Package io.deephaven.base.string.cache

Class MappedCompressedString

java.lang.Object

io.deephaven.base.string.cache.AbstractCompressedString<MappedCompressedString>

io.deephaven.base.string.cache.MappedCompressedString

All Implemented Interfaces:

StringAlike<MappedCompressedString>, StringCompatible, Serializable, CharSequence, Comparable<CharSequence>

public final class MappedCompressedString
extends AbstractCompressedString<MappedCompressedString>

This is a ridiculously simple, light-as-I-can-make-it, but decidedly single-purpose data structure. Specifically, it's a CompressedString with an embedded (to avoid reference or Object instance overhead) open-addressed SimpleReference<Object>-identity -> int hash map with load factor 1 (100%) and no public operations other than "putIfAbsent". The reason for requiring that key objects be SimpleReferences is to allow for O(1) automatic slot reclamation across many MappedCompressedString instances at the same time. A given source of mappings creates a single SimpleReference to use as a key, and may invalidate mappings (creating a deleted slot) simply by clearing the SimpleReference. In practice, a WeakSimpleReference to the source itself is used, in order to also allow garbage collection of the mapping source object to invalidate all of its mappings. Unfortunately, I haven't figured out a way to make this allow concurrent gets. The intended use is in Deephaven import code, for storing SymbolManager -> SymbolId mappings on the CompressedString that represents the Symbol itself, typically inside of a (bounded) StringCache of MappedCompressedString instances. Note that this uses io.deephaven.base.reference.SimpleReference instead of java.lang.ref.Reference so that unit tests can avoid being required to use the concrete sub-classes of Reference, which all come with GC-related side-effects.

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final int	NULL_MAPPING_VALUE

Constructor Summary

Constructors

Constructor	Description
MappedCompressedString(byte[] data)
MappedCompressedString(byte[] data, int offset, int length)
MappedCompressedString(char[] data)
MappedCompressedString(char[] data, int offset, int length)
MappedCompressedString(String data)
MappedCompressedString(ByteBuffer data)
MappedCompressedString(ByteBuffer data, int offset, int length)

Method Summary

Modifier and Type	Method	Description
final int	capacity()
protected final MappedCompressedString	convertValue(byte[] data, int offset, int length)	Convert a byte array to this type, assuming ISO-8859-1
protected final MappedCompressedString	convertValue(String string)	Convert a String to this type.
final int	putIfAbsent(SimpleReference<?> key, int potentialValue)	Add the specified <key, value> pair if no mapping already exists for key.
@NotNull CompressedString	toCompressedString()	Convert this StringCompatible into a CompressedString.
@NotNull MappedCompressedString	toMappedCompressedString()	Convert this StringCompatible into a MappedCompressedString.

Methods inherited from class io.deephaven.base.string.cache.AbstractCompressedString

charAt, codePointAt, codePointBefore, codePointCount, compareTo, compareToIgnoreCase, concat, concat, contains, contentEquals, endsWith, equals, equalsIgnoreCase, getBytes, getChars, getData, hashCode, indexOf, indexOf, indexOf, indexOf, intern, isEmpty, lastIndexOf, lastIndexOf, lastIndexOf, lastIndexOf, length, matches, regionMatches, replace, replace, replaceAll, replaceFirst, split, split, startsWith, startsWith, subSequence, substring, substring, toCharArray, toLowerCase, toLowerCase, toString, toUpperCase, toUpperCase, trim

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.CharSequence

chars, codePoints

Field Details

NULL_MAPPING_VALUE

public static final int NULL_MAPPING_VALUE

See Also:

• Constant Field Values

Constructor Details

MappedCompressedString

public MappedCompressedString(String data)

MappedCompressedString

public MappedCompressedString(char[] data,
 int offset,
 int length)

MappedCompressedString

public MappedCompressedString(char[] data)

MappedCompressedString

public MappedCompressedString(ByteBuffer data,
 int offset,
 int length)

MappedCompressedString

public MappedCompressedString(ByteBuffer data)

MappedCompressedString

public MappedCompressedString(byte[] data,
 int offset,
 int length)

MappedCompressedString

public MappedCompressedString(byte[] data)

Method Details

toCompressedString

@NotNull
public @NotNull CompressedString toCompressedString()

Description copied from interface: StringCompatible

Convert this StringCompatible into a CompressedString. Implementations should not cache result CompressedStrings, in order to avoid inadvertently allowing promotion of short-lived objects under generational garbage collection.

Returns:

A newly constructed CompressedString representing the same sequence of characters as this StringCompatible (or this object, if appropriate).

toMappedCompressedString

@NotNull
public @NotNull MappedCompressedString toMappedCompressedString()

Description copied from interface: StringCompatible

Convert this StringCompatible into a MappedCompressedString. Implementations should not cache result CompressedStrings, in order to avoid inadvertently allowing promotion of short-lived objects under generational garbage collection.

Returns:

A newly constructed MappedCompressedString representing the same sequence of characters as this StringCompatible (or this object, if appropriate).

convertValue

protected final MappedCompressedString convertValue(String string)

Description copied from class: AbstractCompressedString

Convert a String to this type.

Specified by:

convertValue in class AbstractCompressedString<MappedCompressedString>

Parameters:

string - The String to convert

Returns:

A new TYPE with the same contents as String, assuming ISO-8859-1 encoding

convertValue

protected final MappedCompressedString convertValue(byte[] data,
 int offset,
 int length)

Description copied from class: AbstractCompressedString

Convert a byte array to this type, assuming ISO-8859-1

Specified by:

convertValue in class AbstractCompressedString<MappedCompressedString>

Parameters:

data - The data to convert

offset - The starting index from data to convert

length - The length to convert

Returns:

A new TYPE with the same contents as the specified region of data, assuming ISO-8859-1 encoding

capacity

public final int capacity()

putIfAbsent

public final int putIfAbsent(SimpleReference<?> key,
 int potentialValue)

Add the specified <key, value> pair if no mapping already exists for key.

Parameters:

key - A non-null Reference to an arbitrary object whose reachability determines mapping validity.

potentialValue - The value to insert if none already exists. Must not equal NULL_MAPPING_VALUE.

Returns:

The existing mapped value, if present, or NULL_MAPPING_VALUE if potentialValue was used.