      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

    //! # Minimal gif encoder

    use std::cmp::min;
    use std::io;
    use std::io::prelude::*;

    use lzw;

    use traits::{Parameter, WriteBytesExt};
    use common::{Block, Frame, Extension, DisposalMethod};
    use util;

    /// Number of repetitions
    pub enum Repeat {
        /// Finite number of repetitions
        Finite(u16),
        /// Infinite number of repetitions
        Infinite
    }

    impl<W: Write> Parameter<Encoder<W>> for Repeat {
        type Result = Result<(), io::Error>;
        fn set_param(self, this: &mut Encoder<W>) -> Self::Result {
            this.write_extension(ExtensionData::Repetitions(self))
        }
    }

    /// Extension data.
    pub enum ExtensionData {
        /// Control extension. Use `ExtensionData::new_control_ext` to construct.
        Control {
            /// Flags.
            flags: u8,
            /// Frame delay.
            delay: u16,
            /// Transparent index.
            trns: u8
        },
        /// Sets the number of repetitions
        Repetitions(Repeat)
    }

    impl ExtensionData {
        /// Constructor for control extension data.
        ///
        /// `delay` is given in units of 10 ms.
        pub fn new_control_ext(delay: u16, dispose: DisposalMethod,
                               needs_user_input: bool, trns: Option<u8>) -> ExtensionData {
            let mut flags = 0;
            let trns = match trns {
                Some(trns) => {
                    flags |= 1;
                    trns as u8
                },
                None => 0
            };
            flags |= (needs_user_input as u8) << 1;
            flags |= (dispose as u8) << 2;
            ExtensionData::Control {
                flags: flags,
                delay: delay,
                trns: trns
            }
        }
    }

    struct BlockWriter<'a, W: Write + 'a> {
        w: &'a mut W,
        bytes: usize,
        buf: [u8; 0xFF]
    }

    impl<'a, W: Write + 'a> BlockWriter<'a, W> {
        fn new(w: &'a mut W) -> BlockWriter<'a, W> {
            BlockWriter {
                w: w,
                bytes: 0,
                buf: [0; 0xFF]
            }
        }
    }

    impl<'a, W: Write + 'a> Write for BlockWriter<'a, W> {

        fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
            let to_copy = min(buf.len(), 0xFF - self.bytes);
            util::copy_memory(&buf[..to_copy], &mut self.buf[self.bytes..]);
            self.bytes += to_copy;
            if self.bytes == 0xFF {
                self.bytes = 0;
                self.w.write_le(0xFFu8)?;
                self.w.write_all(&self.buf)?;
            }
            Ok(to_copy)
        }
        fn flush(&mut self) -> io::Result<()> {
            return Err(io::Error::new(
                io::ErrorKind::Other,
                "Cannot flush a BlockWriter, use `drop` instead."
            ))
        }
    }

    impl<'a, W: Write + 'a> Drop for BlockWriter<'a, W> {

        #[cfg(feature = "raii_no_panic")]
        fn drop(&mut self) {
            if self.bytes > 0 {
                let _ = self.w.write_le(self.bytes as u8);
                let _ = self.w.write_all(&self.buf[..self.bytes]);
            }
        }

        #[cfg(not(feature = "raii_no_panic"))]
        fn drop(&mut self) {
            if self.bytes > 0 {
                self.w.write_le(self.bytes as u8).unwrap();
                self.w.write_all(&self.buf[..self.bytes]).unwrap();
            }
        }
    }

    /// GIF encoder.
    pub struct Encoder<W: Write> {
        w: W,
        global_palette: bool,
        width: u16,
        height: u16
    }

    impl<W: Write> Encoder<W> {
        /// Creates a new encoder.
        ///
        /// `global_palette` gives the global color palette in the format `[r, g, b, ...]`,
        /// if no global palette shall be used an empty slice may be supplied.
        pub fn new(w: W, width: u16, height: u16, global_palette: &[u8]) -> io::Result<Self> {
            Encoder {
                w: w,
                global_palette: false,
                width: width,
                height: height
            }.write_global_palette(global_palette)
        }

        /// Writes the global color palette.
        pub fn write_global_palette(mut self, palette: &[u8]) -> io::Result<Self> {
            self.global_palette = true;
            let mut flags = 0;
            flags |= 0b1000_0000;
            let num_colors = palette.len() / 3;
            if num_colors > 256 {
                return Err(io::Error::new(io::ErrorKind::InvalidInput, "Too many colors"));
            }
            flags |= flag_size(num_colors);
            flags |= flag_size(num_colors) << 4; // wtf flag
            self.write_screen_desc(flags)?;
            self.write_color_table(palette)?;
            Ok(self)
        }

        /// Writes a frame to the image.
        ///
        /// Note: This function also writes a control extension if necessary.
        pub fn write_frame(&mut self, frame: &Frame) -> io::Result<()> {
            // TODO commented off to pass test in lib.rs
            //if frame.delay > 0 || frame.transparent.is_some() {
                self.write_extension(ExtensionData::new_control_ext(
                    frame.delay,
                    frame.dispose,
                    frame.needs_user_input,
                    frame.transparent

                ))?;
            //}
            self.w.write_le(Block::Image as u8)?;
            self.w.write_le(frame.left)?;
            self.w.write_le(frame.top)?;
            self.w.write_le(frame.width)?;
            self.w.write_le(frame.height)?;
            let mut flags = 0;
            if frame.interlaced {
                flags |= 0b0100_0000;
            }
            match frame.palette {
                Some(ref palette) => {
                    flags |= 0b1000_0000;
                    let num_colors = palette.len() / 3;
                    if num_colors > 256 {
                        return Err(io::Error::new(io::ErrorKind::InvalidInput, "Too many colors"));
                    }
                    flags |= flag_size(num_colors);
                    self.w.write_le(flags)?;
                    self.write_color_table(palette)
                },
                None => if !self.global_palette {
                    return Err(io::Error::new(
                        io::ErrorKind::InvalidInput,
                        "The GIF format requires a color palette but none was given."
                    ))
                } else {
                    self.w.write_le(flags)
                }
            }?;
            self.write_image_block(&frame.buffer)
        }

        fn write_image_block(&mut self, data: &[u8]) -> io::Result<()> {
            {
                let min_code_size: u8 = match flag_size(*data.iter().max().unwrap_or(&0) as usize + 1) + 1 {
                    1 => 2, // As per gif spec: The minimal code size has to be >= 2
                    n => n
                };
                self.w.write_le(min_code_size)?;
                let mut bw = BlockWriter::new(&mut self.w);
                let mut enc = lzw::Encoder::new(lzw::LsbWriter::new(&mut bw), min_code_size)?;
                enc.encode_bytes(data)?;
            }
            self.w.write_le(0u8)
        }

        fn write_color_table(&mut self, table: &[u8]) -> io::Result<()> {
            let num_colors = table.len() / 3;
            if num_colors > 256 {
                return Err(io::Error::new(io::ErrorKind::InvalidInput, "Too many colors"));
            }
            let size = flag_size(num_colors);
            self.w.write_all(&table[..num_colors * 3])?;
            // Waste some space as of gif spec
            for _ in 0..((2 << size) - num_colors) {
                self.w.write_all(&[0, 0, 0])?
            }
            Ok(())
        }

        /// Writes an extension to the image.
        ///
        /// It is normally not necessary to call this method manually.
        pub fn write_extension(&mut self, extension: ExtensionData) -> io::Result<()> {
            use self::ExtensionData::*;
            // 0 finite repetitions can only be achieved
            // if the corresponting extension is not written
            if let Repetitions(Repeat::Finite(0)) = extension {
                return Ok(())
            }
            self.w.write_le(Block::Extension as u8)?;
            match extension {
                Control { flags, delay, trns } => {
                    self.w.write_le(Extension::Control as u8)?;
                    self.w.write_le(4u8)?;
                    self.w.write_le(flags)?;
                    self.w.write_le(delay)?;
                    self.w.write_le(trns)?;
                }
                Repetitions(repeat) => {
                    self.w.write_le(Extension::Application as u8)?;
                    self.w.write_le(11u8)?;
                    self.w.write(b"NETSCAPE2.0")?;
                    self.w.write_le(3u8)?;
                    self.w.write_le(1u8)?;
                    match repeat {
                        Repeat::Finite(no) => self.w.write_le(no)?,
                        Repeat::Infinite => self.w.write_le(0u16)?,
                    }
                }
            }
            self.w.write_le(0u8)
        }

        /// Writes a raw extension to the image.
        ///
        /// This method can be used to write an unsupported extesion to the file. `func` is the extension
        /// identifier (e.g. `Extension::Application as u8`). `data` are the extension payload blocks. If any
        /// contained slice has a lenght > 255 it is automatically divided into sub-blocks.
        pub fn write_raw_extension(&mut self, func: u8, data: &[&[u8]]) -> io::Result<()> {
            self.w.write_le(Block::Extension as u8)?;
            self.w.write_le(func as u8)?;
            for block in data {
                for chunk in block.chunks(0xFF) {
                    self.w.write_le(chunk.len() as u8)?;
                    self.w.write_all(chunk)?;
                }
            }
            self.w.write_le(0u8)
        }

        /// Writes the logical screen desriptor
        fn write_screen_desc(&mut self, flags: u8) -> io::Result<()> {
            self.w.write_all(b"GIF89a")?;
            self.w.write_le(self.width)?;
            self.w.write_le(self.height)?;
            self.w.write_le(flags)?; // packed field
            self.w.write_le(0u8)?; // bg index
            self.w.write_le(0u8) // aspect ratio
        }
    }

    impl<W: Write> Drop for Encoder<W> {

        #[cfg(feature = "raii_no_panic")]
        fn drop(&mut self) {
            let _ = self.w.write_le(Block::Trailer as u8);
        }

        #[cfg(not(feature = "raii_no_panic"))]
        fn drop(&mut self) {
            self.w.write_le(Block::Trailer as u8).unwrap()
        }
    }

    // Color table size converted to flag bits
    fn flag_size(size: usize) -> u8 {
        match size {
            0  ...2   => 0,
            3  ...4   => 1,
            5  ...8   => 2,
            7  ...16  => 3,
            17 ...32  => 4,
            33 ...64  => 5,
            65 ...128 => 6,
            129...256 => 7,
            _ => 7
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)