402 lines
15 KiB
C++
402 lines
15 KiB
C++
/**@file Simplified Vector template with aliases. */
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/*
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* Copyright 2008 Free Software Foundation, Inc.
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*
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* This software is distributed under the terms of the GNU Affero Public License.
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* See the COPYING file in the main directory for details.
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*
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* This use of this software may be subject to additional restrictions.
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* See the LEGAL file in the main directory for details.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef VECTOR_H
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#define VECTOR_H
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#include <string.h>
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#include <iostream>
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#include <assert.h>
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#include <stdio.h>
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// We cant use Logger.h in this file...
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extern int gVectorDebug;
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//#define ENABLE_VECTORDEBUG
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#ifdef ENABLE_VECTORDEBUG
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#define VECTORDEBUG(...) { printf(__VA_ARGS__); printf(" this=%p [%p,%p,%p]\n",(void*)this,(void*)&mData,mStart,mEnd); }
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//#define VECTORDEBUG(msg) { std::cout<<msg<<std::endl; }
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#else
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#define VECTORDEBUG(...)
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#endif
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#define BITVECTOR_REFCNTS 0
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#if BITVECTOR_REFCNTS
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// (pat) Started to add refcnts, decided against it for now.
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template <class T> class RCData : public RefCntBase {
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public:
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T* mPointer;
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};
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#endif
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/**
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A simplified Vector template with aliases.
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Unlike std::vector, this class does not support dynamic resizing.
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Unlike std::vector, this class does support "aliases" and subvectors.
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*/
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// (pat) Nov 2013: Vector and the derived classes BitVector and SoftVector were originally written with behavior
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// that differed for const and non-const cases, making them very difficult to use and resulting in many extremely
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// difficult to find bugs in the code base.
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// Ultimately these classes should all be converted to reference counted methodologies, but as an interim measure
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// I am rationalizing their behavior until we flush out all places in the code base that inadvertently depended
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// on the original behavior. This is done with assert statements in BitVector methods.
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// ====
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// What the behavior was probably supposed to be:
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// Vectors can 'own' the data they point to or not. Only one Vector 'owns' the memory at a time,
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// so that automatic destruction can be used. So whenever there is an operation that yields one
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// vector from another the options were: clone (allocate a new vector from memory), alias (make the
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// new vector point into the memory of the original vector) or shift (the new Vector steals the
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// memory ownership from the original vector.)
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// The const copy-constructor did a clone, the non-const copy constructor did a shiftMem, and the segment and
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// related methods (head, tail, etc) returned aliases.
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// Since a copy-constructor is inserted transparently in sometimes surprising places, this made the
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// class very difficult to use. Moreover, since the C++ standard specifies that a copy-constructor is used
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// to copy the return value from functions, it makes it literally impossible for a function to fully control
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// the return value. Our code has relied on the "Return Value Optimization" which says that the C++ compiler
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// may omit the copy-construction of the return value even if the copy-constructor has side-effects, which ours does.
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// This methodology is fundamentally incompatible with C++.
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// What the original behavior actually was:
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// class Vector:
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// The copy-constructor and assignment operators did a clone for the const case and a shift for the non-const case.
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// This is really horrible.
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// The segment methods were identical for const and non-const cases, always returning an alias.
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// This also resulted in zillions of redundant mallocs and copies throughout the code base.
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// class BitVector:
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// Copy-constructor:
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// BitVector did not have any copy-constructors, and I think the intent was that it would have the same behavior
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// as Vector, but that is not how C++ works: with no copy-constructor the default copy-constructor
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// uses only the const case, so only the const Vector copy-constructor was used. Therefore it always cloned,
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// and the code base relied heavily on the "Return Value Optimization" to work at all.
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// Assignment operator:
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// BitVector did not have one, so C++ makes a default one that calls Vector::operator=() as a side effect,
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// which did a clone; not sure if there was a non-const version and no longer care.
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// segment methods:
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// The non-const segment() returned an alias, and the const segment() returned a clone.
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// I think the intent was that the behavior should be the same as Vector, but there was a conversion
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// of the result of the const segment() method from Vector to BitVector which caused the Vector copy-constructor
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// to be (inadvertently) invoked, resulting in the const version of the segment method returning a clone.
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// What the behavior is now:
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// VectorBase:
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// There is a new VectorBase class that has only the common methods and extremely basic constructors.
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// The VectorBase class MUST NOT CONTAIN: copy constructors, non-trivial constructors called from derived classes,
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// or any method that returns a VectorBase type object. Why? Because any of the above when used in derived classes
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// can cause copy-constructor invocation, often surprisingly, obfuscating the code.
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// Each derived class must provide its own: copy-constructors and segment() and related methods, since we do not
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// want to inadvertently invoke a copy-constructor to convert the segment() result from VectorBase to the derived type.
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// BitVector:
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// The BitVector copy-constructor and assignment operator (inherited from VectorBase) paradigm is:
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// if the copied Vector owned memory, perform a clone so the new vector owns memory also,
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// otherwise just do a simple copy, which is another alias. This isnt perfect but works every place
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// in our code base and easier to use than the previous paradigm.
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// The segment method always returns an alias.
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// If you want a clone of a segment, use cloneSegment(), which replaces the previous: const segment(...) const method.
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// Note that the semantics of cloneSegment still rely on the Return Value Optimization. Oh well, we should use refcnts.
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// Vector:
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// I left Vector alone (except for rearrangement to separate out VectorBase.) Vector should just not be used.
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// SoftVector:
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// SoftVector and signalVector should be updated similar to BitVector, but I did not want to disturb them.
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// What the behavior should be:
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// All these should be reference-counted, similar to ByteVector.
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template <class T> class VectorBase
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{
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// TODO -- Replace memcpy calls with for-loops. (pat) in case class T is not POD [Plain Old Data]
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protected:
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#if BITVECTOR_REFCNTS
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typedef RefCntPointer<RCData<T> > VectorDataType;
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#else
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typedef T* VectorDataType;
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#endif
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VectorDataType mData; ///< allocated data block.
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T* mStart; ///< start of useful data
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T* mEnd; ///< end of useful data + 1
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// Init vector with specified size. Previous contents are completely discarded. This is only used for initialization.
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void vInit(size_t elements)
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{
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mData = elements ? new T[elements] : NULL;
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mStart = mData;
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mEnd = mStart + elements;
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}
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/** Assign from another Vector, shifting ownership. */
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// (pat) This should be eliminated, but it is used by Vector and descendents.
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void shiftMem(VectorBase<T>&other)
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{
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VECTORDEBUG("VectorBase::shiftMem(%p)",(void*)&other);
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this->clear();
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this->mData=other.mData;
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this->mStart=other.mStart;
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this->mEnd=other.mEnd;
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other.mData=NULL;
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}
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// Assign from another Vector, making this an alias to other.
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void makeAlias(const VectorBase<T> &other)
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{
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if (this->getData()) {
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assert(this->getData() != other.getData()); // Not possible by the semantics of Vector.
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this->clear();
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}
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this->mStart=const_cast<T*>(other.mStart);
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this->mEnd=const_cast<T*>(other.mEnd);
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}
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public:
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/** Return the size of the Vector in units, ie, the number of T elements. */
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size_t size() const
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{
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assert(mStart>=mData);
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assert(mEnd>=mStart);
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return mEnd - mStart;
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}
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/** Return size in bytes. */
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size_t bytes() const { return this->size()*sizeof(T); }
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/** Change the size of the Vector in items (not bytes), discarding content. */
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void resize(size_t newElements) {
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//VECTORDEBUG("VectorBase::resize("<<(void*)this<<","<<newElements<<")");
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VECTORDEBUG("VectorBase::resize(%p,%d) %s",this,newElements, (mData?"delete":""));
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if (mData!=NULL) delete[] mData;
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vInit(newElements);
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}
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/** Release memory and clear pointers. */
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void clear() { this->resize(0); }
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/** Copy data from another vector. */
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void clone(const VectorBase<T>& other) {
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this->resize(other.size());
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memcpy(mData,other.mStart,other.bytes());
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}
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void vConcat(const VectorBase<T>&other1, const VectorBase<T>&other2) {
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this->resize(other1.size()+other2.size());
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memcpy(this->mStart, other1.mStart, other1.bytes());
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memcpy(this->mStart+other1.size(), other2.mStart, other2.bytes());
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}
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protected:
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VectorBase() : mData(0), mStart(0), mEnd(0) {}
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/** Build a Vector with explicit values. */
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VectorBase(VectorDataType wData, T* wStart, T* wEnd) :mData(wData),mStart(wStart),mEnd(wEnd) {
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//VECTORDEBUG("VectorBase("<<(void*)wData);
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VECTORDEBUG("VectorBase(%p,%p,%p)",this->getData(),wStart,wEnd);
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}
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public:
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/** Destroy a Vector, deleting held memory. */
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~VectorBase() {
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//VECTORDEBUG("~VectorBase("<<(void*)this<<")");
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VECTORDEBUG("~VectorBase(%p)",this);
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this->clear();
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}
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bool isOwner() { return !!this->mData; } // Do we own any memory ourselves?
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std::string inspect() const {
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char buf[100];
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snprintf(buf,100," mData=%p mStart=%p mEnd=%p ",(void*)mData,mStart,mEnd);
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return std::string(buf);
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}
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/**
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Copy part of this Vector to a segment of another Vector.
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@param other The other vector.
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@param start The start point in the other vector.
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@param span The number of elements to copy.
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*/
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void copyToSegment(VectorBase<T>& other, size_t start, size_t span) const
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{
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T* base = other.mStart + start;
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assert(base+span<=other.mEnd);
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assert(mStart+span<=mEnd);
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memcpy(base,mStart,span*sizeof(T));
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}
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/** Copy all of this Vector to a segment of another Vector. */
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void copyToSegment(VectorBase<T>& other, size_t start=0) const { copyToSegment(other,start,size()); }
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void copyTo(VectorBase<T>& other) const { copyToSegment(other,0,size()); }
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/**
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Copy a segment of this vector into another.
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@param other The other vector (to copt into starting at 0.)
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@param start The start point in this vector.
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@param span The number of elements to copy.
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WARNING: This function does NOT resize the result - you must set the result size before entering.
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*/
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void segmentCopyTo(VectorBase<T>& other, size_t start, size_t span) const
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{
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const T* base = mStart + start;
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assert(base+span<=mEnd);
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assert(other.mStart+span<=other.mEnd);
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memcpy(other.mStart,base,span*sizeof(T));
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}
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void fill(const T& val)
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{
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T* dp=mStart;
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while (dp<mEnd) *dp++=val;
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}
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void fill(const T& val, unsigned start, unsigned length)
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{
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T* dp=mStart+start;
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T* end=dp+length;
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assert(end<=mEnd);
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while (dp<end) *dp++=val;
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}
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/** Assign from another Vector. */
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// (pat) This is used for both const and non-const cases.
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// If the original vector owned memory, clone it, otherwise just copy the segment data.
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void operator=(const VectorBase<T>& other) {
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//std::cout << "Vector=(this="<<this->inspect()<<",other="<<other.inspect()<<")"<<endl;
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if (other.getData()) {
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this->clone(other);
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} else {
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this->makeAlias(other);
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}
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//std::cout << "Vector= after(this="<<this->inspect()<<")"<<endl;
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}
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T& operator[](size_t index)
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{
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assert(mStart+index<mEnd);
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return mStart[index];
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}
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const T& operator[](size_t index) const
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{
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assert(mStart+index<mEnd);
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return mStart[index];
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}
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const T* begin() const { return this->mStart; }
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T* begin() { return this->mStart; }
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const T* end() const { return this->mEnd; }
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T* end() { return this->mEnd; }
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#if BITVECTOR_REFCNTS
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const T*getData() const { return this->mData.isNULL() ? 0 : this->mData->mPointer; }
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#else
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const T*getData() const { return this->mData; }
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#endif
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};
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// (pat) Nov 2013. This class retains the original poor behavior. See comments at VectorBase
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template <class T> class Vector : public VectorBase<T>
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{
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public:
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/** Build an empty Vector of a given size. */
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Vector(size_t wSize=0) { this->resize(wSize); }
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/** Build a Vector by shifting the data block. */
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Vector(Vector<T>& other) : VectorBase<T>(other.mData,other.mStart,other.mEnd) { other.mData=NULL; }
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/** Build a Vector by copying another. */
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Vector(const Vector<T>& other):VectorBase<T>() { this->clone(other); }
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/** Build a Vector with explicit values. */
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Vector(T* wData, T* wStart, T* wEnd) : VectorBase<T>(wData,wStart,wEnd) { }
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/** Build a vector from an existing block, NOT to be deleted upon destruction. */
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Vector(T* wStart, size_t span) : VectorBase<T>(NULL,wStart,wStart+span) { }
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/** Build a Vector by concatenation. */
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Vector(const Vector<T>& other1, const Vector<T>& other2):VectorBase<T>() {
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assert(this->mData == 0);
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this->vConcat(other1,other2);
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}
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//@{
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/** Assign from another Vector, shifting ownership. */
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void operator=(Vector<T>& other) { this->shiftMem(other); }
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/** Assign from another Vector, copying. */
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void operator=(const Vector<T>& other) { this->clone(other); }
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/** Return an alias to a segment of this Vector. */
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Vector<T> segment(size_t start, size_t span)
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{
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T* wStart = this->mStart + start;
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T* wEnd = wStart + span;
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assert(wEnd<=this->mEnd);
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return Vector<T>(NULL,wStart,wEnd);
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}
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/** Return an alias to a segment of this Vector. */
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const Vector<T> segment(size_t start, size_t span) const
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{
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T* wStart = this->mStart + start;
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T* wEnd = wStart + span;
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assert(wEnd<=this->mEnd);
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return Vector<T>(NULL,wStart,wEnd);
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}
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Vector<T> head(size_t span) { return segment(0,span); }
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const Vector<T> head(size_t span) const { return segment(0,span); }
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Vector<T> tail(size_t start) { return segment(start,this->size()-start); }
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const Vector<T> tail(size_t start) const { return segment(start,this->size()-start); }
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/**@name Iterator types. */
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//@{
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typedef T* iterator;
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typedef const T* const_iterator;
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//@}
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//@}
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};
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/** Basic print operator for Vector objects. */
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template <class T>
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std::ostream& operator<<(std::ostream& os, const Vector<T>& v)
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{
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for (unsigned i=0; i<v.size(); i++) os << v[i] << " ";
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return os;
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}
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#endif
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// vim: ts=4 sw=4
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