open.c

一个用C编写的简单的关系数据库系统

int Open(DBF * dbf_name, DBF * cur_dbf, char * commond, char * open_style)
{
	FILE * fp;
	char open_name[TABLE_NAME_LENGTH];/*记录打开的表名*/
	char style;/*记录打开方式*/
	int i = 0;
	int opened_no = -1;/*记录打开的表在表数组中的序号*/

	commond = strtok(commond," ");
	commond = strtok(NULL," ");

	if (commond == NULL)
	{
		puts("	命令错误，请输入关系名");
		return ERROR;
	}
	if (strlen(commond) > TABLE_NAME_LENGTH)
	{
		puts("	输入表名错误");
		return ERROR;
	}
	strcpy(open_name,commond);
	for (i=0; i<MAX_OPENED_COUNT; i++)
	{
		if (strcmpi(open_name,dbf_name[i].dhName) == 0)
		{
			puts("	该表已经打开，请用用use命令使用该表");
			return ERROR;
		}
	}
	commond = strtok(NULL, " ");
	if (commond == NULL)
	{
		puts("	请输入打开方式!!!");
		return ERROR;
	}
	if (strlen(commond) > 1)
	{
		puts("	打开方式错误!!!");
		return ERROR;
	}
	else
	{
		switch (* commond) {
		case 'r':
		case 'w':
		case 'a':
			style = * commond;
			break;
		default :
			puts("	打开方式错误!!!");
			return ERROR;
		}
	}
	commond = strtok(NULL, " ");
	if (commond != NULL)
	{
		printf("	命令错误，多余字符串 %s\n", commond);
		return ERROR;
	}
	fp = fopen(open_name,"rb");
	if (fp == NULL)
	{
		puts("	打开错误，该表不存在!!!");
		return ERROR;
	}
	for (i=0; i<MAX_OPENED_COUNT; i++)
	{
		if (dbf_name[i].dhID == -1)
		{
			opened_no = i;
			cur_dbf = &(dbf_name[i]);
			break;
		}
	}
	fread(cur_dbf,sizeof(DBF),1,fp);
	open_style[opened_no] = style;
	cur_dbf->dhID = opened_no;
	printf("	%s opened in %c style!!\n",open_name,style);
	printf("   记录格式：");
	for (i=0; i<cur_dbf->dhFieldCount; i++)
	{
		switch (cur_dbf->dbf_struct[i].dhFieldType) {
		case Int:
			printf("%s(int)   ",cur_dbf->dbf_struct[i].dhFieldName);
			break;
		case Float:
			printf("%s(float)   ",cur_dbf->dbf_struct[i].dhFieldName);
			break;
		default :
			printf("%s(string %d)   ",cur_dbf->dbf_struct[i].dhFieldName,cur_dbf->dbf_struct[i].dhFieldLen);
			break;
		}
	}
	puts("");	
	fclose(fp);
	return opened_no;
}