const-hex

This crate provides a fast conversion of byte arrays to hexadecimal strings, both at compile time, and at run time.

Extends the hex crate's implementation 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 5900X (AVX2), compiled with rustc 1.75.0-nightly (aa1a71e9e 2023-10-26) 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_32              ... bench:          19 ns/iter (+/- 0)
test decode::const_hex::bench2_256             ... bench:          28 ns/iter (+/- 1)
test decode::const_hex::bench3_2048            ... bench:         133 ns/iter (+/- 4)
test decode::const_hex::bench4_16384           ... bench:         948 ns/iter (+/- 11)
test decode::faster_hex::bench1_32             ... bench:          23 ns/iter (+/- 0)
test decode::faster_hex::bench2_256            ... bench:          46 ns/iter (+/- 0)
test decode::faster_hex::bench3_2048           ... bench:         148 ns/iter (+/- 7)
test decode::faster_hex::bench4_16384          ... bench:       1,063 ns/iter (+/- 22)
test decode::hex::bench1_32                    ... bench:          63 ns/iter (+/- 11)
test decode::hex::bench2_256                   ... bench:         440 ns/iter (+/- 12)
test decode::hex::bench3_2048                  ... bench:       3,346 ns/iter (+/- 574)
test decode::hex::bench4_16384                 ... bench:      43,589 ns/iter (+/- 2,809)

test decode_to_slice::const_hex::bench1_32     ... bench:          11 ns/iter (+/- 1)
test decode_to_slice::const_hex::bench2_256    ... bench:          18 ns/iter (+/- 2)
test decode_to_slice::const_hex::bench3_2048   ... bench:         123 ns/iter (+/- 5)
test decode_to_slice::const_hex::bench4_16384  ... bench:         940 ns/iter (+/- 41)
test decode_to_slice::faster_hex::bench1_32    ... bench:          11 ns/iter (+/- 0)
test decode_to_slice::faster_hex::bench2_256   ... bench:          19 ns/iter (+/- 0)
test decode_to_slice::faster_hex::bench3_2048  ... bench:         130 ns/iter (+/- 7)
test decode_to_slice::faster_hex::bench4_16384 ... bench:       1,011 ns/iter (+/- 33)
test decode_to_slice::hex::bench1_32           ... bench:          22 ns/iter (+/- 2)
test decode_to_slice::hex::bench2_256          ... bench:         171 ns/iter (+/- 8)
test decode_to_slice::hex::bench3_2048         ... bench:       1,650 ns/iter (+/- 221)
test decode_to_slice::hex::bench4_16384        ... bench:      15,614 ns/iter (+/- 736)

test encode::const_hex::bench1_32              ... bench:          13 ns/iter (+/- 1)
test encode::const_hex::bench2_256             ... bench:          26 ns/iter (+/- 0)
test encode::const_hex::bench3_2048            ... bench:         136 ns/iter (+/- 1)
test encode::const_hex::bench4_16384           ... bench:         863 ns/iter (+/- 39)
test encode::faster_hex::bench1_32             ... bench:          19 ns/iter (+/- 0)
test encode::faster_hex::bench2_256            ... bench:          34 ns/iter (+/- 0)
test encode::faster_hex::bench3_2048           ... bench:         135 ns/iter (+/- 1)
test encode::faster_hex::bench4_16384          ... bench:         825 ns/iter (+/- 8)
test encode::hex::bench1_32                    ... bench:         148 ns/iter (+/- 7)
test encode::hex::bench2_256                   ... bench:       1,037 ns/iter (+/- 17)
test encode::hex::bench3_2048                  ... bench:       8,186 ns/iter (+/- 295)
test encode::hex::bench4_16384                 ... bench:      65,257 ns/iter (+/- 15,832)

test encode_to_slice::const_hex::bench1_32     ... bench:           1 ns/iter (+/- 0)
test encode_to_slice::const_hex::bench2_256    ... bench:           8 ns/iter (+/- 0)
test encode_to_slice::const_hex::bench3_2048   ... bench:          79 ns/iter (+/- 1)
test encode_to_slice::const_hex::bench4_16384  ... bench:         577 ns/iter (+/- 11)
test encode_to_slice::faster_hex::bench1_32    ... bench:           5 ns/iter (+/- 0)
test encode_to_slice::faster_hex::bench2_256   ... bench:           9 ns/iter (+/- 0)
test encode_to_slice::faster_hex::bench3_2048  ... bench:          68 ns/iter (+/- 3)
test encode_to_slice::faster_hex::bench4_16384 ... bench:         533 ns/iter (+/- 11)
test encode_to_slice::hex::bench1_32           ... bench:          10 ns/iter (+/- 0)
test encode_to_slice::hex::bench2_256          ... bench:         129 ns/iter (+/- 10)
test encode_to_slice::hex::bench3_2048         ... bench:         844 ns/iter (+/- 75)
test encode_to_slice::hex::bench4_16384        ... bench:       6,711 ns/iter (+/- 461)

test format::const_hex::bench1_32              ... bench:          10 ns/iter (+/- 0)
test format::const_hex::bench2_256             ... bench:          40 ns/iter (+/- 0)
test format::const_hex::bench3_2048            ... bench:         176 ns/iter (+/- 1)
test format::const_hex::bench4_16384           ... bench:       1,399 ns/iter (+/- 12)
test format::std::bench1_32                    ... bench:         503 ns/iter (+/- 4)
test format::std::bench2_256                   ... bench:       3,915 ns/iter (+/- 29)
test format::std::bench3_2048                  ... bench:      30,012 ns/iter (+/- 396)
test format::std::bench4_16384                 ... bench:     242,046 ns/iter (+/- 1,357)

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

const-hex 1.10.0

const-hex

Performance

Acknowledgements

License