Package it.unimi.dsi.big.util

Class ImmutableExternalPrefixMap

java.lang.Object
it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction<CharSequence>
it.unimi.dsi.big.util.AbstractPrefixMap
it.unimi.dsi.big.util.ImmutableExternalPrefixMap
All Implemented Interfaces:
PrefixMap<MutableString>, StringMap<MutableString>, Function<CharSequence,Long>, Object2LongFunction<CharSequence>, Size64, Serializable, Function<CharSequence,Long>, ToLongFunction<CharSequence>
public class ImmutableExternalPrefixMap extends AbstractPrefixMap implements Serializable
An immutable prefix map mostly stored in external memory.
Since:
2.0
Author:
Sebastiano Vigna
See Also:

  • Field Details

    • serialVersionUID

      public static final long serialVersionUID
      See Also:

    • STD_BLOCK_SIZE

      public static final int STD_BLOCK_SIZE
      The standard block size (in bytes).
      See Also:

    • intervalApproximator

      protected final ImmutableBinaryTrie<CharSequence> intervalApproximator
      The in-memory data structure used to approximate intervals..

    • blockSize

      protected final long blockSize
      The block size of this (in bits).

    • decoder

      protected final Decoder decoder
      A decoder used to read data from the dump stream.

    • symbol2char

      protected final char[] symbol2char
      A map (given by an array) from symbols in the coder to characters.

    • char2symbol

      protected final Char2IntOpenHashMap char2symbol
      A map from characters to symbols of the coder.

    • size

      protected final long size
      The number of terms in this map.

    • blockStart

      protected final long[][] blockStart
      The index of the first word in each block, plus an additional entry containing Function.size().

    • blockOffset

      protected final long[][] blockOffset
      A big array array parallel to blockStart giving the offset in blocks in the dump file of the corresponding word in blockStart. If there are no overflows, this will just be an initial segment of the natural numbers, but overflows cause jumps.

    • selfContained

      protected final boolean selfContained
      Whether this map is self-contained.

    • iteratorIsUsable

      protected transient boolean iteratorIsUsable
      If true, the creation of the last DumpStreamIterator was not followed by a call to any get method.

    • dumpStream

      protected transient InputBitStream dumpStream
      A reference to the dump stream.

  • Constructor Details

    • ImmutableExternalPrefixMap

      public ImmutableExternalPrefixMap(Iterable<? extends CharSequence> terms, int blockSizeInBytes, CharSequence dumpStreamFilename) throws IOException
      Creates an external prefix map with specified block size and dump stream.

      This constructor does not assume that CharSequence instances returned by terms.iterator() will be distinct. Thus, it can be safely used with FileLinesMutableStringIterable.

      Parameters:
      terms - an iterable whose iterator will enumerate in lexicographical order the terms for the map.
      blockSizeInBytes - the block size (in bytes).
      dumpStreamFilename - the name of the dump stream, or null for a self-contained map.
      Throws:
      IOException

    • ImmutableExternalPrefixMap

      public ImmutableExternalPrefixMap(Iterable<? extends CharSequence> terms, CharSequence dumpStreamFilename) throws IOException
      Creates an external prefix map with block size STD_BLOCK_SIZE and specified dump stream.

      This constructor does not assume that CharSequence instances returned by terms.iterator() will be distinct. Thus, it can be safely used with FileLinesMutableStringIterable.

      Parameters:
      terms - a collection whose iterator will enumerate in lexicographical order the terms for the map.
      dumpStreamFilename - the name of the dump stream, or null for a self-contained map.
      Throws:
      IOException

    • ImmutableExternalPrefixMap

      public ImmutableExternalPrefixMap(Iterable<? extends CharSequence> terms, int blockSizeInBytes) throws IOException
      Creates an external prefix map with specified block size.

      This constructor does not assume that CharSequence instances returned by terms.iterator() will be distinct. Thus, it can be safely used with FileLinesMutableStringIterable.

      Parameters:
      blockSizeInBytes - the block size (in bytes).
      terms - a collection whose iterator will enumerate in lexicographical order the terms for the map.
      Throws:
      IOException

    • ImmutableExternalPrefixMap

      public ImmutableExternalPrefixMap(Iterable<? extends CharSequence> terms) throws IOException
      Creates an external prefix map with block size STD_BLOCK_SIZE.

      This constructor does not assume that strings returned by terms.iterator() will be distinct. Thus, it can be safely used with FileLinesMutableStringIterable.

      Parameters:
      terms - a collection whose iterator will enumerate in lexicographical order the terms for the map.
      Throws:
      IOException

  • Method Details

    • setDumpStream

      public void setDumpStream(CharSequence dumpStreamFilename) throws FileNotFoundException
      Sets the dump stream of this external prefix map to a given filename.

      This method sets the dump file used by this map, and should be only called after deserialisation, providing exactly the file generated at creation time. Essentially anything can happen if you do not follow the rules.

      Note that this method will attempt to close the old stream, if present.

      Parameters:
      dumpStreamFilename - the name of the dump file.
      Throws:
      FileNotFoundException
      See Also:

    • setDumpStream

      public void setDumpStream(InputBitStream dumpStream)
      Sets the dump stream of this external prefix map to a given input bit stream.

      This method sets the dump file used by this map, and should be only called after deserialisation, providing a repositionable stream containing exactly the file generated at creation time. Essentially anything can happen if you do not follow the rules.

      Using this method you can load an external prefix map in core memory, enjoying the compactness of the data structure, but getting much more speed.

      Note that this method will attemp to close the old stream, if present.

      Parameters:
      dumpStream - a repositionable input bit stream containing exactly the dump stream generated at creation time.
      See Also:

    • getInterval

      public LongInterval getInterval(CharSequence prefix)
      Description copied from class: AbstractPrefixMap
      Returns the range of strings having a given prefix.
      Specified by:
      getInterval in class AbstractPrefixMap
      Parameters:
      prefix - a prefix.
      Returns:
      the corresponding range of strings as an interval.

    • getTerm

      protected MutableString getTerm(long index, MutableString s)
      Description copied from class: AbstractPrefixMap
      Writes a string specified by index into a MutableString.
      Specified by:
      getTerm in class AbstractPrefixMap
      Parameters:
      index - the index of a string.
      s - a mutable string.
      Returns:
      string.

    • containsKey

      public boolean containsKey(Object term)
      Specified by:
      containsKey in interface Function<CharSequence,Long>

    • getLong

      public long getLong(Object o)
      Specified by:
      getLong in interface Object2LongFunction<CharSequence>

    • iterator

      public ObjectIterator<CharSequence> iterator()
      Returns an iterator over the map.

      The iterator returned by this method scans directly the dump stream.

      Note that the returned iterator uses the same stream as all get methods. Calling such methods while the iterator is being used will produce an IllegalStateException.

      Returns:
      an iterator over the map that just scans the dump stream.

    • size64

      public long size64()
      Description copied from interface: StringMap
      Returns the intended number of keys in this function, or -1 if no such number exists.

      Most function implementations will have some knowledge of the intended number of keys in their domain. In some cases, however, this might not be possible. This default implementation, in particular, returns -1.

      Specified by:
      size64 in interface Size64
      Specified by:
      size64 in interface StringMap<MutableString>
      Returns:
      the intended number of keys in this function, or -1 if that number is not available.

    • main

      public static void main(String[] arg) throws ClassNotFoundException, IOException, JSAPException, SecurityException, NoSuchMethodException
      Throws:
      ClassNotFoundException
      IOException
      JSAPException
      SecurityException
      NoSuchMethodException