Hey, All
I'm curious about what happened when map or slice is assigned to interface
variables.
I know the interface implementation in go runtime is:
type iface struct{
tab *itab
data unsafe.Pointer
}
and the interface static and dynamic type infomation are stored in itab,
when we use reflect.TypeOf or reflect.ValueOf,
we can get the dynamic type infomation of this interface.
But it seems that the implementations of slice or map do not have the
underline element type infomation, here is the map implementation:
// A header for a Go map.
type hmap struct {
count int // # live cells == size of map. Must be first (used by len()
builtin)
flags uint8
B uint8 // log_2 of # of buckets (can hold up to loadFactor * 2^B
items)
noverflow uint16 // approximate number of overflow buckets; see
incrnoverflow for details
hash0 uint32 // hash seed
buckets unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.
oldbuckets unsafe.Pointer // previous bucket array of half the size,
non-nil only when growing
nevacuate uintptr // progress counter for evacuation (buckets less
than this have been evacuated)
overflow *[2]*[]*bmap
}
So when we use reflect.TypeOf or reflect.ValueOf, the map variable will be
transformed to interface{} and the empty interface will contains the type
information of the map, how does this happen? where does the interface{}
get the type information?
Thanks in advance.
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