弗雷德没有看到EOF C++
我编写了一个具有以下函数的二进制文件:弗雷德没有看到EOF C++,c++,file-io,binaryfiles,C++,File Io,Binaryfiles,我编写了一个具有以下函数的二进制文件: int writeFile(FILE *f_to, void *from, int size){ int write = fwrite(from, 1, size, f_to); if (write == size) return 0; else return -1; //fails } void createDataFile(const char *fname) { FILE * out_
int writeFile(FILE *f_to, void *from, int size){
int write = fwrite(from, 1, size, f_to);
if (write == size)
return 0;
else
return -1; //fails
}
void createDataFile(const char *fname)
{
FILE * out_file;
out_file = fopen(fname, "ab+");
if (out_file == NULL){
std::cout << "error no file to be written" << endl;
}
writeFile(out_file, (INT32U*)&(newPtr->hdr), sizeof(S_MES_HDR));
writeFile(out_file, (INT32U*)&(newPtr->mon_hdr), sizeof(S_MON_HEADER));
writeFile(out_file, (INT32U*)&(newPtr->data_hdr), sizeof(S_MON_DATA_HEADER));
writeFile(out_file, (INT32U*)&(newPtr->data), ((ptr->hdr.id.data_len*sizeof(INT32U)) - sizeof(S_MON_HEADER)-sizeof(S_MON_DATA_HEADER)));
cout<< sizeof(S_MES_HDR)<<endl;
cout<< sizeof(S_MON_HEADER)<<endl;
cout<< sizeof(S_MON_DATA_HEADER)<<endl;
cout<<((ptr->hdr.id.data_len*sizeof(INT32U)) - sizeof(S_MON_HEADER)-sizeof(S_MON_DATA_HEADER))<<endl;
fclose(out_file);
S_TERM_PACKET *monPacketPointer2;
monPacketPointer2 = new S_TERM_PACKET;
out_file = fopen(fname, "ab+");
createMessage(monPacketPointer2, 1, 'R', 6, out_file);
fclose(out_file);
S_TERM_PACKET *monPacketPointer3;
monPacketPointer3 = new S_TERM_PACKET;
out_file = fopen(fname, "ab+");
createMessage(monPacketPointer3, 3, 'M', 3, out_file);
fclose(out_file);
cout << "output file has been created." << endl;
}
int main()
{
createDataFile("test.data");
return 0;
}
我得到了以下输出:。写入test.data文件的总字节数为*16+8+4+403=204字节
现在,当我使用以下函数读取test.data文件时:
int ReadFile(FILE *f_in, void *dest, int size)
{
int read = fread(dest, 1, size, f_in);
if (read == size){
return 0;
}
return -1;
}
void readData(const char* id, Structure*head)
{
ReadFile(p_file, (INT32U*)&termPacketPointer->hdr, sizeof(S_MES_HDR));
cout << "total read size:" << sizeof(S_MES_HDR)+(termPacketPointer-> hdr.id.data_len)*sizeof(INT32U) << endl;
cout << "data len:" << (termPacketPointer->hdr.id.data_len) << endl;
ReadFile(p_file, (INT32U*)&termPacketPointer->term_data, (termPacketPointer-> hdr.id.data_len)*sizeof(INT32U));
}
int main()
{
// createDataFile("test.data");
File * p_file=fopen("test.data", "rb");
if(p_file==NULL)
return -1;
if (!feof(p_file))
{
readData("25", head);
}
if (!feof(p_file))
{
readData("25", head);
}
if (!feof(p_file))
{
readData("25", head);
}
if (!feof(p_file))
{
readData("25", head);
}
fclose(p_file);
return 0;
}
最后,我得到了以下输出和运行时错误
总读取大小:68
数据长度:13
总读取大小:68
数据长度:13
总读取大小:68
数据长度:13
总读取大小:210756
数据长度:52685
所以,在读取68*3=204字节后,它并没有停止并继续读取,这等于我写入文件的字节数。我的假设是,它没有看到eof,但我知道fclose会自动放置它。我怎样才能解决我的问题?提前感谢。一件非常有用的事情是实际检查fread的退货状态。内部函数执行此操作并返回-1表示错误,但main中的调用不会检查状态
在许多实现中,只有在尝试读取文件末尾之后,feof才会变为真。您得到了作为输出的PNG图像吗?这是意想不到的行为。