path-array.hpp

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/*
  PATH-ARRAY.hpp  -  sequence of path-like component-IDs in fixed storage
 
   Copyright (C)
     2017,            Hermann Vosseler <Ichthyostega@web.de>
 
 **Lumiera** is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the
 Free Software Foundation; either version 2 of the License, or (at your
 option) any later version. See the file COPYING for further details.
 
*/
 
 
#ifndef LIB_PATH_ARRAY_H
#define LIB_PATH_ARRAY_H
 
#include "lib/error.hpp"
#include "lib/symbol.hpp"
#include "lib/iter-adapter.hpp"
#include "lib/meta/variadic-helper.hpp"
#include "lib/format-obj.hpp"
#include "lib/util.hpp"
 
#include <algorithm>
#include <utility>
#include <string>
#include <memory>
#include <array>
 
 
namespace lib {
  namespace error = lumiera::error;
  
  using std::string;
  using std::forward;
  using lib::Literal;
  using util::unConst;
  using util::isnil;
  
  namespace con { // Implementation helper: flexible heap based extension storage....
    
    class Extension
      {
        using PStorage = Literal*;
        
        PStorage storage_;
        
        
        static size_t&
        size (PStorage& p)
          {
            REQUIRE (p);
            return reinterpret_cast<size_t&> (p[0]);
          }
        
        PStorage
        newCopy()  const
          {
            size_t siz = 1 + size (unConst(this)->storage_);
            const char** alloc = new const char*[siz];
            std::copy (storage_, storage_+siz, alloc);
            return reinterpret_cast<PStorage> (alloc);
          }
        
        
      public:
       ~Extension()
          {
            if (storage_)
              delete[] storage_;
          }
        
        Extension()  noexcept
          : storage_{nullptr}
          { }
        
        template<typename...ELMS>
        explicit
        Extension (ELMS&& ...elms)
          : storage_{new Literal[1 + sizeof...(ELMS)]}                        // proper alignment maintained here (TICKET #1204)
          {
            size(storage_) = sizeof...(ELMS);
            new(storage_+1) Literal[sizeof...(ELMS)] {forward<ELMS>(elms)...};
          }
        
        Extension (Extension const& r)
          : storage_{r.storage_? r.newCopy() : nullptr}
          { }
        
        Extension (Extension&& rr)  noexcept
          : storage_{nullptr}
          {
            if (rr.storage_)
              std::swap (storage_, rr.storage_);
          }
        
        Extension& operator= (Extension o)
          {
            std::swap (storage_, o.storage_);
            return *this;
          }
        
        
        
        operator bool() const { return not empty(); }
        bool empty()    const { return not storage_;}
        
        size_t
        size()  const
          {
            return storage_? size(unConst(this)->storage_)
                           : 0;
          }
        
        Literal const&
        operator[] (size_t idx)  const
          {
            REQUIRE (storage_ and idx < size());
            return storage_[1+idx];
          }
        
        size_t
        indexOf (Literal const* pos)  const
          {
            REQUIRE (isValid (pos));
            return pos - (storage_+1);
          }
        
        
        bool
        isValid (Literal const* pos)  const
          {
            return storage_
               and storage_ < pos
               and pos < storage_ + (1 + size (unConst(this)->storage_));
          }
        
        void
        resizeTo (size_t cnt)
          {
            if (cnt > size())
              { // need more storage
                if (storage_)
                  { // copy content to new expanded storage
                    auto target = new const char* [cnt+1];
                    auto pos = std::copy (storage_, storage_+1+size(), target);
                    for ( ; pos < target+1+cnt; ++pos)
                      *pos = nullptr;
                    delete[] storage_;
                    storage_ = reinterpret_cast<PStorage> (target);
                  }
                else // allocate and init empty
                  storage_ = new Literal [cnt+1];
                
                size (storage_) = cnt;
                return;
              }
            if (not storage_) return;
            if (cnt == 0)
              {
                delete[] storage_;
                storage_ = nullptr;
              }
            else
              size(storage_) = cnt;
              // excess elements now unreachable
              // note: delete[] knows original size
          }
      };
  }//(End)Implementation helper
  
  
  
  using meta::pickArg;
  using meta::pickInit;
  using meta::IndexSeq;
  
  template<size_t chunk_size>
  class PathArray
    {
      static_assert (0 < chunk_size, "PathArray chunk_size must be nonempty");
      
      using LiteralArray = std::array<Literal, chunk_size>;
      
      LiteralArray elms_;
      con::Extension tail_;
      
      template<size_t...prefix, size_t...rest, typename...ARGS>
      PathArray (IndexSeq<prefix...>
                ,IndexSeq<rest...>
                ,ARGS&& ...args)
        : elms_{pickInit<prefix, CStr> (forward<ARGS>(args)...) ...}
        , tail_{pickArg<rest>          (forward<ARGS>(args)...) ...}
        {
          this->normalise();
        }
      
      template<typename...ARGS>
      struct Split
        {
          using Prefix = meta::BuildIndexSeq<chunk_size>::Ascending;
          using Rest   = meta::BuildIdxIter<ARGS...>::template After<chunk_size>;
        };
      
    public:
      template<typename...ARGS>
      explicit
      PathArray (ARGS&& ...args)
        : PathArray(typename Split<ARGS...>::Prefix()
                   ,typename Split<ARGS...>::Rest()
                   ,forward<ARGS> (args)...)
        { }
      
      PathArray(PathArray&&)                  = default;
      PathArray(PathArray const&)             = default;
      PathArray(PathArray& o)  : PathArray((PathArray const&)o) { }
      PathArray& operator= (PathArray const&) = default;
      PathArray& operator= (PathArray &&)     = default;
      
      
      size_t
      size()  const
        {
          return tail_? chunk_size + tail_.size()
                      : findInlineEnd() - elms_.begin();
        }
      
      size_t
      leafLevel()  const
        {
          return empty()? 0 : size()-1;
        }
      
      bool
      empty()  const
        {
          return not elms_[0]; // normalise() ensures nonnull unless completely empty
        }
      
      operator string()  const;
      
      
      Literal const&
      operator[] (size_t idx)  const
        {
          Literal* elm = unConst(this)->getPosition (idx);
          if (not elm)
            throw error::Invalid ("Accessing index "+util::toString(idx)
                                 +" on PathArray of size "+ util::toString(size())
                                 ,error::LUMIERA_ERROR_INDEX_BOUNDS);
          return *elm;
        }
      
      size_t
      indexOf (Literal const& content)  const
        {
          if (elms_.begin() <= &content and &content < elms_.end())
            return &content - elms_.begin();
          if (tail_.isValid (&content))
            return chunk_size + tail_.indexOf (&content);
          
          throw error::Invalid ("Referred content "+util::toString(&content)
                               +" is not located within the storage of PathArray "
                               +string(*this));
        }
      
      
    protected:  /* ==== Iteration control API for IterAdapter ==== */
      
      friend void
      iterNext (const PathArray*, const Literal*& pos)
      {
        ++pos;
      }
      
      friend bool
      checkPoint (const PathArray* src, const Literal*& pos)
      {
        REQUIRE (src);
        if (pos == src->elms_.end() and src->tail_)
          pos = &src->tail_[0];
        else
        if (not src->isValid (pos))
          {
            pos = nullptr;
            return false;
          }
        ENSURE (  (src->elms_.begin() <= pos and pos < src->elms_.end())
                or src->tail_.isValid(pos));
        return true;
      }
      
    public:
      using const_iterator = lib::IterAdapter<Literal const*, PathArray const*>;
      using iterator = const_iterator;
      
      using value_type = Literal;
      using reference = Literal&;
      using const_reference = Literal const&;
      
      iterator begin()  const { return firstNonempty(); }
      iterator end()    const { return iterator{}; }
      
      friend iterator begin(PathArray const& pa) { return pa.begin();}
      friend iterator end  (PathArray const& pa) { return pa.end();  }
      
      
      
    private: /* ===== implementation details ===== */
      
      bool
      isValid (Literal const* pos)  const
        {
          return pos
             and (tail_.isValid(pos)
                  or (elms_.begin() <= pos and pos < elms_.end()
                      and *pos));
        }
      
      iterator
      firstNonempty ()  const
        {
          iterator startPos{this, elms_.begin()};
          while (startPos and isnil (*startPos))
            ++startPos;
          return startPos;
        }
      
      Literal const*
      findInlineEnd() const
        {
          Literal const* lastPos = elms_.begin() + chunk_size-1;
          Literal const* beforeStart = elms_.begin() - 1;
          while (lastPos != beforeStart and not *lastPos)
            --lastPos;
          return ++lastPos; // at start if empty, else one behind the last
        }
      
      
      /* ===== manipulation by UICoord and Builder subclasses ===== */
    protected:
      Literal*
      getPosition (size_t idx)
        {
          Literal const* elm =nullptr;
          if (idx < chunk_size)
            elm = elms_[idx]? &elms_[idx] : nullptr;
          else
          if (idx-chunk_size < tail_.size())
            elm = &tail_[idx-chunk_size];
          
          return const_cast<Literal*> (elm);
        }
      
      Literal*
      expandPosition (size_t idx)
        {
          if (chunk_size <= idx and size() <= idx)
            tail_.resizeTo(idx+1 - chunk_size);
          if (idx < chunk_size)
            return elms_.begin() + idx;
          
          ENSURE (idx-chunk_size < tail_.size());
          return const_cast<Literal*> (&tail_[idx-chunk_size]);
        }
      
      void
      setContent (Literal* pos, const char* val)
        {
          REQUIRE (pos);
          *reinterpret_cast<const char**> (pos) = val;
        }
      
      void
      truncateTo (size_t newSize)
        {
          if (newSize < chunk_size)
            {
              Literal* end = elms_.end();
              Literal* pos = getPosition(newSize);
              if (pos)
                for ( ; pos!=end; ++pos)
                  setContent (pos, nullptr);
              tail_.resizeTo (0);
            }
          else
            if (newSize-chunk_size < tail_.size())
              tail_.resizeTo (newSize - chunk_size);
            // otherwise: keep current size, don't grow
        }
      
      void
      normalise()
        {
          if (size() == 0) return;
          CStr fill = Symbol::EMPTY;
          
          Literal* end = elms_.end();
          Literal* pos = elms_.begin();
          for ( ; pos!=end; ++pos)
            if (isnil (*pos))
              setContent (pos, fill);
            else
              if (fill==Symbol::EMPTY)
                fill = Symbol::ANY;
          
          if (tail_)
            {
              // normalise data in extension storage
              pos = getPosition (chunk_size);
              end = pos + tail_.size();
              for ( ; pos!=end; ++pos)
                if (isnil (*pos))
                  setContent (pos, fill);
                else
                  if (fill==Symbol::EMPTY)
                    fill = Symbol::ANY;
            }
          
          size_t idx = size();
          // trim trailing fill
          while (idx and fill == *getPosition (--idx))
            setContent (getPosition(idx), nullptr);
          
          if (idx >= chunk_size-1)
            tail_.resizeTo (idx+1 - chunk_size);
          else
            tail_.resizeTo (0);
        }
    };
  
  
  
  
  template<size_t chunk_size>
  inline
  PathArray<chunk_size>::operator string()  const
  {
    if (this->empty()) return "";
    
    string buff;
    size_t expectedLen = this->size() * 10;
    buff.reserve (expectedLen); // heuristic
    for (Literal elm : *this)
      buff += elm + "/";
    
    // chop off last delimiter
    size_t len = buff.length();
    ASSERT (len >= 1);
    buff.resize(len-1);
    return buff;
  }
  
  
  
  template<size_t cl, size_t cr>
  bool
  operator== (PathArray<cl> const& l, PathArray<cr> const& r)
  {
    if (l.size() != r.size()) return false;
    
    auto lp = l.begin();
    auto rp = r.begin();
    while (lp and rp)
      {
        if (*lp != *rp) return false;
        ++lp;
        ++rp;
      }
    return isnil(lp) and isnil(rp);
  }
  
  template<size_t cl, size_t cr>
  bool
  operator!= (PathArray<cl> const& l, PathArray<cr> const& r)
  {
    return not (l == r);
  }
  
  
  
}// namespace lib
#endif /*LIB_PATH_ARRAY_H*/