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/* Copyright (c) 1998, 1999, 2003, 2004 Lance Arsenault, (GNU GPL (v2+))
*/
// The class FileReader is a Field that can read() another Field (the
// source Field) without effecting the reading by the methods,
// read(void), and rewind(void) of the source Field object that it is
// reading with. The FileReader makes it so that you can have more
// than one object read the data in a Field. This saves having to
// have more than one copy of the data in memory. An example when
// this is needed is when your wish to read two fields which are
// derived from the same series of numbers. The two Fields can share
// the data if one (or both) of them is a FieldReader. This is some
// kind of clone of the source Field, without the memory for the data
// in the Field. This saves memory. We do this stuff because there
// are many different kinds of fields which store and retrieve the
// series (Field) data in many ways.
class Field;
class FieldReader : public Field
{
public:
FieldReader(Field *f);
~FieldReader(void);
// read the list and advance the pointer to the next value in the
// series.
virtual inline value_t read(void)
{
return field->read(dequeuer);
}
// move the pointer to the first value in the series.
virtual inline void rewind(void)
{
field->rewind(dequeuer);
}
virtual inline count_t numberOfValues(void) { return field->numberOfValues(); }
// append the value to the end of the list.
// virtual write(T value);
// Find the minimum values in the range of indexes. Indexing starts
// at 0. i_max=-1 means upto the numberOfValues.
virtual inline value_t max(count_t i_max=((count_t) -1), count_t i_min=0)
{
return field->max(i_max, i_min);
}
// find the minimum values in the range of indexes. Indexing starts
// at 0. i_max=-1 means upto the numberOfValues.
virtual inline value_t min(count_t i_max=((count_t) -1), count_t i_min=0)
{
return field->min(i_max, i_min);
}
// Is monotonically increasing, like time.
virtual inline bool isIncreasing(void) { return field->isIncreasing(); }
virtual inline bool isDecreasing(void) { return field->isDecreasing(); }
virtual void *makeDequeuer(count_t NumberOfValues);
virtual void destroyDequeuer(void *dequeuer);
// The FieldReader object can use this to read.
virtual inline value_t read(void *dequeuer)
{
return field->read(dequeuer);
}
// The FieldReader object can use this to rewind.
virtual inline void rewind(void *dequeuer)
{
field->rewind(dequeuer);
}
private:
friend class Field;
// next is used in a linked list of FieldReaders is kept in the
// source Field object in Field::fieldReader.
FieldReader *next;
void *dequeuer;
// The data source for this Field.
Field *field;
};
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