#ifndef _OUTPUT_DEVICE_H
#define _OUTPUT_DEVICE_H

/*
 *       Multi-threaded Output Device Library 
 *       Author: OS, os@cs.huji.ac.il
 */



/*
 * DESCRIPTION: The function creates the file filename if it does not exist and open the file for writing. 
 *              This function should be called prior to any other functions as a necessary precondition for their success. 
 *	
 * RETURN VALUE: On success 0, -2 for a filesystem error (inability to create the file, etc.), otherwise -1. 
 */
int initdevice(char *filename); 

/*
 * DESCRIPTION: The function writes the input buffer to the file. The buffer may be freed once this call returns. 
 *              You should deal with any memory management issues. 
 * 		Note this is non-blocking package you are required to implement you should return ASAP, 
 * 		even if the buffer has not yet been written to the disk.
 * 
 * RETURN VALUE: On success, the function returns a task_id (>= 0), which identifies this write operation. 
 * 		 Note, you should reuse task_ids when they become available.  On failure, -1 will be returned.
 */
int write2device(char *buffer, int length);

/*
 * DESCRIPTION: Block until the specified task_id has been written to the file. 
 * 		The task_id is a value that was previously returned by write2device function. 
 * 		In case of error, the function should cause the process to exit.
 *
 */
void flush2device(int task_id);


/*
 * DESCRIPTION: return (withoug blocking) whether the specified task_id has been written to the file
 *      (0 if yes, 1 if not).
 * 		The task_id is a value that was previously returned by write2device function. 
 * 		In case of task_id doesn't exist, should return -2; In case of other errors, return -1.
 *
 */
int wasItWritten(int task_id);



/*
 * DESCRIPTION: close the output file and reset the system so that it is possible to call initdevice again. 
 *              All pending task_ids should be written to output disk file.     
 *              Any attempt to write new buffers (or initialize) while the system is shutting down should
 *              cause an error. 
 *              In case of error, the function should cause the process to exit.
 *
 */
void closedevice(); 


#endif