// +build windows

package buf

import "syscall"

type windowsReader struct {
	o     syscall.Overlapped
	bufs  []syscall.WSABuf
	flags uint32
	qty   uint32
}

func (r *windowsReader) Init(bs []*Buffer) {
	if r.bufs == nil {
		r.bufs = make([]syscall.WSABuf, 0, len(bs))
	}
	for _, b := range bs {
		r.bufs = append(r.bufs, syscall.WSABuf{Len: uint32(b.Len()), Buf: &b.v[0]})
	}
}

func (r *windowsReader) Clear() {
	for idx := range r.bufs {
		r.bufs[idx].Buf = nil
	}
	r.bufs = r.bufs[:0]
}

func (r *windowsReader) Read(fd uintptr) int32 {
	var nBytes uint32
	err := syscall.WSARecv(syscall.Handle(fd), &r.bufs[0], uint32(len(r.bufs)), &nBytes, &r.flags, &r.o, nil)
	if err != nil {
		return -1
	}
	return int32(nBytes)
}

func newMultiReader() multiReader {
	return new(windowsReader)
}