commit 7cd259a2e418951032d970bf316a144fda865dc5
from: Stephen J Day <stephen.day@docker.com>
date: Wed Nov 11 00:00:46 2015 UTC

fs/p9p/new: add readdir helpers

Signed-off-by: Stephen J Day <stephen.day@docker.com>

commit - 755621adc48bd5d72563edcaa93d627eee0fef24
commit + 7cd259a2e418951032d970bf316a144fda865dc5
blob - /dev/null
blob + b3ab9d195896f7f19afc47915087d68419801816 (mode 644)
--- /dev/null
+++ readdir.go
@@ -0,0 +1,88 @@
+package p9pnew
+
+import (
+	"io"
+
+	"golang.org/x/net/context"
+)
+
+// ReaddirAll reads all the directory entries for the resource fid.
+func ReaddirAll(session Session, fid Fid) ([]Dir, error) {
+	panic("not implemented")
+}
+
+// Readdir helps one to implement the server-side of Session.Read on
+// directories.
+type Readdir struct {
+	nextfn func() (Dir, error)
+	buf    *Dir // one-item buffer
+	codec  Codec
+	offset int64
+}
+
+func NewReaddir(codec Codec, next func() (Dir, error)) *Readdir {
+	return &Readdir{
+		nextfn: next,
+		codec:  codec,
+	}
+}
+
+func NewFixedReaddir(codec Codec, dir []Dir) *Readdir {
+	dirs := make([]Dir, len(dir))
+	copy(dirs, dir) // make our own copy!
+
+	return NewReaddir(codec,
+		func() (Dir, error) {
+			if len(dirs) == 0 {
+				return Dir{}, io.EOF
+			}
+
+			d := dirs[0]
+			dirs = dirs[1:]
+			return d, nil
+		})
+}
+
+func (rd *Readdir) Read(ctx context.Context, p []byte, offset int64) (n int, err error) {
+	if rd.offset != offset {
+		return 0, ErrBadoffset
+	}
+
+	p = p[:0:len(p)]
+	for len(p) < cap(p) {
+		var d Dir
+		if rd.buf != nil {
+			d = *rd.buf
+			rd.buf = nil
+		} else {
+			d, err = rd.nextfn()
+			if err != nil {
+				goto done
+			}
+		}
+
+		var dp []byte
+		dp, err = rd.codec.Marshal(d)
+		if err != nil {
+			goto done
+		}
+
+		if len(p)+len(dp) > cap(p) {
+			// will over fill buffer. save item and exit.
+			rd.buf = &d
+			goto done
+		}
+
+		p = append(p, dp...)
+	}
+
+done:
+	if err == io.EOF && len(p) > 0 {
+		// Don't let io.EOF escape if we've written to p. 9p doesn't handle
+		// this like Go.
+		err = nil
+	}
+
+	rd.offset += int64(len(p))
+	return len(p), err
+}