/**@file Simplified Vector template with aliases. */
/*
* Copyright 2008 Free Software Foundation, Inc.
* Copyright 2014 Range Networks, Inc.
*
* This software is distributed under the terms of the GNU Affero Public License.
* See the COPYING file in the main directory for details.
*
* This use of this software may be subject to additional restrictions.
* See the LEGAL file in the main directory for details.

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.

	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/




#ifndef VECTOR_H
#define VECTOR_H

#include <string.h>
#include <iostream>
#include <assert.h>
#include <stdio.h>
// We cant use Logger.h in this file...
extern int gVectorDebug;
//#define ENABLE_VECTORDEBUG
#ifdef ENABLE_VECTORDEBUG
#define VECTORDEBUG(...) { printf(__VA_ARGS__); printf(" this=%p [%p,%p,%p]\n",(void*)this,(void*)&mData,mStart,mEnd); }
//#define VECTORDEBUG(msg) { std::cout<<msg<<std::endl; }
#else
#define VECTORDEBUG(...)
#endif

#define BITVECTOR_REFCNTS 0

#if BITVECTOR_REFCNTS
// (pat) Started to add refcnts, decided against it for now.
template <class T> class RCData : public RefCntBase {
	public:
	T* mPointer;
};
#endif


/**
	A simplified Vector template with aliases.
	Unlike std::vector, this class does not support dynamic resizing.
	Unlike std::vector, this class does support "aliases" and subvectors.
*/
// (pat) Nov 2013:  Vector and the derived classes BitVector and SoftVector were originally written with behavior
// that differed for const and non-const cases, making them very difficult to use and resulting in many extremely
// difficult to find bugs in the code base.
// Ultimately these classes should all be converted to reference counted methodologies, but as an interim measure
// I am rationalizing their behavior until we flush out all places in the code base that inadvertently depended
// on the original behavior.  This is done with assert statements in BitVector methods.
// ====
// What the behavior was probably supposed to be:
//		Vectors can 'own' the data they point to or not.  Only one Vector 'owns' the memory at a time,
//		so that automatic destruction can be used.  So whenever there is an operation that yields one
//		vector from another the options were: clone (allocate a new vector from memory), alias (make the
//		new vector point into the memory of the original vector) or shift (the new Vector steals the
//		memory ownership from the original vector.)
//		The const copy-constructor did a clone, the non-const copy constructor did a shiftMem, and the segment and
//		related methods (head, tail, etc) returned aliases.
//		Since a copy-constructor is inserted transparently in sometimes surprising places, this made the
//		class very difficult to use.  Moreover, since the C++ standard specifies that a copy-constructor is used
//		to copy the return value from functions, it makes it literally impossible for a function to fully control
//		the return value.  Our code has relied on the "Return Value Optimization" which says that the C++ compiler
//		may omit the copy-construction of the return value even if the copy-constructor has side-effects, which ours does.
//		This methodology is fundamentally incompatible with C++.
// What the original behavior actually was:
//	class Vector:
//		The copy-constructor and assignment operators did a clone for the const case and a shift for the non-const case.
//			This is really horrible.
//		The segment methods were identical for const and non-const cases, always returning an alias.
//		This also resulted in zillions of redundant mallocs and copies throughout the code base.
//	class BitVector:
//		Copy-constructor:
//			BitVector did not have any copy-constructors, and I think the intent was that it would have the same behavior
//			as Vector, but that is not how C++ works: with no copy-constructor the default copy-constructor
//			uses only the const case, so only the const Vector copy-constructor was used.  Therefore it always cloned,
//			and the code base relied heavily on the "Return Value Optimization" to work at all.
//		Assignment operator:
//			BitVector did not have one, so C++ makes a default one that calls Vector::operator=() as a side effect,
//			which did a clone; not sure if there was a non-const version and no longer care.
//		segment methods:
//			The non-const segment() returned an alias, and the const segment() returned a clone.
//			I think the intent was that the behavior should be the same as Vector, but there was a conversion
//			of the result of the const segment() method from Vector to BitVector which caused the Vector copy-constructor
//			to be (inadvertently) invoked, resulting in the const version of the segment method returning a clone.
// What the behavior is now:
//	VectorBase:
//		There is a new VectorBase class that has only the common methods and extremely basic constructors.
//		The VectorBase class MUST NOT CONTAIN: copy constructors, non-trivial constructors called from derived classes,
//		or any method that returns a VectorBase type object.  Why?  Because any of the above when used in derived classes
//		can cause copy-constructor invocation, often surprisingly, obfuscating the code.
//		Each derived class must provide its own: copy-constructors and segment() and related methods, since we do not
//		want to inadvertently invoke a copy-constructor to convert the segment() result from VectorBase to the derived type.
//	BitVector:
//		The BitVector copy-constructor and assignment operator (inherited from VectorBase) paradigm is:
//		if the copied Vector owned memory, perform a clone so the new vector owns memory also,
//		otherwise just do a simple copy, which is another alias.  This isnt perfect but works every place
//		in our code base and easier to use than the previous paradigm.
//		The segment method always returns an alias.
//		If you want a clone of a segment, use cloneSegment(), which replaces the previous: const segment(...) const method.
//		Note that the semantics of cloneSegment still rely on the Return Value Optimization.  Oh well, we should use refcnts.
//	Vector:
//		I left Vector alone (except for rearrangement to separate out VectorBase.)  Vector should just not be used.
//	SoftVector:
//		SoftVector and signalVector should be updated similar to BitVector, but I did not want to disturb them.
// What the behavior should be:
//		All these should be reference-counted, similar to ByteVector.
template <class T> class VectorBase
{
	// TODO -- Replace memcpy calls with for-loops. (pat) in case class T is not POD [Plain Old Data]

	protected:
#if BITVECTOR_REFCNTS
	typedef RefCntPointer<RCData<T> > VectorDataType;
#else
	typedef T* VectorDataType;
#endif
	VectorDataType mData;		///< allocated data block.
	T* mStart;		///< start of useful data
	T* mEnd;		///< end of useful data + 1

	// Init vector with specified size.  Previous contents are completely discarded.  This is only used for initialization.
	void vInit(size_t elements)
	{
		mData = elements ? new T[elements] : NULL;
		mStart = mData;  // This is where mStart get set to zero
		mEnd = mStart + elements;
	}

	/** Assign from another Vector, shifting ownership. */
	// (pat) This should be eliminated, but it is used by Vector and descendents.
	void shiftMem(VectorBase<T>&other)
	{
		VECTORDEBUG("VectorBase::shiftMem(%p)",(void*)&other);
		this->clear();
		this->mData=other.mData;
		this->mStart=other.mStart;
		this->mEnd=other.mEnd;
		other.mData=NULL;
	}

	// Assign from another Vector, making this an alias to other.
	void makeAlias(const VectorBase<T> &other)
	{
		if (this->getData()) {
			assert(this->getData() != other.getData()); // Not possible by the semantics of Vector.
			this->clear();
		}
		this->mStart=const_cast<T*>(other.mStart);
		this->mEnd=const_cast<T*>(other.mEnd);
	}

	public:

	/** Return the size of the Vector in units, ie, the number of T elements. */
	size_t size() const
	{
		assert(mStart>=mData);
		assert(mEnd>=mStart);
		return mEnd - mStart;
	}

	/** Return size in bytes. */
	size_t bytes() const { return this->size()*sizeof(T); }

	/** Change the size of the Vector in items (not bytes), discarding content. */
	void resize(size_t newElements) {
		//VECTORDEBUG("VectorBase::resize("<<(void*)this<<","<<newElements<<")");
		VECTORDEBUG("VectorBase::resize(%p,%d) %s",this,newElements, (mData?"delete":""));
		if (mData!=NULL) delete[] mData;
		vInit(newElements);
	}

	/** Release memory and clear pointers. */
	void clear() { this->resize(0); }


	/** Copy data from another vector. */
	void clone(const VectorBase<T>& other) {
		this->resize(other.size());
		memcpy(mData,other.mStart,other.bytes());
	}

	void vConcat(const VectorBase<T>&other1, const VectorBase<T>&other2) {
		this->resize(other1.size()+other2.size());
		memcpy(this->mStart, other1.mStart, other1.bytes());
		memcpy(this->mStart+other1.size(), other2.mStart, other2.bytes());
	}

	protected:

	VectorBase() : mData(0), mStart(0), mEnd(0) {}

	/** Build a Vector with explicit values. */
	VectorBase(VectorDataType wData, T* wStart, T* wEnd) :mData(wData),mStart(wStart),mEnd(wEnd) {
		//VECTORDEBUG("VectorBase("<<(void*)wData);
		VECTORDEBUG("VectorBase(%p,%p,%p)",this->getData(),wStart,wEnd);
	}

	public:

	/** Destroy a Vector, deleting held memory. */
	~VectorBase() {
		//VECTORDEBUG("~VectorBase("<<(void*)this<<")");
		VECTORDEBUG("~VectorBase(%p)",this);
		this->clear();
	}

	bool isOwner() { return !!this->mData; }	// Do we own any memory ourselves?

	std::string inspect() const {
		char buf[100];
		snprintf(buf,100," mData=%p mStart=%p mEnd=%p ",(void*)mData,mStart,mEnd);
		return std::string(buf);
	}


	/**
		Copy part of this Vector to a segment of another Vector.
		@param other The other vector.
		@param start The start point in the other vector.
		@param span The number of elements to copy.
	*/
	void copyToSegment(VectorBase<T>& other, size_t start, size_t span) const
	{
		T* base = other.mStart + start;
		assert(base+span<=other.mEnd);
		assert(mStart+span<=mEnd);
		memcpy(base,mStart,span*sizeof(T));
	}

	/** Copy all of this Vector to a segment of another Vector. */
	void copyToSegment(VectorBase<T>& other, size_t start=0) const { copyToSegment(other,start,size()); }

	void copyTo(VectorBase<T>& other) const { copyToSegment(other,0,size()); }

	/**
		Copy a segment of this vector into another.
		@param other The other vector (to copt into starting at 0.)
		@param start The start point in this vector.
		@param span The number of elements to copy.
		WARNING: This function does NOT resize the result - you must set the result size before entering.
	*/
	void segmentCopyTo(VectorBase<T>& other, size_t start, size_t span) const
	{
		const T* base = mStart + start;
		assert(base+span<=mEnd);
		assert(other.mStart+span<=other.mEnd);
		memcpy(other.mStart,base,span*sizeof(T));
	}

	void fill(const T& val)
	{
		T* dp=mStart;
		while (dp<mEnd) *dp++=val;
	}

	void fill(const T& val, unsigned start, unsigned length)
	{
		T* dp=mStart+start;
		T* end=dp+length;
		assert(end<=mEnd);
		while (dp<end) *dp++=val;
	}

	/** Assign from another Vector. */
	// (pat) This is used for both const and non-const cases.
	// If the original vector owned memory, clone it, otherwise just copy the segment data.
	void operator=(const VectorBase<T>& other) {
		//std::cout << "Vector=(this="<<this->inspect()<<",other="<<other.inspect()<<")"<<endl;
		if (other.getData()) {
			this->clone(other);
		} else {
			this->makeAlias(other);
		}
		//std::cout << "Vector= after(this="<<this->inspect()<<")"<<endl;
	}


	T& operator[](size_t index)
	{
		assert(mStart+index<mEnd);
		return mStart[index];
	}

	const T& operator[](size_t index) const
	{
		assert(mStart+index<mEnd);
		return mStart[index];
	}

	const T* begin() const { return this->mStart; }
	T* begin() { return this->mStart; }
	const T* end() const { return this->mEnd; }
	T* end() { return this->mEnd; }
#if BITVECTOR_REFCNTS
	const T*getData() const { return this->mData.isNULL() ? 0 : this->mData->mPointer; }
#else
	const T*getData() const { return this->mData; }
#endif
};

// (pat) Nov 2013.  This class retains the original poor behavior.  See comments at VectorBase
template <class T> class Vector : public VectorBase<T>
{
	public:

	/** Build an empty Vector of a given size. */
	Vector(size_t wSize=0) { this->resize(wSize); }

	/** Build a Vector by shifting the data block. */
	Vector(Vector<T>& other) : VectorBase<T>(other.mData,other.mStart,other.mEnd) { other.mData=NULL; }

	/** Build a Vector by copying another. */
	Vector(const Vector<T>& other):VectorBase<T>() { this->clone(other); }

	/** Build a Vector with explicit values. */
	Vector(T* wData, T* wStart, T* wEnd) : VectorBase<T>(wData,wStart,wEnd) { }

	/** Build a vector from an existing block, NOT to be deleted upon destruction. */
	Vector(T* wStart, size_t span) : VectorBase<T>(NULL,wStart,wStart+span) { }

	/** Build a Vector by concatenation. */
	Vector(const Vector<T>& other1, const Vector<T>& other2):VectorBase<T>() {
		assert(this->mData == 0);
		this->vConcat(other1,other2);
	}

	//@{

	/** Assign from another Vector, shifting ownership. */
	void operator=(Vector<T>& other) { this->shiftMem(other); }

	/** Assign from another Vector, copying. */
	void operator=(const Vector<T>& other) { this->clone(other); }

	/** Return an alias to a segment of this Vector. */
	Vector<T> segment(size_t start, size_t span)
	{
		T* wStart = this->mStart + start;
		T* wEnd = wStart + span;
		assert(wEnd<=this->mEnd);
		return Vector<T>(NULL,wStart,wEnd);
	}

	/** Return an alias to a segment of this Vector. */
	const Vector<T> segment(size_t start, size_t span) const
	{
		T* wStart = this->mStart + start;
		T* wEnd = wStart + span;
		assert(wEnd<=this->mEnd);
		return Vector<T>(NULL,wStart,wEnd);
	}

	Vector<T> head(size_t span) { return segment(0,span); }
	const Vector<T> head(size_t span) const { return segment(0,span); }
	Vector<T> tail(size_t start) { return segment(start,this->size()-start); }
	const Vector<T> tail(size_t start) const { return segment(start,this->size()-start); }

	/**@name Iterator types. */
	//@{
	typedef T* iterator;
	typedef const T* const_iterator;
	//@}

	//@}
};





/** Basic print operator for Vector objects. */
template <class T>
std::ostream& operator<<(std::ostream& os, const Vector<T>& v)
{
	for (unsigned i=0; i<v.size(); i++) os << v[i] << " ";
	return os;
}



#endif
// vim: ts=4 sw=4