#pragma once

#pragma pack(push, 1)

struct DBHeader
{
	unsigned short	m_usRecordLength;		// Record length
	unsigned short	m_usHeaderLength;		// Length of the header block.
	unsigned char	m_ucFileType;			// File type
											// 00 - DB file for an keyed table
											// 02 - DB file for an unkeyed table
	unsigned char	m_ucBlockSize;			// Data block size code	01 - Block size is 1k		02 - Block size is 2k		03 - Block size is 3k (not used in 4.5)		04 - Block size is 4k
	unsigned int	m_uiRecordNum;		// Number of records in DB
	unsigned short	m_usBlockNum;			// Number of blocks in use
	unsigned short	m_usTotalBlockNum;		// Total blocks in file
	unsigned short	m_usFirstBlock;			// First data block (always 1)
	unsigned short	m_usLastBlock;			// Last block in use
	char			m_cSpace1[15];			//
	unsigned char	m_ucFieldNum;			// Number of fields
	char			m_cSpace2;
	unsigned char	m_ucKeyFieldNum;		// Number of key fields
	char			m_cSpace3[41];
	unsigned short	m_usFreeBlock;			// Block number of first free block
};															

struct DBBlock
{
	unsigned short m_usNextBlock;			// Next block number (Zero if last block)
	unsigned short m_usPrevBlock;			// Previous block number (Zero if first block)
	unsigned short m_usLastBlockOffset;		// Offset of last record in block
};

struct FieldInfo
{
	unsigned char m_ucType;//字段的类型
	unsigned char m_ucLength;//字段的长度
};

#pragma pack(pop)

//一个Record里面最多255个Field
#define MAX_FIELD 256

class CDBFile : public NiMemObject
{
private:
	DBHeader* m_pkHeader;
	char* m_pcData;
	unsigned int m_uiSize;

	unsigned int m_uiFieldOffsets[MAX_FIELD];

	unsigned int* m_puiRecordOffsets;

public:
	CDBFile(void);
	virtual ~CDBFile(void);

	virtual bool Load(const char* pcName);
	virtual void Unload();

	unsigned int GetRecordCount() const
	{
		return m_pkHeader->m_uiRecordNum;
	}

	const void* GetField(unsigned int uiRecord, unsigned int uiField)
	{
		NIASSERT( uiRecord < GetRecordCount() );
		NIASSERT( uiField < m_pkHeader->m_ucFieldNum );

		return m_pcData + (m_puiRecordOffsets[uiRecord] + m_uiFieldOffsets[uiField]);
	}

	unsigned int GetFieldLength(unsigned int uiField)
	{
		return m_uiFieldOffsets[uiField + 1] - m_uiFieldOffsets[uiField];
	}


	char GetChar(unsigned int uiRecord, unsigned int uiField)
	{
		return *(char*)GetField(uiRecord, uiField);
	}

	unsigned char GetUChar(unsigned int uiRecord, unsigned int uiField)
	{
		return *(unsigned char*)GetField(uiRecord, uiField);
	}

	short GetShort(unsigned int uiRecord, unsigned int uiField)
	{
		short sValue = *(short*)GetField(uiRecord, uiField);
		NiEndian::Swap16((char*)&sValue);

		return (sValue^0x8000);//反转符号位
	}

	unsigned short GetUShort(unsigned int uiRecord, unsigned int uiField)
	{
		unsigned short usValue = *(unsigned short*)GetField(uiRecord, uiField);
		NiEndian::Swap16((char*)&usValue);

		return (usValue^0x8000);//反转符号位
	}

	int GetInt(unsigned int uiRecord, unsigned int uiField)
	{
		int iValue = *(int*)GetField(uiRecord, uiField);
		NiEndian::Swap32((char*)&iValue);

		return (iValue^0x80000000);//反转符号位
	}

	unsigned int GetUInt(unsigned int uiRecord, unsigned int uiField)
	{
		unsigned int uiValue = *(unsigned int*)GetField(uiRecord, uiField);
		NiEndian::Swap32((char*)&uiValue);

		return (uiValue^0x80000000);//反转符号位
	}

	float GetFloat(unsigned int uiRecord, unsigned int uiField)
	{
		uint64 uiValue = *(uint64*)GetField(uiRecord, uiField);
		NiEndian::Swap64((char*)&uiValue);

		uiValue ^= 0x8000000000000000;

		double d = *reinterpret_cast<double*>(&uiValue);
		return (float)d;
	}

	void GetString(unsigned int uiRecord, unsigned int uiField, std::string& str);
	void GetTranString(unsigned int uiRecord, unsigned int uiField, std::string& str);
	void GetTranAddString(unsigned int uiRecord, unsigned int uiField, std::string& str);
	void GetUTF8String(unsigned int uiRecord, unsigned int uiField, std::string& str);
};