 ns/iter (+/- 340.51)
test encode::hex::bench5_128k                 ... bench:     359,401.72 ns/iter (+/- 1,689.97)
test encode::hex::bench6_1m                   ... bench:   2,966,947.20 ns/iter (+/- 165,738.51)

test encode_to_slice::const_hex::bench1_32b   ... bench:           1.55 ns/iter (+/- 0.04)
test encode_to_slice::const_hex::bench2_256b  ... bench:           6.73 ns/iter (+/- 0.08)
test encode_to_slice::const_hex::bench3_2k    ... bench:          54.23 ns/iter (+/- 2.06)
test encode_to_slice::const_hex::bench4_16k   ... bench:         471.90 ns/iter (+/- 21.13)
test encode_to_slice::const_hex::bench5_128k  ... bench:       3,730.44 ns/iter (+/- 113.80)
test encode_to_slice::const_hex::bench6_1m    ... bench:      29,247.93 ns/iter (+/- 926.38)
test encode_to_slice::faster_hex::bench1_32b  ... bench:           3.95 ns/iter (+/- 0.26)
test encode_to_slice::faster_hex::bench2_256b ... bench:           7.49 ns/iter (+/- 0.47)
test encode_to_slice::faster_hex::bench3_2k   ... bench:          48.56 ns/iter (+/- 1.95)
test encode_to_slice::faster_hex::bench4_16k  ... bench:         424.65 ns/iter (+/- 11.39)
test encode_to_slice::faster_hex::bench5_128k ... bench:       3,317.47 ns/iter (+/- 103.44)
test encode_to_slice::faster_hex::bench6_1m   ... bench:      26,079.18 ns/iter (+/- 889.52)
test encode_to_slice::hex::bench1_32b         ... bench:          11.99 ns/iter (+/- 0.30)
test encode_to_slice::hex::bench2_256b        ... bench:         119.07 ns/iter (+/- 2.85)
test encode_to_slice::hex::bench3_2k          ... bench:         999.68 ns/iter (+/- 26.35)
test encode_to_slice::hex::bench4_16k         ... bench:       8,049.82 ns/iter (+/- 105.51)
test encode_to_slice::hex::bench5_128k        ... bench:      65,186.25 ns/iter (+/- 758.98)
test encode_to_slice::hex::bench6_1m          ... bench:     511,447.00 ns/iter (+/- 4,866.41)

test format::const_hex::bench1_32b            ... bench:           9.84 ns/iter (+/- 0.21)
test format::const_hex::bench2_256b           ... bench:          17.90 ns/iter (+/- 0.55)
test format::const_hex::bench3_2k             ... bench:         119.47 ns/iter (+/- 3.87)
test format::const_hex::bench4_16k            ... bench:       1,161.94 ns/iter (+/- 20.11)
test format::const_hex::bench5_128k           ... bench:       9,580.23 ns/iter (+/- 188.10)
test format::const_hex::bench6_1m             ... bench:      84,316.47 ns/iter (+/- 1,407.10)
test format::std::bench1_32b                  ... bench:         371.37 ns/iter (+/- 3.63)
test format::std::bench2_256b                 ... bench:       2,987.01 ns/iter (+/- 41.26)
test format::std::bench3_2k                   ... bench:      23,989.24 ns/iter (+/- 373.84)
test format::std::bench4_16k                  ... bench:     192,881.92 ns/iter (+/- 9,266.64)
test format::std::bench5_128k                 ... bench:   1,554,062.80 ns/iter (+/- 10,998.30)
test format::std::bench6_1m                   ... bench:  12,378,548.00 ns/iter (+/- 247,626.30)

Acknowledgements

  • hex for the initial encoding/decoding implementations
  • faster-hex for the x86/x86-64 check and decode implementations
  • dtolnay/itoa for the initial crate/library API layout

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in these crates by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Dependencies

~0–0.8MB
~18K SLoC