grelationaltable.h

来自「一个由Mike Gashler完成的机器学习方面的includes neural」· C头文件 代码 · 共 79 行

#ifndef __GRELATIONALTABLE_H__
#define __GRELATIONALTABLE_H__

class GAVLTree;
class GAVLNode;
class GAVLEnumerator;
class GRelationalTable;
class GRelationalTableNode;

typedef int (*GRelationalTableFieldComparerFunc)(const void* pObjA, const void* pObjB);



// This enumerates the results returned by GRelationalTable::Query
class GRelationalTableEnumerator
{
friend class GRelationalTable;
protected:
	GAVLEnumerator* m_pFieldEnumerator;
	GRelationalTableNode* m_pInternalModel;

public:
	GRelationalTableEnumerator();
	~GRelationalTableEnumerator();

	// Returns the next object in the results. Returns NULL if there
	// are no more objects.
	void* GetNext();

	// This is an internal method. You shouldn't ever call it. The GRelationalTable
	// uses it when you perform a query to initialize the enumerator.
	void InternalInit(GAVLTree* pField, GRelationalTableFieldComparerFunc pCompareFunc, const void* pObj);
};







// A GRelationalTable is similar to a table in a relational database, except that
// it is done entirely in memory, not on disk. Instead of rows, it holds
// a collection of objects. Each object is indexed in all of the fields
// that the table defines. Since the virtual memory of the operating system
// will swap unused pages out to disk anyway, it actually behaves almost
// exactly like a table in a relational database, but it's much easier to
// work with.
class GRelationalTable
{
protected:
	int m_nFields;
	GAVLTree* m_pFields;
	GRelationalTableFieldComparerFunc* m_pComparers;

public:
	GRelationalTable(int nFields, const GRelationalTableFieldComparerFunc pCompareFuncs[]);
	~GRelationalTable();

#ifndef NO_TEST_CODE
	static void Test();
#endif // NO_TEST_CODE

	// Adds an object to the table (and indexes all of its fields)
	void AddRow(const void* pObj);

	// This method initializes pEnumerator to point to the first object where
	// field "nField" matches the same field of "pModelObj". To get the results
	// of the query, just call pEnumerator->GetNext() until you're done. It's
	// okay to reuse the same GRelationalTableEnumerator object for multiple queries. (A
	// good implementation is often to make pModelObj an instance of some base
	// class and all the objects in the table instances of a class that inherits
	// from that base class. This way the compare funcs can operate on the
	// base class, but the model objects don't need a full payload.)
	void Query(GRelationalTableEnumerator* pEnumerator, int nField, const void* pModelObj);
};


#endif // __GRELATIONALTABLE_H__