Foundationdb C API example

README.md

This is a simple example program using the foundationdb C API. Its written & tested on macos; but it should be easy to adapt to work on BSD / linux.

This also demonstrates using libuv to integrate foundationdb into a run loop. Promises are run in the main libuv loop.

Compile with

$ clang test.c -Wall -lfdb_c -I/usr/local/include -luv

main.c

#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <stdlib.h>
#include <pthread.h>
#include <uv.h>

#define FDB_API_VERSION 510
#include <foundationdb/fdb_c.h>

void chk(fdb_error_t err) {
  if (err) {
    fprintf(stderr, "Error: %s\n", fdb_get_error(err));
    abort();
  }
}

void warn(fdb_error_t err) {
  if (err) fprintf(stderr, "Warning: %s\n", fdb_get_error(err));
}


void *run_net(void *_unused) {
  chk(fdb_run_network());

  return NULL;
}

FDBCluster* get_cluster() {
  FDBFuture* f = fdb_create_cluster(NULL);
  
  chk(fdb_future_block_until_ready(f));

  FDBCluster* out;
  chk(fdb_future_get_cluster(f, &out));
  return out;
}

FDBDatabase* get_database(FDBCluster *cluster) {
  FDBFuture* f = fdb_cluster_create_database(cluster, (const uint8_t *)"DB", 2);
  
  chk(fdb_future_block_until_ready(f));

  FDBDatabase* out;
  chk(fdb_future_get_database(f, &out));
  return out;
}

void cb(FDBFuture* vf, void* data) {
  char *str = (char *)data;
  printf("callback %s called\n", str);

  if (((char *)data)[0] == 'v') {
    const uint8_t *data;
    int length;

    chk(fdb_future_get_key(vf, &data, &length));

    for (int i = 0; i < length; i++) {
      printf("%d ", data[i]);
      printf("\n");
    }
  }
  //int64_t version = 0;
  //warn(fdb_future_get_error(vf));
  //printf("Version %lld\n", version);
}

FDBCluster* cluster;
FDBDatabase* database;
uv_loop_t mainloop;

void stuff() {
  {
    FDBTransaction* txn;
    chk(fdb_database_create_transaction(database, &txn));
    FDBFuture *f = fdb_transaction_watch(txn, (uint8_t *)"hi", 2);
    chk(fdb_future_set_callback(f, cb, "watch"));

    FDBFuture *cf = fdb_transaction_commit(txn);
    chk(fdb_future_set_callback(cf, cb, "commit"));
  }


  //FDBFuture *vf = fdb_transaction_get_read_version(txn);

  //fdb_future_cancel(vf);
  /*
  chk(fdb_future_block_until_ready(vf));
  int64_t version;
  chk(fdb_future_get_version(vf, &version));
  printf("Version %lld\n", version);
  */
}



typedef struct {
  FDBFuture *future;
  uv_async_t async;
  void *data;
} Ctx;

static void mt_cb(uv_async_t *async) {
  printf("got main thread cb\n");
  Ctx *ctx = (Ctx *)async->data;

  char *d = (char *)ctx->data;
  printf("%s\n", d);

  if (d[0] == 'v') {
    const uint8_t *data;
    int length;

    chk(fdb_future_get_key(ctx->future, &data, &length));

    for (int i = 0; i < length; i++) {
      printf("%d ", data[i]);
      printf("\n");
    }
  }


  fdb_future_destroy(ctx->future);
  uv_close((uv_handle_t *)&ctx->async, NULL);
}


static void future_cb(FDBFuture *f, void *_ctx) {
  printf("future_cb\n");
  Ctx *ctx = (Ctx *)_ctx;
  uv_async_send(&ctx->async);
}


void resolveFutureInMainLoop(FDBFuture *f, void *data) {
  Ctx *ctx = malloc(sizeof(Ctx));
  ctx->data = data;
  ctx->future = f;

  // TODO: Handle error on async_init failing. Probably just assert.
  assert(0 == uv_async_init(&mainloop, &ctx->async, mt_cb));

  ctx->async.data = ctx;

  chk(fdb_future_set_callback(f, future_cb, ctx));
}


void getStamp() {
  FDBTransaction* txn;
  chk(fdb_database_create_transaction(database, &txn));
  uint8_t bytes[20] = {};
  bytes[10] = 123;
  fdb_transaction_atomic_op(txn, (uint8_t *)"x", 1, bytes, sizeof(bytes), FDB_MUTATION_TYPE_SET_VERSIONSTAMPED_VALUE);

  FDBFuture *vf = fdb_transaction_get_versionstamp(txn);
  resolveFutureInMainLoop(vf, "v");
  //chk(fdb_future_set_callback(vf, cb, "vstamp"));

  FDBFuture *cf = fdb_transaction_commit(txn);
  resolveFutureInMainLoop(cf, "c");
  //chk(fdb_future_set_callback(cf, cb, "commit"));
}



int main() {
  uv_loop_init(&mainloop);

  fdb_select_api_version(FDB_API_VERSION);

  chk(fdb_setup_network());

  pthread_t net_thread;
  assert(0 == pthread_create(&net_thread, NULL, run_net, NULL));

  cluster = get_cluster();
  database = get_database(cluster);

  //stuff();
  getStamp();

  uv_run(&mainloop, UV_RUN_DEFAULT);

  sleep(1);
  chk(fdb_stop_network());
  pthread_join(net_thread, NULL);

  return 0;
}

Please update this to latest version

Is this linked / depended on somewhere?

I made a simpler modern version here: https://gist.github.com/gm42/a61d2fff82b9dddc47a449579c9307b8

Using the FoundationDB V7.1+ API.