1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
use std::borrow::Cow;
use std::default::Default;
use std::error;
use std::fmt;
use std::io;
use std::cmp::min;
use std::convert::From;

extern crate inflate;

use self::inflate::InflateStream;
use crc::Crc32;
use traits::ReadBytesExt;
use common::{ColorType, BitDepth, Info, Unit, PixelDimensions, AnimationControl, FrameControl};
use chunk::{self, ChunkType, IHDR, IDAT, IEND};

/// TODO check if these size are reasonable
pub const CHUNCK_BUFFER_SIZE: usize = 32*1024;

#[derive(Debug)]
enum U32Value {
    // CHUNKS
    Length,
    Type(u32),
    Crc(ChunkType)
}

#[derive(Debug)]
enum State {
    Signature(u8, [u8; 7]),
    U32Byte3(U32Value, u32),
    U32Byte2(U32Value, u32),
    U32Byte1(U32Value, u32),
    U32(U32Value),
    ReadChunk(ChunkType, bool),
    PartialChunk(ChunkType),
    DecodeData(ChunkType, usize),
}

#[derive(Debug)]
/// Result of the decoding process
pub enum Decoded {
    /// Nothing decoded yet
    Nothing,
    Header(u32, u32, BitDepth, ColorType, bool),
    ChunkBegin(u32, ChunkType),
    ChunkComplete(u32, ChunkType),
    PixelDimensions(PixelDimensions),
    AnimationControl(AnimationControl),
    FrameControl(FrameControl),
    /// Decoded raw image data.
    ImageData,
    PartialChunk(ChunkType),
    ImageEnd,
}

#[derive(Debug)]
pub enum DecodingError {
    IoError(io::Error),
    Format(Cow<'static, str>),
    InvalidSignature,
    CrcMismatch {
        /// bytes to skip to try to recover from this error
        recover: usize,
        /// Stored CRC32 value
        crc_val: u32,
        /// Calculated CRC32 sum
        crc_sum: u32,
        chunk: ChunkType
    },
    Other(Cow<'static, str>),
    CorruptFlateStream
}

impl error::Error for DecodingError {
    fn description(&self) -> &str {
        use self::DecodingError::*;
        match *self {
            IoError(ref err) => err.description(),
            Format(ref desc) | Other(ref desc) => &desc,
            InvalidSignature => "invalid signature",
            CrcMismatch { .. } => "CRC error",
            CorruptFlateStream => "compressed data stream corrupted"
        }
    }
}

impl fmt::Display for DecodingError {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(fmt, "{}", (self as &error::Error).description())
    }
}

impl From<io::Error> for DecodingError {
    fn from(err: io::Error) -> DecodingError {
        DecodingError::IoError(err)
    }
}

impl From<String> for DecodingError {
    fn from(err: String) -> DecodingError {
        DecodingError::Other(err.into())
    }
}

impl From<DecodingError> for io::Error {
    fn from(err: DecodingError) -> io::Error {
        use std::error::Error;
        match err {
            DecodingError::IoError(err) => err,
            err => io::Error::new(
                io::ErrorKind::Other,
                err.description()
            )
        }
    }
}

/// PNG StreamingDecoder (low-level interface)
pub struct StreamingDecoder {
    state: Option<State>,
    current_chunk: (Crc32, u32, Vec<u8>),
    inflater: InflateStream,
    info: Option<Info>,
    current_seq_no: Option<u32>,
    have_idat: bool,
}

impl StreamingDecoder {
    /// Creates a new StreamingDecoder
    ///
    /// Allocates the internal buffers.
    pub fn new() -> StreamingDecoder {
        StreamingDecoder {
            state: Some(State::Signature(0, [0; 7])),
            current_chunk: (Crc32::new(), 0, Vec::with_capacity(CHUNCK_BUFFER_SIZE)),
            inflater: if cfg!(fuzzing) {InflateStream::from_zlib_no_checksum()} else {InflateStream::from_zlib()},
            info: None,
            current_seq_no: None,
            have_idat: false
        }
    }

    /// Resets the StreamingDecoder
    pub fn reset(&mut self) {
        self.state = Some(State::Signature(0, [0; 7]));
        self.current_chunk.0 = Crc32::new();
        self.current_chunk.1 = 0;
        self.current_chunk.2.clear();
        self.inflater = if cfg!(fuzzing) {InflateStream::from_zlib_no_checksum()} else {InflateStream::from_zlib()};
        self.info = None;
        self.current_seq_no = None;
        self.have_idat = false;
    }

    /// Low level StreamingDecoder interface.
    ///
    /// Allows to stream partial data to the encoder. Returns a tuple containing the bytes that have
    /// been consumed from the input buffer and the current decoding result. If the decoded chunk
    /// was an image data chunk, it also appends the read data to `image_data`.
    pub fn update(&mut self, mut buf: &[u8], image_data: &mut Vec<u8>)
    -> Result<(usize, Decoded), DecodingError> {
        let len = buf.len();
        while buf.len() > 0 && self.state.is_some() {
            match self.next_state(buf, image_data) {
                Ok((bytes, Decoded::Nothing)) => {
                    buf = &buf[bytes..]
                }
                Ok((bytes, result)) => {
                    buf = &buf[bytes..];
                    return Ok((len-buf.len(), result));
                }
                Err(err) => return Err(err)
            }
        }
        Ok((len-buf.len(), Decoded::Nothing))
    }

    fn next_state<'a>(&'a mut self, buf: &[u8], image_data: &mut Vec<u8>)
    -> Result<(usize, Decoded), DecodingError> {
        use self::State::*;

        macro_rules! goto (
            ($n:expr, $state:expr) => ({
                self.state = Some($state);
                Ok(($n, Decoded::Nothing))
            });
            ($state:expr) => ({
                self.state = Some($state);
                Ok((1, Decoded::Nothing))
            });
            ($n:expr, $state:expr, emit $res:expr) => ({
                self.state = Some($state);
                Ok(($n, $res))
            });
            ($state:expr, emit $res:expr) => ({
                self.state = Some($state);
                Ok((1, $res))
            })
        );

        let current_byte = buf[0];

        // Driver should ensure that state is never None
        let state = self.state.take().unwrap();
        //println!("state: {:?}", state);

        match state {
            Signature(i, mut signature) => if i < 7 {
                signature[i as usize] = current_byte;
                goto!(Signature(i+1, signature))
            } else {
                if signature == [137, 80, 78, 71, 13, 10, 26] && current_byte == 10 {
                    goto!(U32(U32Value::Length))
                } else {
                    Err(DecodingError::InvalidSignature)
                }
            },
            U32Byte3(type_, mut val) => {
                use self::U32Value::*;
                val |= current_byte as u32;
                match type_ {
                    Length => goto!(U32(Type(val))),
                    Type(length) => {
                        let type_str = [
                            (val >> 24) as u8,
                            (val >> 16) as u8,
                            (val >> 8) as u8,
                            val as u8
                        ];
                        self.current_chunk.0.reset();
                        self.current_chunk.0.update(&type_str);
                        self.current_chunk.1 = length;
                        goto!(
                            ReadChunk(type_str, true),
                            emit Decoded::ChunkBegin(length, type_str)
                        )
                    },
                    Crc(type_str) => {
                        if cfg!(fuzzing) || val == self.current_chunk.0.checksum() {
                            goto!(
                                State::U32(U32Value::Length),
                                emit if type_str == IEND {
                                    Decoded::ImageEnd
                                } else {
                                    Decoded::ChunkComplete(val, type_str)
                                }
                            )
                        } else {
                            Err(DecodingError::CrcMismatch {
                                recover: 1,
                                crc_val: val,
                                crc_sum: self.current_chunk.0.checksum(),
                                chunk: type_str
                            })
                        }
                    },
                }
            },
            U32Byte2(type_, val) => {
                goto!(U32Byte3(type_, val | (current_byte as u32) << 8))
            },
            U32Byte1(type_, val) => {
                goto!(U32Byte2(type_, val | (current_byte as u32) << 16))
            },
            U32(type_) => {
                goto!(U32Byte1(type_,       (current_byte as u32) << 24))
            },
            PartialChunk(type_str) => {
                match type_str {
                    IDAT => {
                        self.have_idat = true;
                        goto!(
                            0,
                            DecodeData(type_str, 0),
                            emit Decoded::PartialChunk(type_str)
                        )
                    },
                    chunk::fdAT => {
                        if let Some(seq_no) = self.current_seq_no {
                            let mut buf = &self.current_chunk.2[..];
                            let next_seq_no = try!(buf.read_be());
                            if next_seq_no != seq_no + 1 {
                                return Err(DecodingError::Format(format!(
                                    "Sequence is not in order, expected #{} got #{}.",
                                    seq_no + 1,
                                    next_seq_no
                                ).into()))
                            }
                            self.current_seq_no = Some(next_seq_no);
                        } else {
                            return Err(DecodingError::Format("fcTL chunk missing before fdAT chunk.".into()))
                        }
                        goto!(
                            0,
                            DecodeData(type_str, 4),
                            emit Decoded::PartialChunk(type_str)
                        )
                    },
                    // Handle other chunks
                    _ => {
                        if self.current_chunk.1 == 0 { // complete chunk
                            Ok((0, try!(self.parse_chunk(type_str))))
                        } else {
                            goto!(
                                0, ReadChunk(type_str, true),
                                emit Decoded::PartialChunk(type_str)
                            )
                        }
                    }
                }

            },
            ReadChunk(type_str, clear) => {
                if clear {
                    self.current_chunk.2.clear();
                }
                if self.current_chunk.1 > 0 {
                    let (ref mut crc, ref mut remaining, ref mut c_buf) = self.current_chunk;
                    let buf_avail = c_buf.capacity() - c_buf.len();
                    let bytes_avail = min(buf.len(), buf_avail);
                    let n = min(*remaining, bytes_avail as u32);
                    if buf_avail == 0 {
                        goto!(0, PartialChunk(type_str))
                    } else {
                        let buf = &buf[..n as usize];
                        crc.update(buf);
                        c_buf.extend(buf.iter().map(|&v| v));
                        *remaining -= n;
                        if *remaining == 0 {
                            goto!(n as usize, PartialChunk(type_str
                            ))
                        } else {
                            goto!(n as usize, ReadChunk(type_str, false))
                        }

                    }
                } else {
                    goto!(0, U32(U32Value::Crc(type_str)))
                }
            }
            DecodeData(type_str, mut n) => {
                let chunk_len = self.current_chunk.2.len();
                let (c, data) = try!(self.inflater.update(&self.current_chunk.2[n..]));
                image_data.extend_from_slice(data);
                n += c;
                if n == chunk_len && data.len() == 0 && c == 0 {
                    goto!(
                        0,
                        ReadChunk(type_str, true),
                        emit Decoded::ImageData
                    )
                } else {
                    goto!(
                        0,
                        DecodeData(type_str, n),
                        emit Decoded::ImageData
                    )
                }
            }
        }
    }

    fn parse_chunk(&mut self, type_str: [u8; 4])
    -> Result<Decoded, DecodingError> {
        self.state = Some(State::U32(U32Value::Crc(type_str)));
        if self.info.is_none() && type_str != IHDR {
            return Err(DecodingError::Format(format!(
                "{} chunk appeared before IHDR chunk", String::from_utf8_lossy(&type_str)
            ).into()))
        }
        match match type_str {
            IHDR => {
                self.parse_ihdr()
            }
            chunk::PLTE => {
                self.parse_plte()
            }
            chunk::tRNS => {
                self.parse_trns()
            }
            chunk::pHYs => {
                self.parse_phys()
            }
            chunk::acTL => {
                self.parse_actl()
            }
            chunk::fcTL => {
                self.parse_fctl()
            }
            _ => Ok(Decoded::PartialChunk(type_str))
        } {
            Err(err) =>{
                // Borrow of self ends here, because Decoding error does not borrow self.
                self.state = None;
                Err(err)
            },
            ok => ok
        }
    }

    fn get_info_or_err(&self) -> Result<&Info, DecodingError> {
        self.info.as_ref().ok_or(DecodingError::Format(
            "IHDR chunk missing".into()
        ))
    }

    fn parse_fctl(&mut self)
    -> Result<Decoded, DecodingError> {
        let mut buf = &self.current_chunk.2[..];
        let next_seq_no = try!(buf.read_be());

        // Asuming that fcTL is required before *every* fdAT-sequence
        self.current_seq_no = Some(if let Some(seq_no) = self.current_seq_no {
            if next_seq_no != seq_no + 1 {
                return Err(DecodingError::Format(format!(
                    "Sequence is not in order, expected #{} got #{}.",
                    seq_no + 1,
                    next_seq_no
                ).into()))
            }
            next_seq_no
        } else {
            if next_seq_no != 0 {
                return Err(DecodingError::Format(format!(
                    "Sequence is not in order, expected #{} got #{}.",
                    0,
                    next_seq_no
                ).into()))
            }
            0
        });
        self.inflater = if cfg!(fuzzing) {InflateStream::from_zlib_no_checksum()} else {InflateStream::from_zlib()};
        let fc = FrameControl {
            sequence_number: next_seq_no,
            width: try!(buf.read_be()),
            height: try!(buf.read_be()),
            x_offset: try!(buf.read_be()),
            y_offset: try!(buf.read_be()),
            delay_num: try!(buf.read_be()),
            delay_den: try!(buf.read_be()),
            dispose_op: try!(buf.read_be()),
            blend_op : try!(buf.read_be()),
        };
        self.info.as_mut().unwrap().frame_control = Some(fc.clone());
        Ok(Decoded::FrameControl(fc))
    }

    fn parse_actl(&mut self)
    -> Result<Decoded, DecodingError> {
        if self.have_idat {
            Err(DecodingError::Format(
                "acTL chunk appeared after first IDAT chunk".into()
            ))
        } else {
            let mut buf = &self.current_chunk.2[..];
            let actl = AnimationControl {
                num_frames: try!(buf.read_be()),
                num_plays: try!(buf.read_be())
            };
            self.info.as_mut().unwrap().animation_control = Some(actl);
            Ok(Decoded::AnimationControl(actl))
        }
    }

    fn parse_plte(&mut self)
    -> Result<Decoded, DecodingError> {
        let mut vec = Vec::new();
        vec.extend(self.current_chunk.2.iter().map(|&v| v));
        self.info.as_mut().map(
            |info| info.palette = Some(vec)
        );
        Ok(Decoded::Nothing)
    }

    fn parse_trns(&mut self)
    -> Result<Decoded, DecodingError> {
        use common::ColorType::*;
        let (color_type, bit_depth) = {
            let info = try!(self.get_info_or_err());
            (info.color_type, info.bit_depth as u8)
        };
        let mut vec = Vec::new();
        vec.extend(self.current_chunk.2.iter().map(|&v| v));
        let len = vec.len();
        let info = match self.info {
            Some(ref mut info) => info,
            None => return Err(DecodingError::Format(
              "tRNS chunk occured before IHDR chunk".into()
            ))
        };
        info.trns = Some(vec);
        let vec = info.trns.as_mut().unwrap();
        match color_type {
            Grayscale => {
                if len < 2 {
                    return Err(DecodingError::Format(
                        "not enough palette entries".into()
                    ))
                }
                if bit_depth < 16 {
                    vec[0] = vec[1];
                    vec.truncate(1);
                }
                Ok(Decoded::Nothing)
            },
            RGB => {
                if len < 6 {
                    return Err(DecodingError::Format(
                        "not enough palette entries".into()
                    ))
                }
                if bit_depth < 16 {
                    vec[0] = vec[1];
                    vec[1] = vec[3];
                    vec[2] = vec[5];
                    vec.truncate(3);
                }
                Ok(Decoded::Nothing)
            },
            Indexed => {
                let _ = info.palette.as_ref().ok_or(DecodingError::Format(
                    "tRNS chunk occured before PLTE chunk".into()
                ));
                Ok(Decoded::Nothing)
            },
            c => Err(DecodingError::Format(
                format!("tRNS chunk found for color type ({})", c as u8).into()
            ))
        }

    }

    fn parse_phys(&mut self)
    -> Result<Decoded, DecodingError> {
        if self.have_idat {
            Err(DecodingError::Format(
                "pHYs chunk appeared after first IDAT chunk".into()
            ))
        } else {
            let mut buf = &self.current_chunk.2[..];
            let xppu = try!(buf.read_be());
            let yppu = try!(buf.read_be());
            let unit = try!(buf.read_be());
            let unit = match Unit::from_u8(unit) {
                Some(unit) => unit,
                None => return Err(DecodingError::Format(
                    format!("invalid unit ({})", unit).into()
                ))
            };
            let pixel_dims = PixelDimensions {
                xppu: xppu,
                yppu: yppu,
                unit: unit,
            };
            self.info.as_mut().unwrap().pixel_dims = Some(pixel_dims);
            Ok(Decoded::PixelDimensions(pixel_dims))
        }
    }

    fn parse_ihdr(&mut self)
    -> Result<Decoded, DecodingError> {
        // TODO: check if color/bit depths combination is valid
        let mut buf = &self.current_chunk.2[..];
        let width = try!(buf.read_be());
        let height = try!(buf.read_be());
        let bit_depth = try!(buf.read_be());
        let bit_depth = match BitDepth::from_u8(bit_depth) {
            Some(bits) => bits,
            None => return Err(DecodingError::Format(
                format!("invalid bit depth ({})", bit_depth).into()
            ))
        };
        let color_type = try!(buf.read_be());
        let color_type = match ColorType::from_u8(color_type) {
            Some(color_type) => color_type,
            None => return Err(DecodingError::Format(
                format!("invalid color type ({})", color_type).into()
            ))
        };
        match try!(buf.read_be()) { // compression method
            0u8 => (),
            n => return Err(DecodingError::Format(
                format!("unknown compression method ({})", n).into()
            ))
        }
        match try!(buf.read_be()) { // filter method
            0u8 => (),
            n => return Err(DecodingError::Format(
                format!("unknown filter method ({})", n).into()
            ))
        }
        let interlaced = match try!(buf.read_be()) {
            0u8 => false,
            1 => {
                true
            },
            n => return Err(DecodingError::Format(
                format!("unknown interlace method ({})", n).into()
            ))
        };
        let mut info = Info::default();

        info.width = width;
        info.height = height;
        info.bit_depth = bit_depth;
        info.color_type = color_type;
        info.interlaced = interlaced;
        self.info = Some(info);
        Ok(Decoded::Header(
            width,
            height,
            bit_depth,
            color_type,
            interlaced
        ))
    }
}

#[inline(always)]
pub fn get_info(d: &StreamingDecoder) -> Option<&Info> {
    d.info.as_ref()
}