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array.go
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array.go
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package flyline
import (
"math"
"unsafe"
)
type entry struct {
value interface{}
}
func newArray(capacity int64) (a *array) {
if capacity > 0 && (capacity&(capacity-1)) != 0 {
panic("The array capacity must be a power of two, e.g. 2, 4, 8, 16, 32, 64, etc.")
return
}
var items []*entry = nil
align := int64(unsafe.Alignof(items))
mask := capacity - 1
shift := int64(math.Log2(float64(capacity)))
size := capacity * align
items = make([]*entry, size)
itemBasePtr := uintptr(unsafe.Pointer(&items[0]))
itemMSize := unsafe.Sizeof(items[0])
for i := int64(0); i < size; i++ {
items[i&mask*align] = &entry{}
}
return &array{
capacity: capacity,
size: size,
shift: shift,
align: align,
mask: mask,
items: items,
itemBasePtr: itemBasePtr,
itemMSize: itemMSize,
}
}
// shared array
type array struct {
capacity int64
size int64
shift int64
align int64
mask int64
items []*entry
itemBasePtr uintptr
itemMSize uintptr
}
func (a *array) elementAt(seq int64) (e *entry) {
mask := a.mask
align := a.align
basePtr := a.itemBasePtr
mSize := a.itemMSize
entryPtr := basePtr + uintptr(seq&mask*align)*mSize
e = *((*(*entry))(unsafe.Pointer(entryPtr)))
return
}
func (a *array) set(seq int64, v interface{}) {
a.elementAt(seq).value = v
}
func (a *array) get(seq int64) (v interface{}) {
v = a.elementAt(seq).value
return
}