FoundationDB C Example - Hello World!

README.md

FoundationDB Hello World example in C

This is an example C program which sets a key, commits a transaction and then reads it back using a new transaction.

Compile it with:

$ clang -ofdbhello fdbhello.c -Wall -lfdb_c -I/usr/local/include

That's all!

Based on https://gist.github.com/josephg/7fa89ec0f7cfa2d5dd66c352dd0bebfa

fdbhello.c

/*

Example C API Hello World program for FoundationDB v7.1+
Author: gm42

Compile it with:
```
$ clang -ofdbhello fdbhello.c -Wall -lfdb_c -I/usr/local/include
```
*/

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// See also: https://apple.github.io/foundationdb/api-c.html
#define FDB_API_VERSION 710
#include <foundationdb/fdb_c.h>

FDBDatabase *database;

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

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

  return NULL;
}

FDBDatabase *get_database(const char *cluster_file) {
  FDBDatabase *out;
  abort_on_error(fdb_create_database(cluster_file, &out));
  return out;
}

void setValueAndCommit(const char *key, const char *value) {
  FDBTransaction *txn;
  abort_on_error(fdb_database_create_transaction(database, &txn));

  fdb_transaction_set(txn, (uint8_t *)key, strlen(key), (uint8_t *)value,
                      strlen(value));

  FDBFuture *cf = fdb_transaction_commit(txn);
  abort_on_error(fdb_future_block_until_ready(cf));
  fdb_future_destroy(cf);

  printf("fdbhello: set key '%s' to value '%s'\n", key, value);
}

void getValue(const char *key) {
  FDBTransaction *txn;
  abort_on_error(fdb_database_create_transaction(database, &txn));

  FDBFuture *rf = fdb_transaction_get(txn, (uint8_t *)key, strlen(key), 0);

  abort_on_error(fdb_future_block_until_ready(rf));
  fdb_bool_t present;
  const uint8_t *out_value = NULL;
  int out_value_length;
  abort_on_error(
      fdb_future_get_value(rf, &present, &out_value, &out_value_length));
  fdb_future_destroy(rf);

  if (present) {
    printf("fdbhello: value for key '%s' is '%s'\n", key, out_value);
  } else {
    printf("fdbhello: key '%s' not found\n", key);
  }

  // read-only transactions don't need to be committed
  fdb_transaction_destroy(txn);
}

int main(int argc, char *argv[]) {
  char *clusterFilePath;
  if (argc == 2) {
    clusterFilePath = argv[1];
  } else {
    fprintf(stderr, "Usage: fdbhello /etc/foundationdb/fdb.cluster\n");
    exit(1);
  }

  fdb_select_api_version(FDB_API_VERSION);
  printf("fdbhello: selected API version %d\n", FDB_API_VERSION);

  abort_on_error(fdb_setup_network());

  pthread_t net_thread;
  int rv = pthread_create(&net_thread, NULL, run_net, NULL);
  if (rv) {
    fprintf(stderr, "fdbhello: failed to create network thread\n");
    exit(rv);
  }

  database = get_database(clusterFilePath);
  printf("fdbhello: connected to cluster described by %s\n", clusterFilePath);

  const char *key = "/fdbhello/test/value";

  // set the value of a key
  setValueAndCommit(key, "hello world!");
  // then read it back
  getValue(key);

  fdb_database_destroy(database);
  abort_on_error(fdb_stop_network());
  pthread_join(net_thread, NULL);

  return 0;
}