test on how to copy worker env for spawning

env_copy_test.c

/*
  gcc env_copy_test.c; ./a.out
*/

#include <stdio.h>

#include <time.h> /* clock */
#include <stdlib.h> /* free */
#include <string.h> /* sprintf */

extern char **environ;

static inline void type_a(const char *worker_id, const char *ipc_filename) {
  int env_cnt = 0;
  char **entry;
  for (entry = environ; *entry; entry++, env_cnt++);
  char *worker_env[2 + env_cnt + 1];
  worker_env[0] = malloc(sizeof("LEN_WORKER_ID=") + strlen(worker_id));
  sprintf(worker_env[0], "LEV_WORKER_ID=%s", worker_id);
  worker_env[1] = malloc(sizeof("LEV_IPC_FILENAME=") + strlen(ipc_filename));
  sprintf(worker_env[1], "LEV_IPC_FILENAME=%s", ipc_filename);
  memcpy(worker_env + 2, environ, sizeof(char *) * (env_cnt + 1));
  free( worker_env[0] ); /* free LEV_WORKER_ID */
  free( worker_env[1] ); /* free LEV_IPC_FILENAME */
}

static inline void type_b(const char *worker_id, const char *ipc_filename) {
  int n = 0;
  char **env_item;
  char env_temp[1024];
  char *worker_env[256];

  sprintf(env_temp, "LEV_WORKER_ID=%s", worker_id);
  worker_env[n++] = strdup(env_temp);
  sprintf(env_temp, "LEV_IPC_FILENAME=%s", ipc_filename);
  worker_env[n++] = strdup(env_temp);
  for (env_item=environ;*env_item&&n<254;env_item++) {
    worker_env[n++] = *env_item;
  }
  worker_env[n] = NULL; /* terminate */

  free( worker_env[0] ); /* free LEV_WORKER_ID */
  free( worker_env[1] ); /* free LEV_IPC_FILENAME */

}

static inline void type_c(const char *worker_id, const char *ipc_filename) {
  int env_cnt = 0;
  char **entry;
  for (entry = environ; *entry; entry++, env_cnt++);
  char *worker_env[2 + env_cnt + 1];
  char worker_env0_buf[sizeof("LEN_WORKER_ID=") + strlen(worker_id)];
  sprintf(worker_env0_buf, "LEV_WORKER_ID=%s", worker_id);
  worker_env[0] = worker_env0_buf;
  char worker_env1_buf[sizeof("LEV_IPC_FILENAME=") + strlen(ipc_filename)];
  sprintf(worker_env1_buf, "LEV_IPC_FILENAME=%s", ipc_filename);
  worker_env[1] = worker_env1_buf;
  memcpy(worker_env + 2, environ, sizeof(char *) * (env_cnt + 1));
}

int main(void)
{
  int i;
  clock_t begin, end;

  char worker_id[8];
  char *ipc_filename = "/tmp/lev_12345.tmp";

  begin = clock();
  for (i=0;i<2000000;i++) {
    sprintf(worker_id, "%d", i);
    type_a(worker_id, ipc_filename);
  }
  end = clock();
  printf("type_a: %f seconds\n", (double)(end - begin) / CLOCKS_PER_SEC);

  begin = clock();
  for (i=0;i<2000000;i++) {
    sprintf(worker_id, "%d", i);
    type_b(worker_id, ipc_filename);
  }
  end = clock();
  printf("type_b: %f seconds\n", (double)(end - begin) / CLOCKS_PER_SEC);

  begin = clock();
  for (i=0;i<2000000;i++) {
    sprintf(worker_id, "%d", i);
    type_c(worker_id, ipc_filename);
  }
  end = clock();
  printf("type_c: %f seconds\n", (double)(end - begin) / CLOCKS_PER_SEC);

  return 0;
}