C++ reading and writing a file results in garbage

Question

I'm simply trying to read a small 1KB binary file into a buffer and then write the buffer back to the disk. It seems that for some files the outputfile is completely different from the Inputfile, what am I doing wrong? Thank you very much.

std::ifstream myfile; myfile.open (testinput.rar); myfile.seekg (0, myfile.end); filesize = myfile.tellg(); myfile.seekg (0, myfile.beg); char *mybuffer= new char[filesize]; myfile.read(mybuffer,filesize); myfile.close(); ofstream myfile3; myfile3.open ("testoutput.rar"); for(unsigned int i=0; i<filesize; i++) myfile3 << mybuffer[i]; myfile3.close();

It's been a while, but I think the file variable needs to be set to binary mode for binary data... — abiessu
– abiessu, Commented Oct 23, 2013 at 14:58
Should there be quotes round the parameter in myfile.open (testinput.rar);? Can't imagine that would even build. — Grimm The Opiner
– Grimm The Opiner, Commented Oct 23, 2013 at 14:59
@user1158692 Yes, of course there should be quotes around the file name parameter. cplusplus.com/doc/tutorial/files — Bucket
– Bucket, Commented Oct 23, 2013 at 15:06

Andriy · Accepted Answer · 2013-10-23 15:01:47Z

1

You have to open the file as binary.

myfile.open ("testinput.rar", std::ios::binary);

answered Oct 23, 2013 at 15:01

Andriy

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Bucket · Accepted Answer · 2013-10-23 15:01:54Z

myfile3 should be opened in binary mode:

myfile3.open("testoutput.rar", ios::out | ios::binary);

Additionally, you may want to consider using write() to modify files:

myfile3.write(mybuffer[i], sizeOfBuffer);

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