Skip to content

Usage C Cpp

Jump to bottom
Rylan Meilutis edited this page Feb 10, 2026 · 22 revisions

C/C++ Usage

The C API is exposed via C-Headers/sedsprintf.h (GitHub, GitLab) and a static library built by Cargo.

CMake integration (recommended)

# Example: building for an embedded target
set(SEDSPRINTF_RS_TARGET "thumbv7em-none-eabihf" CACHE STRING "" FORCE)
set(SEDSPRINTF_EMBEDDED_BUILD ON CACHE BOOL "" FORCE)

# set the sender name
set(SEDSPRINTF_RS_DEVICE_IDENTIFIER "FC26_MAIN" CACHE STRING "" FORCE)

# optional compile-time env overrides
set(SEDSPRINTF_RS_MAX_STACK_PAYLOAD "256" CACHE STRING "" FORCE)
set(SEDSPRINTF_RS_ENV_MAX_QUEUE_SIZE "65536" CACHE STRING "" FORCE)

add_subdirectory(${CMAKE_SOURCE_DIR}/sedsprintf_rs sedsprintf_rs_build)

target_link_libraries(${CMAKE_PROJECT_NAME} PRIVATE sedsprintf_rs::sedsprintf_rs)

Important CMake variables:

  • SEDSPRINTF_EMBEDDED_BUILD (ON/OFF)
  • SEDSPRINTF_RS_TARGET (Rust target triple)
  • SEDSPRINTF_RS_DEVICE_IDENTIFIER
  • SEDSPRINTF_RS_MAX_STACK_PAYLOAD
  • SEDSPRINTF_RS_ENV_<KEY> for any config env var

Manual build (no CMake)

If you want to call Cargo directly:

DEVICE_IDENTIFIER=FC26_MAIN cargo build --release

The static library will be under target/release/ (or under target/<triple>/release for embedded targets).

Minimal C example

#include "sedsprintf.h"

static uint64_t now_ms(void *user) { (void)user; return 0; }
static SedsResult tx_send(const uint8_t *bytes, size_t len, void *user)
{
    (void)bytes; (void)len; (void)user;
    return SEDS_OK;
}

static SedsResult on_packet(const SedsPacketView *pkt, void *user)
{
    (void)user;
    char buf[seds_pkt_to_string_len(pkt)];
    seds_pkt_to_string(pkt, buf, sizeof(buf));
    return SEDS_OK;
}

int main(void)
{
    const SedsLocalEndpointDesc locals[] = {
        { .endpoint = SEDS_EP_SD_CARD, .packet_handler = on_packet, .user = NULL },
    };

    SedsRouter *r = seds_router_new(
        Seds_RM_Sink,
        now_ms,
        NULL,
        locals,
        sizeof(locals) / sizeof(locals[0])
    );
    seds_router_add_side_serialized(r, "TX", 2, tx_send, NULL, true);

    float data[3] = {1.0f, 2.0f, 3.0f};
    seds_router_log(r, SEDS_DT_GPS_DATA, data, sizeof(data));
    seds_router_process_all_queues(r);

    seds_router_free(r);
    return 0;
}

See c-example-code/ (GitHub, GitLab) for a more complete example. Time sync is demonstrated in c-example-code/src/timesync_example.c (GitHub, GitLab). See Time-Sync for the time sync packet flow and roles.

Sending and receiving

Common calls:

  • seds_router_log / seds_router_log_ts: log typed payloads.
  • seds_router_transmit_serialized_message: send raw bytes.
  • seds_router_receive_serialized: receive bytes immediately.
  • seds_router_rx_serialized_packet_to_queue: enqueue for later processing.
  • seds_router_process_all_queues: process queued RX/TX.

As of v3.0.0, most applications should call the plain receive APIs above. Side IDs are tracked internally by the router. If you need to explicitly override ingress (custom relay or bridge), use the side-aware variants:

  • seds_router_receive_serialized_from_side
  • seds_router_receive_from_side
  • seds_router_rx_serialized_packet_to_queue_from_side
  • seds_router_rx_packet_to_queue_from_side

Payload layout expectations

Payloads are little-endian. The schema defines element type and count. For dynamic payloads, sizes must be a multiple of element width.

Strings must be valid UTF-8. For static strings, the payload is padded or truncated to STATIC_STRING_LENGTH.

Embedded allocator hooks

Bare-metal builds must provide:

  • void *telemetryMalloc(size_t)
  • void telemetryFree(void *)
  • void seds_error_msg(const char *, size_t)

A simple stub is shown in README.md and can be adapted for your platform.

Threading and reentrancy

The router uses internal locking, so the C API is safe to call from multiple threads if your platform supports it. In bare-metal contexts, you may still want to serialize access around interrupts.

Clone this wiki locally