C

C11 implementation of the spec — also the core that the C++ wrapper builds on. Requires GCC or Clang (uses unsigned __int128) and OpenSSL libcrypto 1.1+/3.x; consumers link with -lcrypto.

Source of truth: c/ on GitHub · full README

Install

Vendored / static library by design — there is no package registry step:

make            # in c/ — builds the static library libdealcode.a
make test       # generates test vectors and runs the test suite

cc -Ic/include myapp.c c/libdealcode.a -lcrypto

Minimal example

#include <dealcode.h>

dealcode_config_t cfg = {0};
cfg.key_string = "example-key";   /* string rule: always SHA-256 derived  */
cfg.alphabet   = "hex";           /* preset name or custom alphabet chars */
cfg.domain     = "orders";        /* namespace label, bound into the tweak */

dealcode_t *dc = NULL;
dealcode_err_t err = dealcode_new(&cfg, &dc);
if (err != DEALCODE_OK) {
    fprintf(stderr, "dealcode: %s\n", dealcode_strerror(err));
    return 1;
}

char code[DEALCODE_MAX_CODE_SIZE];
dealcode_encode(dc, 42, code, sizeof code);   /* -> e.g. "59e5f2" */

uint64_t n;
dealcode_decode(dc, code, &n);                /* -> 42 */

dealcode_free(dc);

API surface

Item	Notes
dealcode_new / dealcode_free	codec lifecycle — opaque handle, no global state
dealcode_encode / dealcode_decode	the counter ↔ code bijection
dealcode_capacity, dealcode_min_length, dealcode_max_length, dealcode_radix, dealcode_alphabet	introspection
dealcode_strerror	human-readable error descriptions
dealcode_cycle_* (_new, _encode, _decode, _free, …)	fixed-length cycling mode, SPEC §11 — see the configuration guide
Errors	explicit dealcode_err_t return codes; on failure nothing is written to output parameters (except *out = NULL in dealcode_new)

The full, documented API lives in include/dealcode.h. A dealcode_t is immutable after construction and may be shared freely across threads — encode/decode allocate a fresh OpenSSL cipher context per call.

Tests

cd c && make test

Covers the 9 official NIST FF1 sample vectors, every dealcode v1 test-vector config, error behaviour, and large roundtrip sweeps across stage boundaries — including configurations where radix^max_length is exactly 2^128.