1 package p9p
2 
3 import (
4 	"bytes"
5 	"encoding/binary"
6 	"fmt"
7 	"io"
8 	"log"
9 	"reflect"
10 	"strings"
11 	"time"
12 )
13 
14 // Codec defines the interface for encoding and decoding of 9p types.
15 // Unsupported types will throw an error.
16 type Codec interface {
17 	// Unmarshal from data into the value pointed to by v.
18 	Unmarshal(data []byte, v interface{}) error
19 
20 	// Marshal the value v into a byte slice.
21 	Marshal(v interface{}) ([]byte, error)
22 
23 	// Size returns the encoded size for the target of v.
24 	Size(v interface{}) int
25 }
26 
27 func NewCodec() Codec {
28 	return codec9p{}
29 }
30 
31 type codec9p struct{}
32 
33 func (c codec9p) Unmarshal(data []byte, v interface{}) error {
34 	dec := &decoder{bytes.NewReader(data)}
35 	return dec.decode(v)
36 }
37 
38 func (c codec9p) Marshal(v interface{}) ([]byte, error) {
39 	var b bytes.Buffer
40 	enc := &encoder{&b}
41 
42 	if err := enc.encode(v); err != nil {
43 		return nil, err
44 	}
45 
46 	return b.Bytes(), nil
47 }
48 
49 func (c codec9p) Size(v interface{}) int {
50 	return int(size9p(v))
51 }
52 
53 // DecodeDir decodes a directory entry from rd using the provided codec.
54 func DecodeDir(codec Codec, rd io.Reader, d *Dir) error {
55 	var ll uint16
56 
57 	// pull the size off the wire
58 	if err := binary.Read(rd, binary.LittleEndian, &ll); err != nil {
59 		return err
60 	}
61 
62 	p := make([]byte, ll+2)
63 	binary.LittleEndian.PutUint16(p, ll) // must have size at start
64 
65 	// read out the rest of the record
66 	if _, err := io.ReadFull(rd, p[2:]); err != nil {
67 		return err
68 	}
69 
70 	return codec.Unmarshal(p, d)
71 }
72 
73 // EncodeDir writes the directory to wr.
74 func EncodeDir(codec Codec, wr io.Writer, d *Dir) error {
75 	p, err := codec.Marshal(d)
76 	if err != nil {
77 		return err
78 	}
79 
80 	_, err = wr.Write(p)
81 	return err
82 }
83 
84 type encoder struct {
85 	wr io.Writer
86 }
87 
88 func (e *encoder) encode(vs ...interface{}) error {
89 	for _, v := range vs {
90 		switch v := v.(type) {
91 		case uint8, uint16, uint32, uint64, FcallType, Tag, QType, Fid, Flag,
92 			*uint8, *uint16, *uint32, *uint64, *FcallType, *Tag, *QType, *Fid, *Flag:
93 			if err := binary.Write(e.wr, binary.LittleEndian, v); err != nil {
94 				return err
95 			}
96 		case []byte:
97 			if err := e.encode(uint32(len(v))); err != nil {
98 				return err
99 			}
100 
101 			if err := binary.Write(e.wr, binary.LittleEndian, v); err != nil {
102 				return err
103 			}
104 
105 		case *[]byte:
106 			if err := e.encode(*v); err != nil {
107 				return err
108 			}
109 		case string:
110 			if err := binary.Write(e.wr, binary.LittleEndian, uint16(len(v))); err != nil {
111 				return err
112 			}
113 
114 			_, err := io.WriteString(e.wr, v)
115 			if err != nil {
116 				return err
117 			}
118 		case *string:
119 			if err := e.encode(*v); err != nil {
120 				return err
121 			}
122 
123 		case []string:
124 			if err := e.encode(uint16(len(v))); err != nil {
125 				return err
126 			}
127 
128 			for _, m := range v {
129 				if err := e.encode(m); err != nil {
130 					return err
131 				}
132 			}
133 		case *[]string:
134 			if err := e.encode(*v); err != nil {
135 				return err
136 			}
137 		case time.Time:
138 			if err := e.encode(uint32(v.Unix())); err != nil {
139 				return err
140 			}
141 		case *time.Time:
142 			if err := e.encode(*v); err != nil {
143 				return err
144 			}
145 		case Qid:
146 			if err := e.encode(v.Type, v.Version, v.Path); err != nil {
147 				return err
148 			}
149 		case *Qid:
150 			if err := e.encode(*v); err != nil {
151 				return err
152 			}
153 		case []Qid:
154 			if err := e.encode(uint16(len(v))); err != nil {
155 				return err
156 			}
157 
158 			elements := make([]interface{}, len(v))
159 			for i := range v {
160 				elements[i] = &v[i]
161 			}
162 
163 			if err := e.encode(elements...); err != nil {
164 				return err
165 			}
166 		case *[]Qid:
167 			if err := e.encode(*v); err != nil {
168 				return err
169 			}
170 		case Dir:
171 			elements, err := fields9p(v)
172 			if err != nil {
173 				return err
174 			}
175 
176 			if err := e.encode(uint16(size9p(elements...))); err != nil {
177 				return err
178 			}
179 
180 			if err := e.encode(elements...); err != nil {
181 				return err
182 			}
183 		case *Dir:
184 			if err := e.encode(*v); err != nil {
185 				return err
186 			}
187 		case Fcall:
188 			if err := e.encode(v.Type, v.Tag, v.Message); err != nil {
189 				return err
190 			}
191 		case *Fcall:
192 			if err := e.encode(*v); err != nil {
193 				return err
194 			}
195 		case Message:
196 			elements, err := fields9p(v)
197 			if err != nil {
198 				return err
199 			}
200 
201 			switch v.(type) {
202 			case MessageRstat, *MessageRstat:
203 				// NOTE(stevvooe): Prepend size preceeding Dir. See bugs in
204 				// http://man.cat-v.org/plan_9/5/stat to make sense of this.
205 				// The field has been included here but we need to make sure
206 				// to double emit it for Rstat.
207 				if err := e.encode(uint16(size9p(elements...))); err != nil {
208 					return err
209 				}
210 			}
211 
212 			if err := e.encode(elements...); err != nil {
213 				return err
214 			}
215 		}
216 	}
217 
218 	return nil
219 }
220 
221 type decoder struct {
222 	rd io.Reader
223 }
224 
225 // read9p extracts values from rd and unmarshals them to the targets of vs.
226 func (d *decoder) decode(vs ...interface{}) error {
227 	for _, v := range vs {
228 		switch v := v.(type) {
229 		case *uint8, *uint16, *uint32, *uint64, *FcallType, *Tag, *QType, *Fid, *Flag:
230 			if err := binary.Read(d.rd, binary.LittleEndian, v); err != nil {
231 				return err
232 			}
233 		case *[]byte:
234 			var ll uint32
235 
236 			if err := d.decode(&ll); err != nil {
237 				return err
238 			}
239 
240 			*v = make([]byte, int(ll))
241 
242 			if err := binary.Read(d.rd, binary.LittleEndian, v); err != nil {
243 				return err
244 			}
245 		case *string:
246 			var ll uint16
247 
248 			// implement string[s] encoding
249 			if err := d.decode(&ll); err != nil {
250 				return err
251 			}
252 
253 			b := make([]byte, ll)
254 
255 			n, err := io.ReadFull(d.rd, b)
256 			if err != nil {
257 				return err
258 			}
259 
260 			if n != int(ll) {
261 				return fmt.Errorf("unexpected string length")
262 			}
263 
264 			*v = string(b)
265 		case *[]string:
266 			var ll uint16
267 
268 			if err := d.decode(&ll); err != nil {
269 				return err
270 			}
271 
272 			elements := make([]interface{}, int(ll))
273 			*v = make([]string, int(ll))
274 			for i := range elements {
275 				elements[i] = &(*v)[i]
276 			}
277 
278 			if err := d.decode(elements...); err != nil {
279 				return err
280 			}
281 		case *time.Time:
282 			var epoch uint32
283 			if err := d.decode(&epoch); err != nil {
284 				return err
285 			}
286 
287 			*v = time.Unix(int64(epoch), 0).UTC()
288 		case *Qid:
289 			if err := d.decode(&v.Type, &v.Version, &v.Path); err != nil {
290 				return err
291 			}
292 		case *[]Qid:
293 			var ll uint16
294 
295 			if err := d.decode(&ll); err != nil {
296 				return err
297 			}
298 
299 			elements := make([]interface{}, int(ll))
300 			*v = make([]Qid, int(ll))
301 			for i := range elements {
302 				elements[i] = &(*v)[i]
303 			}
304 
305 			if err := d.decode(elements...); err != nil {
306 				return err
307 			}
308 		case *Dir:
309 			var ll uint16
310 
311 			if err := d.decode(&ll); err != nil {
312 				return err
313 			}
314 
315 			b := make([]byte, ll)
316 			// must consume entire dir entry.
317 			n, err := io.ReadFull(d.rd, b)
318 			if err != nil {
319 				log.Println("dir readfull failed:", err, ll, n)
320 				return err
321 			}
322 
323 			elements, err := fields9p(v)
324 			if err != nil {
325 				return err
326 			}
327 
328 			dec := &decoder{bytes.NewReader(b)}
329 
330 			if err := dec.decode(elements...); err != nil {
331 				return err
332 			}
333 		case *Fcall:
334 			if err := d.decode(&v.Type, &v.Tag); err != nil {
335 				return err
336 			}
337 
338 			message, err := newMessage(v.Type)
339 			if err != nil {
340 				return err
341 			}
342 
343 			// NOTE(stevvooe): We do a little pointer dance to allocate the
344 			// new type, write to it, then assign it back to the interface as
345 			// a concrete type, avoiding a pointer (the interface) to a
346 			// pointer.
347 			rv := reflect.New(reflect.TypeOf(message))
348 			if err := d.decode(rv.Interface()); err != nil {
349 				return err
350 			}
351 
352 			v.Message = rv.Elem().Interface().(Message)
353 		case Message:
354 			elements, err := fields9p(v)
355 			if err != nil {
356 				return err
357 			}
358 
359 			switch v.(type) {
360 			case *MessageRstat, MessageRstat:
361 				// NOTE(stevvooe): Consume extra size preceeding Dir. See bugs
362 				// in http://man.cat-v.org/plan_9/5/stat to make sense of
363 				// this. The field has been included here but we need to make
364 				// sure to double emit it for Rstat. decode extra size header
365 				// for stat structure.
366 				var ll uint16
367 				if err := d.decode(&ll); err != nil {
368 					return err
369 				}
370 			}
371 
372 			if err := d.decode(elements...); err != nil {
373 				return err
374 			}
375 		}
376 	}
377 
378 	return nil
379 }
380 
381 // size9p calculates the projected size of the values in vs when encoded into
382 // 9p binary protocol. If an element or elements are not valid for 9p encoded,
383 // the value 0 will be used for the size. The error will be detected when
384 // encoding.
385 func size9p(vs ...interface{}) uint32 {
386 	var s uint32
387 	for _, v := range vs {
388 		if v == nil {
389 			continue
390 		}
391 
392 		switch v := v.(type) {
393 		case uint8, uint16, uint32, uint64, FcallType, Tag, QType, Fid, Flag,
394 			*uint8, *uint16, *uint32, *uint64, *FcallType, *Tag, *QType, *Fid, *Flag:
395 			s += uint32(binary.Size(v))
396 		case []byte:
397 			s += uint32(binary.Size(uint32(0)) + len(v))
398 		case *[]byte:
399 			s += size9p(uint32(0), *v)
400 		case string:
401 			s += uint32(binary.Size(uint16(0)) + len(v))
402 		case *string:
403 			s += size9p(*v)
404 		case []string:
405 			s += size9p(uint16(0))
406 
407 			for _, sv := range v {
408 				s += size9p(sv)
409 			}
410 		case *[]string:
411 			s += size9p(*v)
412 		case time.Time, *time.Time:
413 			// BUG(stevvooe): Y2038 is coming.
414 			s += size9p(uint32(0))
415 		case Qid:
416 			s += size9p(v.Type, v.Version, v.Path)
417 		case *Qid:
418 			s += size9p(*v)
419 		case []Qid:
420 			s += size9p(uint16(0))
421 			elements := make([]interface{}, len(v))
422 			for i := range elements {
423 				elements[i] = &v[i]
424 			}
425 			s += size9p(elements...)
426 		case *[]Qid:
427 			s += size9p(*v)
428 
429 		case Dir:
430 			// walk the fields of the message to get the total size. we just
431 			// use the field order from the message struct. We may add tag
432 			// ignoring if needed.
433 			elements, err := fields9p(v)
434 			if err != nil {
435 				// BUG(stevvooe): The options here are to return 0, panic or
436 				// make this return an error. Ideally, we make it safe to
437 				// return 0 and have the rest of the package do the right
438 				// thing. For now, we do this, but may want to panic until
439 				// things are stable.
440 				panic(err)
441 			}
442 
443 			s += size9p(elements...) + size9p(uint16(0))
444 		case *Dir:
445 			s += size9p(*v)
446 		case Fcall:
447 			s += size9p(v.Type, v.Tag, v.Message)
448 		case *Fcall:
449 			s += size9p(*v)
450 		case Message:
451 			// special case twstat and rstat for size fields. See bugs in
452 			// http://man.cat-v.org/plan_9/5/stat to make sense of this.
453 			switch v.(type) {
454 			case *MessageRstat, MessageRstat:
455 				s += size9p(uint16(0)) // for extra size field before dir
456 			}
457 
458 			// walk the fields of the message to get the total size. we just
459 			// use the field order from the message struct. We may add tag
460 			// ignoring if needed.
461 			elements, err := fields9p(v)
462 			if err != nil {
463 				// BUG(stevvooe): The options here are to return 0, panic or
464 				// make this return an error. Ideally, we make it safe to
465 				// return 0 and have the rest of the package do the right
466 				// thing. For now, we do this, but may want to panic until
467 				// things are stable.
468 				panic(err)
469 			}
470 
471 			s += size9p(elements...)
472 		}
473 	}
474 
475 	return s
476 }
477 
478 // fields9p lists the settable fields from a struct type for reading and
479 // writing. We are using a lot of reflection here for fairly static
480 // serialization but we can replace this in the future with generated code if
481 // performance is an issue.
482 func fields9p(v interface{}) ([]interface{}, error) {
483 	rv := reflect.Indirect(reflect.ValueOf(v))
484 
485 	if rv.Kind() != reflect.Struct {
486 		return nil, fmt.Errorf("cannot extract fields from non-struct: %v", rv)
487 	}
488 
489 	var elements []interface{}
490 	for i := 0; i < rv.NumField(); i++ {
491 		f := rv.Field(i)
492 
493 		if !f.CanInterface() {
494 			// unexported field, skip it.
495 			continue
496 		}
497 
498 		if f.CanAddr() {
499 			f = f.Addr()
500 		}
501 
502 		elements = append(elements, f.Interface())
503 	}
504 
505 	return elements, nil
506 }
507 
508 func string9p(v interface{}) string {
509 	if v == nil {
510 		return "nil"
511 	}
512 
513 	rv := reflect.Indirect(reflect.ValueOf(v))
514 
515 	if rv.Kind() != reflect.Struct {
516 		panic("not a struct")
517 	}
518 
519 	var s string
520 
521 	for i := 0; i < rv.NumField(); i++ {
522 		f := rv.Field(i)
523 
524 		s += fmt.Sprintf(" %v=%v", strings.ToLower(rv.Type().Field(i).Name), f.Interface())
525 	}
526 
527 	return s
528 }