BitMatrix.icc

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/**
 * @file BitMatrix.icc
 *
 * Inline implementation of BitMatrix class.
 *
 * @author Pekka Jääskeläinen 2007 (pekka.jaaskelainen-no.spam-tut.fi)
 * @note rating: red
 */
 
#include "BaseType.hh"
 
/**
 * Count of rows in the bit matrix.
 *
 * @return Count of rows.
 */
inline int
BitMatrix::rowCount() const {
    return rows_;
}
 
/**
 * Count of columns in the bit matrix.
 *
 * @return Count of columns.
 */
inline int
BitMatrix::columnCount() const {
    return columns_;
}
 
/**
 * Performs an AND operation between the matrices for all elements and 
 * returns true in case any result is nonzero.
 *
 * This is used to check for conflicts between two bit matrices, that is,
 * to look for element in which both matrices have value '1'.
 *
 * @note Both matrices must be of same size. This is not checked by the
 * method.
 *
 * @param another The bit matrix to AND with.
 */
inline bool
BitMatrix::conflictsWith(const BitMatrix& another) const {
    for (int word = 0; word < rows_ * wordsPerRow_; ++word) {
        RowWord conflicts = 
            matrix_[word] & another.matrix_[word];
        if (conflicts != 0)
            return true;
    }
    return false;
}
 
/**
 * ORs the given matrix with this one.
 *
 * The resulting matrix has '1' in an element in case either the merged
 * matrix or the original had '1' there.
 *
 * @param another The resource table of the merged.
 */
inline void
BitMatrix::orWith(const BitMatrix& another) {
    for (int word = 0; word < rows_ * wordsPerRow_; ++word) {
        matrix_[word] |= another.matrix_[word];
    }
}
 
/**
 * Sets the bit at given element.
 *
 * @param column The column.
 * @param row The row.
 * @param value The bit.
 */
inline void
BitMatrix::setBit(int column, int row, bool value) {
 
    const int wordPos = column / (sizeof(RowWord) * BYTE_BITWIDTH);
    const int bitPos = column % (sizeof(RowWord) * BYTE_BITWIDTH);
    const RowWord oldWord = matrix_[row * wordsPerRow_ + wordPos];
    RowWord newWord = 0;
    if (value) {
        // set bit to 1 by ORing
        RowWord mask = 1 << bitPos;
        newWord = oldWord | mask;
    } else {
        // set the bit to 0 by ANDing with all ones except the bit to set
        RowWord mask = 1 << bitPos;
        mask = ~mask;
        newWord = oldWord & mask;
    }
    matrix_[row * wordsPerRow_ + wordPos] = newWord;
}
 
/**
 * Checks if the given bit is set.
 *
 * @param column The column.
 * @param row The row.
 * @return Value of the bit.
 */
inline bool
BitMatrix::bitAt(int column, int row) const {
 
    const int wordPos = column / (sizeof(RowWord) * BYTE_BITWIDTH);
    const int bitPos = column % (sizeof(RowWord) * BYTE_BITWIDTH);
    const RowWord word = matrix_[row * wordsPerRow_ + wordPos];
    // reset all bits except that one by ANDing
    RowWord mask = 1 << bitPos;
    return (word & mask) != 0;
}
 
/**
 * Shifts the matrix left one step.
 */
inline void
BitMatrix::shiftLeft() {
 
    const int shiftAmount = sizeof(RowWord)*BYTE_BITWIDTH - 1;
 
    for (int col = 0; col < wordsPerRow_; ++col) {
        for (int row = 0; row < rows_; ++row) {
            RowWord word = matrix_[row*wordsPerRow_ + col];
            word >>= 1;
            // transfer the upper bit from the next column
            if (col + 1 < wordsPerRow_) {
                unsigned upperBit = 
                    matrix_[row*wordsPerRow_ + col + 1] << shiftAmount;
                word |= upperBit;
            }
            matrix_[row*wordsPerRow_ + col] = word;
        }
    }
}