How Can I Accurately Determine a File's Size in C Instead of Using `tellg()`?

tellg() Function and File Sizing

tellg() is a function in C used to retrieve the current position in a file. However, it's important to note that tellg() does not provide the actual size of the file in bytes. Instead, it returns a token value that can be used later to seek back to the same position.

In the provided code, it appears that there is a misunderstanding regarding the expected behavior of tellg(). The code uses tellg() to determine the size of the file, which is then used to allocate a buffer to hold the file contents. However, tellg() should not be relied upon for this purpose.

According to the C language specification, tellg() returns a token value that is specific to the implementation. While it often corresponds to the byte offset in Unix systems, this behavior is not guaranteed under Windows. In text mode, Windows may return a value greater than the actual number of bytes needed to reach the current position.

To accurately determine the size of a file, it is recommended to use alternative methods, such as:

#include <limits>

...

file.ignore(std::numeric_limits<std::streamsize>::max());
std::streamsize length = file.gcount(); // Retrieve the size of the file in bytes
file.clear(); // Reset the file stream
file.seekg(0, std::ios_base::beg); // Return to the beginning of the file

Additionally, there are several issues in the provided code:

• *buffer = new char[length]; should be corrected to buffer = new char[length];.
• The use of int for size is inappropriate; std::streamsize should be used instead.
• Error handling is not provided in case the file fails to open.

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