wp

storage/misc.go

@@ -0,0 +1,92 @@
+package storage
+
+import (
+	"fmt"
+
+	bin "gordenko.dev/dima/bin/little"
+	"gordenko.dev/dima/qb"
+	"gordenko.dev/dima/qb/enc"
+)
+
+// func (s *BackwardCursor) makeDecompressors() error {
+// 	timestampsSize, _ := bin.GetUint16(s.pageData[timestampsSizeIdx:])
+// 	valuesSize, _ := bin.GetUint16(s.pageData[valuesSizeIdx:])
+
+// 	payloadSize := timestampsSize + valuesSize
+
+// 	if payloadSize > dataFooterIdx {
+// 		return fmt.Errorf("corrupted data page %d: timestamps + values size %d gt payload size",
+// 			s.pageNo, payloadSize)
+// 	}
+
+// 	s.timestampDecompressor = enc.NewTimeDeltaDecompressor(
+// 		s.pageData[:timestampsSize],
+// 	)
+
+// 	vbuf := s.pageData[timestampsSize : timestampsSize+valuesSize]
+
+// 	switch s.metricType {
+// 	case qb.Instant:
+// 		s.valueDecompressor = enc.NewInstantDeltaDecompressor(
+// 			vbuf, s.fracDigits)
+
+// 	case qb.Cumulative:
+// 		s.valueDecompressor = enc.NewCumulativeDeltaDecompressor(
+// 			vbuf, s.fracDigits)
+
+// 	default:
+// 		return fmt.Errorf("bug: wrong metricType %d", s.metricType)
+// 	}
+// 	return nil
+// }
+
+func makeDecompressors(pageData []byte, metricType qb.MetricType, fracDigits byte) (
+	qb.TimestampDecompressor, qb.ValueDecompressor, error,
+) {
+
+	valuesSize, _ := bin.GetUint16(pageData[valuesSizeIdx:])
+
+	payloadSize := timestampsSize + valuesSize
+
+	if payloadSize > dataFooterIdx {
+		return nil, nil, fmt.Errorf("corrupted: timestamps + values size %d > payload size",
+			payloadSize)
+	}
+
+	timestampDecompressor := enc.NewTimeDeltaDecompressor(
+		pageData[:timestampsSize],
+	)
+
+	vbuf := pageData[timestampsSize : timestampsSize+valuesSize]
+
+	var valueDecompressor qb.ValueDecompressor
+	switch metricType {
+	case qb.Instant:
+		valueDecompressor = enc.NewInstantDeltaDecompressor(
+			vbuf, fracDigits)
+
+	case qb.Cumulative:
+		valueDecompressor = enc.NewCumulativeDeltaDecompressor(
+			vbuf, fracDigits)
+
+	default:
+		return nil, nil, fmt.Errorf("bug: wrong metricType %d", metricType)
+	}
+	return timestampDecompressor, valueDecompressor, nil
+	return nil, nil, nil
+}
+
+func CreateTimeDeltaDecompressor(page []byte) qb.TimestampDecompressor {
+	size, _ := bin.GetUint16(page[timestampsSizeIdx:])
+	pos := DataPagePayloadSize - int(size)
+	d := enc.NewTimeDeltaDecompressor()
+	d.RestoreFromEnd(page[pos:DataPagePayloadSize])
+	return d
+}
+
+func CreateValueDeltaDecompressor(page []byte, metricType qb.MetricType, fracDigits byte) qb.ValueDecompressor {
+	size, _ := bin.GetUint16(page[valuesSizeIdx:])
+	d := enc.NewValueDeltaDecompressor(metricType, fracDigits)
+	d.RestoreFromEnd(page[:size])
+	return d
+}