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// +build 386 amd64,!appengine
package roaring
import (
"errors"
"io"
"reflect"
"runtime"
"unsafe"
)
func (ac *arrayContainer) writeTo(stream io.Writer) (int, error) {
buf := uint16SliceAsByteSlice(ac.content)
return stream.Write(buf)
}
func (bc *bitmapContainer) writeTo(stream io.Writer) (int, error) {
if bc.cardinality <= arrayDefaultMaxSize {
return 0, errors.New("refusing to write bitmap container with cardinality of array container")
}
buf := uint64SliceAsByteSlice(bc.bitmap)
return stream.Write(buf)
}
func uint64SliceAsByteSlice(slice []uint64) []byte {
// make a new slice header
header := *(*reflect.SliceHeader)(unsafe.Pointer(&slice))
// update its capacity and length
header.Len *= 8
header.Cap *= 8
// instantiate result and use KeepAlive so data isn't unmapped.
result := *(*[]byte)(unsafe.Pointer(&header))
runtime.KeepAlive(&slice)
// return it
return result
}
func uint16SliceAsByteSlice(slice []uint16) []byte {
// make a new slice header
header := *(*reflect.SliceHeader)(unsafe.Pointer(&slice))
// update its capacity and length
header.Len *= 2
header.Cap *= 2
// instantiate result and use KeepAlive so data isn't unmapped.
result := *(*[]byte)(unsafe.Pointer(&header))
runtime.KeepAlive(&slice)
// return it
return result
}
func (bc *bitmapContainer) asLittleEndianByteSlice() []byte {
return uint64SliceAsByteSlice(bc.bitmap)
}
// Deserialization code follows
////
// These methods (byteSliceAsUint16Slice,...) do not make copies,
// they are pointer-based (unsafe). The caller is responsible to
// ensure that the input slice does not get garbage collected, deleted
// or modified while you hold the returned slince.
////
func byteSliceAsUint16Slice(slice []byte) (result []uint16) { // here we create a new slice holder
if len(slice)%2 != 0 {
panic("Slice size should be divisible by 2")
}
// reference: https://go101.org/article/unsafe.html
// make a new slice header
bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
// transfer the data from the given slice to a new variable (our result)
rHeader.Data = bHeader.Data
rHeader.Len = bHeader.Len / 2
rHeader.Cap = bHeader.Cap / 2
// instantiate result and use KeepAlive so data isn't unmapped.
runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
// return result
return
}
func byteSliceAsUint64Slice(slice []byte) (result []uint64) {
if len(slice)%8 != 0 {
panic("Slice size should be divisible by 8")
}
// reference: https://go101.org/article/unsafe.html
// make a new slice header
bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
// transfer the data from the given slice to a new variable (our result)
rHeader.Data = bHeader.Data
rHeader.Len = bHeader.Len / 8
rHeader.Cap = bHeader.Cap / 8
// instantiate result and use KeepAlive so data isn't unmapped.
runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
// return result
return
}
func byteSliceAsInterval16Slice(slice []byte) (result []interval16) {
if len(slice)%4 != 0 {
panic("Slice size should be divisible by 4")
}
// reference: https://go101.org/article/unsafe.html
// make a new slice header
bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
// transfer the data from the given slice to a new variable (our result)
rHeader.Data = bHeader.Data
rHeader.Len = bHeader.Len / 4
rHeader.Cap = bHeader.Cap / 4
// instantiate result and use KeepAlive so data isn't unmapped.
runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
// return result
return
}
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