Queue.h

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/*****************************************************************************************[Queue.h]
Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
Copyright (c) 2007-2010, Niklas Sorensson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
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The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
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**************************************************************************************************/

#ifndef Minisat_Queue_h
#define Minisat_Queue_h

#include "Vec.h"

namespace Minisat {

//=================================================================================================

template<class T>
class Queue {
    vec<T>  buf;
    int     first;
    int     end;

public:
    typedef T Key;

    Queue() : buf(1), first(0), end(0) {}

    void clear (bool dealloc = false) { buf.clear(dealloc); buf.growTo(1); first = end = 0; }
    int  size  () const { return (end >= first) ? end - first : end - first + buf.size(); }

    const T& operator [] (int index) const  { assert(index >= 0); assert(index < size()); return buf[(first + index) % buf.size()]; }
    T&       operator [] (int index)        { assert(index >= 0); assert(index < size()); return buf[(first + index) % buf.size()]; }

    T    peek  () const { assert(first != end); return buf[first]; }
    void pop   () { assert(first != end); first++; if (first == buf.size()) first = 0; }
    void insert(T elem) {   // INVARIANT: buf[end] is always unused
        buf[end++] = elem;
        if (end == buf.size()) end = 0;
        if (first == end){  // Resize:
            vec<T>  tmp((buf.size()*3 + 1) >> 1);
            //**/printf("queue alloc: %d elems (%.1f MB)\n", tmp.size(), tmp.size() * sizeof(T) / 1000000.0);
            int     i = 0;
            for (int j = first; j < buf.size(); j++) tmp[i++] = buf[j];
            for (int j = 0    ; j < end       ; j++) tmp[i++] = buf[j];
            first = 0;
            end   = buf.size();
            tmp.moveTo(buf);
        }
    }
};


//=================================================================================================
}

#endif