iobuffer.hpp

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#pragma once
#include <fc/io/iostream.hpp>
#include <fc/exception/exception.hpp>
 
namespace fc
{
  class size_stream : public virtual fc::ostream
  {
      public:
      size_stream( size_t s  = 0):_size(s){}
 
      size_t size()const { return _size; }
      size_t seek( size_t pos ) { return _size = pos; }
 
      virtual size_t     writesome( const char* /*ignored buf*/, size_t len )
      {
         _size += len;
         return len;
      }
 
      virtual void       close(){}
      virtual void       flush(){}
 
      private:
      size_t            _size;
  };
 
  
  class iobuffer : public virtual fc::iostream
  {
      public:
      iobuffer( size_t s )
      :_data(s){}
 
      size_t size()const { return _data.size(); }
      size_t pos()const  { return _pos;  }
      size_t seek( size_t pos ) 
      { 
         return _pos = std::min<size_t>(_data.size(),pos); 
      }
 
      virtual size_t     readsome( char* buf, size_t len )
      {
          auto avail = std::min<size_t>( _data.size()-_pos, len );
          if( avail == 0 ) throw fc::eof_exception();
          memcpy( buf, _data.data()+_pos, avail );
          _pos += avail;
          return avail;
      }
      char               peek()const 
      { 
          if( _pos == _data.size() ) throw fc::eof_exception();
         return _data[_pos]; 
      }
 
      virtual size_t     writesome( const char* buf, size_t len )
      {
         auto avail = std::max<size_t>( _data.size(), _pos + len );
         _data.resize(avail);
         memcpy( _data.data()+_pos, buf, len );
         _pos += avail;
         return avail;
      }
      char* data() { return _data.data(); }
 
      virtual void       close(){}
      virtual void       flush(){}
 
      private:
        std::vector<char> _data;
        size_t            _pos;
  };
 
}