evgeny
38c9f229bc
- u_async.c: process immediate_queue BEFORE epoll_wait in uasync_poll - stcp_link.c: defensive NULL etcp_conn/etcp_link in stcp_link_close - utun_instance.c: move stcp_server_list_destroy_all to Phase J (before ETCP), add deferred drain in both Phase J and L - stcp.h/c: STCP_HS_ENC_CLIENT 6→38, STCP_HS_ENC_SERVER 7→39, exchange ed25519_pubkey in both handshake directions - etcp_connections.c: copy peer_ed25519 from STCP to ETCP_CONN in etcp_link_enter_ready_tcp; guard link->etcp in tcp_link_close_cb - chat_sync.c: fix lk->conn NULL dereference for TCP links - test_stcp.c: update stcp_server_create/stcp_client_connect callsites - tools/chat_tcp_test: change transport udp→tcp
librscpp
librscpp is a small header-only Reed-Solomon implementation in C++20.
Pick a Galois field that matches your symbology or protocol, then call encode() or decode() on a codeword.
Example
#include "librscpp/encode.h"
#include "librscpp/decode.h"
#include <string>
#include <print>
int main()
{
// GF(256) used in QR Codes with polynomial = x^8 + x^4 + x^3 + x^2 + 1 and fcr = 0.
auto field = librscpp::GF2n<uint8_t>(0b1'0001'1101, 0);
std::println("Using field: GF({}) and fcr: {}", field.size(), field.fcr());
const std::string data = "Hello, World!";
constexpr int paritySize = 4;
auto codeword = librscpp::encode(field, data, paritySize);
std::println("Encoded codeword: '{}'", codeword);
// Simulate a couple of symbol errors.
codeword[3] = codeword[8] = '*';
std::println("Corrupt codeword: '{}'", codeword);
auto res = librscpp::decode(field, codeword, paritySize);
if (res)
std::println("Decoded codeword: '{}'\nUsed parity symbols: {}", codeword, *res);
else
std::println("Failed to decode codeword.");
return 0;
}
Running this example program produces the following output:
Using field: GF(256) and fcr: 0
Encoded codeword: 'Hello, World!??t'
Corrupt codeword: 'Hel*o, W*rld!??t'
Decoded codeword: 'Hello, World!??t'
Used parity symbols: 4
Configuration
The PDF417 symbology uses the prime GF(929) with primitive root 3 and fcr 1: librscpp::GFp<>(929, 3, 1).
If you are low on memory, you can #define LIBRSCPP_SAVE_MEMORY before including the header to save 1/3 of runtime memory used by the GF internal lookup tables. Without that, each GF2n/GFp instance allocates 3 * field_size * sizeof(T) bytes. Also the default value_type of GF2n<> and GFp<> is uint16_t. If your field size is <=256 (like the one in the sample code), you can save 50% by using uint8_t.
Other common/usable GF2n configurations are:
GF2n<> gf_0x0013(0x0013, 1); // x^4 + x + 1
GF2n<> gf_0x0043(0x0043, 1); // x^6 + x + 1
GF2n<> gf_0x012D(0x012D, 1); // x^8 + x^5 + x^3 + x^2 + 1 : DataMatrix
GF2n<> gf_0x011D(0x011D, 0); // x^8 + x^4 + x^3 + x^2 + 1 : QRCode
GF2n<> gf_0x0409(0x0409, 1); // x^10 + x^3 + 1
GF2n<> gf_0x1069(0x1069, 1); // x^12 + x^6 + x^5 + x^3 + 1