求教怎么完成剩下那个功能（修改资金账户）
/*程序的功能：添加新流水账记录，修改资金账户，查询资金账户最后余额。
*/
#include"stdio.h"
#include"stdlib.h"
long size; //当前最近一次的流水号
struct LogData{ //记录的结构
long logid; //记录ID
char logdate[11]; //记录发生日期
char lognote[15]; //记录事件说明
double charge; //发生费用：负表示支出，正表示收入
double balance; //余额
};
int inputchoice() //选择参数
{
int mychoice;
printf("\nEnter your choice: \n");
printf("1 - Add a new cash LOG. \n2 - List All Cash LOG. \n");
printf("3 - Query Last Cash LOG. \n4 - Modify the Cash LOG. \n");
printf("0 - End program. \n");
scanf("%d",&mychoice);
return mychoice;
}
long getLogcount (FILE *cfptr) //获取文件记录总数
{
long begin,end,logcount;
fseek(cfptr, 0L, SEEK_SET);
begin=ftell(cfptr);
fseek(cfptr,size,SEEK_END);
end=ftell(cfptr);
logcount=(end-begin)/size-1;
return logcount;
}
void ListAllLog(FILE *cfptr) //列出所有收支流水账
{
struct LogData log;
fseek(cfptr,0L,SEEK_SET); //定位指针到文件开始位置
fread(&log,size,1,cfptr);
printf("logid logdate lognote charge balance \n");
while(!feof(cfptr))
{
printf("% 6ld %-11s %-15s %10.2lf %10.2lf\n",log.logid,log.logdate,log.lognote,log.charge,log.balance);
fread(&log,size,1,cfptr);
};
}
void QueryLastLog(FILE *cfptr) //查询显示最后一条记录
{
struct LogData log;
long logcount;
logcount=getLogcount(cfptr);
if(logcount>0) //表示有记录存在
{
fseek(cfptr,size* (logcount-1),SEEK_SET); //定位最后记录
fread(&log,size,1,cfptr); //读取最后记录
printf("The last log is: \n");
printf("logid:%-6ld \nlogdate:%-11s \nlognote:%-15s \n",log.logid,log.logdate,log.lognote);
printf("charge:%-10.2lf \nbalance:%-10.2lf \n",log.charge,log.balance); //显示最后记录内容
}
else printf("no logs in file! \n");
}
void AddNewLog(FILE *cfptr) //添加新纪录
{
struct LogData log,lastlog;
long logcount;
printf("Input logdate(format:2006-01-01):");
scanf("%s",log.logdate);
printf("Input lognote:");
scanf("%s",log.lognote);
printf("Input Charge(Income+ and expend-):");
scanf("%lf",&log.charge);
logcount=getLogcount(cfptr); //获取记录数
if(logcount>0)
{
fseek(cfptr,size* (logcount-1),SEEK_SET);
fread(&lastlog,size,1,cfptr); //读入最后记录
log.logid=lastlog.logid+1; //记录号按顺序是上次的号+1
log.balance=log.charge+lastlog.balance;
}
else //如果文件是初始状态，记录数为0
{
log.logid=1;
log.balance=log.charge;
}
rewind(cfptr);
printf("logid=%ld \n",log.logid);
fwrite(&log,sizeof(struct LogData),1,cfptr); //写入记录
}
void UpdateLog(FILE *cfptr) //修改资金账户
{
//待补充
}
FILE *openfile(char *openmode) //打开文件
{
FILE *fp;
if((fp=fopen("cashbox.dat",openmode))==NULL)
{
printf("can not open file cashbox.dat! \n");
exit(0);
}
return (fp);
}
int main(void)
{
FILE *fp;
int choice;
size=sizeof(struct LogData);
while((choice=inputchoice())!=0)
{
switch(choice)
{
case 1:
fp=openfile("ab+");
AddNewLog(fp);
fclose(fp);
break;
case 2: //列出所有的收入支出情况
fp=openfile("rb");
ListAllLog(fp);
fclose(fp);
break;
case 3:
fp=openfile("rb");
QueryLastLog(fp);
fclose(fp);
break;
case 4:
fp=openfile("rb");
UpdateLog(fp);
break;
default:
printf("Input Error.");
break;
}
}
if(fclose(fp))
{
printf("Can not close the file! \n");
exit(0);
}
return 0;
}
