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org.h2.store.fs.FilePathMem Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.store.fs;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.channels.NonWritableChannelException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.atomic.AtomicReference;
import org.h2.api.ErrorCode;
import org.h2.compress.CompressLZF;
import org.h2.message.DbException;
import org.h2.util.MathUtils;
/**
* This file system keeps files fully in memory. There is an option to compress
* file blocks to save memory.
*/
public class FilePathMem extends FilePath {
private static final TreeMap MEMORY_FILES =
new TreeMap<>();
private static final FileMemData DIRECTORY = new FileMemData("", false);
@Override
public FilePathMem getPath(String path) {
FilePathMem p = new FilePathMem();
p.name = getCanonicalPath(path);
return p;
}
@Override
public long size() {
return getMemoryFile().length();
}
@Override
public void moveTo(FilePath newName, boolean atomicReplace) {
synchronized (MEMORY_FILES) {
if (!atomicReplace && !newName.name.equals(name) &&
MEMORY_FILES.containsKey(newName.name)) {
throw DbException.get(ErrorCode.FILE_RENAME_FAILED_2, name, newName + " (exists)");
}
FileMemData f = getMemoryFile();
f.setName(newName.name);
MEMORY_FILES.remove(name);
MEMORY_FILES.put(newName.name, f);
}
}
@Override
public boolean createFile() {
synchronized (MEMORY_FILES) {
if (exists()) {
return false;
}
getMemoryFile();
}
return true;
}
@Override
public boolean exists() {
if (isRoot()) {
return true;
}
synchronized (MEMORY_FILES) {
return MEMORY_FILES.get(name) != null;
}
}
@Override
public void delete() {
if (isRoot()) {
return;
}
synchronized (MEMORY_FILES) {
FileMemData old = MEMORY_FILES.remove(name);
if (old != null) {
old.truncate(0);
}
}
}
@Override
public List newDirectoryStream() {
ArrayList list = new ArrayList<>();
synchronized (MEMORY_FILES) {
for (String n : MEMORY_FILES.tailMap(name).keySet()) {
if (n.startsWith(name)) {
if (!n.equals(name) && n.indexOf('/', name.length() + 1) < 0) {
list.add(getPath(n));
}
} else {
break;
}
}
return list;
}
}
@Override
public boolean setReadOnly() {
return getMemoryFile().setReadOnly();
}
@Override
public boolean canWrite() {
return getMemoryFile().canWrite();
}
@Override
public FilePathMem getParent() {
int idx = name.lastIndexOf('/');
return idx < 0 ? null : getPath(name.substring(0, idx));
}
@Override
public boolean isDirectory() {
if (isRoot()) {
return true;
}
synchronized (MEMORY_FILES) {
FileMemData d = MEMORY_FILES.get(name);
return d == DIRECTORY;
}
}
@Override
public boolean isAbsolute() {
// TODO relative files are not supported
return true;
}
@Override
public FilePathMem toRealPath() {
return this;
}
@Override
public long lastModified() {
return getMemoryFile().getLastModified();
}
@Override
public void createDirectory() {
if (exists()) {
throw DbException.get(ErrorCode.FILE_CREATION_FAILED_1,
name + " (a file with this name already exists)");
}
synchronized (MEMORY_FILES) {
MEMORY_FILES.put(name, DIRECTORY);
}
}
@Override
public OutputStream newOutputStream(boolean append) throws IOException {
FileMemData obj = getMemoryFile();
FileMem m = new FileMem(obj, false);
return new FileChannelOutputStream(m, append);
}
@Override
public InputStream newInputStream() {
FileMemData obj = getMemoryFile();
FileMem m = new FileMem(obj, true);
return new FileChannelInputStream(m, true);
}
@Override
public FileChannel open(String mode) {
FileMemData obj = getMemoryFile();
return new FileMem(obj, "r".equals(mode));
}
private FileMemData getMemoryFile() {
synchronized (MEMORY_FILES) {
FileMemData m = MEMORY_FILES.get(name);
if (m == DIRECTORY) {
throw DbException.get(ErrorCode.FILE_CREATION_FAILED_1,
name + " (a directory with this name already exists)");
}
if (m == null) {
m = new FileMemData(name, compressed());
MEMORY_FILES.put(name, m);
}
return m;
}
}
private boolean isRoot() {
return name.equals(getScheme() + ":");
}
/**
* Get the canonical path for this file name.
*
* @param fileName the file name
* @return the canonical path
*/
protected static String getCanonicalPath(String fileName) {
fileName = fileName.replace('\\', '/');
int idx = fileName.indexOf(':') + 1;
if (fileName.length() > idx && fileName.charAt(idx) != '/') {
fileName = fileName.substring(0, idx) + "/" + fileName.substring(idx);
}
return fileName;
}
@Override
public String getScheme() {
return "memFS";
}
/**
* Whether the file should be compressed.
*
* @return if it should be compressed.
*/
boolean compressed() {
return false;
}
}
/**
* A memory file system that compresses blocks to conserve memory.
*/
class FilePathMemLZF extends FilePathMem {
@Override
public FilePathMem getPath(String path) {
FilePathMemLZF p = new FilePathMemLZF();
p.name = getCanonicalPath(path);
return p;
}
@Override
boolean compressed() {
return true;
}
@Override
public String getScheme() {
return "memLZF";
}
}
/**
* This class represents an in-memory file.
*/
class FileMem extends FileBase {
/**
* The file data.
*/
FileMemData data;
private final boolean readOnly;
private long pos;
FileMem(FileMemData data, boolean readOnly) {
this.data = data;
this.readOnly = readOnly;
}
@Override
public long size() {
return data.length();
}
@Override
public FileChannel truncate(long newLength) throws IOException {
// compatibility with JDK FileChannel#truncate
if (readOnly) {
throw new NonWritableChannelException();
}
if (data == null) {
throw new ClosedChannelException();
}
if (newLength < size()) {
data.touch(readOnly);
pos = Math.min(pos, newLength);
data.truncate(newLength);
}
return this;
}
@Override
public FileChannel position(long newPos) {
this.pos = newPos;
return this;
}
@Override
public int write(ByteBuffer src, long position) throws IOException {
if (data == null) {
throw new ClosedChannelException();
}
int len = src.remaining();
if (len == 0) {
return 0;
}
data.touch(readOnly);
data.readWrite(position, src.array(),
src.arrayOffset() + src.position(), len, true);
src.position(src.position() + len);
return len;
}
@Override
public int write(ByteBuffer src) throws IOException {
if (data == null) {
throw new ClosedChannelException();
}
int len = src.remaining();
if (len == 0) {
return 0;
}
data.touch(readOnly);
pos = data.readWrite(pos, src.array(),
src.arrayOffset() + src.position(), len, true);
src.position(src.position() + len);
return len;
}
@Override
public int read(ByteBuffer dst, long position) throws IOException {
if (data == null) {
throw new ClosedChannelException();
}
int len = dst.remaining();
if (len == 0) {
return 0;
}
long newPos = data.readWrite(position, dst.array(),
dst.arrayOffset() + dst.position(), len, false);
len = (int) (newPos - position);
if (len <= 0) {
return -1;
}
dst.position(dst.position() + len);
return len;
}
@Override
public int read(ByteBuffer dst) throws IOException {
if (data == null) {
throw new ClosedChannelException();
}
int len = dst.remaining();
if (len == 0) {
return 0;
}
long newPos = data.readWrite(pos, dst.array(),
dst.arrayOffset() + dst.position(), len, false);
len = (int) (newPos - pos);
if (len <= 0) {
return -1;
}
dst.position(dst.position() + len);
pos = newPos;
return len;
}
@Override
public long position() {
return pos;
}
@Override
public void implCloseChannel() throws IOException {
pos = 0;
data = null;
}
@Override
public void force(boolean metaData) throws IOException {
// do nothing
}
@Override
public synchronized FileLock tryLock(long position, long size,
boolean shared) throws IOException {
if (data == null) {
throw new ClosedChannelException();
}
if (shared) {
if (!data.lockShared()) {
return null;
}
} else {
if (!data.lockExclusive()) {
return null;
}
}
return new FileLock(FakeFileChannel.INSTANCE, position, size, shared) {
@Override
public boolean isValid() {
return true;
}
@Override
public void release() throws IOException {
data.unlock();
}
};
}
@Override
public String toString() {
return data == null ? "" : data.getName();
}
}
/**
* This class contains the data of an in-memory random access file.
* Data compression using the LZF algorithm is supported as well.
*/
class FileMemData {
private static final int CACHE_SIZE = 8;
private static final int BLOCK_SIZE_SHIFT = 10;
private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_SHIFT;
private static final int BLOCK_SIZE_MASK = BLOCK_SIZE - 1;
private static final CompressLZF LZF = new CompressLZF();
private static final byte[] BUFFER = new byte[BLOCK_SIZE * 2];
private static final byte[] COMPRESSED_EMPTY_BLOCK;
private static final Cache COMPRESS_LATER =
new Cache<>(CACHE_SIZE);
private String name;
private final int id;
private final boolean compress;
private long length;
private AtomicReference[] data;
private long lastModified;
private boolean isReadOnly;
private boolean isLockedExclusive;
private int sharedLockCount;
static {
byte[] n = new byte[BLOCK_SIZE];
int len = LZF.compress(n, BLOCK_SIZE, BUFFER, 0);
COMPRESSED_EMPTY_BLOCK = Arrays.copyOf(BUFFER, len);
}
@SuppressWarnings("unchecked")
FileMemData(String name, boolean compress) {
this.name = name;
this.id = name.hashCode();
this.compress = compress;
this.data = new AtomicReference[0];
lastModified = System.currentTimeMillis();
}
/**
* Get the page if it exists.
*
* @param page the page id
* @return the byte array, or null
*/
byte[] getPage(int page) {
AtomicReference[] b = data;
if (page >= b.length) {
return null;
}
return b[page].get();
}
/**
* Set the page data.
*
* @param page the page id
* @param oldData the old data
* @param newData the new data
* @param force whether the data should be overwritten even if the old data
* doesn't match
*/
void setPage(int page, byte[] oldData, byte[] newData, boolean force) {
AtomicReference[] b = data;
if (page >= b.length) {
return;
}
if (force) {
b[page].set(newData);
} else {
b[page].compareAndSet(oldData, newData);
}
}
int getId() {
return id;
}
/**
* Lock the file in exclusive mode if possible.
*
* @return if locking was successful
*/
synchronized boolean lockExclusive() {
if (sharedLockCount > 0 || isLockedExclusive) {
return false;
}
isLockedExclusive = true;
return true;
}
/**
* Lock the file in shared mode if possible.
*
* @return if locking was successful
*/
synchronized boolean lockShared() {
if (isLockedExclusive) {
return false;
}
sharedLockCount++;
return true;
}
/**
* Unlock the file.
*/
synchronized void unlock() throws IOException {
if (isLockedExclusive) {
isLockedExclusive = false;
} else if (sharedLockCount > 0) {
sharedLockCount--;
} else {
throw new IOException("not locked");
}
}
/**
* This small cache compresses the data if an element leaves the cache.
*/
static class Cache extends LinkedHashMap {
private static final long serialVersionUID = 1L;
private final int size;
Cache(int size) {
super(size, (float) 0.75, true);
this.size = size;
}
@Override
public synchronized V put(K key, V value) {
return super.put(key, value);
}
@Override
protected boolean removeEldestEntry(Map.Entry eldest) {
if (size() < size) {
return false;
}
CompressItem c = (CompressItem) eldest.getKey();
c.file.compress(c.page);
return true;
}
}
/**
* Points to a block of bytes that needs to be compressed.
*/
static class CompressItem {
/**
* The file.
*/
FileMemData file;
/**
* The page to compress.
*/
int page;
@Override
public int hashCode() {
return page ^ file.getId();
}
@Override
public boolean equals(Object o) {
if (o instanceof CompressItem) {
CompressItem c = (CompressItem) o;
return c.page == page && c.file == file;
}
return false;
}
}
private void compressLater(int page) {
CompressItem c = new CompressItem();
c.file = this;
c.page = page;
synchronized (LZF) {
COMPRESS_LATER.put(c, c);
}
}
private byte[] expand(int page) {
byte[] d = getPage(page);
if (d.length == BLOCK_SIZE) {
return d;
}
byte[] out = new byte[BLOCK_SIZE];
if (d != COMPRESSED_EMPTY_BLOCK) {
synchronized (LZF) {
LZF.expand(d, 0, d.length, out, 0, BLOCK_SIZE);
}
}
setPage(page, d, out, false);
return out;
}
/**
* Compress the data in a byte array.
*
* @param page which page to compress
*/
void compress(int page) {
byte[] old = getPage(page);
if (old == null || old.length != BLOCK_SIZE) {
// not yet initialized or already compressed
return;
}
synchronized (LZF) {
int len = LZF.compress(old, BLOCK_SIZE, BUFFER, 0);
if (len <= BLOCK_SIZE) {
byte[] d = Arrays.copyOf(BUFFER, len);
// maybe data was changed in the meantime
setPage(page, old, d, false);
}
}
}
/**
* Update the last modified time.
*
* @param openReadOnly if the file was opened in read-only mode
*/
void touch(boolean openReadOnly) throws IOException {
if (isReadOnly || openReadOnly) {
throw new IOException("Read only");
}
lastModified = System.currentTimeMillis();
}
/**
* Get the file length.
*
* @return the length
*/
long length() {
return length;
}
/**
* Truncate the file.
*
* @param newLength the new length
*/
void truncate(long newLength) {
changeLength(newLength);
long end = MathUtils.roundUpLong(newLength, BLOCK_SIZE);
if (end != newLength) {
int lastPage = (int) (newLength >>> BLOCK_SIZE_SHIFT);
byte[] d = expand(lastPage);
byte[] d2 = Arrays.copyOf(d, d.length);
for (int i = (int) (newLength & BLOCK_SIZE_MASK); i < BLOCK_SIZE; i++) {
d2[i] = 0;
}
setPage(lastPage, d, d2, true);
if (compress) {
compressLater(lastPage);
}
}
}
private void changeLength(long len) {
length = len;
len = MathUtils.roundUpLong(len, BLOCK_SIZE);
int blocks = (int) (len >>> BLOCK_SIZE_SHIFT);
if (blocks != data.length) {
AtomicReference[] n = Arrays.copyOf(data, blocks);
for (int i = data.length; i < blocks; i++) {
n[i] = new AtomicReference<>(COMPRESSED_EMPTY_BLOCK);
}
data = n;
}
}
/**
* Read or write.
*
* @param pos the position
* @param b the byte array
* @param off the offset within the byte array
* @param len the number of bytes
* @param write true for writing
* @return the new position
*/
long readWrite(long pos, byte[] b, int off, int len, boolean write) {
long end = pos + len;
if (end > length) {
if (write) {
changeLength(end);
} else {
len = (int) (length - pos);
}
}
while (len > 0) {
int l = (int) Math.min(len, BLOCK_SIZE - (pos & BLOCK_SIZE_MASK));
int page = (int) (pos >>> BLOCK_SIZE_SHIFT);
byte[] block = expand(page);
int blockOffset = (int) (pos & BLOCK_SIZE_MASK);
if (write) {
byte[] p2 = Arrays.copyOf(block, block.length);
System.arraycopy(b, off, p2, blockOffset, l);
setPage(page, block, p2, true);
} else {
System.arraycopy(block, blockOffset, b, off, l);
}
if (compress) {
compressLater(page);
}
off += l;
pos += l;
len -= l;
}
return pos;
}
/**
* Set the file name.
*
* @param name the name
*/
void setName(String name) {
this.name = name;
}
/**
* Get the file name
*
* @return the name
*/
String getName() {
return name;
}
/**
* Get the last modified time.
*
* @return the time
*/
long getLastModified() {
return lastModified;
}
/**
* Check whether writing is allowed.
*
* @return true if it is
*/
boolean canWrite() {
return !isReadOnly;
}
/**
* Set the read-only flag.
*
* @return true
*/
boolean setReadOnly() {
isReadOnly = true;
return true;
}
}
