How Can I Inspect the Header of a Go Slice?

Inspecting Slice Header

In Go, slices are references to underlying arrays, and their headers hold essential information about the slice. While the contents of a slice argument can be modified by a function, its header cannot. To inspect a slice's header, we can delve into the details hidden in its structure.

The slice header is defined by the reflect.SliceHeader type, which comprises three fields: Data, Len, and Cap. We can convert a slice pointer to a *reflect.SliceHeader using the unsafe package:

sh := (*reflect.SliceHeader)(unsafe.Pointer(&newSlice2))

Once we have the slice header, we can access its fields directly:

• Data can be obtained via &newSlice2[0]
• Len can be retrieved using len(newSlice2)
• Cap can be accessed through cap(newSlice2)

By printing the SliceHeader value using fmt.Printf(% v, sh), we get the following output:

&{Data:1792106 Len:8 Cap:246}

This tells us that newSlice2 points to data stored at memory address 1792106, has a length of 8, and has a capacity of 246.

To conclude, while the header of a slice cannot be modified directly, we can inspect its contents using techniques like converting to reflect.SliceHeader or using indirect methods like &newSlice2[0] or len(newSlice2) to retrieve specific fields.

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