parser: implement whole-block parsing and publicize constructors

parser/block.go

@@ -0,0 +1,47 @@
+package parser
+
+import (
+	"fmt"
+
+	"github.com/gtank/ctxd/parser/internal/bytestring"
+	"github.com/pkg/errors"
+)
+
+type block struct {
+	hdr *blockHeader
+	vtx []*transaction
+}
+
+func NewBlock() *block {
+	return &block{}
+}
+
+func (b *block) ParseFromSlice(data []byte) (rest []byte, err error) {
+	hdr := NewBlockHeader()
+	data, err = hdr.ParseFromSlice(data)
+	if err != nil {
+		return nil, errors.Wrap(err, "parsing block header")
+	}
+
+	s := bytestring.String(data)
+	var txCount int
+	if ok := s.ReadCompactSize(&txCount); !ok {
+		return nil, errors.New("could not read tx_count")
+	}
+	data = []byte(s)
+
+	vtx := make([]*transaction, 0, txCount)
+	for i := 0; len(data) > 0; i++ {
+		tx := NewTransaction()
+		data, err = tx.ParseFromSlice(data)
+		if err != nil {
+			return nil, errors.Wrap(err, fmt.Sprintf("parsing transaction %d", i))
+		}
+		vtx = append(vtx, tx)
+	}
+
+	b.hdr = hdr
+	b.vtx = vtx
+
+	return data, nil
+}