55 lines
1.4 KiB
Go
55 lines
1.4 KiB
Go
package blackmagic
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import (
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"fmt"
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"reflect"
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)
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// AssignIfCompatible is a convenience function to safely
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// assign arbitrary values. dst must be a pointer to an
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// empty interface, or it must be a pointer to a compatible
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// variable type that can hold src.
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func AssignIfCompatible(dst, src interface{}) error {
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orv := reflect.ValueOf(src) // save this value for error reporting
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result := orv
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// t can be a pointer or a slice, and the code will slightly change
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// depending on this
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var isSlice bool
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switch result.Kind() {
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case reflect.Ptr:
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// no op
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case reflect.Slice:
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isSlice = true
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default:
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return fmt.Errorf("argument t to AssignIfCompatible must be a pointer or a slice: %T", src)
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}
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rv := reflect.ValueOf(dst)
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if rv.Kind() != reflect.Ptr {
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return fmt.Errorf(`argument to AssignIfCompatible() must be a pointer: %T`, dst)
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}
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actualDst := rv.Elem()
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switch actualDst.Kind() {
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case reflect.Interface:
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// If it's an interface, we can just assign the pointer to the interface{}
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default:
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// If it's a pointer to the struct we're looking for, we need to set
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// the de-referenced struct
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if !isSlice {
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result = result.Elem()
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}
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}
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if !result.Type().AssignableTo(actualDst.Type()) {
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return fmt.Errorf(`argument to AssignIfCompatible() must be compatible with %T (was %T)`, orv.Interface(), dst)
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}
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if !actualDst.CanSet() {
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return fmt.Errorf(`argument to AssignIfCompatible() must be settable`)
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}
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actualDst.Set(result)
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return nil
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}
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