ltbitmatrix.h

/*
Copyright 2013-present Barefoot Networks, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#ifndef LIB_LTBITMATRIX_H_
#define LIB_LTBITMATRIX_H_

#include "bitvec.h"

namespace P4 {

/* A lower-triangular bit matrix, held in a bit vector */
class LTBitMatrix : private bitvec {
 public:
    nonconst_bitref operator()(unsigned r, unsigned c) {
        return r >= c ? bitvec::operator[]((r * r + r) / 2 + c) : end();
    }
    bool operator()(unsigned r, unsigned c) const {
        return r >= c ? bitvec::operator[]((r * r + r) / 2 + c) : false;
    }
    unsigned size() const {
        if (empty()) return 0;
        unsigned m = *max();
        unsigned r = 1;
        while ((r * r + r) / 2 <= m) r++;
        return r;
    }
    using bitvec::clear;
    using bitvec::empty;
    using bitvec::operator bool;

 private:
    template <class T>
    class rowref {
        friend class LTBitMatrix;
        T &self;
        unsigned row;
        rowref(T &s, unsigned r) : self(s), row(r) {}

     public:
        rowref(const rowref &) = default;
        rowref(rowref &&) = default;
        explicit operator bool() const {
            if (row < bits_per_unit)
                return self.getrange((row * row + row) / 2, row + 1) != 0;
            else
                return self.getslice((row * row + row) / 2, row + 1) ? true : false;
        }
        operator bitvec() const { return self.getslice((row * row + row) / 2, row + 1); }
    };
    class nonconst_rowref : public rowref<LTBitMatrix> {
     public:
        friend class LTBitMatrix;
        using rowref<LTBitMatrix>::rowref;
        void operator|=(bitvec a) const {
            for (size_t v : a) {
                if (v > row) break;
                self(row, v) = 1;
            }
        }
        nonconst_bitref operator[](unsigned col) const { return self(row, col); }
    };
    class const_rowref : public rowref<const LTBitMatrix> {
     public:
        friend class LTBitMatrix;
        using rowref<const LTBitMatrix>::rowref;
        bool operator[](unsigned col) const { return self(row, col); }
    };

 public:
    nonconst_rowref operator[](unsigned r) { return nonconst_rowref(*this, r); }
    const_rowref operator[](unsigned r) const { return const_rowref(*this, r); }

    bool operator==(const LTBitMatrix &a) const { return bitvec::operator==(a); }
    bool operator!=(const LTBitMatrix &a) const { return bitvec::operator!=(a); }
    friend bool operator>>(const char *p, LTBitMatrix &bm);
};

inline std::ostream &operator<<(std::ostream &out, const LTBitMatrix &bm) {
    for (unsigned i = 1; i < bm.size(); i++) {
        if (i > 1) out << ' ';
        for (unsigned j = 0; j < i; j++) out << (bm[i][j] ? '1' : '0');
    }
    return out;
}

inline bool operator>>(const char *p, LTBitMatrix &bm) {
    bitvec rv;
    for (int i = 0; *p; ++p, ++i) switch (*p) {
            case ' ':
                --i;
                break;
            case '0':
                break;
            case '1':
                rv[i] = 1;
                break;
            default:
                return false;
        }
    bm.bitvec::operator=(rv);
    return true;
}

}  // namespace P4

#endif /* LIB_LTBITMATRIX_H_ */