From 3cd8af2c7d1cbb82b5733fc12c3b292fa1ee7e88 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <brad@danga.com>
Date: Fri, 4 Jan 2013 20:20:41 -0800
Subject: [PATCH] schema: more incremental work on making FileReader faster

Change-Id: I033df1654a062dfa57dfe0afce7030f605e88450
---
 pkg/schema/filereader.go | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/pkg/schema/filereader.go b/pkg/schema/filereader.go
index 01a942c04..3b45eba7c 100644
--- a/pkg/schema/filereader.go
+++ b/pkg/schema/filereader.go
@@ -173,6 +173,16 @@ func (sw *sliceWriter) Write(p []byte) (n int, err error) {
 
 var eofReader io.ReadCloser = ioutil.NopCloser(strings.NewReader(""))
 
+func (fr *FileReader) getSuperset(br *blobref.BlobRef) (*Superset, error) {
+	// TODO: cache this. use a new pkg/cacher type.
+	rsc, _, err := fr.fetcher.Fetch(br)
+	if err != nil {
+		return nil, fmt.Errorf("schema/filereader: fetching file schema blob: %v", err)
+	}
+	defer rsc.Close()
+	return ParseSuperset(rsc)
+}
+
 // readerForOffset returns a ReadCloser that reads some number of bytes and then EOF
 // from the provided offset.  Seeing EOF doesn't mean the end of the whole file; just the
 // chunk at that offset.  The caller must close the ReadCloser when done reading.
@@ -203,7 +213,16 @@ func (fr *FileReader) readerForOffset(off int64) (io.ReadCloser, error) {
 	case p0.BlobRef != nil:
 		rsc, _, err = fr.fetcher.Fetch(p0.BlobRef)
 	case p0.BytesRef != nil:
-		rsc, err = NewFileReader(fr.fetcher, p0.BytesRef)
+		var ss *Superset
+		ss, err = fr.getSuperset(p0.BytesRef)
+		if err != nil {
+			return nil, err
+		}
+		rsc, err = ss.NewFileReader(fr.fetcher)
+		if err == nil && fr.readAll.Get() {
+			rsc.(*FileReader).readAll.Set(true)
+			// TODO: tell it to start faulting everything in
+		}
 	}
 	if err != nil {
 		return nil, err