func newWriter()

in pq/writer.go [64:119]

• 46 lines of code
• 5 McCabe index (conditional complexity)

func newWriter(
	accessor *access,
	off uintptr,
	o Observer,
	pagePool *pagePool,
	writeBuffer uint,
	end position,
	flushCB func(uint),
) (*Writer, reason) {
	const op = "pq/create-writer"

	pageSize := accessor.PageSize()
	if pageSize <= 0 {
		return nil, &Error{op: op, kind: InvalidPageSize}
	}

	pages := int(writeBuffer) / pageSize
	if pages <= defaultMinPages {
		pages = defaultMinPages
	}

	tracef("create queue writer with initBufferSize=%v, actualBufferSize=%v, pageSize=%v, pages=%v\n",
		writeBuffer, pageSize*pages, pageSize, pages)

	var tail *page
	if end.page != 0 {
		traceln("writer load endpage: ", end)

		page := end.page
		off := end.off

		var err reason
		tail, err = accessor.readPageByID(pagePool, page)
		if err != nil {
			return nil, (&Error{op: op}).causedBy(err)
		}

		tail.Meta.EndOff = uint32(off)
	}

	w := &Writer{
		active:    true,
		hdrOffset: off,
		observer:  o,
		accessor:  accessor,
		state: writeState{
			buf:     newBuffer(pagePool, tail, pages, pageSize, szEventPageHeader),
			eventID: end.id,
		},
		flushCB: flushCB,
	}

	// init buffer with 'first' event to be written
	w.state.buf.ReserveHdr(szEventHeader)
	return w, nil
}