Package net.sf.saxon.str

Class ZenoString

  • All Implemented Interfaces:
    java.lang.Comparable<UnicodeString>, AtomicMatchKey
    public class ZenoString
extends UnicodeString
    A ZenoString is an implementation of UnicodeString that comprises a list of segments representing substrings of the total string. By convention the segments are not themselves ZenoStrings, so the structure is a shallow tree. An index holds pointers to the segments and their offsets within the string as a whole; this is used to locate the codepoint at any particular location in the string.

    The segments will always be non-empty. An empty string contains no segments.

    The key to the performance of the data structure (and its name) is the algorithm for consolidating segments when strings are concatenated, so as to keep the number of segments increasing logarithmically with the string size, with short segments at the extremities to allow efficient further concatenation at the ends.

    For further details see the paper by Michael Kay at Balisage 2021.

    • Field Detail

      • EMPTY

        public static final ZenoString EMPTY
        An empty ZenoString

    • Method Detail

      • of

        public static ZenoString of​(UnicodeString content)
        Construct a ZenoString from a supplied UnicodeString
        Parameters:
        content - the supplied UnicodeString
        Returns:
        the resulting ZenoString

      • codePoints

        public IntIterator codePoints()
        Get an iterator over the code points present in the string.
        Specified by:
        codePoints in class UnicodeString
        Returns:
        an iterator that delivers the individual code points

      • length

        public long length()
        Get the length of the string
        Specified by:
        length in class UnicodeString
        Returns:
        the number of code points in the string

      • isEmpty

        public boolean isEmpty()
        Ask whether the string is empty
        Overrides:
        isEmpty in class UnicodeString
        Returns:
        true if the length of the string is zero

      • getWidth

        public int getWidth()
        Get the number of bits needed to hold all the characters in this string
        Specified by:
        getWidth in class UnicodeString
        Returns:
        7 for ascii characters, 8 for latin-1, 16 for BMP, 24 for general Unicode.

      • indexOf

        public long indexOf​(int codePoint,
                    long from)
        Get the position of the first occurrence of the specified codepoint, starting the search at a given position in the string
        Specified by:
        indexOf in class UnicodeString
        Parameters:
        codePoint - the sought codePoint
        from - the position from which the search should start (0-based), in the range 0 to length()-1
        Returns:
        the position (0-based) of the first occurrence found, or -1 if not found
        Throws:
        java.lang.IndexOutOfBoundsException - if the from value is out of range

      • indexWhere

        public long indexWhere​(java.util.function.IntPredicate predicate,
                       long from)
        Description copied from class: UnicodeString
        Get the position of the first occurrence of a codepoint that matches a supplied predicate, starting the search at a given position in the string
        Overrides:
        indexWhere in class UnicodeString
        Parameters:
        predicate - condition that the codepoint must satisfy
        from - the position from which the search should start (0-based)
        Returns:
        the position (0-based) of the first codepoint to match the predicate, or -1 if not found

      • codePointAt

        public int codePointAt​(long index)
        Get the code point at a given position in the string
        Specified by:
        codePointAt in class UnicodeString
        Parameters:
        index - the given position (0-based)
        Returns:
        the code point at the given position
        Throws:
        java.lang.IndexOutOfBoundsException - if the index is out of range

      • substring

        public UnicodeString substring​(long start,
                               long end)
        Get a substring of this codepoint sequence, with a given start and end position
        Specified by:
        substring in class UnicodeString
        Parameters:
        start - the start position (0-based): that is, the position of the first code point to be included
        end - the end position (0-based): specifically, the position of the first code point not to be included
        Returns:
        the requested substring

      • concat

        public ZenoString concat​(UnicodeString other)
        Concatenate another string
        Overrides:
        concat in class UnicodeString
        Parameters:
        other - the string to be appended to this one
        Returns:
        the result of the concatenation (neither input string is altered)

      • writeSegments

        public void writeSegments​(UnicodeWriter writer)
                   throws java.io.IOException
        Write each of the segments in turn to a UnicodeWriter
        Parameters:
        writer - the writer to which the string is to be written
        Throws:
        java.io.IOException

      • economize

        public UnicodeString economize()
        Get an equivalent UnicodeString that uses the most economical representation available
        Overrides:
        economize in class UnicodeString
        Returns:
        an equivalent UnicodeString

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • debugSegmentLengths

        public java.util.List<java.lang.Long> debugSegmentLengths()
        This method is for diagnostics and unit testing only: it exposes the lengths of the internal segments. This is an implementation detail that is subject to change and does not affect the exposed functionality.
        Returns:
        the lengths of the segments