From 654be91de3768f7c01acb36ab82460765927493a Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Mon, 1 Mar 2021 22:10:12 +0530
Subject: add decode logic

---
 src/decode.rs | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/encode.rs | 11 ++++++-----
 src/lib.rs    |  8 ++++++++
 3 files changed, 64 insertions(+), 5 deletions(-)
 create mode 100644 src/decode.rs

diff --git a/src/decode.rs b/src/decode.rs
new file mode 100644
index 0000000..59dae97
--- /dev/null
+++ b/src/decode.rs
@@ -0,0 +1,50 @@
+use std::io::{self, Cursor, Read};
+
+use bitvec::prelude::*;
+use byteorder::{LittleEndian, ReadBytesExt};
+
+use crate::{FileHeader, Image, ImageInfoHeader};
+
+pub fn decode_image(obi_data: &mut Cursor<Vec<u8>>) -> io::Result<Image> {
+    // file header
+    let version = obi_data.read_u16::<LittleEndian>()?;
+    let file_size = obi_data.read_u32::<LittleEndian>()?;
+    let data_offset = obi_data.read_u32::<LittleEndian>()?;
+    let file_header = FileHeader {
+        version,
+        file_size,
+        data_offset,
+    };
+
+    // image info header
+    let width = obi_data.read_u32::<LittleEndian>()?;
+    let height = obi_data.read_u32::<LittleEndian>()?;
+    let compression_type = obi_data.read_u32::<LittleEndian>()?;
+    let post_compression_size = obi_data.read_u32::<LittleEndian>()?;
+    let image_info_header = ImageInfoHeader {
+        width,
+        height,
+        compression_type,
+        post_compression_size,
+    };
+
+    // pixmap data
+    let mut data_bytes = vec![];
+    obi_data.read_to_end(&mut data_bytes)?;
+    let data = data_bytes
+        .iter()
+        .map(|&b| {
+            BitVec::<Lsb0, u8>::from_element(b)
+                .into_iter()
+                .map(|e| e as bool)
+                .collect::<Vec<bool>>()
+        })
+        .flatten()
+        .collect::<Vec<_>>();
+
+    return Ok(Image {
+        file_header,
+        image_info_header,
+        data,
+    });
+}
diff --git a/src/encode.rs b/src/encode.rs
index 24d3792..e5760a8 100644
--- a/src/encode.rs
+++ b/src/encode.rs
@@ -1,7 +1,6 @@
 use std::io;
 
-use bitvec::prelude::*;
-use bitvec::slice::BitSlice;
+use bitvec::{prelude::*, vec::BitVec};
 use byteorder::{LittleEndian, WriteBytesExt};
 
 use crate::Image;
@@ -25,9 +24,11 @@ pub fn encode_image(obi_image: Image) -> io::Result<Vec<u8>> {
     // pixmap data
     let pixmap = obi_image.data;
     for byte in pixmap.chunks(8) {
-        let bits_as_u8 = byte.iter().map(|&e| e as u8).collect::<Vec<_>>();
-        let slice = BitSlice::<Lsb0, _>::from_slice(&bits_as_u8).unwrap();
-        obi_data.write_u8(slice.load::<u8>())?;
+        let mut bv = BitVec::<Lsb0, u8>::new();
+        for &b in byte {
+            bv.push(b);
+        }
+        obi_data.write_u8(bv.load::<u8>())?;
     }
 
     return Ok(obi_data);
diff --git a/src/lib.rs b/src/lib.rs
index 61ca7a8..cd7923c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 #![allow(unreachable_patterns)]
 #![allow(non_snake_case)]
 
+pub mod decode;
 pub mod encode;
 
 #[non_exhaustive]
@@ -107,4 +108,11 @@ mod tests {
         let file_header_size = size_of::<ImageInfoHeader>();
         assert_eq!(16, file_header_size);
     }
+
+    #[test]
+    fn encode_decode() {
+        let img = Image::new(100, 80);
+        let encoded = encode::encode_image(img).unwrap();
+        assert_eq!(encoded.len(), 1026);
+    }
 }
-- 
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