我试图找出我正在写入特定数据的文件中不需要的尾随数据的原因，并且不相信我在写入文件时犯了错误。
输出如下所示：
building room_numbr capacity
packard | 101 | 500 |
painter | 514 | 10 |
ÿÿÿÿÿÿÿÿÿÿ | Attempt to seek file pointer error
这Attempt to seek file pointer error是正常的，因为它表示尝试在无效流上移动文件指针时引发的异常。但是，ÿÿÿÿÿÿÿÿÿÿ使用 10 或 20 字节写入数据的固定大小文件格式既不正常也不预期。
在此处创建文件：
BinarySearchFile::BinarySearchFile(std::string file_name){
// concatenate extension to fileName
file_name += ".dat";
// form complete table data filename
data_file_name = file_name;
// create or reopen table data file for reading and writing
binary_search_file.open(data_file_name, std::ios::out | std::ios::in | std::ios::app);
if(!binary_search_file.is_open()){
binary_search_file.clear();
binary_search_file.open(data_file_name, std::ios::out);
binary_search_file.close();
binary_search_file.open(data_file_name, std::ios::out | std::ios::in | std::ios::app);
}
try{
if(binary_search_file.fail()){
throw CustomException("Unspecified table data file error");
}
}
catch (CustomException &custom_exception){ // Using custom exception class
std::cout << custom_exception.what() << std::endl;
return;
}
}
将数据写入文件
void BinarySearchFile::writeT(std::string attribute){
try{
if(binary_search_file){
for(auto start = attribute.begin(); start != attribute.end(); ++start){
binary_search_file.put(' ');
binary_search_file.put(*start);
}
binary_search_file.flush();
/*
attribute.resize(attribute.length() * 2);
const char *write_this = attribute.data();
binary_search_file.write(write_this, attribute.length());
*/
}else if(binary_search_file.fail()){
throw CustomException("Attempt to write attribute error");
}
}
catch(CustomException &custom_exception){ // Using custom exception class
std::cout << custom_exception.what() << std::endl;
return;
}
}
在此处读取数据文件：
std::string BinarySearchFile::readT(long file_pointer_location, long size_of_data)
{
try{
if(binary_search_file){
std::string data = "";
binary_search_file.seekp(file_pointer_location);
binary_search_file.seekg(file_pointer_location);
while (size_of_data > 0 ){
binary_search_file.get();
data += binary_search_file.get();
size_of_data -= 2;
}
/*
char data[20];
binary_search_file.seekp(filePointerLocation);
binary_search_file.seekg(filePointerLocation);
binary_search_file.read(data, sizeOfData);
*/
return data;
}else if(binary_search_file.fail()){
throw CustomException("Attempt to read attribute error");
}
}
catch(CustomException &custom_exception){ // Using custom exception class
std::cout << custom_exception.what() << std::endl;
}
}
读取文件并将结果打印到屏幕的代码：
while(true){
//reinitialize the catalog pointer to the beginning
catalog->setPointerBegin();
//display data
do{
if (boost::iequals((domain = catalog->getAttributeDomain()), "string")){
if(dataFile->binary_search_file_status()){
std::cout << dataFile->read_data(filePointer, 20) << " | ";
if (!writer_.fail())
writer_ << dataFile->read_data(filePointer, 20) << " | ";
}
else{
std::cout << "\n";
if (!writer_.fail())
writer_ << "\n";
return true;
}
// update the file pointer
filePointer += 20;
dataFile->set_file_pointer(filePointer);
}
else{
if(dataFile->binary_search_file_status()){
std::cout << dataFile->read_data(filePointer, 10);
if (!writer_.fail())
writer_ << dataFile->read_data(filePointer, 10);
for(int i = 0; i < 5; i++){
std::cout << " ";
if (!writer_.fail())
writer_ << " ";
}
std::cout << " | ";
if (!writer_.fail()){
writer_ << " | ";
}
}
else{
std::cout << "\n";
if (!writer_.fail()){
writer_ << "\n";
}
return true;
}
// update the file pointer
filePointer += 10;
}
} while(catalog->traverseForward() != nullptr);
std::cout << "\n";
if (!writer_.fail())
writer_ << "\n";
}
}