tablecreate.c

linux下

#include<stdlib.h>
#include<stdio.h>
#include<sys/types.h>
#include<fcntl.h>
#include<sys/stat.h>
#include<unistd.h>
#include<string.h>
#include"table.h"



T_TableDes* table_create( const char *szTableName,T_ColumnInfo* pColumnInfos,unsigned int TotalColumns)
{

	T_TableHeader  *pTableHeader;
	unsigned int   nRecSize=0;
	T_RecField*		pRecFields;
	int nOffset=0;
	int i,j;
	long  fd;
	T_TableDes*  pTableDes;
	int fsyncd;

	if((fd=open(szTableName,O_CREAT|O_RDWR|O_SYNC|O_TRUNC,S_IFREG|S_IRWXU|S_IRWXG|S_IROTH))<0)/*�ļ,�����ʧ� */
	{
		perror("create");
	 	exit(EXIT_FAILURE);
	}
	pTableHeader=malloc(sizeof(T_TableHeader)); 	/* Ϊ�ṹ��ڴ� */
	pTableHeader->nColumnCount=TotalColumns;		/* ʼ��Ϣ*/
	pTableHeader->nValidRecordCount=0;
	pTableHeader->nColSize=sizeof(T_ColumnInfo);    /*��㶨�*/
	
	for(i=0;i<TotalColumns;i++)						/*����ijȲд��ṹ*/
	{
		switch(pColumnInfos[i].ColumnType)
		{
			case conchars:
				nRecSize+=MAX_CONSTRINGLEN;
				break;                               
			case shortint: 
				nRecSize+=sizeof(short);
				break;
			case longint:
				nRecSize+=sizeof(long int);
				break;
			case floatval:
				nRecSize+=sizeof(float);
				break;
		}
	}
	pTableHeader->nRecSize=nRecSize;
	pTableHeader->nDataOffset=sizeof(T_TableHeader)+(sizeof(T_ColumnInfo)*TotalColumns)+(sizeof(T_RecField)*TotalColumns);
	
	
	//lseek(fd,(long)sizeof(NULL),SEEK_SET);			/*�ṹд��*/
	lseek(fd,0,SEEK_SET);
	write(fd,pTableHeader,sizeof(T_TableHeader));

	write(fd,pColumnInfos,sizeof(T_ColumnInfo)*TotalColumns);/*����*/
	
	pRecFields=malloc(sizeof(T_RecField)*TotalColumns);		/*void* pField=new Field[nColumnCount]????*/

	for(j=0;j<TotalColumns;j++)			/*�ֶ��pColumnInfosķָ�����T_RecField�,ʼT_RecField*/
	{
		pRecFields[j].nFieldStart=nOffset;
		pRecFields[j].nFieldSize=GetFieldSize(pColumnInfos[j].ColumnType);
		nOffset+=pRecFields[j].nFieldSize;
	}

	write(fd,pRecFields,sizeof(T_RecField)*TotalColumns);/*�ηָ��ϢpRecFieldд��*/
    
	pTableDes=malloc(sizeof(T_TableDes));                    /*ʼ��еı��ṹpTableDes*/
	strcpy(pTableDes->szTableName,szTableName);
	pTableDes->fd=fd;                      /*�벻�?*/
	pTableDes->pTableHeader=pTableHeader;
	pTableDes->pColInfos=pColumnInfos;
	pTableDes->pRecFields=pRecFields;
	pTableDes->TableStatus=0;

	if((fsyncd=fsync(fd))==-1)		   	/*�fdдش��*/
	{
		perror("file synchronize failed");
		exit(EXIT_FAILURE);             /*free���?*/
		}

	return  pTableDes;

}

unsigned int GetFieldSize(T_ColumnType ColumnType)   /*�ֶ�olumnType��ֶ�ݳ�*/
{
	unsigned int nSize;
	switch(ColumnType)
		{
			case conchars:
				nSize=MAX_CONSTRINGLEN;
				break; 
			case shortint:
				nSize=sizeof(short);
				break;
			case longint:
				nSize=sizeof(long int);
				break;
			case floatval:
				nSize=sizeof(float);
				break;
		}
	return nSize;
}