create_fs.c

/* create a file  to act as a disk  and format the file system residing on the disk */

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(int argc, char *argv[]){
  int i, fd;
  char *buf;

  if (argc == 1 ){
    fprintf(stderr,"usage: %s <diskFileName> \n",argv[0]);
    exit(0);
  }

  printf( "Creating  a 128KB  file in %s\n",argv[1]);
  printf("This file will act as a dummy disk and will hold your filesystem\n");

  /* open the disk file for writing */
  fd = open(argv[1],O_WRONLY | O_CREAT | O_TRUNC,  S_IRUSR | S_IWUSR);

  printf("Formatting your filesystem...\n");

  buf = (char *) calloc(1024,sizeof(char));
  
  /* write super block */
  buf[0]=1;  /* mark superblock as allocated in the free block list 
                         all other blocks are free, all inodes are zeroed out */

  /* write out the super block */
  if(write(fd,buf, 1024)<0)
    printf("error: write failed \n");  

  buf[0]=0;
  /* write out the remaining 127 data blocks, all zeroed out */
  for(i=0;i<127;i++){
    if(write(fd,buf,1024)<0)
      printf("error: write failed \n");  
  }

  close(fd);
  exit(1);

}

ex2.c

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

int create(char name[16], int size){ 
  /*create a file with this name and this size*/

  // Step 1: check to see if we have sufficient free space on disk by
  // reading in the free block list. To do this:
  // move the file pointer to the start of the disk file.
  // Read the first 128 bytes (the free/in-use block information)
  // Scan the list to make sure you have sufficient free blocks to
  // allocate a new file of this size

  // Step 2: we look  for a free inode on disk
  // Read in a inode
  // check the "used" field to see if it is free
  // If not, repeat the above two steps until you find a free inode
  // Set the "used" field to 1
  // Copy the filename to the "name" field
  // Copy the file size (in units of blocks) to the "size" field

  // Step 3: Allocate data blocks to the file
  // for(i=0;i<size;i++)
    // Scan the block list that you read in Step 1 for a free block
    // Once you find a free block, mark it as in-use (Set it to 1)
    // Set the blockPointer[i] field in the inode to this block number.
    // 
 // end for

  // Step 4: Write out the inode and free block list to disk
  //  Move the file pointer to the start of the file 
  // Write out the 128 byte free block list
  // Move the file pointer to the position on disk where this inode was stored
  // Write out the inode

} // End Create



int detete(char name[16]){
  // Delete the file with this name

  // Step 1: Locate the inode for this file
  // Move the file pointer to the 1st inode (129th byte)
  // Read in a inode
  // If the inode is free, repeat above step.
  // If the inode is in use, check if the "name" field in the
  // inode matches the file we want to delete. IF not, read the next
  //  inode and repeat
  
  // Step 2: free blocks of the file being deleted
  // Read in the 128 byte free block list (move file pointer to start of the disk and read in 128 bytes)
  // Free each block listed in the blockPointer fields as follows:
  // for(i=0;i< inode.size; i++) 
     // freeblockList[ inode.blockPointer[i] ] = 0;

  // Step 3: mark inode as free
  // Set the "used" field to 0.

  // Step 4: Write out the inode and free block list to disk
  //  Move the file pointer to the start of the file 
  // Write out the 128 byte free block list
  // Move the file pointer to the position on disk where this inode was stored
  // Write out the inode

} // End Delete


int ls(void){ 
  // List names of all files on disk

  // Step 1: read in each inode and print!
  // Move file pointer to the position of the 1st inode (129th byte)
  // for(i=0;i<16;i++)
    // REad in a inode
    // If the inode is in-use
      // print the "name" and "size" fields from the inode
 // end for

} // End ls

int read(char name[16], int blockNum, char buf[1024]){

   // read this block from this file

   // Step 1: locate the inode for this file
   // Move file pointer to the position of the 1st inode (129th byte)
   // Read in a inode
   // If the inode is in use, compare the "name" field with the above file
   // IF the file names don't match, repeat

   // Step 2: Read in the specified block
   // Check that blockNum < inode.size, else flag an error
   // Get the disk address of the specified block
   // That is, addr = inode.blockPointer[blockNum]
   // move the file pointer to the block location (i.e., to byte # addr*1024 in the file)

    // Read in the block! => Read in 1024 bytes from this location into the buffer "buf"
    
} // End read


int write(char name[16], int blockNum, char buf[1024]){

   // write this block to this file

   // Step 1: locate the inode for this file
   // Move file pointer to the position of the 1st inode (129th byte)
   // Read in a inode
   // If the inode is in use, compare the "name" field with the above file
   // IF the file names don't match, repeat

   // Step 2: Write to the specified block
   // Check that blockNum < inode.size, else flag an error
   // Get the disk address of the specified block
   // That is, addr = inode.blockPointer[blockNum]
   // move the file pointer to the block location (i.e., byte # addr*1024)

    // Write the block! => Write 1024 bytes from the buffer "buff" to this location

    
} // end write



int main(int argc, char *argv[]){
 
// Todo
  
}

input.txt

disk0
C file1.c 3
C file2.c 8
C file3.c 4
C a.out   5
C lab1.c 6
L
W file1.c 0
W file1.c 1
W file1.c 2
W file2.c 3
W file2.c 7
W file2.c 2
W file2.c 4
W file2.c 5
W a.out 0
W a.out 1
W a.out 2
W a.out 3
W a.out 4
D file3.c
R file1.c 2
C file4.c 7
L
R file2.c 4
R file2.c 5
R file2.c 6
D lab1.c
C lab2.c 7
R a.out 1
R a.out 3
R a.out 0
L