Refactor Group4 reader into stream module

Cargo.toml

@@ -20,7 +20,7 @@ exclude = ["tests/images/*", "tests/fuzz_images/*"]
 half = { version = "2.4.1" }
 quick-error = "2.0.1"
 
-fax = { version = "0.2.2", optional = true }
+fax = { version = "0.2.4", optional = true }
 flate2 = { version = "1.0.20", optional = true }
 weezl = { version = "0.1.10", optional = true }
 zstd = { version = "0.13", optional = true }

src/decoder/image.rs

@@ -10,8 +10,6 @@ use crate::{
     ColorType, Directory, TiffError, TiffFormatError, TiffResult, TiffUnsupportedError, UsageError,
 };
 
-#[cfg(feature = "fax")]
-use std::collections::VecDeque;
 use std::io::{self, Cursor, Read, Seek};
 use std::num::NonZeroUsize;
 use std::sync::Arc;
@@ -458,68 +456,11 @@ impl Image {
                 Box::new(Cursor::new(data))
             }
             #[cfg(feature = "fax")]
-            CompressionMethod::Fax4 => {
-                let width = u16::try_from(dimensions.0)?;
-                let height = u16::try_from(dimensions.1)?;
-
-                struct Group4Reader<R2> {
-                    decoder: fax::decoder::Group4Decoder<std::io::Bytes<R2>>,
-                    bits: bitvec::vec::BitVec<u8, bitvec::prelude::Msb0>,
-                    byte_buf: VecDeque<u8>,
-                    y: u16,
-                    height: u16,
-                    width: u16,
-                }
-
-                impl<R2: Read> Read for Group4Reader<R2> {
-                    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-                        if self.byte_buf.is_empty() && self.y < self.height {
-                            let next = self
-                                .decoder
-                                .advance()
-                                .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e))?;
-
-                            match next {
-                                fax::decoder::DecodeStatus::End => {
-                                    // eprintln!("DONE!");
-                                    self.byte_buf.extend(self.bits.as_raw_slice())
-                                }
-                                fax::decoder::DecodeStatus::Incomplete => {
-                                    self.y += 1;
-                                    // eprintln!("{:?}", self.y);
-                                    for c in
-                                        fax::decoder::pels(self.decoder.transition(), self.width)
-                                    {
-                                        self.bits.push(match c {
-                                            fax::Color::Black => true,
-                                            fax::Color::White => false,
-                                        });
-                                        if self.bits.len() == 8 {
-                                            self.byte_buf.extend(self.bits.as_raw_slice());
-                                            self.bits.clear()
-                                        }
-                                    }
-                                }
-                            }
-                        }
-                        // eprintln!("{:?}: {:?} / {:?}", self.y, self.byte_buf.len(), self.bits.len());
-
-                        self.byte_buf.read(buf)
-                    }
-                }
-
-                Box::new(Group4Reader {
-                    decoder: fax::decoder::Group4Decoder::new(
-                        reader.take(compressed_length).bytes(),
-                        width,
-                    )?,
-                    bits: bitvec::vec::BitVec::new(),
-                    byte_buf: VecDeque::new(),
-                    y: 0,
-                    width: width,
-                    height: height,
-                })
-            }
+            CompressionMethod::Fax4 => Box::new(super::stream::Group4Reader::new(
+                dimensions,
+                reader,
+                compressed_length,
+            )?),
             method => {
                 return Err(TiffError::UnsupportedError(
                     TiffUnsupportedError::UnsupportedCompressionMethod(method),

src/decoder/mod.rs

@@ -547,7 +547,6 @@ fn fix_endianness(buf: &mut [u8], byte_order: ByteOrder, bit_depth: u8) {
 }
 
 impl<R: Read + Seek> Decoder<R> {
-    /// Create a new decoder that decodes from the stream ```r```
     pub fn new(mut r: R) -> TiffResult<Decoder<R>> {
         let mut endianess = Vec::with_capacity(2);
         (&mut r).take(2).read_to_end(&mut endianess)?;

src/decoder/stream.rs

@@ -1,5 +1,7 @@
 //! All IO functionality needed for TIFF decoding
 
+#[cfg(feature = "fax")]
+use std::collections::VecDeque;
 use std::io::{self, BufRead, BufReader, Read, Seek, Take};
 
 /// Byte order of the TIFF file.
@@ -276,6 +278,71 @@ impl<R: Read> Read for PackBitsReader<R> {
     }
 }
 
+#[cfg(feature = "fax")]
+pub struct Group4Reader<R: Read> {
+    decoder: fax::decoder::Group4Decoder<io::Bytes<io::Take<R>>>,
+    bits: bitvec::vec::BitVec<u8, bitvec::prelude::Msb0>,
+    byte_buf: VecDeque<u8>,
+    height: u16,
+    width: u16,
+    y: u16,
+}
+
+#[cfg(feature = "fax")]
+impl<R: Read> Group4Reader<R> {
+    pub fn new(
+        dimensions: (u32, u32),
+        reader: R,
+        compressed_length: u64,
+    ) -> crate::TiffResult<Self> {
+        let width = u16::try_from(dimensions.0)?;
+        let height = u16::try_from(dimensions.1)?;
+
+        Ok(Self {
+            decoder: fax::decoder::Group4Decoder::new(
+                reader.take(compressed_length).bytes(),
+                width,
+            )?,
+            bits: bitvec::vec::BitVec::new(),
+            byte_buf: VecDeque::new(),
+            width: width,
+            height: height,
+            y: 0,
+        })
+    }
+
+    pub fn dump_bits(&mut self) -> () {
+        self.byte_buf.extend(self.bits.as_raw_slice());
+        self.bits.clear()
+    }
+}
+
+#[cfg(feature = "fax")]
+impl<R: Read> Read for Group4Reader<R> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        if self.byte_buf.is_empty() && self.y < self.height {
+            let next = self
+                .decoder
+                .advance()
+                .map_err(|e| std::io::Error::new(std::io::ErrorKind::Other, e))?;
+            match next {
+                fax::decoder::DecodeStatus::End => self.dump_bits(),
+                fax::decoder::DecodeStatus::Incomplete => {
+                    self.y += 1;
+                    for c in fax::decoder::pels(self.decoder.transition(), self.width) {
+                        self.bits.push(match c {
+                            fax::Color::Black => true,
+                            fax::Color::White => false,
+                        });
+                    }
+                    self.dump_bits();
+                }
+            }
+        }
+        self.byte_buf.read(buf)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;

tests/decode_images.rs

@@ -676,5 +676,5 @@ fn bytes_gray_f32() {
 #[test]
 #[cfg(feature = "fax")]
 fn test_fax4() {
-    test_image_sum_u8("fax4.tiff", ColorType::Gray(1), 62384985);
+    test_image_sum_u8("fax4.tiff", ColorType::Gray(1), 7802706);
 }