slice.go

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// the Apache License, Version 2.0 (the "License"); you may
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//
//     http://www.apache.org/licenses/LICENSE-2.0
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package modeldecoderutil

// Reslice increases the slice's capacity, if necessary, to match n.
// If specified, the newFn function is used to create the elements
// to populate the additional space appended to the slice.
func Reslice[Slice ~[]model, model any](slice Slice, n int, newFn func() model) Slice {
	if diff := n - cap(slice); diff > 0 {
		// start of the extra space
		idx := cap(slice)

		// Grow the slice
		// Note: append gives no guarantee on the capacity of the resulting slice
		// and might overallocate as long as there's enough space for n elements.
		slice = append([]model(slice)[:cap(slice)], make([]model, diff)...)
		if newFn != nil {
			// extend the slice to its capacity
			slice = slice[:cap(slice)]

			// populate the extra space
			for ; idx < len(slice); idx++ {
				slice[idx] = newFn()
			}
		}
	}

	return slice[:n]
}