Add series file reader

reader.go

@@ -0,0 +1,62 @@
+package tsdb
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/fabxc/tsdb/chunks"
+)
+
+// SeriesReader provides reading access of serialized time series data.
+type SeriesReader interface {
+	// Chunk returns the series data chunk at the given offset.
+	Chunk(offset uint32) (chunks.Chunk, error)
+}
+
+// seriesReader implements a SeriesReader for a serialized byte stream
+// of series data.
+type seriesReader struct {
+	// The underlying byte slice holding the encoded series data.
+	b []byte
+}
+
+func newSeriesReader(b []byte) (*seriesReader, error) {
+	// Verify magic number.
+	if m := binary.BigEndian.Uint32(b[:4]); m != MagicSeries {
+		return nil, fmt.Errorf("invalid magic number %x", m)
+	}
+	return &seriesReader{b: b}, nil
+}
+
+func (s *seriesReader) Chunk(offset uint32) (chunks.Chunk, error) {
+	b := s.b[offset:]
+
+	l, n := binary.Uvarint(b)
+	if n < 0 {
+		return nil, fmt.Errorf("reading chunk length failed")
+	}
+	b = b[n:]
+	enc := chunks.Encoding(b[0])
+
+	c, err := chunks.FromData(enc, b[1:1+l])
+	if err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// IndexReader provides reading access of serialized index data.
+type IndexReader interface {
+	//
+
+	// Close releases resources associated with the reader.
+	Close()
+}
+
+type indexReader struct {
+	// The underlying byte slice holding the encoded series data.
+	b []byte
+
+	// Cached hashmaps of sections for label values
+	labelOffsets map[string]uint32
+}

writer.go

@@ -277,7 +277,7 @@ func (w *indexWriter) writeSymbols() error {
 	sort.Strings(symbols)
 
 	buf := [binary.MaxVarintLen32]byte{}
-	b := append(make([]byte, 4096), flagStd)
+	b := append(make([]byte, 0, 4096), flagStd)
 
 	for _, s := range symbols {
 		w.symbols[s] = uint32(w.n) + uint32(len(b))