tmp

txlog/snapshot.go

@@ -0,0 +1,122 @@
+package txlog
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	bin "gordenko.dev/dima/bin/little"
+	"gordenko.dev/dima/qb"
+	"gordenko.dev/dima/qb/atree"
+	"gordenko.dev/dima/qb/util"
+)
+
+func LoadSnapshot(fileName string) (snapshot Snapshot, err error) {
+	var (
+		hasher = util.NewHasher()
+		header = make([]byte, metricHeaderSize)
+		body   = make([]byte, atree.PageSize)
+	)
+
+	file, err := os.Open(fileName)
+	if err != nil {
+		return
+	}
+
+	src := io.TeeReader(file, hasher)
+	metricsQty, err := bin.ReadVarSize(src)
+	if err != nil {
+		return
+	}
+
+	for range metricsQty {
+		var metric Metric
+		err = bin.ReadNInto(src, header)
+		if err != nil {
+			return
+		}
+
+		metric.MetricID, _ = bin.GetUint32(header[0:])
+		metric.MetricType = qb.MetricType(header[4])
+		metric.FracDigits = header[5]
+		metric.LastPageNo, _ = bin.GetUint32(header[6:])
+		metric.Since, _ = bin.GetUint32(header[10:])
+		metric.SinceValue, _ = bin.GetFloat64(header[14:])
+		metric.Until, _ = bin.GetUint32(header[22:])
+		metric.UntilValue, _ = bin.GetFloat64(header[26:])
+		tSize, _ := bin.GetUint16(header[34:])
+		vSize, _ := bin.GetUint16(header[36:])
+
+		buf := body[:tSize]
+		err = bin.ReadNInto(src, buf)
+		if err != nil {
+			return
+		}
+		// FIX
+		// metric.Timestamps = chunkenc.NewReverseTimeDeltaCompressor(
+		// 	conbuf.NewFromBuffer(buf),
+		// 	int(tSize),
+		// )
+
+		buf = body[:vSize]
+		err = bin.ReadNInto(src, buf)
+		if err != nil {
+			return
+		}
+
+		// FIX
+		// if metric.MetricType == qb.Cumulative {
+		// 	metric.Values = chunkenc.NewReverseCumulativeDeltaCompressor(
+		// 		conbuf.NewFromBuffer(buf),
+		// 		int(vSize),
+		// 		metric.FracDigits,
+		// 	)
+		// } else {
+		// 	metric.Values = chunkenc.NewReverseInstantDeltaCompressor(
+		// 		conbuf.NewFromBuffer(buf),
+		// 		int(vSize),
+		// 		metric.FracDigits,
+		// 	)
+		// }
+		// s.metrics[metricID] = &metric
+	}
+	// FIX
+	// err = restoreFreeList(s.dataFreeList, src)
+	// if err != nil {
+	// 	return fmt.Errorf("restore dataFreeList: %s", err)
+	// }
+	// FIX
+	// err = restoreFreeList(s.indexFreeList, src)
+	// if err != nil {
+	// 	return fmt.Errorf("restore indexFreeList: %s", err)
+	// }
+
+	calculatedChecksum := hasher.Sum32()
+
+	writtenChecksum, err := bin.ReadUint32(file)
+	if err != nil {
+		return
+	}
+
+	if calculatedChecksum != writtenChecksum {
+		err = fmt.Errorf("calculated checksum %d not equal written checksum %d",
+			calculatedChecksum, writtenChecksum)
+		return
+	}
+	return
+}
+
+// serialized + frozen pages count
+
+// func restoreFreeList(freeList *freelist.FreeList, src io.Reader) error {
+// 	size, err := bin.ReadVarSize(src)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	serialized, err := bin.ReadN(src, size)
+// 	if err != nil {
+// 		return err
+// 	}
+// 	freeList.Restore(serialized)
+// 	return nil
+// }