seek.c

来自「一个用C编写的简单的关系数据库系统」· C语言 代码 · 共 40 行

void Seek(DBF * dbf_name, char * commond, FILE ** opened_fp)
{
	unsigned j = 0;

	int tempInt = 0;
	int fushu = FALSE;

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

	if (commond == NULL)
	{
		puts("	请输入偏移值");
		return;
	}
	
	if (commond[j] == '-')
	{
		fushu = TRUE;
		j++;
	}
	for (;j<strlen(commond); j++)
	{
		if (!isdigit(commond[j]))
		{
			printf("	输入错误，%s 改为整型\n",commond);
			return;
		}
		tempInt = tempInt * 10 + (int)commond[j] - 48;
	}
	if (fushu)
		tempInt = 0 - tempInt;
	if (dbf_name->dhRecNO + tempInt < 0)
		dbf_name->dhRecNO = 0;
	else if (dbf_name->dhRecNO + tempInt >= dbf_name->dhRecCount)
		dbf_name->dhRecNO = dbf_name->dhRecCount - 1;
	else
		dbf_name->dhRecNO = dbf_name->dhRecNO + tempInt;
	return;
}