Reading binary file C++

Question

Please, help me. I can't read binary file. The file's length is 198944, but my code reads 374. I tried to use fread, ifstream, WinAPI ReadFile. This is the function that reads file:

std::string ReadThisFile(std::string aPath) {
   FILE *inputstream = fopen(aPath.c_str(),"rb");
   long size;
   size_t result; 
   fseek(inputstream,0,SEEK_END); 
   size = ftell(inputstream); 
   rewind(inputstream); 
   char *buff = new char [size];
   result = fread (buff,1,size,inputstream); 
   std::string ret=buff; 
   fclose(inputstream); 
   delete[]buff; 
   return ret; 
}

File sample

Any help is needed, thank you!

Are you using strlen to get the final size? You can't do store binary content in a string. — Mahmoud Al-Qudsi
– Mahmoud Al-Qudsi, Commented Feb 15, 2013 at 6:33
Is the file supposed to be an ASCII text file you want to load into a single std::string? If not, use a different container. (like a std::vector<unsigned char> or something similar). — WhozCraig
– WhozCraig, Commented Feb 15, 2013 at 6:42
Btw, fseek(binary_stream, offset, SEEK_END) is not guaranteed to work (according to the C standard from 1999). — Alexey Frunze
– Alexey Frunze, Commented Feb 15, 2013 at 7:15

Jonas Byström · Accepted Answer · 2013-02-15 06:47:03Z

1

As long as you're aware of that the std::string that you return contains binary data, replace

std::string ret=buff;

with

std::string ret(buff, size);

answered Feb 15, 2013 at 6:47

Jonas Byström

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Some programmer dude · Accepted Answer · 2013-02-15 06:34:26Z

0

You can't put binary data in a string. Remember that a string is terminated by the special character '\0' which is the same as the value zero. If the binary data contains a zero, that is the same as the end of the string.

You should probably use a std::vector<int8_t> to store binary data.

answered Feb 15, 2013 at 6:34

Some programmer dude

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1 Comment

Boleslav Over a year ago

Thanks. Yes, that was my problem.

Bernhard Barker · Accepted Answer · 2013-02-15 06:42:15Z

0

The problem is here:

std::string ret = buff;

According to this, it:

"Copies the null-terminated character sequence (C-string) pointed by s."

So it stops as soon as a 0x00 character is reached.

If you were to return buff (which is a dangerous practice) or have your function take a char array as an input parameter and merely store it there, it should work. And you may want to return a length indicator, since otherwise C++ will not know how large the array is.

answered Feb 15, 2013 at 6:42

Bernhard Barker

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1 Comment

Boleslav Over a year ago

Thanks. Yes, that was my problem.

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