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181 lines
7.2 KiB
C
181 lines
7.2 KiB
C
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///////////////////////////////////////////////////////////////////////
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// File: indexmapbidi.h
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// Description: Bi-directional mapping between a sparse and compact space.
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// Author: rays@google.com (Ray Smith)
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// Created: Tue Apr 06 11:33:59 PDT 2010
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//
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// (C) Copyright 2010, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_CCUTIL_INDEXMAPBIDI_H_
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#define TESSERACT_CCUTIL_INDEXMAPBIDI_H_
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#include <stdio.h>
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#include "genericvector.h"
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namespace tesseract {
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class IndexMapBiDi;
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// Bidirectional one-to-one mapping between a sparse and a compact discrete
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// space. Many entries in the sparse space are unmapped, but those that are
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// mapped have a 1-1 mapping to (and from) the compact space, where all
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// values are used. This is useful for forming subsets of larger collections,
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// such as subsets of character sets, or subsets of binary feature spaces.
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//
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// This base class provides basic functionality with binary search for the
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// SparseToCompact mapping to save memory.
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// For a faster inverse mapping, or to allow a many-to-one mapping, use
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// IndexMapBiDi below.
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// NOTE: there are currently no methods to setup an IndexMap on its own!
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// It must be initialized by copying from an IndexMapBiDi or by DeSerialize.
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class IndexMap {
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public:
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virtual ~IndexMap() {}
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// SparseToCompact takes a sparse index to an index in the compact space.
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// Uses a binary search to find the result. For faster speed use
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// IndexMapBiDi, but that takes more memory.
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virtual int SparseToCompact(int sparse_index) const;
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// CompactToSparse takes a compact index to the corresponding index in the
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// sparse space.
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int CompactToSparse(int compact_index) const {
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return compact_map_[compact_index];
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}
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// The size of the sparse space.
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virtual int SparseSize() const {
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return sparse_size_;
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}
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// The size of the compact space.
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int CompactSize() const {
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return compact_map_.size();
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}
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// Copy from the input.
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void CopyFrom(const IndexMap& src);
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void CopyFrom(const IndexMapBiDi& src);
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// Writes to the given file. Returns false in case of error.
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bool Serialize(FILE* fp) const;
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// Reads from the given file. Returns false in case of error.
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// If swap is true, assumes a big/little-endian swap is needed.
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bool DeSerialize(bool swap, FILE* fp);
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protected:
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// The sparse space covers integers in the range [0, sparse_size_-1].
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int sparse_size_;
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// The compact space covers integers in the range [0, compact_map_.size()-1].
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// Each element contains the corresponding sparse index.
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GenericVector<inT32> compact_map_;
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};
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// Bidirectional many-to-one mapping between a sparse and a compact discrete
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// space. As with IndexMap, many entries may be unmapped, but unlike IndexMap,
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// of those that are, many may be mapped to the same compact index.
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// If the map is many-to-one, it is not possible to directly obtain all the
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// sparse indices that map to a single compact index.
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// This map is time- rather than space-efficient. It stores the entire sparse
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// space.
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// IndexMapBiDi may be initialized in one of 3 ways:
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// 1. Init(size, true);
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// Setup();
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// Sets a complete 1:1 mapping with no unmapped elements.
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// 2. Init(size, false);
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// for ... SetMap(index, true);
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// Setup();
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// Specifies precisely which sparse indices are mapped. The mapping is 1:1.
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// 3. Either of the above, followed by:
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// for ... Merge(index1, index2);
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// CompleteMerges();
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// Allows a many-to-one mapping by merging compact space indices.
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class IndexMapBiDi : public IndexMap {
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public:
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virtual ~IndexMapBiDi() {}
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// Top-level init function in a single call to initialize a map to select
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// a single contiguous subrange [start, end) of the sparse space to be mapped
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// 1 to 1 to the compact space, with all other elements of the sparse space
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// left unmapped.
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// No need to call Setup after this.
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void InitAndSetupRange(int sparse_size, int start, int end);
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// Initializes just the sparse_map_ to the given size with either all
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// forward indices mapped (all_mapped = true) or none (all_mapped = false).
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// Call Setup immediately after, or make calls to SetMap first to adjust the
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// mapping and then call Setup before using the map.
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void Init(int size, bool all_mapped);
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// Sets a given index in the sparse_map_ to be mapped or not.
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void SetMap(int sparse_index, bool mapped);
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// Sets up the sparse_map_ and compact_map_ properly after Init and
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// some calls to SetMap. Assumes an ordered 1-1 map from set indices
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// in the sparse space to the compact space.
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void Setup();
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// Merges the two compact space indices. May be called many times, but
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// the merges must be concluded by a call to CompleteMerges.
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// Returns true if a merge was actually performed.
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bool Merge(int compact_index1, int compact_index2);
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// Returns true if the given compact index has been deleted.
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bool IsCompactDeleted(int index) const {
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return MasterCompactIndex(index) < 0;
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}
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// Completes one or more Merge operations by further compacting the
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// compact space.
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void CompleteMerges();
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// SparseToCompact takes a sparse index to an index in the compact space.
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virtual int SparseToCompact(int sparse_index) const {
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return sparse_map_[sparse_index];
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}
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// The size of the sparse space.
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virtual int SparseSize() const {
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return sparse_map_.size();
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}
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// Copy from the input.
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void CopyFrom(const IndexMapBiDi& src);
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// Writes to the given file. Returns false in case of error.
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bool Serialize(FILE* fp) const;
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// Reads from the given file. Returns false in case of error.
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// If swap is true, assumes a big/little-endian swap is needed.
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bool DeSerialize(bool swap, FILE* fp);
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// Bulk calls to SparseToCompact.
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// Maps the given array of sparse indices to an array of compact indices.
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// Assumes the input is sorted. The output indices are sorted and uniqued.
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// Return value is the number of "missed" features, being features that
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// don't map to the compact feature space.
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int MapFeatures(const GenericVector<int>& sparse,
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GenericVector<int>* compact) const;
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private:
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// Returns the master compact index for a given compact index.
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// During a multiple merge operation, several compact indices may be
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// combined, so we need to be able to find the master of all.
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int MasterCompactIndex(int compact_index) const {
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while (compact_index >= 0 &&
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sparse_map_[compact_map_[compact_index]] != compact_index)
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compact_index = sparse_map_[compact_map_[compact_index]];
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return compact_index;
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}
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// Direct look-up of the compact index for each element in sparse space.
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GenericVector<inT32> sparse_map_;
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};
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} // namespace tesseract.
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#endif // TESSERACT_CCUTIL_INDEXMAPBIDI_H_
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