org.rocksdb.AbstractSlice Maven / Gradle / Ivy
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
package org.rocksdb;
/**
* Slices are used by RocksDB to provide
* efficient access to keys and values.
*
* This class is package private, implementers
* should extend either of the public abstract classes:
* @see org.rocksdb.Slice
* @see org.rocksdb.DirectSlice
*
* Regards the lifecycle of Java Slices in RocksDB:
* At present when you configure a Comparator from Java, it creates an
* instance of a C++ BaseComparatorJniCallback subclass and
* passes that to RocksDB as the comparator. That subclass of
* BaseComparatorJniCallback creates the Java
* @see org.rocksdb.AbstractSlice subclass Objects. When you dispose
* the Java @see org.rocksdb.AbstractComparator subclass, it disposes the
* C++ BaseComparatorJniCallback subclass, which in turn destroys the
* Java @see org.rocksdb.AbstractSlice subclass Objects.
*/
public abstract class AbstractSlice extends RocksMutableObject {
protected AbstractSlice() {
super();
}
protected AbstractSlice(final long nativeHandle) {
super(nativeHandle);
}
/**
* Returns the data of the slice.
*
* @return The slice data. Note, the type of access is
* determined by the subclass
* @see org.rocksdb.AbstractSlice#data0(long)
*/
public T data() {
return data0(getNativeHandle());
}
/**
* Access to the data is provided by the
* subtype as it needs to handle the
* generic typing.
*
* @param handle The address of the underlying
* native object.
*
* @return Java typed access to the data.
*/
protected abstract T data0(long handle);
/**
* Drops the specified {@code n}
* number of bytes from the start
* of the backing slice
*
* @param n The number of bytes to drop
*/
public abstract void removePrefix(final int n);
/**
* Clears the backing slice
*/
public abstract void clear();
/**
* Return the length (in bytes) of the data.
*
* @return The length in bytes.
*/
public int size() {
return size0(getNativeHandle());
}
/**
* Return true if the length of the
* data is zero.
*
* @return true if there is no data, false otherwise.
*/
public boolean empty() {
return empty0(getNativeHandle());
}
/**
* Creates a string representation of the data
*
* @param hex When true, the representation
* will be encoded in hexadecimal.
*
* @return The string representation of the data.
*/
public String toString(final boolean hex) {
return toString0(getNativeHandle(), hex);
}
@Override
public String toString() {
return toString(false);
}
/**
* Three-way key comparison
*
* @param other A slice to compare against
*
* @return Should return either:
* 1) < 0 if this < other
* 2) == 0 if this == other
* 3) > 0 if this > other
*/
public int compare(final AbstractSlice other) {
assert (other != null);
if (isOwningHandle() && other.isOwningHandle()) {
return compare0(getNativeHandle(), other.getNativeHandle());
}
if (!isOwningHandle() && !other.isOwningHandle()) {
return 0;
}
if (isOwningHandle()) {
return 1;
} else {
return -1;
}
}
@Override
public int hashCode() {
return toString().hashCode();
}
/**
* If other is a slice object, then
* we defer to {@link #compare(AbstractSlice) compare}
* to check equality, otherwise we return false.
*
* @param other Object to test for equality
*
* @return true when {@code this.compare(other) == 0},
* false otherwise.
*/
@Override
public boolean equals(final Object other) {
if (other instanceof AbstractSlice) {
return compare((AbstractSlice)other) == 0;
} else {
return false;
}
}
/**
* Determines whether this slice starts with
* another slice
*
* @param prefix Another slice which may of may not
* be a prefix of this slice.
*
* @return true when this slice starts with the
* {@code prefix} slice
*/
public boolean startsWith(final AbstractSlice prefix) {
if (prefix != null) {
return startsWith0(getNativeHandle(), prefix.getNativeHandle());
} else {
return false;
}
}
protected static native long createNewSliceFromString(final String str);
private static native int size0(long handle);
private static native boolean empty0(long handle);
private static native String toString0(long handle, boolean hex);
private static native int compare0(long handle, long otherHandle);
private static native boolean startsWith0(long handle, long otherHandle);
/**
* Deletes underlying C++ slice pointer.
* Note that this function should be called only after all
* RocksDB instances referencing the slice are closed.
* Otherwise, an undefined behavior will occur.
*/
@Override
protected final void disposeInternal(final long handle) {
disposeInternalJni(handle);
}
private static native void disposeInternalJni(final long handle);
}