/**
* Extends a <code>File</code> by the given size in bytes. Pre-condition: size must be greater
* than 0 Post-condition: <code>File</code> with the given filename will be extended by passed in
* amount of bytes, and additional <code>Blocks</code> will be allocated to it as needed
*
* @param filename the name of the <code>File</code>
* @param size number of bytes to increase the <code>File</code> by
* @return successful extension message
* @throws InSufficientDiskSpaceException if there are not enough blocks to extend <code>File
* </code>
* @throws NoSuchFileException if the filename does not match any existing <code>File</code>
*/
public String extend(String filename, int size)
throws InsufficientDiskSpaceException, NoSuchFileException {
Iterator<File> findFile = FAT32.iterator();
boolean fileFound = false;
// Check if file exists
while (findFile.hasNext()) {
if (findFile.next().getName().equalsIgnoreCase(filename)) {
fileFound = true;
}
}
// Throw exception if it doesn't
if (fileFound == false) {
throw new NoSuchFileException(filename + " does not exist!");
}
// Check there is enough space to extend file
if (size > (freeBlocks.size() * blockSize)) {
throw new InsufficientDiskSpaceException(
"Not enough disk space to extend " + filename + " \n");
} else {
Iterator<File> itr = FAT32.iterator();
// Iterate through list of files to find filename
while (itr.hasNext()) {
File file = itr.next();
if (file.getName().equals(filename)) {
// Calculate the extended size and how many blocks need to be added
int newSize = file.getBytes() + size;
int blocksToAdd = bytesBlocks(newSize) - bytesBlocks(file.getBytes());
// Take blocks from available blocks and add them to the file
for (int i = 0; i < blocksToAdd; i++) {
file.add(freeBlocks.remove(0));
}
file.addBytes(size);
}
}
// Throw exception or return appropriate message
if (fileFound == false) {
throw new NoSuchFileException(filename + " does not exist!");
} else {
return filename + " extended successfully!\n";
}
}
}
/**
* Deletes a <code>File</code> with the given name from the internal <code>File</code> list
* Post-condition: <code>File</code> with the passed in filename will be deleted and its <code>
* Blocks</code> added back to available <code>Blocks</code>
*
* @param filename the name of the <code>File</code>
* @return successful deletion message
* @throws NoSuchFileException if the filename does not match any existing <code>File</code>
*/
public String delete(String filename) throws NoSuchFileException {
Iterator<File> itr = FAT32.iterator();
boolean fileFound = false;
// Iterate through list of files to look for filename
while (itr.hasNext()) {
File file = itr.next();
if (file.getName().equals(filename)) {
fileFound = true;
// Iterate through file's blocks, adding them back to available blocks
for (int i = 0; i < bytesBlocks(file.getBytes()); i++) {
freeBlocks.add(file.remove());
}
// Remove file
itr.remove();
}
}
// Throw an exception or return appropriate message
if (fileFound == false) {
throw new NoSuchFileException(filename + " does not exist!");
} else {
return filename + " deleted successfully!\n";
}
}
/**
* Truncates a <code>File</code> by the given size in bytes. Pre-condition: size must be greater
* than 0 Post-condition: <code>File</code> with the given filename will be truncated by passed in
* amount of bytes, and <code>Blocks</code> will be de-allocated to it as needed
*
* @param filename the name of the <code>File</code>
* @param size number of bytes to truncate the <code>File</code> by
* @return successful truncation message
* @throws NoSuchFileException if the filename does not match any existing <code>File</code>
* @throws FileUnderflowException if number of truncating bytes is greater than <code>File</code>
* size
*/
public String truncate(String filename, int size)
throws NoSuchFileException, FileUnderflowException {
Iterator<File> itr = FAT32.iterator();
boolean fileFound = false;
// Iterate through list of files to find filename
while (itr.hasNext()) {
File file = itr.next();
if (file.getName().equals(filename)) {
fileFound = true;
// If truncating by total file size, delete the file instead
if (file.getBytes() == size) {
delete(filename);
} else if (file.getBytes() < size) {
throw new FileUnderflowException(
"Tried to truncate "
+ filename
+ " by "
+ size
+ " bytes, but it is only "
+ file.getBytes()
+ " bytes!\n");
} else {
// Calculate the truncated size and how many blocks need to be removed
int newSize = file.getBytes() - size;
int blocksToRemove = bytesBlocks(file.getBytes()) - bytesBlocks(newSize);
// Take blocks from file and add them to available blocks
for (int i = 0; i < blocksToRemove; i++) {
freeBlocks.add(file.remove());
}
file.delBytes(size);
}
}
}
// Throw exception or return appropriate message
if (fileFound == false) {
throw new NoSuchFileException(filename + " does not exist!");
} else {
return filename + " truncated successfully!\n";
}
}
