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bndlib: A Swiss Army Knife for OSGi
package aQute.libg.cafs;
import static aQute.lib.io.IO.copy;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.DataInput;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.InflaterInputStream;
import aQute.lib.index.Index;
import aQute.libg.cryptography.SHA1;
/**
* CAFS implements a SHA-1 based file store. The basic idea is that every file
* in the universe has a unique SHA-1. Hard to believe but people smarter than
* me have come to that conclusion. This class maintains a compressed store of
* SHA-1 identified files. So if you have the SHA-1, you can get the contents.
* This makes it easy to store a SHA-1 instead of the whole file or maintain a
* naming scheme. An added advantage is that it is always easy to verify you get
* the right stuff. The SHA-1 Content Addressable File Store is the core
* underlying idea in Git.
*/
public class CAFS implements Closeable, Iterable {
final static byte[] CAFS;
final static byte[] CAFE;
final static String INDEXFILE = "index.idx";
final static String STOREFILE = "store.cafs";
final static String ALGORITHM = "SHA-1";
final static int KEYLENGTH = 20;
final static int HEADERLENGTH = 4 // CAFS
+ 4 // flags
+ 4 // compressed length
+ 4 // uncompressed length
+ KEYLENGTH // key
+ 2 // header checksum
;
final File home;
Index index;
RandomAccessFile store;
FileChannel channel;
static {
try {
CAFS = "CAFS".getBytes("UTF-8");
CAFE = "CAFE".getBytes("UTF-8");
} catch (Throwable e) {
throw new ExceptionInInitializerError(e);
}
}
/**
* Constructor for a Content Addressable File Store
*
* @param home
* @param create
* @throws Exception
*/
public CAFS(File home, boolean create) throws Exception {
this.home = home;
if (!home.isDirectory()) {
if (create) {
if (home.exists()) {
throw new IOException(home + " is not a directory");
}
if (!home.mkdirs()) {
throw new IOException("Could not create directory " + home);
}
} else
throw new IllegalArgumentException("CAFS requires a directory with create=false");
}
index = new Index(new File(home, INDEXFILE), KEYLENGTH);
store = new RandomAccessFile(new File(home, STOREFILE), "rw");
channel = store.getChannel();
if (store.length() < 0x100) {
if (create) {
store.write(CAFS);
for (int i = 1; i < 64; i++)
store.writeInt(0);
channel.force(true);
} else
throw new IllegalArgumentException("Invalid store file, length is too short " + store);
System.err.println(store.length());
}
store.seek(0);
if (!verifySignature(store, CAFS))
throw new IllegalArgumentException("Not a valid signature: CAFS at start of file");
}
/**
* Store an input stream in the CAFS while calculating and returning the
* SHA-1 code.
*
* @param in The input stream to store.
* @return The SHA-1 code.
* @throws Exception if anything goes wrong
*/
public SHA1 write(InputStream in) throws Exception {
Deflater deflater = new Deflater();
MessageDigest md = MessageDigest.getInstance(ALGORITHM);
DigestInputStream din = new DigestInputStream(in, md);
ByteArrayOutputStream bout = new ByteArrayOutputStream();
DeflaterOutputStream dout = new DeflaterOutputStream(bout, deflater);
copy(din, dout);
synchronized (store) {
// First check if it already exists
SHA1 sha1 = new SHA1(md.digest());
long search = index.search(sha1.digest());
if (search > 0)
return sha1;
byte[] compressed = bout.toByteArray();
// we need to append this file to our store,
// which requires a lock. However, we are in a race
// so others can get the lock between us getting
// the length and someone else getting the lock.
// So we must verify after we get the lock that the
// length was unchanged.
FileLock lock = null;
try {
long insertPoint;
int recordLength = compressed.length + HEADERLENGTH;
while (true) {
insertPoint = store.length();
lock = channel.lock(insertPoint, recordLength, false);
if (store.length() == insertPoint)
break;
// We got the wrong lock, someone else
// got in between reading the length
// and locking
lock.release();
}
int totalLength = deflater.getTotalIn();
store.seek(insertPoint);
update(sha1.digest(), compressed, totalLength);
index.insert(sha1.digest(), insertPoint);
return sha1;
} finally {
if (lock != null)
lock.release();
}
}
}
/**
* Read the contents of a sha 1 key.
*
* @param sha1 The key
* @return An Input Stream on the content or null of key not found
* @throws Exception
*/
public InputStream read(final SHA1 sha1) throws Exception {
synchronized (store) {
long offset = index.search(sha1.digest());
if (offset < 0)
return null;
byte[] readSha1;
byte[] buffer;
store.seek(offset);
if (!verifySignature(store, CAFE))
throw new IllegalArgumentException("No signature");
int flags = store.readInt();
int compressedLength = store.readInt();
int uncompressedLength = store.readInt();
readSha1 = new byte[KEYLENGTH];
store.read(readSha1);
SHA1 rsha1 = new SHA1(readSha1);
if (!sha1.equals(rsha1))
throw new IOException("SHA1 read and asked mismatch: " + sha1 + " " + rsha1);
short crc = store.readShort(); // Read CRC
if (crc != checksum(flags, compressedLength, uncompressedLength, readSha1))
throw new IllegalArgumentException("Invalid header checksum: " + sha1);
buffer = new byte[compressedLength];
store.readFully(buffer);
return getSha1Stream(sha1, buffer, uncompressedLength);
}
}
public boolean exists(byte[] sha1) throws Exception {
return index.search(sha1) >= 0;
}
public void reindex() throws Exception {
long length;
synchronized (store) {
length = store.length();
if (length < 0x100)
throw new IllegalArgumentException("Store file is too small, need to be at least 256 bytes: " + store);
}
RandomAccessFile in = new RandomAccessFile(new File(home, STOREFILE), "r");
try {
byte[] signature = new byte[4];
in.readFully(signature);
if (!Arrays.equals(CAFS, signature))
throw new IllegalArgumentException("Store file does not start with CAFS: " + in);
in.seek(0x100);
File ixf = new File(home, "index.new");
Index index = new Index(ixf, KEYLENGTH);
while (in.getFilePointer() < length) {
long entry = in.getFilePointer();
SHA1 sha1 = verifyEntry(in);
index.insert(sha1.digest(), entry);
}
synchronized (store) {
index.close();
File indexFile = new File(home, INDEXFILE);
ixf.renameTo(indexFile);
this.index = new Index(indexFile, KEYLENGTH);
}
} finally {
in.close();
}
}
public void close() throws IOException {
synchronized (store) {
try {
store.close();
} finally {
index.close();
}
}
}
private SHA1 verifyEntry(RandomAccessFile in) throws IOException, NoSuchAlgorithmException {
byte[] signature = new byte[4];
in.readFully(signature);
if (!Arrays.equals(CAFE, signature))
throw new IllegalArgumentException("File is corrupted: " + in);
/* int flags = */in.readInt();
int compressedSize = in.readInt();
int uncompressedSize = in.readInt();
byte[] key = new byte[KEYLENGTH];
in.readFully(key);
SHA1 sha1 = new SHA1(key);
byte[] buffer = new byte[compressedSize];
in.readFully(buffer);
InputStream xin = getSha1Stream(sha1, buffer, uncompressedSize);
xin.skip(uncompressedSize);
xin.close();
return sha1;
}
private boolean verifySignature(DataInput din, byte[] org) throws IOException {
byte[] read = new byte[org.length];
din.readFully(read);
return Arrays.equals(read, org);
}
private InputStream getSha1Stream(final SHA1 sha1, byte[] buffer, final int total) throws NoSuchAlgorithmException {
ByteArrayInputStream in = new ByteArrayInputStream(buffer);
InflaterInputStream iin = new InflaterInputStream(in) {
int count = 0;
final MessageDigest digestx = MessageDigest.getInstance(ALGORITHM);
final AtomicBoolean calculated = new AtomicBoolean();
@Override
public int read(byte[] data, int offset, int length) throws IOException {
int size = super.read(data, offset, length);
if (size <= 0)
eof();
else {
count += size;
this.digestx.update(data, offset, size);
}
return size;
}
@Override
public int read() throws IOException {
int c = super.read();
if (c < 0)
eof();
else {
count++;
this.digestx.update((byte) c);
}
return c;
}
void eof() throws IOException {
if (calculated.getAndSet(true))
return;
if (count != total)
throw new IOException(
"Counts do not match. Expected to read: " + total + " Actually read: " + count);
SHA1 calculatedSha1 = new SHA1(digestx.digest());
if (!sha1.equals(calculatedSha1))
throw (new IOException(
"SHA1 caclulated and asked mismatch, asked: " + sha1 + ", \nfound: " + calculatedSha1));
}
@Override
public void close() throws IOException {
eof();
super.close();
}
};
return iin;
}
/**
* Update a record in the store, assuming the store is at the right
* position.
*
* @param sha1 The checksum
* @param compressed The compressed length
* @param totalLength The uncompressed length
* @throws IOException The exception
*/
private void update(byte[] sha1, byte[] compressed, int totalLength) throws IOException {
// System.err.println("pos: " + store.getFilePointer());
store.write(CAFE); // 00-03 Signature
store.writeInt(0); // 04-07 Flags for the future
store.writeInt(compressed.length); // 08-11 Length deflated data
store.writeInt(totalLength); // 12-15 Length
store.write(sha1); // 16-35
store.writeShort(checksum(0, compressed.length, totalLength, sha1));
store.write(compressed);
channel.force(false);
}
short checksum(int flags, int compressedLength, int totalLength, byte[] sha1) {
CRC32 crc = new CRC32();
crc.update(flags);
crc.update(flags >> 8);
crc.update(flags >> 16);
crc.update(flags >> 24);
crc.update(compressedLength);
crc.update(compressedLength >> 8);
crc.update(compressedLength >> 16);
crc.update(compressedLength >> 24);
crc.update(totalLength);
crc.update(totalLength >> 8);
crc.update(totalLength >> 16);
crc.update(totalLength >> 24);
crc.update(sha1);
return (short) crc.getValue();
}
public Iterator iterator() {
return new Iterator() {
long position = 0x100;
public boolean hasNext() {
synchronized (store) {
try {
return position < store.length();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
public SHA1 next() {
synchronized (store) {
try {
store.seek(position);
byte[] signature = new byte[4];
store.readFully(signature);
if (!Arrays.equals(CAFE, signature))
throw new IllegalArgumentException("No signature");
int flags = store.readInt();
int compressedLength = store.readInt();
int totalLength = store.readInt();
byte[] sha1 = new byte[KEYLENGTH];
store.readFully(sha1);
short crc = store.readShort();
if (crc != checksum(flags, compressedLength, totalLength, sha1))
throw new IllegalArgumentException("Header checksum fails");
position += HEADERLENGTH + compressedLength;
return new SHA1(sha1);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
public void remove() {
throw new UnsupportedOperationException("Remvoe not supported, CAFS is write once");
}
};
}
public boolean isEmpty() throws IOException {
synchronized (store) {
return store.getFilePointer() <= 256;
}
}
}