In some code that does a lot of file i/o using std::ofstream
, I'm caching the stream for efficiency. However, sometimes I need to change the openmode of the file (e.g. append vs truncate). Here is some similar mock code:
class Logger {
public:
void write(const std::string& str, std::ios_base::openmode mode) {
if (!myStream.is_open) myStream.open(path.c_str(), mode);
/* Want: if (myStream.mode != mode) {
myStream.close();
myStream.open(path.c_str(), mode);
}
*/
myStream << str;
}
private:
std::ofstream myStream;
std::string path = "/foo/bar/baz";
}
Does anyone know if:
ofstream
?openmode
of an ofstream
is so I can close and reopen it only when necessary?@Ari Since the default implementation doesn't allow what you want todo, you might have to encapsulate ofstream and provide the additional get/set open mode functionality in which your new object would simulate the desired behavior.
Maybe something like so
class FileOutput{
private:
ostream& streamOut;
std::ios_base::openmode currentOpemMode;
public:
FileOutput(ostream& out, std::ios_base::openmode mode)
: streamOut(out), currentOpemMode(mode){}
void setOpenMode(const std::ios_base::openmode newOpenMode){
if(newOpenMode != currentOpemMode){
currentOpemMode = newOpenMode;
updateUsedMode();
}
}
private:
void updateUsedMode(){
if(currentOpemMode == ios_base::app){ /* use seekg/tellg to move pointer to end of file */}
else if(currentOpenMode == binary){ /* close stream and reopen in binary mode*/}
//...and so on
};
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