C++ QStack::reserve方法代码示例

QList<ListDigraph::Node> ProcessModel::topolSortReachableFrom(const QList<ListDigraph::Node>& s) {
	ListDigraph::NodeMap<bool > nodevisited(graph, false);
	QList<ListDigraph::Node> res;
	QStack<ListDigraph::Node> stack;
	ListDigraph::Node curnode;
	ListDigraph::Node pnode;
	ListDigraph::Node snode;
	QList<ListDigraph::Node> reachable = reachableFrom(s);

	// Reserve memory
	res.reserve(countNodes(graph));
	stack.reserve(countNodes(graph));

	for (int i = 0; i < s.size(); i++) {
		if (s[i] != INVALID) {
			stack.push(s[i]);
		}
	}

	bool psched;
	while (!stack.empty()) {
		curnode = stack.pop();

		if (!nodevisited[curnode]) { // This node has not been visited yet

			// Check whether all predecessors in reachable are scheduled
			psched = true;
			for (ListDigraph::InArcIt iait(graph, curnode); iait != INVALID; ++iait) {
				pnode = graph.source(iait);
				if (reachable.contains(pnode)) { // Consider only nodes which can be reached from s
					if (!nodevisited[pnode]) {
						psched = false;
						break;
					}
				}
			}

			if (psched) { // All predecessors have been visited
				res.append(curnode);
				nodevisited[curnode] = true;

				// Push the succeeding nodes
				for (ListDigraph::OutArcIt oait(graph, curnode); oait != INVALID; ++oait) {
					snode = graph.target(oait);
					if (!nodevisited[snode]) {
						stack.push(snode);
					}
				}
			} else {
				stack.prepend(curnode);
			}

		} // Else ignore the visited node
	}

	return res;
}

bool QMakeParser::read(ProFile *pro, const QString &in, int line, SubGrammar grammar)
{
    m_proFile = pro;
    m_lineNo = line;

    // Final precompiled token stream buffer
    QString tokBuff;
    // Worst-case size calculations:
    // - line marker adds 1 (2-nl) to 1st token of each line
    // - empty assignment "A=":2 =>
    //   TokHashLiteral(1) + hash(2) + len(1) + "A"(1) + TokAssign(1) + 0(1) +
    //   TokValueTerminator(1) == 8 (9)
    // - non-empty assignment "A=B C":5 =>
    //   TokHashLiteral(1) + hash(2) + len(1) + "A"(1) + TokAssign(1) + 2(1) +
    //   TokLiteral(1) + len(1) + "B"(1) +
    //   TokLiteral(1) + len(1) + "C"(1) + TokValueTerminator(1) == 14 (15)
    // - variable expansion: "$$f":3 =>
    //   TokVariable(1) + hash(2) + len(1) + "f"(1) = 5
    // - function expansion: "$$f()":5 =>
    //   TokFuncName(1) + hash(2) + len(1) + "f"(1) + TokFuncTerminator(1) = 6
    // - scope: "X:":2 =>
    //   TokHashLiteral(1) + hash(2) + len(1) + "A"(1) + TokCondition(1) +
    //   TokBranch(1) + len(2) + ... + len(2) + ... == 10
    // - test: "X():":4 =>
    //   TokHashLiteral(1) + hash(2) + len(1) + "A"(1) + TokTestCall(1) + TokFuncTerminator(1) +
    //   TokBranch(1) + len(2) + ... + len(2) + ... == 11
    // - "for(A,B):":9 =>
    //   TokForLoop(1) + hash(2) + len(1) + "A"(1) +
    //   len(2) + TokLiteral(1) + len(1) + "B"(1) + TokValueTerminator(1) +
    //   len(2) + ... + TokTerminator(1) == 14 (15)
    tokBuff.reserve((in.size() + 1) * 5);
    ushort *tokPtr = (ushort *)tokBuff.constData(); // Current writing position

    // Expression precompiler buffer.
    QString xprBuff;
    xprBuff.reserve(tokBuff.capacity()); // Excessive, but simple
    ushort *buf = (ushort *)xprBuff.constData();

    // Parser state
    m_blockstack.clear();
    m_blockstack.resize(1);

    QStack<ParseCtx> xprStack;
    xprStack.reserve(10);

    // We rely on QStrings being null-terminated, so don't maintain a global end pointer.
    const ushort *cur = (const ushort *)in.unicode();
    m_canElse = false;
  freshLine:
    m_state = StNew;
    m_invert = false;
    m_operator = NoOperator;
    m_markLine = m_lineNo;
    m_inError = false;
    int parens = 0; // Braces in value context
    int argc = 0;
    int wordCount = 0; // Number of words in currently accumulated expression
    int lastIndent = 0; // Previous line's indentation, to detect accidental continuation abuse
    bool lineMarked = true; // For in-expression markers
    ushort needSep = TokNewStr; // Met unquoted whitespace
    ushort quote = 0;
    ushort term = 0;

    Context context;
    ushort *ptr;
    if (grammar == ValueGrammar) {
        context = CtxPureValue;
        ptr = tokPtr + 2;
    } else {
        context = CtxTest;
        ptr = buf + 4;
    }
    ushort *xprPtr = ptr;

#define FLUSH_LHS_LITERAL() \
    do { \
        if ((tlen = ptr - xprPtr)) { \
            finalizeHashStr(xprPtr, tlen); \
            if (needSep) { \
                wordCount++; \
                needSep = 0; \
            } \
        } else { \
            ptr -= 4; \
        } \
    } while (0)

#define FLUSH_RHS_LITERAL() \
    do { \
        if ((tlen = ptr - xprPtr)) { \
            xprPtr[-2] = TokLiteral | needSep; \
            xprPtr[-1] = tlen; \
            if (needSep) { \
                wordCount++; \
                needSep = 0; \
            } \
        } else { \
            ptr -= 2; \
        } \
    } while (0)
//.........这里部分代码省略.........

/*!
  \param points Series of data points
  \return Curve points
*/
QPolygonF QwtWeedingCurveFitter::fitCurve( const QPolygonF &points ) const
{
    QStack<Line> stack;
    stack.reserve( 500 );

    const QPointF *p = points.data();
    const int nPoints = points.size();

    QVector<bool> usePoint( nPoints, false );

    double distToSegment;

    stack.push( Line( 0, nPoints - 1 ) );

    while ( !stack.isEmpty() )
    {
        const Line r = stack.pop();

        // initialize line segment
        const double vecX = p[r.to].x() - p[r.from].x();
        const double vecY = p[r.to].y() - p[r.from].y();

        const double vecLength = qSqrt( vecX * vecX + vecY * vecY );

        const double unitVecX = ( vecLength != 0.0 ) ? vecX / vecLength : 0.0;
        const double unitVecY = ( vecLength != 0.0 ) ? vecY / vecLength : 0.0;

        double maxDist = 0.0;
        int nVertexIndexMaxDistance = r.from + 1;
        for ( int i = r.from + 1; i < r.to; i++ )
        {
            //compare to anchor
            const double fromVecX = p[i].x() - p[r.from].x();
            const double fromVecY = p[i].y() - p[r.from].y();
            const double fromVecLength =
                qSqrt( fromVecX * fromVecX + fromVecY * fromVecY );

            if ( fromVecX * unitVecX + fromVecY * unitVecY < 0.0 )
            {
                distToSegment = fromVecLength;
            }
            if ( fromVecX * unitVecX + fromVecY * unitVecY < 0.0 )
            {
                distToSegment = fromVecLength;
            }
            else
            {
                const double toVecX = p[i].x() - p[r.to].x();
                const double toVecY = p[i].y() - p[r.to].y();
                const double toVecLength = qSqrt( toVecX * toVecX + toVecY * toVecY );
                const double s = toVecX * ( -unitVecX ) + toVecY * ( -unitVecY );
                if ( s < 0.0 )
                    distToSegment = toVecLength;
                else
                {
                    distToSegment = qSqrt( qFabs( toVecLength * toVecLength - s * s ) );
                }
            }

            if ( maxDist < distToSegment )
            {
                maxDist = distToSegment;
                nVertexIndexMaxDistance = i;
            }
        }
        if ( maxDist <= d_data->tolerance )
        {
            usePoint[r.from] = true;
            usePoint[r.to] = true;
        }
        else
        {
            stack.push( Line( r.from, nVertexIndexMaxDistance ) );
            stack.push( Line( nVertexIndexMaxDistance, r.to ) );
        }
    }

    int cnt = 0;

    QPolygonF stripped( nPoints );
    for ( int i = 0; i < nPoints; i++ )
    {
        if ( usePoint[i] )
            stripped[cnt++] = p[i];
    }
    stripped.resize( cnt );
    return stripped;
}