/*
* Create a SFS with one superblock, one freemap block and 1022 data blocks
*
* The freemap is initialized be 0x3(11b), meaning that
* the first two blocks are used (sb and the freemap block).
*
* This function always returns zero on success.
*/
int sfs_mkfs()
{
/* one block in-memory space for freemap (avoid malloc) */
static char freemap_space[BLOCK_SIZE];
int i;
sb.magic = SFS_MAGIC;
sb.nblocks = 1024;
sb.nfreemap_blocks = 1;
sb.first_dir = 0;
for (i = 0; i < SFS_MAX_OPENED_FILES; ++i) {
/* no opened files */
fdtable[i].valid = 0;
}
sfs_write_block(&sb, 0);
freemap = (u32 *)freemap_space;
memset(freemap, 0, BLOCK_SIZE);
/* just to enlarge the whole file */
sfs_write_block(freemap, sb.nblocks);
/* initializing freemap */
freemap[0] = 0x3; /* 11b, freemap block and sb used*/
sfs_write_block(freemap, 1);
// Parameters(*buffer, blockId)
memset(&sb, 0, BLOCK_SIZE);
// Fills the first BLOCK_SIZE bytes at pointer &sb with 0s.
return 0;
}
/*
* Remove an existing empty directory and return 0 on success.
* If the dir does not exist or still contains files, return -1.
*/
int sfs_rmdir(char *dirname)
{
sfs_dirblock_t currentDir, prevDir, nextDir;
blkid bid, prevBlkid, nextBlkid;
/* TODO: check if the dir exists */
bid = sfs_find_dir(dirname);
if (bid != 0) {
// Directory exists
sfs_read_block((char*)¤tDir, bid);
/* TODO: check if no files */
int i;
for (i = 0; i < SFS_DB_NINODES; i++)
{
if (currentDir.inodes[i] != 0) {
// directory is not empty
printf("ERROR: inodes not empty = %d\n", currentDir.inodes[i]);
return -1;
}
}
/* TODO: go thru the linked list to delete the dir*/
// Need to change the next_dir pointer of the previous dir and dir to be deleted
nextBlkid = sb.first_dir;
if (nextBlkid == bid) {
// Deleting the root directory
sb.first_dir = 0;
sfs_read_block((char*)¤tDir, nextBlkid);
currentDir.next_dir = 0;
memset(currentDir.dir_name, 0, sizeof(currentDir.dir_name));
return 0;
}
else
{
while (nextBlkid != bid)
{
prevBlkid = nextBlkid;
sfs_read_block((char*)&prevDir, nextBlkid);
nextBlkid = prevDir.next_dir;
}
nextBlkid = currentDir.next_dir;
}
// Remove the directory: update the linked list next_dir variable
prevDir.next_dir = nextBlkid;
currentDir.next_dir = 0;
// Remove the dir_name of the dir to be deleted
memset(currentDir.dir_name, 0, sizeof(currentDir.dir_name));
// Flush the removed directory and prevDir
sfs_write_block((char*)¤tDir, bid);
sfs_write_block((char*)&prevDir, prevBlkid);
// Update the freemap so that deleted dir is empty
sfs_free_block(bid);
return 0;
}
return -1;
}
/*
* Resize a file.
* This file should be opened (in the file descriptor table). The new size
* should be larger than the old one (not supposed to shrink a file)
*/
static void sfs_resize_file(int fd, u32 new_size)
{
/* the length of content that can be hold by a full frame (in bytes) */
int frame_size = BLOCK_SIZE * SFS_FRAME_COUNT;
/* old file size */
int old_size = fdtable[fd].inode.size;
/* how many frames are used before resizing */
int old_nframe = (old_size + frame_size -1) / frame_size;
/* how many frames are required after resizing */
int new_nframe = (new_size + frame_size - 1) / frame_size;
int i, j;
blkid frame_bid = 0;
sfs_inode_frame_t frame;
blkid bid, content_bid;
/* TODO: check if new frames are required */
if (new_nframe - old_nframe > 0)
{
/* TODO: allocate a full frame */
frame_bid = sfs_alloc_block();
for (j = 0; j < SFS_FRAME_COUNT; j++)
{
content_bid = sfs_alloc_block();
frame.content[j] = content_bid;
// Empty content block
char tmp[BLOCK_SIZE];
memset(tmp, 0, BLOCK_SIZE);
sfs_write_block((char*)&tmp, content_bid);
}
/* TODO: add the new frame to the inode frame list
Note that if the inode is changed, you need to write it to the disk
*/
bid = fdtable[fd].inode.first_frame;
if (bid == 0)
{
fdtable[fd].inode.first_frame = frame_bid;
sfs_write_block((char*)&fdtable[fd].inode, fdtable[fd].inode_bid);
}
else
{
for (i = 0; i < SFS_FRAME_COUNT; i++)
{
if (bid == 0)
{
frame.next = frame_bid;
break;
}
sfs_read_block((char*)&frame, bid);
bid = frame.next;
}
}
// Write the new frame block
sfs_write_block((char*)&frame, frame_bid);
}
}
/*
* Remove/delete an existing file
*
* This function returns zero on success.
*/
int sfs_remove(int fd)
{
blkid frame_bid, next_frame_bid;
sfs_dirblock_t dir;
sfs_inode_frame_t frame;
int i, j;
char *tmp;
/* TODO: update dir */
sfs_read_block((char*)&dir, fdtable[fd].dir_bid);
for (i = 0; i < SFS_DB_NINODES; i++)
{
if (dir.inodes[i] == fdtable[fd].inode_bid)
{
dir.inodes[i] = 0;
}
}
// Write dir block to update inode values
sfs_write_block((char*)&dir, fdtable[fd].dir_bid);
/* TODO: free inode and all its frames */
frame_bid = fdtable[fd].inode.first_frame;
while (frame_bid != 0)
{
sfs_read_block((char*)&frame, frame_bid);
// Free all the content blocks for each frame
for (j = 0; j < SFS_FRAME_COUNT; j++)
{
tmp = (char*)malloc(BLOCK_SIZE);
memset(tmp, 0, BLOCK_SIZE);
sfs_write_block(tmp, frame.content[j]);
sfs_free_block(frame.content[j]);
free(tmp);
}
next_frame_bid = frame.next;
memset(&frame, 0, BLOCK_SIZE);
sfs_write_block((char*)&frame, frame_bid);
sfs_free_block(frame_bid);
frame_bid = next_frame_bid;
}
// Free the inode
memset((char*)&fdtable[fd].inode, 0, BLOCK_SIZE);
sfs_write_block((char*)&fdtable[fd].inode, fdtable[fd].inode_bid);
sfs_free_block(fdtable[fd].inode_bid);
/* TODO: close the file */
sfs_close(fd);
return 0;
}
/*
* Allocate a free block, mark it in the freemap and flush the freemap to disk
*/
static blkid sfs_alloc_block()
{
u32 size = sb.nfreemap_blocks * BLOCK_SIZE / sizeof(u32);
// size = 1 * 512 / 4 = 128 four-byte sections = 4096 bits
//Renaming variables i and j to be more specific
u32 fm_blk, fm_byte;
blkid free_block_id;
//Search each freemap block
for(fm_blk = 0; fm_blk < sb.nfreemap_blocks; fm_blk++){
//Read the freemap block located at the block ID
int count;
int freemap_id = fm_blk + 1;
sfs_read_block(freemap, freemap_id);
//Search each index of the freemap block
for(fm_byte = 0; fm_byte < BLOCK_SIZE; fm_byte++){
u32 bitmap = freemap[fm_byte];
if((bitmap ^ 0xffffffff) != 0){
//There is a free bit at this index in the freemap
u32 mask = 0x1;
u32 result;
count = 0;
//Search each bit of the freemap block
while(count < SFS_NBITS_IN_FREEMAP_ENTRY){
result = bitmap & mask;
if(result == mask){
mask = mask << 1;
count++;
} else{
free_block_id = fm_byte * SFS_NBITS_IN_FREEMAP_ENTRY + count;
//Set the bit and flush to disk
u32 newBitmap = bitmap | mask;
freemap[fm_byte] = newBitmap;
sfs_flush_freemap();
//Clear the data stored in the block
char empty_blk[BLOCK_SIZE];
memset(empty_blk, 0, BLOCK_SIZE);
sfs_write_block(empty_blk, free_block_id);
return free_block_id;
}
}
}
}
}
return 0;
}
/*
* Create a new directory and return 0 on success.
* If the dir already exists, return -1.
*/
int sfs_mkdir(char *dirname)
{
/* TODO: test if the dir exists */
/* TODO: insert a new dir to the linked list */
blkid nextBlkid;
sfs_dirblock_t dir, new_dir;
// Try finding the directory if it exists
blkid bid = sfs_find_dir(dirname);
if (bid == 0)
{
// Directory does not exists, create a new one
bid = sfs_alloc_block();
// Add the new directory to the directory linked list
nextBlkid = sb.first_dir;
if (nextBlkid == 0) {
sb.first_dir = bid;
sfs_write_block((char*)&sb, 0);
}
else
{
sfs_read_block((char*)&dir, nextBlkid);
while (dir.next_dir != 0)
{
nextBlkid = dir.next_dir;
sfs_read_block((char*)&dir, nextBlkid);
}
dir.next_dir = bid;
sfs_write_block((char*)&dir, nextBlkid);
}
// Create new directory with next_dir=0 and dir_name
new_dir.next_dir = 0;
memset(new_dir.dir_name, 0, sizeof(new_dir.dir_name)); // Empty dir_name
memset(new_dir.inodes, 0, sizeof(new_dir.inodes)); // Empty inodes
strcpy(new_dir.dir_name, dirname); // Copy new dir_name
sfs_write_block((char*)&new_dir, bid);
return 0;
}
// Directory already exists
return -1;
}
/*
* Get the bids of content blocks that hold the file content starting from cur
* to cur+length. These bids are stored in the given array.
* The caller of this function is supposed to allocate the memory for this
* array. It is guaranteed that cur+length<size
*
* This function returns the number of bids being stored to the array.
*/
static u32 sfs_get_file_content(blkid *bids, int fd, u32 cur, u32 length)
{
u32 start; //Starting block of content
u32 end; //Ending block of content
sfs_inode_t inode;
sfs_inode_frame_t frame;
blkid frame_bid;
char tmp[BLOCK_SIZE];
char frame_ptr[BLOCK_SIZE];
u32 num_bids = 0; //Counts the number of bids in the array
//Get the bid of the desired frame
fd_struct_t fd_struct = fdtable[fd];
sfs_read_block(tmp, fd_struct.inode_bid);
inode = *(sfs_inode_t*)tmp;
frame_bid = inode.first_frame;
start = cur / BLOCK_SIZE;
end = (cur + length) / BLOCK_SIZE;
u32 numBlocks = end - start + 1;
u32 blocks_remaining = numBlocks;
u32 original_blocks = blocks_remaining;
//Start searching at an offset determined by the start position
u32 block_count = start % SFS_FRAME_COUNT;
//This loop will iterate through the frames
while(blocks_remaining > 0){
sfs_read_block(frame_ptr, frame_bid);
frame = *(sfs_inode_frame_t*)frame_ptr;
//Iterate through the content array of the frame
while(block_count < SFS_FRAME_COUNT && blocks_remaining > 0){
//Allocate a content block if it is not yet set
if(frame.content[block_count] == 0){
frame.content[block_count] = sfs_alloc_block();
}
bids[num_bids] = frame.content[block_count];
num_bids++;
block_count++;
blocks_remaining--;
}
sfs_write_block(&frame, frame_bid);
if(blocks_remaining != 0){
frame_bid = frame.next;
block_count = 0;
}
}
return num_bids;
}
/*
* Flush the in-memory freemap to disk
*/
static void sfs_flush_freemap()
{
blkid bid = 1;
char *p = (char *)freemap;
do{
sfs_write_block(p, bid);
bid++;
} while(bid < sb.nfreemap_blocks);
}
/*
* Flush the in-memory freemap to disk
*/
static void sfs_flush_freemap()
{
size_t i;
blkid bid = 1;
char *p = (char *)freemap;
/* TODO: write freemap block one by one */
i = sb.nfreemap_blocks;
int j;
for (j = 1; j <= i; j++)
{
sfs_write_block(&p, j);
}
}
/*
* Write to a file. This function can potentially enlarge the file if the
* cur+length exceeds the size of file. Also you should be aware that the
* cur may already be larger than the size (due to sfs_seek). In such
* case, you will need to expand the file as well.
*
* This function returns number of bytes written.
*/
int sfs_write(int fd, void *buf, int length)
{
int remaining, offset, to_copy;
char *p = (char *)buf;
char tmp[BLOCK_SIZE];
char inode_ptr[BLOCK_SIZE];
u32 cur = fdtable[fd].cur;
u32 buf_offset = 0;
sfs_inode_t inode;
remaining = length;
offset = cur % BLOCK_SIZE;
int numBids = (length / BLOCK_SIZE) + 1;
blkid bids[numBids];
sfs_read_block(inode_ptr, fdtable[fd].inode_bid);
inode = *(sfs_inode_t*)inode_ptr;
blkid frame_bid = inode.first_frame;
/* TODO: check if we need to resize */
sfs_inode_frame_t frame;
sfs_read_block(tmp, frame_bid);
frame = *(sfs_inode_frame_t*)tmp;
if( (length + cur) > inode.size){
u32 new_size = length + cur;
fdtable[fd].inode = inode;
sfs_resize_file(fd, new_size);
}
/* TODO: get the block ids of all contents (using sfs_get_file_content() */
int num_blocks = sfs_get_file_content(bids, fd, cur, length);
/* TODO: main loop, go through every block, copy the necessary parts
to the buffer, consult the hint in the document. Do not forget to
flush to the disk.
*/
char block_ptr[BLOCK_SIZE];
int bid_count = 0;
//The block numbers should already be known by this part
while(remaining > 0){
to_copy = 0;
sfs_read_block(block_ptr, bids[bid_count]);
//Case 1: Write to block with offset
if(offset != 0){
//Partially fill block
if(remaining < (BLOCK_SIZE - offset)){
to_copy = remaining;
} else{
//Fill entire block
to_copy = BLOCK_SIZE - offset;
}
strncpy(block_ptr+offset, buf, to_copy);
offset = 0;
} else if(remaining > BLOCK_SIZE){
//Case 2: Write to a full block
to_copy = BLOCK_SIZE;
strncpy(block_ptr, buf, to_copy);
} else{
//Case 3: Write a partial block
to_copy = remaining;
strncpy(block_ptr, buf, to_copy);
}
sfs_write_block(&block_ptr, bids[bid_count]);
remaining = remaining - to_copy;
cur = cur + to_copy;
bid_count++;
}
fdtable[fd].cur = cur;
return length - remaining;
}
W
sfs_i_write (struct inode *ip,
W start,
B *buf,
W size,
W *rsize)
{
#ifdef notdef
B blockbuf[ip->i_fs->fs_private.sfs_fs.sfs_blocksize]; /* GCC の拡張機能を使っている */
#endif
int copysize;
int offset;
int retsize;
int filesize;
ID fd;
struct fs *fsp;
W bn;
W cn;
B *cbuf;
#ifdef FMDEBUG
printk ("sfs_i_write:(start = %d, size = %d)\n", start, size); /* */
#endif
*rsize = 0;
retsize = size;
filesize = start + retsize;
fd = ip->i_device;
fsp = ip->i_fs;
#ifdef FMDEBUG
printk ("sfs_i_write: size = %d\n", size); /* */
#endif
while (size > 0)
{
#ifdef FMDEBUG
printk ("%s\n",
(sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize) <= 0) ?
"allocate block" : "read block");
#endif
if (sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize) <= 0)
{
/* ファイルサイズを越えて書き込む場合には、新しくブロックをアロケートする
*/
bn = sfs_set_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize,
sfs_alloc_block (fd, fsp));
/*
* ip->sfs_i_direct[start / fsp->fs_blksize] = alloc_block (fd, fsp);
*/
#ifdef notdef
bzero (blockbuf, fsp->fs_blksize);
#else
if (bn < 0) {
return (EP_IO);
}
sfs_get_cache(fd, bn, &cn, &cbuf);
#endif
}
else
{
#ifdef FMDEBUG
printk ("read block %d\n",
sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize));
#endif
bn = sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize);
if (bn < 0) {
return (EP_IO);
}
#ifdef notdef
sfs_read_block (fd, bn, fsp->fs_blksize, blockbuf);
#else
sfs_get_cache(fd, bn, &cn, &cbuf);
#endif
}
/* 読み込んだブロックの内容を更新する
*/
offset = start % fsp->fs_blksize;
copysize = MIN (fsp->fs_blksize - offset, size);
#ifdef FMDEBUG
printk ("*** read block contents ***\n");
{
int i;
char tmpbuf[2];
tmpbuf[1] = '\0';
printk ("copy size: %d\n", copysize);
for (i = 0; i < copysize; i++)
{
tmpbuf[0] = blockbuf[i];
printk ("%s", tmpbuf);
}
}
#endif
#ifdef notdef
bcopy (buf, &blockbuf[offset], copysize);
#else
bcopy(buf, &cbuf[offset], copysize);
#endif
#ifdef notdef
printk ("sfs write block: block number = %d\n",
sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize)); /* */
#endif
/* 更新したブロックを書き込む
*/
#ifdef notdef
bn = sfs_get_block_num (fd, fsp, &(ip->i_private.sfs_inode),
start / fsp->fs_blksize);
if (bn < 0) {
return (EP_IO);
}
sfs_write_block (fd, bn, fsp->fs_blksize, blockbuf);
#else
sfs_put_cache(cn, 1);
#endif
buf += copysize;
start += copysize;
size -= copysize;
}
/* cache の sync をここで行う必要はあるか? */
sfs_sync_cache(fd);
/* もし、書き込みをおこなった後にファイルのサイズが増えていれば、
* サイズを更新して inode を書き込む。
*/
if (filesize > ip->i_private.sfs_inode.sfs_i_size)
{
ip->i_size = filesize;
ip->i_size_blk =
ROUNDUP(filesize, fsp->fs_blksize)/fsp->fs_blksize;
ip->i_dirty = 1;
/* これは deallocate の中で処理するのが普通 */
sfs_i_sync(ip);
}
else if (filesize < ip->i_private.sfs_inode.sfs_i_size) {
sfs_i_truncate (ip, filesize);
}
*rsize = retsize - size;
#ifdef FMDEBUG
printk ("write size: %d bytes\n", *rsize);
#endif
return (EP_OK);
}
/*
* Open a file. If it does not exist, create a new one.
* Allocate a file desriptor for the opened file and return the fd.
*/
int sfs_open(char *dirname, char *name)
{
blkid dir_bid = 0, inode_bid = 0;
char inode_ptr[BLOCK_SIZE];
sfs_inode_t inode;
sfs_dirblock_t dir;
fd_struct_t *fd_ptr;
fd_struct_t fd;
//Finds a free file descriptor number
int fd_num = 0;
while(fd_num < SFS_MAX_OPENED_FILES){
fd = fdtable[fd_num];
if(fd.valid == 0){
fd.valid = 1;
fd.cur = 0;
break;
} else if(fd_num == SFS_MAX_OPENED_FILES - 1){
printf("The maximum number of files are already in use\n");
return -1;
} else{
fd_num++;
}
}
//Find the directory in which the specified file is contained
dir_bid = sfs_find_dir(dirname);
sfs_read_block(&dir, dir_bid);
fd.dir_bid = dir_bid;
//Iterate through all the indices of the inodes to find the file
int count = 0;
int fd_set = 0;
int free_inode = -1;
char *file_name;
while(count < SFS_DB_NINODES){
inode_bid = dir.inodes[count];
if(inode_bid == 0){
if(free_inode == -1){
free_inode = count;
}
count++;
continue;
}
//Read the inode at the specified index
sfs_read_block(inode_ptr, inode_bid);
inode = *(sfs_inode_t*)inode_ptr;
file_name = inode.file_name;
if(strcmp(file_name, name) == 0){
fd.inode = inode;
fd.inode_bid = inode_bid;
fd_set = 1;
break;
}
count++;
}
//Create a new file
if(fd_set == 0){
//Allocate a block for the inode
blkid new_inode_bid = sfs_alloc_block();
//Put the inode bid into the directory inode array
dir.inodes[free_inode] = new_inode_bid;
sfs_write_block(&dir, dir_bid);
strcpy(inode.file_name, name);
//Allocate a block for the first frame
blkid new_frame_bid = sfs_alloc_block();
inode.first_frame = new_frame_bid;
inode.size = 0;
//Place the inode in the file descriptor array
fd.inode = inode;
fd.inode_bid = new_inode_bid;
sfs_write_block(&inode, new_inode_bid);
sfs_read_block(&inode, new_inode_bid);
//Allocate a block for the first content block of the frame
char tmp[BLOCK_SIZE];
sfs_read_block(tmp, new_frame_bid);
sfs_inode_frame_t new_frame = *(sfs_inode_frame_t*)tmp;
blkid new_content_bid = sfs_alloc_block();
new_frame.content[0] = new_content_bid;
sfs_write_block(&new_frame, new_frame_bid);
}
//Set the file descriptor in the file descriptor table
fdtable[fd_num] = fd;
return fd_num;
}
/*
* Remove/delete an existing file
* This function returns zero on success.
*/
int sfs_remove(int fd_num)
{
blkid frame_bid;
sfs_dirblock_t dir;
char block_ptr[BLOCK_SIZE];
int i;
fd_struct_t fd = fdtable[fd_num];
//Set the index of the inode to zero
blkid dir_bid = fd.dir_bid;
blkid inode_bid = fd.inode_bid;
//Remove the inode from the directory
sfs_read_block(block_ptr, dir_bid);
dir = *(sfs_dirblock_t*)block_ptr;
//Find the index at which the inode is stored
int count = 0;
while(count < SFS_DB_NINODES){
if(dir.inodes[count] == inode_bid){
dir.inodes[count] = 0;
break;
}
count++;
}
dir.inodes[inode_bid] = 0;
sfs_write_block(&dir, dir_bid);
/* TODO: free inode and all its frames */
sfs_inode_t inode;
sfs_read_block(block_ptr, inode_bid);
inode = *(sfs_inode_t*)block_ptr;
char frame_ptr[BLOCK_SIZE];
sfs_inode_frame_t frame;
blkid next_frame = inode.first_frame;
//Iterate through each of the nonzero content blocks
//sfs_free_block() on all of them
while(next_frame != 0){
sfs_read_block(frame_ptr, next_frame);
frame = *(sfs_inode_frame_t*)frame_ptr;
//Check each of the entries of the frame and free nonzero blocks
int i;
for(i = 0; i < SFS_FRAME_COUNT; i++){
blkid content_blk = frame.content[i];
if(content_blk != 0){
sfs_free_block(content_blk);
}
}
sfs_free_block(next_frame);
next_frame = frame.next;
}
/* TODO: close the file */
sfs_free_block(inode_bid);
//Reset the file description to default
fd.valid = 0;
memset(&fd.inode, 0, sizeof(sfs_inode_t));
fd.dir_bid = 0;
fd.inode_bid = 0;
return 0;
}
/*
* Open a file. If it does not exist, create a new one.
* Allocate a file desriptor for the opened file and return the fd.
*/
int sfs_open(char *dirname, char *name)
{
blkid dir_bid = 0, inode_bid = 0;
sfs_inode_t *inode, new_inode;
sfs_dirblock_t dir;
int fd;
int i;
/* TODO: find a free fd number */
for (i = 0; i < SFS_MAX_OPENED_FILES; i++)
{
if (fdtable[i].valid == 0)
{
// Found a free fd
fd = i;
break;
}
}
/* TODO: find the dir first */
dir_bid = sfs_find_dir(dirname);
if (dir_bid == 0)
{
printf("ERROR: the directory does not exists\n");
return -1;
}
sfs_read_block((char*)&dir, dir_bid);
/* TODO: traverse the inodes to see if the file exists.
If it exists, load its inode. Otherwise, create a new file.
*/
for (i = 0; i < SFS_DB_NINODES; i++)
{
if (dir.inodes[i] != 0)
{
sfs_read_block((char*)&new_inode, dir.inodes[i]);
if (strcmp(new_inode.file_name, name) == 0) {
inode_bid = dir.inodes[i];
break;
}
}
}
if (inode_bid == 0)
{
// Allocate a block to store new inode
inode_bid = sfs_alloc_block();
// Find empty space in dir.inodes[] and set inode_bid
for (i=0; i<SFS_DB_NINODES; i++)
{
if (dir.inodes[i] == 0)
{
dir.inodes[i] = inode_bid;
break;
}
}
// Did not find the inode, create a new one
new_inode.first_frame = 0;
new_inode.size = 0;
memset(new_inode.file_name, 0, sizeof(new_inode.file_name));
strcpy(new_inode.file_name, name);
sfs_write_block((char*)&new_inode, inode_bid);
sfs_write_block((char*)&dir, dir_bid);
}
/* TODO: create a new file */
fdtable[fd].dir_bid = dir_bid;
fdtable[fd].inode_bid = inode_bid;
fdtable[fd].inode = new_inode;
fdtable[fd].cur = 0;
fdtable[fd].valid = 1;
return fd;
}
/*
* Remove an existing empty directory and return 0 on success.
* If the dir does not exist or still contains files, return -1.
*/
int sfs_rmdir(char *dirname)
{
/* TODO: check if the dir exists */
blkid dir_bid = sfs_find_dir(dirname);
if(dir_bid == 0){
printf("ERROR sfs_rmdir: Specified directory does not exist\n");
return -1;
}
if(sb.first_dir == 0 || dir_bid == 0){
//The directory does not exist
return -1;
} else{
//Unset the corresponding bit in the freemap
sfs_free_block(dir_bid);
}
//Find the directories that come before and after the
//directory we want to delete
blkid next_dir = sb.first_dir; //First block
blkid current_dir; //Current block is sb
blkid previous_dir = 0; //No previous blocks
char block_ptr[BLOCK_SIZE];
sfs_dirblock_t dir;
if(next_dir == dir_bid){
sfs_read_block(block_ptr, next_dir);
dir = *(sfs_dirblock_t*)block_ptr;
blkid block_to_copy = dir.next_dir;
sfs_read_block(&sb, 0);
sb.first_dir = block_to_copy;
sfs_write_block(&sb, 0);
}
//General case
while(next_dir != dir_bid){
previous_dir = current_dir;
current_dir = next_dir;
sfs_read_block(block_ptr, next_dir);
dir = *(sfs_dirblock_t*)block_ptr;
next_dir = dir.next_dir;
//The next block is what we want to remove
if(next_dir == dir_bid){
//Set the next dir of the current block to the next+1 block
sfs_read_block(block_ptr, next_dir);
dir = *(sfs_dirblock_t*)block_ptr;
blkid block_to_copy = dir.next_dir;
sfs_read_block(block_ptr, current_dir);
dir = *(sfs_dirblock_t*)block_ptr;
dir.next_dir = block_to_copy;
sfs_write_block(&dir, current_dir);
}
}
return 0;
}
/*
* Create a new directory and return 0 on success.
* If the dir already exists, return -1.
*/
int sfs_mkdir(char *dirname)
{
//Check if the directory has a valid name
if(sizeof(dirname) > 120){
printf("Dir name exceeds max allowed characters.\n");
return -1;
}
//Test if the dir exists
if(sfs_find_dir(dirname) != 0){
return -1;
} else{
//Initialize variables
blkid next_dir_id;
char block_ptr[BLOCK_SIZE];
sfs_dirblock_t dir;
//Allocate space for a new block
blkid new_bid = sfs_alloc_block();
//Set the next_dir in the last directory block
next_dir_id = sb.first_dir;
sfs_read_block(block_ptr, next_dir_id);
dir = *(sfs_dirblock_t*)block_ptr;
if(next_dir_id == 0){
sb.first_dir = new_bid;
sfs_write_block(&sb, 0);
} else{
while(next_dir_id != 0){
sfs_read_block(block_ptr, next_dir_id);
dir = *(sfs_dirblock_t*)block_ptr;
//Next dir is zero, set it to the next available block
if(dir.next_dir == 0){
blkid modified_dir_id = next_dir_id;
sfs_read_block(block_ptr, modified_dir_id);
dir = *(sfs_dirblock_t*)block_ptr;
dir.next_dir = new_bid;
//A value was changed, so this must be flushed to disk
sfs_write_block(&dir, modified_dir_id);
next_dir_id = 0;
} else{
next_dir_id = dir.next_dir;
}
}
}
//Create a temporary directory and initialize its members
//Set the next dir, name, and set all its inodes to zero
sfs_dirblock_t temp_dir;
temp_dir.next_dir = 0;
strcpy(temp_dir.dir_name, dirname);
memset(&temp_dir.inodes[0], 0, SFS_DB_NINODES * sizeof(blkid));
//Write the temporary block into the disk
sfs_write_block(&temp_dir, new_bid);
}
return 0;
}
/*
* Write to a file. This function can potentially enlarge the file if the
* cur+length exceeds the size of file. Also you should be aware that the
* cur may already be larger than the size (due to sfs_seek). In such
* case, you will need to expand the file as well.
*
* This function returns number of bytes written.
*/
int sfs_write(int fd, void *buf, int length)
{
int remaining, offset, to_copy;
blkid *bids;
int i, n;
char *p = (char *)buf;
char tmp[BLOCK_SIZE];
u32 cur = fdtable[fd].cur;
int frame_size, new_nframe, old_nframe;
/* TODO: check if we need to resize */
frame_size = BLOCK_SIZE * SFS_FRAME_COUNT;
old_nframe = (fdtable[fd].inode.size + frame_size-1)/frame_size;
new_nframe = ((cur+length) + frame_size-1)/frame_size;
if (new_nframe > old_nframe)
{
// Need to allocate a new frame
sfs_resize_file(fd, fdtable[fd].inode.size + length);
}
/* TODO: get the block ids of all contents (using sfs_get_file_content() */
bids = malloc(length/BLOCK_SIZE + 1);
n = sfs_get_file_content(bids, fd, cur, length);
/* TODO: main loop, go through every block, copy the necessary parts
to the buffer, consult the hint in the document. Do not forget to
flush to the disk.
*/
remaining = length;
offset = cur % BLOCK_SIZE;
if (BLOCK_SIZE - offset > remaining)
{
to_copy = remaining;
}
else
{
to_copy = BLOCK_SIZE - offset;
}
for (i = 0; i < n; i++)
{
memcpy(tmp + offset , buf, to_copy);
sfs_write_block((char*)&tmp, bids[i]);
remaining -= to_copy;
offset = 0;
if (remaining > BLOCK_SIZE)
{
to_copy = BLOCK_SIZE - offset;
}
else
{
to_copy = remaining;
}
}
/* TODO: update the cursor and free the temp buffer
for sfs_get_file_content()
*/
fdtable[fd].cur += length;
if (fdtable[fd].inode.size < fdtable[fd].cur)
{
fdtable[fd].inode.size = fdtable[fd].cur;
}
sfs_write_block((char*)&(fdtable[fd].inode), fdtable[fd].inode_bid);
free(bids);
return length;
}
/*
* Resize a file.
* This file should be opened (in the file descriptor table). The new size
* should be larger than the old one (not supposed to shrink a file)
*/
static void sfs_resize_file(int fd, u32 new_size)
{
/* the length of content that can be hold by a full frame (in bytes) */
int frame_size = BLOCK_SIZE * SFS_FRAME_COUNT;
/* old file size */
int old_size = fdtable[fd].inode.size;
/* how many frames are used before resizing */
int old_nframe = (old_size + frame_size -1) / frame_size;
//Opening a file always results in at least one frame
if(old_nframe == 0){
old_nframe++;
}
/* how many frames are required after resizing */
int new_nframe = (new_size + frame_size - 1) / frame_size;
int i, j;
char inode_ptr[BLOCK_SIZE];
char tmp[BLOCK_SIZE];
sfs_inode_t inode;
sfs_read_block(inode_ptr, fdtable[fd].inode_bid);
inode = *(sfs_inode_t*)inode_ptr;
blkid frame_bid = inode.first_frame;
sfs_inode_frame_t frame;
/* TODO: check if new frames are required */
int count = old_nframe;
while(count < new_nframe){
sfs_read_block(tmp, frame_bid);
frame = *(sfs_inode_frame_t*)tmp;
blkid new_frame_bid = sfs_alloc_block();
//Update the next frame bid for the current frame
frame.next = new_frame_bid;
sfs_write_block(&frame, frame_bid);
//Read the new frame bid and add the content blocks
sfs_read_block(tmp, new_frame_bid);
frame = *(sfs_inode_frame_t*)tmp;
for(i = 0; i < SFS_FRAME_COUNT; i++){
frame.content[i] = sfs_alloc_block();
}
sfs_write_block(&frame, new_frame_bid);
frame_bid = new_frame_bid;
count++;
}
sfs_read_block(tmp, inode.first_frame);
frame = *(sfs_inode_frame_t*)tmp;
inode.size = new_size;
sfs_write_block(&inode, fdtable[fd].inode_bid);
sfs_read_block(tmp, fdtable[fd].inode_bid);
inode = *(sfs_inode_t*)tmp;
}