Get file size of file that contains EOF
How can I get the file size of a file if the file contains EOF? I tried
but it's stopping at the first EOF (0 byte) it finds.Code:in_file.open(fname.c_str(), ios::binary); if (in_file == NULL) return -1; in_file.seekg(0, ios::end); fsize = in_file.tellg(); in_file.seekg(0, ios::beg); tmp_buffer = new char[fsize]; in_file.get(tmp_buffer, fsize, '\0'); in_file.close();
Try this:
Code:std::fstream iFile(filename.c_str(), std::ios::ate); // ios::ate == At the end of the file. int size = iFile.tellg(); // Get the size of the file. iFile.seekg(0, std::ios::beg); // Seek to the beginning of the file.
No luck
EDIT: Actually, it got the file size correctly. So, that worked. Let me play around with the rest of the code and I'll post my results.
Last edited by ChadJohnson; 03-12-2005 at 09:04 PM.
Well, I got the file size, but any attempt to input the entire file using ifstream::get or fread don't work. They apparently stop at the first 0 byte.
Do you use "ios::in | ios::ate" as your input flags, or just ate? If you don't have ios::in and use fstream (not ifstream), then you won't be able to read().
Also, use tellg() to see if you're at byte 0. If not, you need to seek there.
Can I see your code? Or at least the pertinant parts?
Edit: http://www.cplusplus.com/doc/tutorial/tut6-1.html
See that link for more help with file I/O. It's very nice.
Last edited by Lithorien; 03-12-2005 at 10:39 PM.
It does input and print the first character, which is non-zero, then it stops. The second character is a 0-byte;
Code:fstream in_file; char *tmp_buffer; in_file.open(fname.c_str(), ios::in|ios::ate); if (in_file == NULL) return -1; // get size of file fsize = in_file.tellg(); in_file.seekg(0, ios::beg); tmp_buffer = new char[fsize]; // read file into buffer in_file.read(tmp_buffer, fsize); in_file.close(); cout << tmp_buffer;
The reason that you might not be seeing the whole output is your cout << statement.
cout stops when it reaches a \0 or 'null' character. A 0-byte character from a binary file will translate to NULL when you read it in. So you probally want another way to display your data.. a for loop might do what you want, or a while loop (even better).
I believe this is your problem, anyway..
That was the problem. Thanks a lot! I think I'll be using C from now on instead of the STL to handle stuff with memory, and C++ for other stuff.
Don't cout << or loop it.
Use cout's member function write().
Even better than a loop. Nice catch.Originally Posted by Kybo_Ren
>>but it's stopping at the first EOF (0 byte) it finds.
Actually, there is no such thing as an EOF byte. What you're talking about is a NULL byte
>>I think I'll be using C from now on instead of the STL to handle stuff with memory
Why? If you use STL, you don't even have to delete your memory.
Anyway, pretty much anything written in C is valid C++ too.Code:ifstream file(fname.c_str()); file.seekg(0, ios::end); streampos fileSize = file.tellg(); file.seekg(0, ios::beg); vector<char> data(fileSize); file.read(&(data[0]), fileSize); ... cout.write(&(data[0]), fileSize);
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Example
Here's a good example why. Maybe (hopefully) you can give me a solution.
The file is now cached in memory in a variable of type std::string. The first two bytes in hex are 12 00, which give the length of a substring within the buffer following these two bytes.
How can I copy the value of these two bytes to an integer variable directly from the buffer (NOT from the original file), giving it the value 18?
Last edited by ChadJohnson; 03-13-2005 at 04:51 PM.
Well, first of all (as far as I can tell) your string will only contain these first two bytes - since the second byte is 0x00, i.e. 0 or NULL, the string is terminated after the first character. You should use a vector of char or unsigned char if you're planning on handling binary data, to avoid this sort of conflict.
Anyway, assuming these 2 bytes represent a short (or unsigned short):
This basically reinterprets the address of the first byte as a pointer to unsigned short, then dereferences it to retrieve the value of the first (sizeof(unsigned short)) bytes, interpreted as an unsigned short.Code://Assuming the data's stored in a vector<char>: unsigned short substrLen = *(unsigned short*)(&(data[0]));
You could also use reinterpret_cast<unsigned short*> or whatever instead of just (unsigned short*) for the typecast, but I'm not too familiar with exactly which cast does what, so I usually just stick with good 'ol C-style typecasting.
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