1st

atree/misc.go

@@ -0,0 +1,214 @@
+package atree
+
+import (
+	"hash/crc32"
+
+	"gordenko.dev/dima/qb/bin"
+)
+
+type ValueAtComparator struct {
+	buf       []byte
+	timestamp uint32
+}
+
+func (s ValueAtComparator) CompareTo(elemIdx int) int {
+	var (
+		pos  = elemIdx * timestampSize
+		elem = bin.GetUint32(s.buf[pos:])
+	)
+
+	if s.timestamp < elem {
+		return -1
+	} else if s.timestamp > elem {
+		return 1
+	} else {
+		return 0
+	}
+}
+
+func BinarySearch(qty int, keyComparator bin.KeyComparator) (elemIdx int, isFound bool) {
+	if qty == 0 {
+		return
+	}
+	a := 0
+	b := qty - 1
+	for {
+		var (
+			elemIdx = (b-a)/2 + a
+			code    = keyComparator.CompareTo(elemIdx)
+		)
+		if code == 1 {
+			a = elemIdx + 1
+			if a > b {
+				return elemIdx, false // +1
+			}
+		} else if code == -1 {
+			b = elemIdx - 1
+			if b < a {
+				if elemIdx == 0 {
+					return 0, false
+				} else {
+					return elemIdx - 1, false
+				}
+			}
+		} else {
+			return elemIdx, true
+		}
+	}
+}
+
+type chunksToDataPageReq struct {
+	PrevPageNo       uint32
+	TimestampsChunks [][]byte
+	TimestampsSize   uint16
+	ValuesChunks     [][]byte
+	ValuesSize       uint16
+}
+
+func chunksToDataPage(buf []byte, req chunksToDataPageReq) {
+	bin.PutUint32(buf[prevPageIdx:], req.PrevPageNo)
+	bin.PutUint16(buf[timestampsSizeIdx:], req.TimestampsSize)
+	bin.PutUint16(buf[valuesSizeIdx:], req.ValuesSize)
+
+	var (
+		remainingSize = int(req.TimestampsSize)
+		pos           = 0
+	)
+	for _, chunk := range req.TimestampsChunks {
+		if remainingSize >= len(chunk) {
+			copy(buf[pos:], chunk)
+			remainingSize -= len(chunk)
+			pos += len(chunk)
+		} else {
+			copy(buf[pos:], chunk[:remainingSize])
+			break
+		}
+	}
+
+	remainingSize = int(req.ValuesSize)
+	pos = int(req.TimestampsSize)
+
+	for _, chunk := range req.ValuesChunks {
+		if remainingSize >= len(chunk) {
+			copy(buf[pos:], chunk)
+			remainingSize -= len(chunk)
+			pos += len(chunk)
+		} else {
+			copy(buf[pos:], chunk[:remainingSize])
+			break
+		}
+	}
+	bin.PutUint32(buf[dataCRC32Idx:], crc32.ChecksumIEEE(buf[:dataCRC32Idx]))
+}
+
+func setPrevPageNo(buf []byte, pageNo uint32) {
+	bin.PutUint32(buf[prevPageIdx:], pageNo)
+}
+
+func getPrevPageNo(buf []byte) uint32 {
+	return bin.GetUint32(buf[prevPageIdx:])
+}
+
+func findPageNo(buf []byte, timestamp uint32) (pageNo uint32) {
+	var (
+		qty        = bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+		comparator = ValueAtComparator{
+			buf:       buf,
+			timestamp: timestamp,
+		}
+	)
+	elemIdx, _ := BinarySearch(qty, comparator)
+	pos := indexFooterIdx - (elemIdx+1)*PageNoSize
+	return bin.GetUint32(buf[pos:])
+}
+
+func findPageNoIdx(buf []byte, timestamp uint32) (idx int) {
+	var (
+		qty        = bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+		comparator = ValueAtComparator{
+			buf:       buf,
+			timestamp: timestamp,
+		}
+	)
+	elemIdx, _ := BinarySearch(qty, comparator)
+	return elemIdx
+}
+
+func findPageNoForDeleteSince(buf []byte, since uint32) (uint32, int, int) {
+	var (
+		qty        = bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+		comparator = ValueAtComparator{
+			buf:       buf,
+			timestamp: since,
+		}
+	)
+	elemIdx, _ := BinarySearch(qty, comparator)
+	pos := elemIdx * timestampSize
+	timestamp := bin.GetUint32(buf[pos:])
+
+	if timestamp == since {
+		if elemIdx == 0 {
+			return 0, qty, -1
+		}
+		elemIdx--
+	}
+	pos = indexFooterIdx - (elemIdx+1)*PageNoSize
+	return bin.GetUint32(buf[pos:]), qty, elemIdx
+}
+
+func getLastPageNo(buf []byte) (pageNo uint32) {
+	qty := bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+	pos := indexFooterIdx - qty*PageNoSize
+	return bin.GetUint32(buf[pos:])
+}
+
+func getPageNo(buf []byte, idx int) (pageNo uint32) {
+	pos := indexFooterIdx - (idx+1)*PageNoSize
+	return bin.GetUint32(buf[pos:])
+}
+
+func listPageNumbers(buf []byte) (pageNumbers []uint32) {
+	qty := bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+	pos := indexFooterIdx - PageNoSize
+	for range qty {
+		pageNumbers = append(pageNumbers, bin.GetUint32(buf[pos:]))
+		pos -= PageNoSize
+	}
+	return
+}
+
+// include since timestamp
+func listPageNumbersSince(buf []byte, timestamp uint32) (pageNumbers []uint32) {
+	var (
+		qty        = bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+		comparator = ValueAtComparator{
+			buf:       buf,
+			timestamp: timestamp,
+		}
+	)
+	elemIdx, _ := BinarySearch(qty, comparator)
+	pos := indexFooterIdx - (elemIdx+1)*PageNoSize
+	for range qty {
+		pageNumbers = append(pageNumbers, bin.GetUint32(buf[pos:]))
+		pos -= PageNoSize
+	}
+	return
+}
+
+func getSince(buf []byte) uint32 {
+	return bin.GetUint32(buf[0:])
+}
+
+func appendPair(buf []byte, timestamp uint32, pageNo uint32) bool {
+	qty := bin.GetUint16AsInt(buf[indexRecordsQtyIdx:])
+	free := indexFooterIdx - qty*pairSize
+	if free < pairSize {
+		return false
+	}
+	pos := qty * timestampSize
+	bin.PutUint32(buf[pos:], timestamp)
+	pos = indexFooterIdx - (qty+1)*PageNoSize
+	bin.PutUint32(buf[pos:], pageNo)
+	bin.PutIntAsUint16(buf[indexRecordsQtyIdx:], qty+1)
+	return true
+}