com.alibaba.fastjson2

Class SymbolTable

java.lang.Object

com.alibaba.fastjson2.SymbolTable

public final class SymbolTable
extends java.lang.Object

Symbol table for fast name lookup.

This class provides a way to efficiently map names (strings) to ordinals and vice versa. It uses FNV-1a hash algorithm for fast hashing and maintains sorted hash codes for binary search.

SymbolTable is designed to be immutable after construction, making it thread-safe.

Since:

2.0.58

Field Summary

Fields

Modifier and Type	Field and Description
private long	hashCode64
private long[]	hashCodes
private long[]	hashCodesOrigin
private short[]	mapping
private java.lang.String[]	names

Constructor Summary

Constructors

Constructor and Description
SymbolTable(java.lang.Class<?>... input) Create a symbol table from class names.
SymbolTable(java.lang.String... input) Create a symbol table from string names.

Method Summary

Modifier and Type	Method and Description
private static java.lang.String[]	classNames(java.lang.Class<?>... input) Extract class names from Class objects.
long	getHashCode(int ordinal) Get the hash code of a name by its ordinal.
java.lang.String	getName(int ordinal) Get the name by its ordinal.
java.lang.String	getNameByHashCode(long hashCode) Get the name by its hash code.
int	getOrdinal(java.lang.String name) Get the ordinal of a name.
int	getOrdinalByHashCode(long hashCode) Get the ordinal of a name by its hash code.
long	hashCode64() Get the 64-bit hash code of this symbol table.
int	size() Get the number of names in this symbol table.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

names

private final java.lang.String[] names

hashCode64

private final long hashCode64

mapping

private final short[] mapping

hashCodes

private final long[] hashCodes

hashCodesOrigin

private final long[] hashCodesOrigin

Constructor Detail

SymbolTable

public SymbolTable(java.lang.Class<?>... input)

Create a symbol table from class names.

Parameters:

input - classes whose names will be added to the symbol table

Since:

2.0.58

SymbolTable

public SymbolTable(java.lang.String... input)

Create a symbol table from string names.

The names will be sorted and deduplicated. Each name is assigned a unique ordinal starting from 1. The ordinal 0 is reserved and means "not found".

Parameters:

input - names to be added to the symbol table

Method Detail

classNames

private static java.lang.String[] classNames(java.lang.Class<?>... input)

Extract class names from Class objects.

Parameters:

input - Class objects

Returns:

array of class names

size

public int size()

Get the number of names in this symbol table.

Returns:

the number of names

hashCode64

public long hashCode64()

Get the 64-bit hash code of this symbol table.

The hash code is computed from all the names in the symbol table. It can be used to quickly compare if two symbol tables have the same content.

Returns:

the 64-bit hash code of this symbol table

getNameByHashCode

public java.lang.String getNameByHashCode(long hashCode)

Get the name by its hash code.

Parameters:

hashCode - the FNV-1a 64-bit hash code of the name

Returns:

the name if found, null otherwise

getOrdinalByHashCode

public int getOrdinalByHashCode(long hashCode)

Get the ordinal of a name by its hash code.

Parameters:

hashCode - the FNV-1a 64-bit hash code of the name

Returns:

the ordinal (1-based) if found, -1 otherwise

getOrdinal

public int getOrdinal(java.lang.String name)

Get the ordinal of a name.

Parameters:

name - the name to look up

Returns:

the ordinal (1-based) if found, -1 otherwise

getName

public java.lang.String getName(int ordinal)

Get the name by its ordinal.

Parameters:

ordinal - the ordinal (1-based) of the name

Returns:

the name at the specified ordinal

Throws:

java.lang.ArrayIndexOutOfBoundsException - if the ordinal is invalid

getHashCode

public long getHashCode(int ordinal)

Get the hash code of a name by its ordinal.

Parameters:

ordinal - the ordinal (1-based) of the name

Returns:

the FNV-1a 64-bit hash code of the name at the specified ordinal

Throws:

java.lang.ArrayIndexOutOfBoundsException - if the ordinal is invalid