basenc: add base58 support

A 58 character encoding that:
 - avoids visually ambiguous 0OIl characters
 - uses only alphanumeric characters
Described at:
 - https://tools.ietf.org/html/draft-msporny-base58-03

This implementation uses GMP (or gnulib's gmp fallback).
Performance is good in comparison to other implementations.
For example when using libgmp on an i7-5600U system,
encoding is 530 times faster, and decoding 830 times faster
than the implementation using arbitrary precision ints in cpython 3.13.

Memory use is proportional to the size of input.

Encoding benchmarks:

  $ time yes | head -c65535 | src/basenc --base58 -w0 >file.enc
  real    0m0.018s

  ./configure --quiet --without-libgmp && make -j $(nproc)
  $ time yes | head -c65535 | src/basenc --base58 -w0 >file.enc
  real    0m3.431s

  # dnf install python3-base58
  $ time yes | head -c65535 | base58 >file.enc  # cpython 3.13
  real    0m9.700s

Decoding benchmarks:

  $ time src/basenc --base58 -d <file.enc >/dev/null
  real    0m0.010s

  $ ./configure --without-libgmp && make  # gnulib gmp
  $ time src/basenc --base58 -d <file.enc >/dev/null
  real    0m0.145s

  $ time base58 -d <file.enc >/dev/null  # cpython 3.13
  real    0m8.302s

* src/basenc.c (base_decode_ctx_finalize, base_encode_ctx_init,
base_encode_ctx, base_encode_ctx_finalize): New functions to
provide more general processing functionality.
(base58_{de,en}code_ctx{_init,,_finalize}): New functions to
accumulate all input before calling ...
(base58_{de,en}code): ... the GMP based encoding/decoding routines.
(do_encode, do_decode): Call the ctx variants if enabled.
* doc/coreutils.texi (basenc invocation): Describe the new option,
and indicate the main use case being interactive user use.
* src/local.mk: Link basenc with GMP.
* tests/basenc/basenc.pl: Add test cases.
* NEWS: Mention the new feature.

0 files changed, 0 insertions, 0 deletions