Copyright (c) 2000, 2010 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2010 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.localstore;

import java.io.InputStream;
import java.util.Set;
import org.eclipse.core.filesystem.EFS;
import org.eclipse.core.filesystem.IFileStore;
import org.eclipse.core.internal.utils.UniversalUniqueIdentifier;
import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;

Blob store which maps UUIDs to blobs on disk. The UUID is mapped
to a file in the file-system and the blob is the file contents. For scalability,
the blobs are split among 255 directories with the names 00 to FF.
/**
 * Blob store which maps UUIDs to blobs on disk. The UUID is mapped
 * to a file in the file-system and the blob is the file contents. For scalability,
 * the blobs are split among 255 directories with the names 00 to FF.
 */
public class BlobStore {
	protected IFileStore localStore;

	
Limits the range of directories' names. /** Limits the range of directories' names. */
	protected byte mask;

	//private static short[] randomArray = {213, 231, 37, 85, 211, 29, 161, 175, 187, 3, 147, 246, 170, 30, 202, 183, 242, 47, 254, 189, 25, 248, 193, 2, 119, 133, 125, 12, 76, 213, 219, 79, 69, 133, 202, 80, 150, 190, 157, 190, 80, 190, 219, 150, 169, 117, 95, 10, 77, 214, 233, 70, 5, 188, 44, 91, 165, 149, 177, 93, 17, 112, 4, 41, 230, 148, 188, 107, 213, 31, 52, 60, 111, 246, 226, 121, 129, 197, 144, 248, 92, 133, 96, 116, 104, 67, 74, 144, 185, 141, 96, 34, 182, 90, 36, 217, 28, 205, 107, 52, 201, 14, 8, 1, 27, 216, 60, 35, 251, 194, 7, 156, 32, 5, 145, 29, 96, 61, 110, 145, 50, 56, 235, 239, 170, 138, 17, 211, 56, 98, 101, 126, 27, 57, 211, 144, 206, 207, 179, 111, 160, 50, 243, 69, 106, 118, 155, 159, 28, 57, 11, 175, 43, 173, 96, 181, 99, 169, 171, 156, 246, 243, 30, 198, 251, 81, 77, 92, 160, 235, 215, 187, 23, 71, 58, 247, 127, 56, 118, 132, 79, 188, 42, 188, 158, 121, 255, 65, 154, 118, 172, 217, 4, 47, 105, 204, 135, 27, 43, 90, 9, 31, 59, 115, 193, 28, 55, 101, 9, 117, 211, 112, 61, 55, 23, 235, 51, 104, 123, 138, 76, 148, 115, 119, 81, 54, 39, 46, 149, 191, 79, 16, 222, 69, 219, 136, 148, 181, 77, 250, 101, 223, 140, 194, 141, 44, 195, 217, 31, 223, 207, 149, 245, 115, 243, 183};
	private static byte[] randomArray = {-43, -25, 37, 85, -45, 29, -95, -81, -69, 3, -109, -10, -86, 30, -54, -73, -14, 47, -2, -67, 25, -8, -63, 2, 119, -123, 125, 12, 76, -43, -37, 79, 69, -123, -54, 80, -106, -66, -99, -66, 80, -66, -37, -106, -87, 117, 95, 10, 77, -42, -23, 70, 5, -68, 44, 91, -91, -107, -79, 93, 17, 112, 4, 41, -26, -108, -68, 107, -43, 31, 52, 60, 111, -10, -30, 121, -127, -59, -112, -8, 92, -123, 96, 116, 104, 67, 74, -112, -71, -115, 96, 34, -74, 90, 36, -39, 28, -51, 107, 52, -55, 14, 8, 1, 27, -40, 60, 35, -5, -62, 7, -100, 32, 5, -111, 29, 96, 61, 110, -111, 50, 56, -21, -17, -86, -118, 17, -45, 56, 98, 101, 126, 27, 57, -45, -112, -50, -49, -77, 111, -96, 50, -13, 69, 106, 118, -101, -97, 28, 57, 11, -81, 43, -83, 96, -75, 99, -87, -85, -100, -10, -13, 30,
			-58, -5, 81, 77, 92, -96, -21, -41, -69, 23, 71, 58, -9, 127, 56, 118, -124, 79, -68, 42, -68, -98, 121, -1, 65, -102, 118, -84, -39, 4, 47, 105, -52, -121, 27, 43, 90, 9, 31, 59, 115, -63, 28, 55, 101, 9, 117, -45, 112, 61, 55, 23, -21, 51, 104, 123, -118, 76, -108, 115, 119, 81, 54, 39, 46, -107, -65, 79, 16, -34, 69, -37, -120, -108, -75, 77, -6, 101, -33, -116, -62, -115, 44, -61, -39, 31, -33, -49, -107, -11, 115, -13, -73,};

	
The limit is the maximum number of directories managed by this store.
This number must be power of 2 and do not exceed 256. The location
should be an existing valid directory.
/**
	 * The limit is the maximum number of directories managed by this store.
	 * This number must be power of 2 and do not exceed 256. The location
	 * should be an existing valid directory.
	 */
	public BlobStore(IFileStore store, int limit) {
		Assert.isNotNull(store);
		localStore = store;
		Assert.isTrue(localStore.fetchInfo().isDirectory());
		Assert.isTrue(limit == 256 || limit == 128 || limit == 64 || limit == 32 || limit == 16 || limit == 8 || limit == 4 || limit == 2 || limit == 1);
		mask = (byte) (limit - 1);
	}

	public UniversalUniqueIdentifier addBlob(IFileStore target, boolean moveContents) throws CoreException {
		UniversalUniqueIdentifier uuid = new UniversalUniqueIdentifier();
		folderFor(uuid).mkdir(EFS.NONE, null);
		IFileStore destination = fileFor(uuid);
		if (moveContents)
			target.move(destination, EFS.NONE, null);
		else
			target.copy(destination, EFS.NONE, null);
		return uuid;
	}

	
See Also:
appendByteString.appendByteString(StringBuilder, byte)/**
	 * @see UniversalUniqueIdentifier#appendByteString(StringBuilder, byte)
	 */
	@SuppressWarnings("javadoc")
	private void appendByteString(StringBuilder buffer, byte value) {
		String hexString;
		if (value < 0)
			hexString = Integer.toHexString(256 + value);
		else
			hexString = Integer.toHexString(value);
		if (hexString.length() == 1)
			buffer.append("0"); //$NON-NLS-1$
		buffer.append(hexString);
	}

	
Converts an array of bytes into a String.
See Also:
toString.toString()/**
	 * Converts an array of bytes into a String.
	 *
	 * @see UniversalUniqueIdentifier#toString()
	 */
	private String bytesToHexString(byte[] b) {
		StringBuilder buffer = new StringBuilder();
		for (byte element : b)
			appendByteString(buffer, element);
		return buffer.toString();
	}

	
Deletes a blobFile.
/**
	 * Deletes a blobFile.
	 */
	public void deleteBlob(UniversalUniqueIdentifier uuid) {
		Assert.isNotNull(uuid);
		try {
			fileFor(uuid).delete(EFS.NONE, null);
		} catch (CoreException e) {
			//ignore
		}
	}

	
Delete all of the blobs in the given set.
/**
	 * Delete all of the blobs in the given set.
	 */
	public void deleteBlobs(Set<UniversalUniqueIdentifier> set) {
		for (UniversalUniqueIdentifier id : set)
			deleteBlob(id);
	}

	public IFileStore fileFor(UniversalUniqueIdentifier uuid) {
		IFileStore root = folderFor(uuid);
		return root.getChild(bytesToHexString(uuid.toBytes()));
	}

	
Find out the name of the directory that fits better to this UUID.
/**
	 * Find out the name of the directory that fits better to this UUID.
	 */
	public IFileStore folderFor(UniversalUniqueIdentifier uuid) {
		byte hash = hashUUIDbytes(uuid);
		hash &= mask; // limit the range of the directory
		String dirName = Integer.toHexString(hash + (128 & mask)); // +(128 & mask) makes sure 00h is the lower value
		return localStore.getChild(dirName);
	}

	public InputStream getBlob(UniversalUniqueIdentifier uuid) throws CoreException {
		IFileStore blobFile = fileFor(uuid);
		return blobFile.openInputStream(EFS.NONE, null);
	}

	
Converts a byte array into a byte hash representation. It is used to
get a directory name.
/**
	 * Converts a byte array into a byte hash representation. It is used to
	 * get a directory name.
	 */
	protected byte hashUUIDbytes(UniversalUniqueIdentifier uuid) {
		byte[] bytes = uuid.toBytes();
		byte hash = 0;
		for (byte b : bytes)
			hash ^= randomArray[b + 128]; // +128 makes sure the index is >0
		return hash;
	}
}