Understanding the Key Differences Between unsafe.Sizeof and reflect.TypeOf().Size() in Go скачать в хорошем качестве

Understanding the Key Differences Between unsafe.Sizeof and reflect.TypeOf().Size() in Go

Dive deep into the differences between `unsafe.Sizeof(T)` and `reflect.TypeOf(T).Size()` in Go, with clear explanations and examples to improve your understanding! --- This video is based on the question https://stackoverflow.com/q/76726144/ asked by the user 'noob-Programmer' ( https://stackoverflow.com/u/12162950/ ) and on the answer https://stackoverflow.com/a/76726155/ provided by the user 'hobbs' ( https://stackoverflow.com/u/152948/ ) 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: What is the difference between unsafe.Sizeof(T) and reflect.TypeOf(T).Size() 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. --- Understanding the Key Differences Between unsafe.Sizeof and reflect.TypeOf().Size() in Go In Go, there are various methods to determine the size of a type or variable in memory. Two commonly used functions are unsafe.Sizeof() and reflect.TypeOf().Size(). While both appear to provide similar functionality, they can yield different results, especially when working with interfaces and dynamic types. In this guide, we'll dive into the specifics of these functions, illustrate their differences, and help you understand when to use each. The Problem When using these functions on numerical types like int and float64, you may observe discrepancies in their output. For example, a struct may return the same size from both functions, while a fundamental type can produce different sizes: Example Scenario: unsafe.Sizeof(int) returns 16 reflect.TypeOf(int).Size() returns 8 This inconsistency raises a valid question: Why do these methods return different values despite being described as analogous? The Explanation What Each Function Does unsafe.Sizeof(): This function returns the size in bytes of the type representation including its metadata. When you pass an interface{} type to unsafe.Sizeof(), it essentially provides the size of the underlying interface{} structure itself, rather than the size of the dynamic type stored within the interface. reflect.TypeOf().Size(): This function returns the size of the dynamic type that is actually stored in the variable you provided. It reflects on the internal representation and manages to give a more accurate size of the actual type stored, ignoring the interface’s metadata. Key Differences Illustrated When you call these functions within a function like describe() that uses an interface{}, they will behave differently: [[See Video to Reveal this Text or Code Snippet]] Here, unsafe.Sizeof(i) evaluates to the size of the interface{} which is 16 bytes on a 64-bit architecture, indicating the memory needed for the interfacing structure itself. In contrast, reflect.TypeOf(i).Size() evaluates the dynamic type held within the interface{}. Practical Example Let’s illustrate this with the output from the provided program: For each type and its size: String: Type = string, size = 16, reflect.Size = 16 Int: Type = int, size = 16, reflect.Size = 8 Float64: Type = float64, size = 16, reflect.Size = 8 Struct: Type = struct { name string }, size = 16, reflect.Size = 16 From this output, you can see how unsafe.Sizeof(i) gives a large size for fundamental types because it is accounting for the interface itself, while reflect.TypeOf(i).Size() shows the more intuitive size of the actual dynamic type. Conclusion Understanding the distinctions between unsafe.Sizeof(T) and reflect.TypeOf(T).Size() is crucial for manipulating memory efficiently in Go, especially when working with interfaces. By knowing when to use each function, you can ensure that you're retrieving the correct sizes for your variables, leading to improved memory handling in your applications. If you find yourself confused at any point between these two methods, remember that unsafe.Sizeof refers to the interface's structure, while reflect.TypeOf().Size() reflects the actual dynamic type's size. By mastering these nuances, you'll enhance your understanding of memory management in Go.