Add Inliner CID Builder.

inliner.go

@@ -0,0 +1,31 @@
+package cidutil
+
+import (
+	cid "github.com/ipfs/go-cid"
+	mhash "github.com/multiformats/go-multihash"
+)
+
+// Inliner is a cid.Builder that will use the id multihash when the
+// size of the content is no more than limit
+type Inliner struct {
+	base  cid.Builder
+	limit int
+}
+
+// GetCodec implements the cid.Builder interface
+func (p Inliner) GetCodec() uint64 {
+	return p.base.GetCodec()
+}
+
+// WithCodec implements the cid.Builder interface
+func (p Inliner) WithCodec(c uint64) cid.Builder {
+	return Inliner{p.base.WithCodec(c), p.limit}
+}
+
+// Sum implements the cid.Builder interface
+func (p Inliner) Sum(data []byte) (*cid.Cid, error) {
+	if len(data) > p.limit {
+		return p.base.Sum(data)
+	}
+	return cid.V1Builder{Codec: p.base.GetCodec(), MhType: mhash.ID}.Sum(data)
+}