org.hd.d.pg2k.svrCore
Class Compact7BitString.StaticDictionary

java.lang.Object
  org.hd.d.pg2k.svrCore.Compact7BitString.StaticDictionary

Enclosing class:

Compact7BitString

public static final class Compact7BitString.StaticDictionary
extends java.lang.Object

Immutable static dictionary to improve in-memory compression. It is not permitted to serialise as-is a Compact7BitString that is using one of these so as to prevent decompression errors/ambiguities.

MAX_TOKENS

public static final int MAX_TOKENS

The maximum number of simple tokens for the static dictionary; strictly positive.

See Also:

Constant Field Values

FIRST_VIRTUAL_OFFSET

private static final int FIRST_VIRTUAL_OFFSET

First (numerically most positive) "virtual" offset used by the static dictionary; strictly negative. We start at -2 to avoid conflict with -1 used to escape/start an MTM sequence.

See Also:

Constant Field Values

name

public final java.lang.String name

The name of this dictionary, never null.

tokens

public final java.util.List<java.lang.String> tokens

The immutable (non-empty) list of unique, best-first tokens; never null nor empty.

virtualOffsets

private final java.util.HashMap<java.lang.String,java.lang.Integer> virtualOffsets

Virtual offsets of tokens in static dictionary; never null nor empty. Logically immutable.

Kept private because it is faster to keep it unwrapped and mutable.

_uncompEarlyTokens

private final java.util.concurrent.ConcurrentMap<java.lang.String,Tuple.Pair<java.util.concurrent.atomic.AtomicInteger,java.util.concurrent.atomic.AtomicInteger>> _uncompEarlyTokens

Thread-safe map from text of uncompressed token (close to start of input) to count and summed-position of the token; non-null iff LOG_STATS is true. Updated when attempting to compress String data.

This map is for early tokens of length 2 or more characters, ie that we might be able to compress better using a static dictionary.

This is kept for statistical purposes.

Only the first occurrence of each token in each compress/input is counted.

Compact7BitString.StaticDictionary

public Compact7BitString.StaticDictionary(java.lang.String name,
                                          java.util.List<java.lang.String> tokens)

Create an instance of a static dictionary.

Parameters:

name - dictionary name; must not be null

tokens - unique tokens, non-null, best first, each of length > 1, non-empty, no longer than MAX_TOKENS

toString

public java.lang.String toString()

Human-readable summary: including the dictionary name; never null.

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Only equal if all non-stats fields are.

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

We don't expect to have to distinguish other than on name in practice, but we use the table size too.

Overrides:

hashCode in class java.lang.Object

isStatsEnabled

public boolean isStatsEnabled()

Returns true if stats-collecting is enabled.

resetStats

public void resetStats()

Resets the stats (if any) being recorded for this dictionary.

dumpStats

public void dumpStats(java.io.PrintStream out)

Dump stats (if any) to the given (non-null) stream. This dumps the stats of compressions against this dictionary instance.

Parameters:

out - never null