Class BytesTrie

java.lang.Object
com.ibm.icu.util.BytesTrie
All Implemented Interfaces:
Cloneable, Iterable<BytesTrie.Entry>

public final class BytesTrie extends Object implements Cloneable, Iterable<BytesTrie.Entry>
Light-weight, non-const reader class for a BytesTrie. Traverses a byte-serialized data structure with minimal state, for mapping byte sequences to non-negative integer values.

This class is not intended for public subclassing.

Author:
Markus W. Scherer
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static final class 
    Return value type for the Iterator.
    static final class 
    Iterator for all of the (byte sequence, value) pairs in a BytesTrie.
    static enum 
    Return values for BytesTrie.next(), CharsTrie.next() and similar methods.
    static final class 
    BytesTrie state object, for saving a trie's current state and resetting the trie back to this state later.
  • Constructor Summary

    Constructors
    Constructor
    Description
    BytesTrie(byte[] trieBytes, int offset)
    Constructs a BytesTrie reader instance.
    Copy constructor.
  • Method Summary

    Modifier and Type
    Method
    Description
    Clones this trie reader object and its state, but not the byte array which will be shared.
    Determines whether the byte sequence so far matches, whether it has a value, and whether another input byte can continue a matching byte sequence.
    first(int inByte)
    Traverses the trie from the initial state for this input byte.
    int
    Finds each byte which continues the byte sequence from the current state.
    long
    Returns the state of this trie as a 64-bit integer.
    long
    Determines whether all byte sequences reachable from the current state map to the same value, and if so, returns that value.
    int
    Returns a matching byte sequence's value if called immediately after current()/first()/next() returned Result.INTERMEDIATE_VALUE or Result.FINAL_VALUE.
    Iterates from the current state of this trie.
    iterator(byte[] trieBytes, int offset, int maxStringLength)
    Iterates from the root of a byte-serialized BytesTrie.
    iterator(int maxStringLength)
    Iterates from the current state of this trie.
    static int
    jumpByDelta(byte[] bytes, int pos)
    Deprecated.
    This API is ICU internal only.
    next(byte[] s, int sIndex, int sLimit)
    Traverses the trie from the current state for this byte sequence.
    next(int inByte)
    Traverses the trie from the current state for this input byte.
    Resets this trie to its initial state.
    Resets this trie to the saved state.
    resetToState64(long state)
    Resets this trie to the saved state.
    Saves the state of this trie.

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface java.lang.Iterable

    forEach, spliterator
  • Constructor Details

    • BytesTrie

      public BytesTrie(byte[] trieBytes, int offset)
      Constructs a BytesTrie reader instance.

      The array must contain a copy of a byte sequence from the BytesTrieBuilder, with the offset indicating the first byte of that sequence. The BytesTrie object will not read more bytes than the BytesTrieBuilder generated in the corresponding build() call.

      The array is not copied/cloned and must not be modified while the BytesTrie object is in use.

      Parameters:
      trieBytes - Bytes array that contains the serialized trie.
      offset - Root offset of the trie in the array.
    • BytesTrie

      public BytesTrie(BytesTrie other)
      Copy constructor. Makes a shallow copy of the other trie reader object and its state. Does not copy the byte array which will be shared. Same as clone() but without the throws clause.
  • Method Details

    • clone

      public BytesTrie clone() throws CloneNotSupportedException
      Clones this trie reader object and its state, but not the byte array which will be shared.
      Overrides:
      clone in class Object
      Returns:
      A shallow clone of this trie.
      Throws:
      CloneNotSupportedException
    • reset

      public BytesTrie reset()
      Resets this trie to its initial state.
      Returns:
      this
    • getState64

      public long getState64()
      Returns the state of this trie as a 64-bit integer. The state value is never 0.
      Returns:
      opaque state value
      See Also:
    • resetToState64

      public BytesTrie resetToState64(long state)
      Resets this trie to the saved state. Unlike resetToState(State), the 64-bit state value must be from getState64() from the same trie object or from one initialized the exact same way. Because of no validation, this method is faster.
      Parameters:
      state - The opaque trie state value from getState64().
      Returns:
      this
      See Also:
    • saveState

      public BytesTrie saveState(BytesTrie.State state)
      Saves the state of this trie.
      Parameters:
      state - The State object to hold the trie's state.
      Returns:
      this
      See Also:
    • resetToState

      public BytesTrie resetToState(BytesTrie.State state)
      Resets this trie to the saved state. Slower than resetToState64(long) which does not validate the state value.
      Parameters:
      state - The State object which holds a saved trie state.
      Returns:
      this
      Throws:
      IllegalArgumentException - if the state object contains no state, or the state of a different trie
      See Also:
    • current

      public BytesTrie.Result current()
      Determines whether the byte sequence so far matches, whether it has a value, and whether another input byte can continue a matching byte sequence.
      Returns:
      The match/value Result.
    • first

      public BytesTrie.Result first(int inByte)
      Traverses the trie from the initial state for this input byte. Equivalent to reset().next(inByte).
      Parameters:
      inByte - Input byte value. Values -0x100..-1 are treated like 0..0xff. Values below -0x100 and above 0xff will never match.
      Returns:
      The match/value Result.
    • next

      public BytesTrie.Result next(int inByte)
      Traverses the trie from the current state for this input byte.
      Parameters:
      inByte - Input byte value. Values -0x100..-1 are treated like 0..0xff. Values below -0x100 and above 0xff will never match.
      Returns:
      The match/value Result.
    • next

      public BytesTrie.Result next(byte[] s, int sIndex, int sLimit)
      Traverses the trie from the current state for this byte sequence. Equivalent to
       Result result=current();
       for(each c in s)
         if(!result.hasNext()) return Result.NO_MATCH;
         result=next(c);
       return result;
       
      Parameters:
      s - Contains a string or byte sequence.
      sIndex - The start index of the byte sequence in s.
      sLimit - The (exclusive) end index of the byte sequence in s.
      Returns:
      The match/value Result.
    • getValue

      public int getValue()
      Returns a matching byte sequence's value if called immediately after current()/first()/next() returned Result.INTERMEDIATE_VALUE or Result.FINAL_VALUE. getValue() can be called multiple times. Do not call getValue() after Result.NO_MATCH or Result.NO_VALUE!
      Returns:
      The value for the byte sequence so far.
    • getUniqueValue

      public long getUniqueValue()
      Determines whether all byte sequences reachable from the current state map to the same value, and if so, returns that value.
      Returns:
      The unique value in bits 32..1 with bit 0 set, if all byte sequences reachable from the current state map to the same value; otherwise returns 0.
    • getNextBytes

      public int getNextBytes(Appendable out)
      Finds each byte which continues the byte sequence from the current state. That is, each byte b for which it would be next(b)!=Result.NO_MATCH now.
      Parameters:
      out - Each next byte is 0-extended to a char and appended to this object. (Only uses the out.append(c) method.)
      Returns:
      The number of bytes which continue the byte sequence from here.
    • iterator

      public BytesTrie.Iterator iterator()
      Iterates from the current state of this trie.
      Specified by:
      iterator in interface Iterable<BytesTrie.Entry>
      Returns:
      A new BytesTrie.Iterator.
    • iterator

      public BytesTrie.Iterator iterator(int maxStringLength)
      Iterates from the current state of this trie.
      Parameters:
      maxStringLength - If 0, the iterator returns full strings/byte sequences. Otherwise, the iterator returns strings with this maximum length.
      Returns:
      A new BytesTrie.Iterator.
    • iterator

      public static BytesTrie.Iterator iterator(byte[] trieBytes, int offset, int maxStringLength)
      Iterates from the root of a byte-serialized BytesTrie.
      Parameters:
      trieBytes - Bytes array that contains the serialized trie.
      offset - Root offset of the trie in the array.
      maxStringLength - If 0, the iterator returns full strings/byte sequences. Otherwise, the iterator returns strings with this maximum length.
      Returns:
      A new BytesTrie.Iterator.
    • jumpByDelta

      @Deprecated public static int jumpByDelta(byte[] bytes, int pos)
      Deprecated.
      This API is ICU internal only.
      Reads a jump delta and jumps.