Direct Known Subclasses:

CharTrie, IntTrie
```
public abstract class Trie
extends Object
```
A trie is a kind of compressed, serializable table of values associated with Unicode code points (0..0x10ffff).

This class defines the basic structure of a trie and provides methods to retrieve the offsets to the actual data.

Data will be the form of an array of basic types, char or int.

The actual data format will have to be specified by the user in the inner static interface com.ibm.icu.impl.Trie.DataManipulate.

This trie implementation is optimized for getting offset while walking forward through a UTF-16 string. Therefore, the simplest and fastest access macros are the fromLead() and fromOffsetTrail() methods. The fromBMP() method are a little more complicated; they get offsets even for lead surrogate codepoints, while the fromLead() method get special "folded" offsets for lead surrogate code units if there is relevant data associated with them. From such a folded offsets, an offset needs to be extracted to supply to the fromOffsetTrail() methods. To handle such supplementary codepoints, some offset information are kept in the data.

Methods in com.ibm.icu.impl.Trie.DataManipulate are called to retrieve that offset from the folded value for the lead surrogate unit.

For examples of use, see com.ibm.icu.impl.CharTrie or com.ibm.icu.impl.IntTrie.

Since:

release 2.1, Jan 01 2002

See Also:

CharTrie, IntTrie

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static interface Trie.DataManipulate
Character data in com.ibm.impl.Trie have different user-specified format for different purposes.

Field Summary

Fields
Modifier and Type	Field	Description
`protected static int`	`BMP_INDEX_LENGTH`	Length of the BMP portion of the index (stage 1) array.
`protected static int`	`DATA_BLOCK_LENGTH`	Number of data values in a stage 2 (data array) block.
`protected static int`	`HEADER_LENGTH_`	Size of Trie header in bytes
`protected static int`	`HEADER_OPTIONS_DATA_IS_32_BIT_`
`protected static int`	`HEADER_OPTIONS_INDEX_SHIFT_`
`protected static int`	`HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_`	Latin 1 option mask
`protected static int`	`HEADER_SIGNATURE_`	Constant number to authenticate the byte block
`protected static int`	`INDEX_STAGE_1_SHIFT_`	Shift size for shifting right the input index. 1..9
`protected static int`	`INDEX_STAGE_2_SHIFT_`	Shift size for shifting left the index array values.
`protected static int`	`INDEX_STAGE_3_MASK_`	Mask for getting the lower bits from the input index.
`protected static int`	`LEAD_INDEX_OFFSET_`	Lead surrogate code points' index displacement in the index array. 0x10000-0xd800=0x2800 0x2800 >> INDEX_STAGE_1_SHIFT_
`protected int`	`m_dataLength_`	Length of the data array
`protected Trie.DataManipulate`	`m_dataManipulate_`	Internal TrieValue which handles the parsing of the data value.
`protected int`	`m_dataOffset_`	Start index of the data portion of the trie.
`protected char[]`	`m_index_`	Index or UTF16 characters
`protected static int`	`SURROGATE_BLOCK_BITS`	Number of bits of a trail surrogate that are used in index table lookups.
`protected static int`	`SURROGATE_BLOCK_COUNT`	Number of index (stage 1) entries per lead surrogate.
`protected static int`	`SURROGATE_MASK_`	Surrogate mask to use when shifting offset to retrieve supplementary values

Constructor Summary

Constructors
Modifier	Constructor	Description
`protected`	`Trie(char[] index, int options, Trie.DataManipulate dataManipulate)`	Trie constructor
`protected`	`Trie(ByteBuffer bytes, Trie.DataManipulate dataManipulate)`	Trie constructor for CharTrie use.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`equals(Object other)`	Checks if the argument Trie has the same data as this Trie.
`protected int`	`getBMPOffset(char ch)`	Gets the offset to data which the BMP character points to Treats a lead surrogate as a normal code point.
`protected int`	`getCodePointOffset(int ch)`	Internal trie getter from a code point.
`protected abstract int`	`getInitialValue()`	Gets the default initial value
`protected int`	`getLeadOffset(char ch)`	Gets the offset to the data which this lead surrogate character points to.
`protected int`	`getRawOffset(int offset, char ch)`	Gets the offset to the data which the index ch after variable offset points to.
`int`	`getSerializedDataSize()`	Gets the serialized data file size of the Trie.
`protected abstract int`	`getSurrogateOffset(char lead, char trail)`	Gets the offset to the data which the surrogate pair points to.
`protected abstract int`	`getValue(int index)`	Gets the value at the argument index
`int`	`hashCode()`	Returns an integer hash code for this object.
`protected boolean`	`isCharTrie()`	Determines if this is a 16 bit trie
`protected boolean`	`isIntTrie()`	Determines if this is a 32 bit trie
`boolean`	`isLatin1Linear()`	Determines if this trie has a linear latin 1 array
`protected void`	`unserialize(ByteBuffer bytes)`	Parses the byte buffer and creates the trie index with it.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LEAD_INDEX_OFFSET_
```
protected static final int LEAD_INDEX_OFFSET_
```
    Lead surrogate code points' index displacement in the index array. 0x10000-0xd800=0x2800 0x2800 >> INDEX_STAGE_1_SHIFT_
    
    See Also:
    
    Constant Field Values
  - INDEX_STAGE_1_SHIFT_
```
protected static final int INDEX_STAGE_1_SHIFT_
```
    Shift size for shifting right the input index. 1..9
    
    See Also:
    
    Constant Field Values
  - INDEX_STAGE_2_SHIFT_
```
protected static final int INDEX_STAGE_2_SHIFT_
```
    Shift size for shifting left the index array values. Increases possible data size with 16-bit index values at the cost of compactability. This requires blocks of stage 2 data to be aligned by DATA_GRANULARITY. 0..INDEX_STAGE_1_SHIFT
    
    See Also:
    
    Constant Field Values
  - DATA_BLOCK_LENGTH
```
protected static final int DATA_BLOCK_LENGTH
```
    Number of data values in a stage 2 (data array) block.
    
    See Also:
    
    Constant Field Values
  - INDEX_STAGE_3_MASK_
```
protected static final int INDEX_STAGE_3_MASK_
```
    Mask for getting the lower bits from the input index. DATA_BLOCK_LENGTH - 1.
    
    See Also:
    
    Constant Field Values
  - SURROGATE_BLOCK_BITS
```
protected static final int SURROGATE_BLOCK_BITS
```
    Number of bits of a trail surrogate that are used in index table lookups.
    
    See Also:
    
    Constant Field Values
  - SURROGATE_BLOCK_COUNT
```
protected static final int SURROGATE_BLOCK_COUNT
```
    Number of index (stage 1) entries per lead surrogate. Same as number of index entries for 1024 trail surrogates, ==0x400>>INDEX_STAGE_1_SHIFT_
    
    See Also:
    
    Constant Field Values
  - BMP_INDEX_LENGTH
```
protected static final int BMP_INDEX_LENGTH
```
    Length of the BMP portion of the index (stage 1) array.
    
    See Also:
    
    Constant Field Values
  - SURROGATE_MASK_
```
protected static final int SURROGATE_MASK_
```
    Surrogate mask to use when shifting offset to retrieve supplementary values
    
    See Also:
    
    Constant Field Values
  - m_index_
```
protected char[] m_index_
```
    Index or UTF16 characters
  - m_dataManipulate_
```
protected Trie.DataManipulate m_dataManipulate_
```
    Internal TrieValue which handles the parsing of the data value. This class is to be implemented by the user
  - m_dataOffset_
```
protected int m_dataOffset_
```
    Start index of the data portion of the trie. CharTrie combines index and data into a char array, so this is used to indicate the initial offset to the data portion. Note this index always points to the initial value.
  - m_dataLength_
```
protected int m_dataLength_
```
    Length of the data array
  - HEADER_LENGTH_
```
protected static final int HEADER_LENGTH_
```
    Size of Trie header in bytes
    
    See Also:
    
    Constant Field Values
  - HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_
```
protected static final int HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_
```
    Latin 1 option mask
    
    See Also:
    
    Constant Field Values
  - HEADER_SIGNATURE_
```
protected static final int HEADER_SIGNATURE_
```
    Constant number to authenticate the byte block
    
    See Also:
    
    Constant Field Values
  - HEADER_OPTIONS_INDEX_SHIFT_
```
protected static final int HEADER_OPTIONS_INDEX_SHIFT_
```
    See Also:
    
    Constant Field Values
  - HEADER_OPTIONS_DATA_IS_32_BIT_
```
protected static final int HEADER_OPTIONS_DATA_IS_32_BIT_
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Trie
```
protected Trie(ByteBuffer bytes,
               Trie.DataManipulate dataManipulate)
```
    Trie constructor for CharTrie use.
    
    Parameters:
    
    bytes - data of an ICU data file, containing the trie
    
    dataManipulate - object containing the information to parse the trie data
  - Trie
```
protected Trie(char[] index,
               int options,
               Trie.DataManipulate dataManipulate)
```
    Trie constructor
    
    Parameters:
    
    index - array to be used for index
    
    options - used by the trie
    
    dataManipulate - object containing the information to parse the trie data
- Method Detail
  - isLatin1Linear
```
public final boolean isLatin1Linear()
```
    Determines if this trie has a linear latin 1 array
    
    Returns:
    
    true if this trie has a linear latin 1 array, false otherwise
  - equals
```
public boolean equals(Object other)
```
    Checks if the argument Trie has the same data as this Trie. Attributes are checked but not the index data.
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    other - Trie to check
    
    Returns:
    
    true if the argument Trie has the same data as this Trie, false otherwise
    
    See Also:
    
    Object.hashCode()
  - hashCode
```
public int hashCode()
```
    Description copied from class: Object
    
    Returns an integer hash code for this object. By contract, any two objects for which Object.equals(java.lang.Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.
    Note that hash values must not change over time unless information used in equals comparisons also changes.
    See Writing a correct hashCode method if you intend implementing your own hashCode method.
    
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    this object's hash code.
    
    See Also:
    
    Object.equals(java.lang.Object)
  - getSerializedDataSize
```
public int getSerializedDataSize()
```
    Gets the serialized data file size of the Trie. This is used during trie data reading for size checking purposes.
    
    Returns:
    
    size size of serialized trie data file in terms of the number of bytes
  - getSurrogateOffset
```
protected abstract int getSurrogateOffset(char lead,
                                          char trail)
```
    Gets the offset to the data which the surrogate pair points to.
    
    Parameters:
    
    lead - lead surrogate
    
    trail - trailing surrogate
    
    Returns:
    
    offset to data
  - getValue
```
protected abstract int getValue(int index)
```
    Gets the value at the argument index
    
    Parameters:
    
    index - value at index will be retrieved
    
    Returns:
    
    32 bit value
  - getInitialValue
```
protected abstract int getInitialValue()
```
    Gets the default initial value
    
    Returns:
    
    32 bit value
  - getRawOffset
```
protected final int getRawOffset(int offset,
                                 char ch)
```
    Gets the offset to the data which the index ch after variable offset points to. Note for locating a non-supplementary character data offset, calling
    getRawOffset(0, ch);
    will do. Otherwise if it is a supplementary character formed by surrogates lead and trail. Then we would have to call getRawOffset() with getFoldingIndexOffset(). See getSurrogateOffset().
    
    Parameters:
    
    offset - index offset which ch is to start from
    
    ch - index to be used after offset
    
    Returns:
    
    offset to the data
  - getBMPOffset
```
protected final int getBMPOffset(char ch)
```
    Gets the offset to data which the BMP character points to Treats a lead surrogate as a normal code point.
    
    Parameters:
    
    ch - BMP character
    
    Returns:
    
    offset to data
  - getLeadOffset
```
protected final int getLeadOffset(char ch)
```
    Gets the offset to the data which this lead surrogate character points to. Data at the returned offset may contain folding offset information for the next trailing surrogate character.
    
    Parameters:
    
    ch - lead surrogate character
    
    Returns:
    
    offset to data
  - getCodePointOffset
```
protected final int getCodePointOffset(int ch)
```
    Internal trie getter from a code point. Could be faster(?) but longer with if((c32)<=0xd7ff) { (result)=_TRIE_GET_RAW(trie, data, 0, c32); } Gets the offset to data which the codepoint points to
    
    Parameters:
    
    ch - codepoint
    
    Returns:
    
    offset to data
  - unserialize
```
protected void unserialize(ByteBuffer bytes)
```
    Parses the byte buffer and creates the trie index with it.
    
    The position of the input ByteBuffer must be right after the trie header.
    
    This is overwritten by the child classes.
    
    Parameters:
    
    bytes - buffer containing trie data
  - isIntTrie
```
protected final boolean isIntTrie()
```
    Determines if this is a 32 bit trie
    
    Returns:
    
    true if options specifies this is a 32 bit trie
  - isCharTrie
```
protected final boolean isCharTrie()
```
    Determines if this is a 16 bit trie
    
    Returns:
    
    true if this is a 16 bit trie

Class Trie

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LEAD_INDEX_OFFSET_

INDEX_STAGE_1_SHIFT_

INDEX_STAGE_2_SHIFT_

DATA_BLOCK_LENGTH

INDEX_STAGE_3_MASK_

SURROGATE_BLOCK_BITS

SURROGATE_BLOCK_COUNT

BMP_INDEX_LENGTH

SURROGATE_MASK_

m_index_

m_dataManipulate_

m_dataOffset_

m_dataLength_

HEADER_LENGTH_

HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_

HEADER_SIGNATURE_

HEADER_OPTIONS_INDEX_SHIFT_

HEADER_OPTIONS_DATA_IS_32_BIT_

Constructor Detail

Trie

Trie

Method Detail

isLatin1Linear

equals

hashCode

getSerializedDataSize

getSurrogateOffset

getValue

getInitialValue

getRawOffset

getBMPOffset

getLeadOffset

getCodePointOffset

unserialize

isIntTrie

isCharTrie