Efficiently Initialize Arrays in C99: Solving Pointer Problems скачать в хорошем качестве

Efficiently Initialize Arrays in C99: Solving Pointer Problems

Discover how to `initialize arrays` through pointers in C99 without loops, along with helpful tips on designated initializers and memory copying techniques. --- This video is based on the question https://stackoverflow.com/q/68432975/ asked by the user 'Nils' ( https://stackoverflow.com/u/44232/ ) and on the answer https://stackoverflow.com/a/68433011/ provided by the user 'Nate Eldredge' ( https://stackoverflow.com/u/634919/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: C99 Initialize an array through a pointer with braces Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Efficiently Initialize Arrays in C99: Solving Pointer Problems When working with C programming, especially in graphics or game development, dealing with vertex positions and arrays is a common task. For example, if you want to create a rectangle for mapping a texture based on its position and height, it's essential to understand how to initialize such arrays. This could raise a question for many: How can you effectively initialize an array through a pointer without using a loop, particularly with C99's designated initializers? Let's explore this topic and discover some effective solutions. Understanding the Problem You've likely encountered a scenario where you need to calculate vertex positions for a rectangle. The function make_vertex_rect takes parameters for the rectangle's position (x, y), width (w), height (h), and a pointer to an array (vertex_positions). The goal is to fill this array with vertex positions in a specific format. Here's the initial implementation you might be working with: [[See Video to Reveal this Text or Code Snippet]] While this works perfectly, you may wonder if there's a way to initialize the array without that tedious loop, especially since C99 introduced designated initializers. The Reality of C99 Designated Initializers Unfortunately, C99's designated initializers can only be used when you declare objects, not when you're trying to overwrite an existing array. What this means is that while you can initialize arrays at the time of their declaration using braces { ... }, you cannot simply assign new values to an already defined array using that same syntax. What Are Your Options? If you want to efficiently fill an array using pointers, here are three viable methods you can consider: Stick with a Loop: This remains the most straightforward approach. It allows for full control over the data transferred from the source to the target array, as shown in your original code. Use memcpy: If your arrays are fixed in size and you're confident of the data being copied, using the memcpy function can help streamline your code. It eliminates the need for manual copying using a loop: [[See Video to Reveal this Text or Code Snippet]] Explicit Assignments: If the size of your array is small and manageable, you could opt to write out each assignment explicitly. However, this can lead to less readable code, especially for larger arrays. Example using memcpy Here's how to implement this using memcpy for efficiency: [[See Video to Reveal this Text or Code Snippet]] Conclusion In conclusion, while C99 offers some conveniences with designated initializers, it's crucial to recognize the limitations when it comes to initializing arrays through pointers. You can either maintain the loop approach, utilize memcpy for better efficiency, or write explicit assignments for small arrays. Each option has its merits, so choose the one that best fits your situation! By understanding how to initialize arrays effectively in C, you'll find yourself writing cleaner, more efficient code in your programming projects.