testcases/kernel/fs/mongo/mongo_slinks.c

//
//  A simple symlink test
//

#define _GNU_SOURCE

#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

//
// Creates symlink [new-path] to [old-path], checks it,
// returnes  0 - if everything looks fine and
//  1 - otherwise.
// mongo_slinks reads arguments from stdin.

int main (int argc, char * argv [])
{
  char * old_path;
  char * new_path;

  struct stat statbuf;

  int num;
  char * buffer = NULL;
  char *line_buffer = NULL;
  size_t line_buffer_size = 0;
  int size = 1;

  if ((buffer = (char *) malloc (size+1)) == NULL) {
	  perror ("checklink: malloc failed");
	  return 1;
  }

  while (getline(&line_buffer, &line_buffer_size, stdin) != -1) {

	  old_path = strtok(line_buffer, "\t ");
	  new_path = strtok(NULL, "\t\n ");

	  if (!old_path || !new_path) /* empty lines at the end of file */
		  break;

	  // Create symlink
	  if (symlink(old_path, new_path) != 0) {
		  perror ("checklink : symlink failed ");
		  return 1;
	  }

	  // stat data of symlink itself
	  if (lstat(new_path, &statbuf)== -1) {
		  perror ("checklink: lstat failed");
		  return 1;
	  }

	  if (! (S_ISLNK (statbuf.st_mode))) {
		  printf ("checklink : file %s is not a symbol link\n", new_path);
		  return 1;
	  }

	  // Test readlink
	  //
	  // Increase size of buffer to readlink untile whole symlink body will be read.
	  // Check readlink result on every iteration.

	  while (1) {
		  memset (buffer, 0, size+1);
		  num = readlink (new_path, buffer, size);
		  if (num < 1 || num > size) {
			  perror ("checklink: readlink failed");
			  free (buffer);
			  return 1;
		  }

		  // Make sure that readlink did not break things
		  if (buffer [num] != 0) {
			  printf ("checklink : readlink corrupts memory\n");
			  free (buffer);
			  return 1;
		  }

		  // Whole expected symlink body is read
		  if (num < size)
			  break;

		  // Only part of symlink body was read. So we  make a bigger buffer
		  // and call `readlink' again.
		  size *= 2;
		  if ((buffer = realloc(buffer, size+1)) == NULL) {
			  perror("checklink: realloc failed");
			  return 1;
		  }
	  }
  }
  free (buffer);
  free (line_buffer);
        return 0;
}