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
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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 j, i = 0;
            for (j = first; j < buf.size(); j++) tmp[i++] = buf[j];
            for (j = 0    ; j < end       ; j++) tmp[i++] = buf[j];
            first = 0;
            end   = buf.size();
            tmp.moveTo(buf);
        }
    }
};


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

#endif