What is the slicing capacity expansion mechanism in Go language
Slices in Go (slice) are dynamic arrays that are implemented at the bottom by an array and two pointers (pointing to the beginning and end of the array). When the capacity of the slice is not enough to accommodate more elements, Go will automatically expand. The following is a brief overview of the slicing capacity expansion mechanism in Go language:
Initial Capacity: When you create a new slice, it has an initial capacity and length. Length is the number of elements in a slice, and capacity is the maximum number of elements that the underlying array of slices can accommodate.
Scale expansion conditions: When you add elements to the slice so that their length exceeds the current capacity, Go will automatically expand.
Scaling expansion policy: When the Go language expands, the new capacity will be determined based on the current capacity and length. Normally, if the current capacity is less than 1024, the new capacity will be twice the original; if the current capacity is greater than or equal to 1024, the new capacity will be 1.25 times the original capacity. This strategy is designed to balance memory usage and performance.
Copy elements: After expansion, Go will copy all elements from the old slice into the new underlying array.
Update pointer: After expansion, the sliced pointer will be updated to point to the new underlying array.
Memory Allocation: The new underlying array is allocated on the heap, which means it may involve garbage collection.
Zero value padding: The newly allocated array part is filled with zero value to ensure that elements in the slice do not have undefined behavior when accessed.
In summary, the slice scaling mechanism in Go is an automatic and dynamic process that determines the new capacity based on the current capacity and length, and performs memory allocation and element copying when needed to ensure that the slice can continue to grow. This process is transparent and does not require manual management for developers.