Writing a smart contract in C

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

static int envAtoi(const char* env) {
  const char* val = getenv(env);
  if (val == NULL) {
    return 0;
  }
  return atoi(val);
}

int maxUser = 100;

static void construct() {
  const char* val = getenv("DB_QVM_INITIALIZED");
  if (val && strcmp(val, "true") == 0) {
    fprintf(stderr, "contract is already initialized\n");
    exit(1);
  }
  printf("DBW=QVM_INIT_MAXUSER=%d\n", maxUser);
}

static void initialize() {
  const char* val = getenv("DB_QVM_INITIALIZED");
  if (val == NULL || strcmp(val, "true") != 0) {
    fprintf(stderr, "contract is not initialized\n");
    exit(1);
  }
  maxUser = envAtoi("DB_QVM_INIT_MAXUSER");
}

int main(int argc, char *argv[]) {
  if (argc == 2 && strcmp(argv[1], "construct") == 0) {
    construct();
    exit(0);
  }
  // THIS SAMPLE ONLY SUPPORTS THE "register" FUNCTION
  if (argc == 3 && strcmp(argv[1], "register") == 0) {
    initialize();
    // GET THE CURRENT USER'S NAME
    const char *previousName = getenv("DB_USER_CURRENT");
    // OR DEFAULT TO "unknown" IF THIS IS THE FIRST CALL
    if (previousName == NULL || strlen(previousName) == 0) {
      previousName = "unknown";
    }
    // GET THE TOTAL USER COUNT
    int totalUserCount = envAtoi("DB_TOTALUSERS");
    if (totalUserCount+1 > maxUser) {
      fprintf(stderr, "exceeded max user\n");
      exit(1);
    }
    // WRITE PREVIOUS USER NAME TO STDOUT
    printf("OUT=prevname: %s\n", previousName);
    // UPDATE CURRENT USER NAME BY WRITING IT TO DB
    printf("DBW=USER_CURRENT=%s\n", argv[2]);
    // STORE USER NAME UNDER A STORAGE SLOT FOR PERSISTENCE (CURRENT GETS OVERWRITTEN ON EACH CALL)
    printf("DBW=USER_%d=%s\n", totalUserCount, argv[2]);
    // INCREMENT THE TOTAL USER COUNT
    printf("DBW=TOTALUSERS=%d\n", totalUserCount+1);
    return 0;
  }
  if (argc >= 2) {
    fprintf(stderr, "Wrong CMD: %s\n", argv[1]);
    exit(1);
  }
  fprintf(stderr, "Wrong args!\n");
  exit(1);
}