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

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/un.h>

char* escape_directory(char* unescaped_directory) {

  // The maximum possible length of the path after adding escape
  // characters is double the length of the unescaped path, when all characters
  // need to be escaped.  Then add one for the null.
  size_t unescaped_length = strlen(unescaped_directory);
  char* escaped_directory = malloc(2*unescaped_length + 1);

  // Now, we start to do the escaping.  Start with the first character.
  size_t escaped_position = 0;
  char* unescaped_character = unescaped_directory;
  do  {
    switch (*unescaped_character) {
    case ':':
    case '\\':
    case ',':
      // If the character needs to be escaped, then add a backslash
      escaped_directory[escaped_position++] = '\\';

    default:
      // Then, add the character itself
      escaped_directory[escaped_position++] = *unescaped_character;
    }

    // The original path should be null-terminated, so use this to decide when
    // to finish.
  } while ('\0' != *(unescaped_character++));

  // To be neat and tidy, realloc the escaped path to use only the needed space
  escaped_directory = realloc(escaped_directory, escaped_position);
  return escaped_directory;
}

void append_string(char** lhs, char* rhs) {
  // Work out what the length of the combined string is, and reallocate to match
  size_t final_length = strlen(*lhs) + strlen(rhs) + 1;
  *lhs = realloc(*lhs, final_length);

  // Finally, concatenate the rhs on the end
  strncat(*lhs, rhs, final_length);
}

char* allocate_stack(size_t size) {
  // Allocate memory that is read/write, page-aligned, and various other
  // things that you can find in the mmap(2) man page.
  return mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
}