task.c

/*
 *
 * task.c
 *
 * Baltasar Dinis 89416
 * IAED project
 *
 * defines the task datatype
 */

#include "task.h"

/* buffer for the description of a task (8000 chars as per specification) */
#define DESCRIPT_BUFFER 8000

/* max size of an ulong */
#if ULONG_WIDTH == 32
#define ULONG_BUFFER 10
#else
#define ULONG_BUFFER 20
#endif

/*-------------------------------*/
/* prototypes */
/*-------------------------------*/

/* verifies correctess of the input string */
static bool verify_quoted_str(char *str, size_t buffer_size);

/*-------------------------------*/
/*-------------------------------*/
/*-------------------------------*/


/* 
 * function: task_
 *
 * constructor for the task datatype
 *   id: task identifier, must be 32-bit positive integer
 *   descript: task description, enclosed in quotes
 *   dur: task duration, must be 32-bit positive integer
 *
 * return: ptr to task
 *
 * if an error is detected in the input, return NULL 
 * (without the quotes or exceeds DESCRIPT_BUFFER)
 */
task *task_(unsigned long id, char *descript, unsigned long dur)
{
  size_t src_len;
  task *a = NULL;

  /* verify input correctness
   * exits with error if the input is incorrect */
  if (!verify_quoted_str(descript, DESCRIPT_BUFFER)) {
    return NULL;
  }

  a = (task *) malloc(sizeof(task));
  id(*a) = id;
  dur(*a) = dur;

  src_len = strlen(descript);
  descript(*a) = (char *) malloc((src_len + 1) * sizeof(char));
  strncpy(descript(*a), descript, src_len + 1);

  return a;
}


/*
 * function: verify_quoted_str
 *
 * verifies correctess of the input string
 *   str: string to be verified
 *   buffer_size: maximum size of the string
 *
 * return: true if str is correct; false otherwise
 *
 * str is said to be incorrect if it isn't delimited by quotes
 *                                or exceeds the buffer
 */
static bool verify_quoted_str(char *str, size_t buffer_size)
{
  size_t len;

  if (str == NULL) return false;

  len = strlen(str);
  
  if (str[0] != '\"' || str[len - 1] != '\"' || len > buffer_size) 
    return false;

  return true;
}


/*
 * function: free_task
 *
 * destructor for the task datatype
 *   a: ptr to task
 *
 * frees task a
 */
void free_task(task *a)
{
  if (a != NULL) {
    free(descript(*a));
    descript(*a) = NULL;

    free(a);
    a = NULL;
  }
}


/*
 * function: change_task_description
 *
 * modifier for the task datatype
 *   t: ptr to a task
 *   new_desc: new description string
 *
 * returns: true if the change was successful;
 *   if it wasn't the description remains the same
 */
bool change_task_description(task *t, char *new_desc)
{
  size_t src_len;

  if (!verify_quoted_str(new_desc, DESCRIPT_BUFFER))
    return false;

  src_len = strlen(new_desc);
  free(descript(*t));
  descript(*t) = (char *) malloc((src_len + 1) * sizeof(char));
  strncpy(descript(*t), new_desc, src_len + 1);

  return true;
}


/*
 * function: change_task_duration
 *
 * modifier for the task datatype
 *   t: ptr to a task
 *   new_dur: new task duration
 *
 * returns: true if the change was successful;
 */
bool change_task_duration(task *t, unsigned long new_dur)
{
  dur(*t) = new_dur;
  return true;
}


/*
 * function: print_task
 *
 * external representation function for task datatype
 *   a: task
 *
 * return: str with external representation of a task
 *
 * representation: <id> <description> <duration>
 */
char *print_task(task *a)
{
  size_t len;
  char *str;

  /* note: 2 spaces between values */
  len = 2 * ULONG_BUFFER + strlen(descript(*a)) + 2;
  str = malloc((len + 1) * sizeof(char));

  sprintf(str, "%lu %s %lu", id(*a), descript(*a), dur(*a));
  return str;
}