Class CharsTrie

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

public final class CharsTrie extends Object implements Cloneable, Iterable<CharsTrie.Entry>
Light-weight, non-const reader class for a CharsTrie. Traverses a char-serialized data structure with minimal state, for mapping strings (16-bit-unit sequences) to non-negative integer values.

This class is not intended for public subclassing.

Author:
Markus W. Scherer
  • Constructor Details

    • CharsTrie

      public CharsTrie(CharSequence trieChars, int offset)
      Constructs a CharsTrie reader instance.

      The CharSequence must contain a copy of a char sequence from the CharsTrieBuilder, with the offset indicating the first char of that sequence. The CharsTrie object will not read more chars than the CharsTrieBuilder generated in the corresponding build() call.

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

      Parameters:
      trieChars - CharSequence that contains the serialized trie.
      offset - Root offset of the trie in the CharSequence.
    • CharsTrie

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

    • clone

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

      public CharsTrie 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 CharsTrie 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 CharsTrie saveState(CharsTrie.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 CharsTrie resetToState(CharsTrie.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 string so far matches, whether it has a value, and whether another input char can continue a matching string.
      Returns:
      The match/value Result.
    • first

      public BytesTrie.Result first(int inUnit)
      Traverses the trie from the initial state for this input char. Equivalent to reset().next(inUnit).
      Parameters:
      inUnit - Input char value. Values below 0 and above 0xffff will never match.
      Returns:
      The match/value Result.
    • firstForCodePoint

      public BytesTrie.Result firstForCodePoint(int cp)
      Traverses the trie from the initial state for the one or two UTF-16 code units for this input code point. Equivalent to reset().nextForCodePoint(cp).
      Parameters:
      cp - A Unicode code point 0..0x10ffff.
      Returns:
      The match/value Result.
    • next

      public BytesTrie.Result next(int inUnit)
      Traverses the trie from the current state for this input char.
      Parameters:
      inUnit - Input char value. Values below 0 and above 0xffff will never match.
      Returns:
      The match/value Result.
    • nextForCodePoint

      public BytesTrie.Result nextForCodePoint(int cp)
      Traverses the trie from the current state for the one or two UTF-16 code units for this input code point.
      Parameters:
      cp - A Unicode code point 0..0x10ffff.
      Returns:
      The match/value Result.
    • next

      public BytesTrie.Result next(CharSequence s, int sIndex, int sLimit)
      Traverses the trie from the current state for this string. 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.
      sIndex - The start index of the string in s.
      sLimit - The (exclusive) end index of the string in s.
      Returns:
      The match/value Result.
    • getValue

      public int getValue()
      Returns a matching string'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 string so far.
    • getUniqueValue

      public long getUniqueValue()
      Determines whether all strings 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 strings reachable from the current state map to the same value; otherwise returns 0.
    • getNextChars

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

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

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

      public static CharsTrie.Iterator iterator(CharSequence trieChars, int offset, int maxStringLength)
      Iterates from the root of a char-serialized BytesTrie.
      Parameters:
      trieChars - CharSequence that contains the serialized trie.
      offset - Root offset of the trie in the CharSequence.
      maxStringLength - If 0, the iterator returns full strings. Otherwise, the iterator returns strings with this maximum length.
      Returns:
      A new CharsTrie.Iterator.