Скачать или смотреть How to Create a Compile-time Constant String with a Prepend Length Byte in C+ +

Learn how to avoid using macros in C+ + by creating a compile-time constant string that prepends a length byte. This guide covers solutions suitable for C+ + 17 and earlier.
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Understanding the Need for Compile-Time Constant Strings in C+ +

When programming in C+ + , you might face situations where you need to define string literals while also requiring the length of the string to be included. Traditionally, many programmers have used # define directives to accomplish this. However, with evolving C+ + standards and best practices, moving away from # define is encouraged due to issues such as code readability and maintainability.

The Problem with # define

Here's a basic example of using # define to create a string literal:

[[See Video to Reveal this Text or Code Snippet]]

While this approach works, it has significant drawbacks:

Lack of Type Safety: # define creates a preprocessor directive, which means it gets substituted literally, leading to potential bugs and difficulties in debugging.

Limited Functionality: You cannot easily manipulate or interact with the defined string in a type-safe manner.

The Modern Approach

You can achieve a compile-time constant string with just a bit of C+ + syntax. Below, we will introduce a clean method to prepend a length byte to a string without relying on # define. This solution is compatible with C+ + 17 and earlier versions.

Step-by-Step Solution

1. Create a Function Template

To properly prepend the length byte, we will utilize a template function. This function will accept a string and return an array with the prepended length.

Here's the implementation:

[[See Video to Reveal this Text or Code Snippet]]

Template Parameters: We use N to represent the size of the incoming string.

Return Type: We return a std::array that has a size of N+ 1 to accommodate the length byte.

2. Define Your String

Now, you can redefine your FredString using the function we just created:

[[See Video to Reveal this Text or Code Snippet]]

By calling AddLenPrefix, we not only create a new constant string but also include its length in the first byte.

Benefits of This Approach

Type Safety: The string is type-checked at compile-time, which reduces the chances of errors.

Easier Maintenance and Readability: The code is more straightforward to read and manage compared to # define.

Future-Proofing: As C+ + continues to evolve, using modern features allows your code to be more compatible with future standards.

Conclusion

Switching from # define to a template function for creating compile-time constant strings with prepended length bytes is a great practice in modern C+ + . It improves readability, maintainability, and ensures type safety in your code. By following the steps outlined above, you can efficiently enhance your string handling practices in C+ + while avoiding common pitfalls associated with old techniques.

Now you can confidently define your strings, knowing that you can also get their lengths seamlessly!