1 package p9p
2 
3 import (
4 	"io"
5 
6 	"golang.org/x/net/context"
7 )
8 
9 // ReaddirAll reads all the directory entries for the resource fid.
10 func ReaddirAll(session Session, fid Fid) ([]Dir, error) {
11 	panic("not implemented")
12 }
13 
14 // Readdir helps one to implement the server-side of Session.Read on
15 // directories.
16 type Readdir struct {
17 	nextfn func() (Dir, error)
18 	buf    *Dir // one-item buffer
19 	codec  Codec
20 	offset int64
21 }
22 
23 func NewReaddir(codec Codec, next func() (Dir, error)) *Readdir {
24 	return &Readdir{
25 		nextfn: next,
26 		codec:  codec,
27 	}
28 }
29 
30 func NewFixedReaddir(codec Codec, dir []Dir) *Readdir {
31 	dirs := make([]Dir, len(dir))
32 	copy(dirs, dir) // make our own copy!
33 
34 	return NewReaddir(codec,
35 		func() (Dir, error) {
36 			if len(dirs) == 0 {
37 				return Dir{}, io.EOF
38 			}
39 
40 			d := dirs[0]
41 			dirs = dirs[1:]
42 			return d, nil
43 		})
44 }
45 
46 func (rd *Readdir) Read(ctx context.Context, p []byte, offset int64) (n int, err error) {
47 	if rd.offset != offset {
48 		return 0, ErrBadoffset
49 	}
50 
51 	p = p[:0:len(p)]
52 	for len(p) < cap(p) {
53 		var d Dir
54 		if rd.buf != nil {
55 			d = *rd.buf
56 			rd.buf = nil
57 		} else {
58 			d, err = rd.nextfn()
59 			if err != nil {
60 				goto done
61 			}
62 		}
63 
64 		var dp []byte
65 		dp, err = rd.codec.Marshal(d)
66 		if err != nil {
67 			goto done
68 		}
69 
70 		if len(p)+len(dp) > cap(p) {
71 			// will over fill buffer. save item and exit.
72 			rd.buf = &d
73 			goto done
74 		}
75 
76 		p = append(p, dp...)
77 	}
78 
79 done:
80 	if err == io.EOF && len(p) > 0 {
81 		// Don't let io.EOF escape if we've written to p. 9p doesn't handle
82 		// this like Go.
83 		err = nil
84 	}
85 
86 	rd.offset += int64(len(p))
87 	return len(p), err
88 }