diff --git a/src/catar/decoder.rs b/src/catar/decoder.rs
index caf2734c..373a1fc5 100644
--- a/src/catar/decoder.rs
+++ b/src/catar/decoder.rs
@@ -1,3 +1,253 @@
 //! *catar* format decoder.
+//!
+//! This module contain the code to decode *catar* archive files.
 
+use failure::*;
 
+use super::format_definition::*;
+use crate::tools;
+
+use std::io::{Read, Seek, SeekFrom};
+use std::path::PathBuf;
+
+use std::os::unix::ffi::{OsStrExt, OsStringExt};
+use std::ffi::{OsStr, OsString};
+
+pub struct CaDirectoryEntry {
+    start: u64,
+    end: u64,
+    pub filename: OsString,
+    pub entry: CaFormatEntry,
+}
+
+// This one needs Read+Seek (we may want one without Seek?)
+pub struct CaTarDecoder<'a, R: Read + Seek> {
+    reader: &'a mut R,
+    root_start: u64,
+    root_end: u64,
+}
+
+const HEADER_SIZE: u64 = std::mem::size_of::<CaFormatHeader>() as u64;
+
+impl <'a, R: Read + Seek> CaTarDecoder<'a, R> {
+
+    pub fn new(reader: &'a mut R) -> Result<Self, Error> {
+
+        let root_end = reader.seek(SeekFrom::End(0))?;
+
+        Ok(Self {
+            reader: reader,
+            root_start: 0,
+            root_end: root_end,
+        })
+    }
+
+    pub fn root(&self) -> CaDirectoryEntry {
+        CaDirectoryEntry {
+            start: self.root_start,
+            end: self.root_end,
+            filename: OsString::new(), // Empty
+            entry: CaFormatEntry {
+                feature_flags: 0,
+                mode: 0,
+                flags: 0,
+                uid: 0,
+                gid: 0,
+                mtime: 0,
+            }
+        }
+    }
+
+    fn read_directory_entry(&mut self, start: u64, end: u64) -> Result<CaDirectoryEntry, Error> {
+
+        self.reader.seek(SeekFrom::Start(start))?;
+        let mut buffer = [0u8; HEADER_SIZE as usize];
+        self.reader.read_exact(&mut buffer)?;
+        let head = tools::map_struct::<CaFormatHeader>(&buffer)?;
+
+        if u64::from_le(head.htype) != CA_FORMAT_FILENAME {
+            bail!("wrong filename header type for object [{}..{}]", start, end);
+        }
+
+        let mut name_len = u64::from_le(head.size);
+
+        let entry_start = start + name_len;
+
+        if name_len < (HEADER_SIZE + 2) {
+            bail!("filename size too short for object [{}..{}]", start, end);
+        }
+        name_len -= HEADER_SIZE;
+
+        if name_len > ((libc::FILENAME_MAX as u64) + 1) {
+            bail!("filename too long for object [{}..{}]", start, end);
+        }
+
+        let mut buffer = vec![0u8; name_len as usize];
+        self.reader.read_exact(&mut buffer)?;
+
+        // fixme: check nul termination
+        let last_byte = buffer.pop().unwrap();
+        if last_byte != 0u8 {
+            bail!("filename entry not nul terminated, object [{}..{}]", start, end);
+
+        }
+
+        let filename = std::ffi::OsString::from_vec(buffer);
+
+        let mut buffer = [0u8; HEADER_SIZE as usize];
+        self.reader.read_exact(&mut buffer)?;
+        let head = tools::map_struct::<CaFormatHeader>(&buffer)?;
+
+        if u64::from_le(head.htype) != CA_FORMAT_ENTRY {
+            bail!("wrong entry header type for object [{}..{}]", start, end);
+        }
+
+        const ENTRY_SIZE: u64 = std::mem::size_of::<CaFormatEntry>() as u64;
+
+        let mut entry_len = u64::from_le(head.size);
+        if entry_len != (HEADER_SIZE + ENTRY_SIZE) {
+            bail!("wrong entry header size for object [{}..{}]", start, end);
+        }
+        entry_len -= HEADER_SIZE;
+
+        let mut buffer = [0u8; ENTRY_SIZE as usize];
+        self.reader.read_exact(&mut buffer)?;
+        let entry = tools::map_struct::<CaFormatEntry>(&buffer)?;
+
+        Ok(CaDirectoryEntry {
+            start: entry_start,
+            end: end,
+            filename: filename,
+            entry: CaFormatEntry {
+                feature_flags: u64::from_le(entry.feature_flags),
+                mode: u64::from_le(entry.mode),
+                flags: u64::from_le(entry.flags),
+                uid: u64::from_le(entry.uid),
+                gid: u64::from_le(entry.gid),
+                mtime: u64::from_le(entry.mtime),
+            },
+        })
+    }
+
+    pub fn list_dir(&mut self, dir: &CaDirectoryEntry) -> Result<Vec<CaDirectoryEntry>, Error> {
+
+        const GOODBYE_ITEM_SIZE: u64 = std::mem::size_of::<CaFormatGoodbyeItem>() as u64;
+
+        let start = dir.start;
+        let end = dir.end;
+
+        //println!("list_dir1: {} {}", start, end);
+
+        if (end - start) < (HEADER_SIZE + GOODBYE_ITEM_SIZE) {
+            bail!("detected short object [{}..{}]", start, end);
+        }
+
+        self.reader.seek(SeekFrom::Start(end - GOODBYE_ITEM_SIZE))?;
+        let mut buffer = [0u8; GOODBYE_ITEM_SIZE as usize];
+        self.reader.read_exact(&mut buffer)?;
+
+        let item = tools::map_struct::<CaFormatGoodbyeItem>(&buffer)?;
+
+        if u64::from_le(item.hash) != CA_FORMAT_GOODBYE_TAIL_MARKER {
+            bail!("missing goodbye tail marker for object [{}..{}]", start, end);
+        }
+
+        let goodbye_table_size = u64::from_le(item.size);
+        if goodbye_table_size < (HEADER_SIZE + GOODBYE_ITEM_SIZE) {
+            bail!("short goodbye table size for object [{}..{}]", start, end);
+
+        }
+        let goodbye_inner_size = goodbye_table_size - HEADER_SIZE - GOODBYE_ITEM_SIZE;
+        if (goodbye_inner_size % GOODBYE_ITEM_SIZE) != 0 {
+            bail!("wrong goodbye inner table size for entry [{}..{}]", start, end);
+        }
+
+        let goodbye_start = end - goodbye_table_size;
+
+        if u64::from_le(item.offset) != (goodbye_start - start) {
+            println!("DEBUG: {} {}", u64::from_le(item.offset), goodbye_start - start);
+            bail!("wrong offset in goodbye tail marker for entry [{}..{}]", start, end);
+        }
+
+        self.reader.seek(SeekFrom::Start(goodbye_start))?;
+        let mut buffer = [0u8; HEADER_SIZE as usize];
+        self.reader.read_exact(&mut buffer)?;
+        let head = tools::map_struct::<CaFormatHeader>(&buffer)?;
+
+        if u64::from_le(head.htype) != CA_FORMAT_GOODBYE {
+            bail!("wrong goodbye table header type for entry [{}..{}]", start, end);
+        }
+
+        if u64::from_le(head.size) != goodbye_table_size {
+            bail!("wrong goodbye table size for entry [{}..{}]", start, end);
+        }
+
+        let mut buffer = [0u8; GOODBYE_ITEM_SIZE as usize];
+
+        let mut range_list = Vec::new();
+
+        for i in 0..goodbye_inner_size/GOODBYE_ITEM_SIZE {
+            self.reader.read_exact(&mut buffer)?;
+            let item = tools::map_struct::<CaFormatGoodbyeItem>(&buffer)?;
+            let item_offset = u64::from_le(item.offset);
+            if item_offset > (goodbye_start - start) {
+                bail!("goodbye entry {} offset out of range [{}..{}] {} {} {}",
+                      i, start, end, item_offset, goodbye_start, start);
+            }
+            let item_start = goodbye_start - item_offset;
+            let item_hash = u64::from_le(item.hash);
+            let item_end = item_start + u64::from_le(item.size);
+            if item_end > goodbye_start {
+                bail!("goodbye entry {} end out of range [{}..{}]",
+                      i, start, end);
+            }
+
+            range_list.push((item_start, item_end));
+        }
+
+        let mut result = vec![];
+
+        for (item_start, item_end) in range_list {
+            let entry = self.read_directory_entry(item_start, item_end)?;
+            //println!("ENTRY: {} {} {:?}", item_start, item_end, entry.filename);
+            result.push(entry);
+        }
+
+        Ok(result)
+    }
+
+    pub fn print_filenames<W: std::io::Write>(
+        &mut self,
+        output: &mut W,
+        prefix: &mut PathBuf,
+        dir: &CaDirectoryEntry,
+    ) -> Result<(), Error> {
+
+        let mut list = self.list_dir(dir)?;
+
+        list.sort_unstable_by(|a, b| a.filename.cmp(&b.filename));
+
+        for item in &list {
+
+            prefix.push(item.filename.clone());
+
+            let mode = item.entry.mode as u32;
+
+            let osstr: &OsStr =  prefix.as_ref();
+            output.write(osstr.as_bytes())?;
+            output.write(b"\n")?;
+
+            if (mode & libc::S_IFMT) == libc::S_IFDIR {
+                self.print_filenames(output, prefix, item)?;
+            } else if (mode & libc::S_IFMT) == libc::S_IFREG {
+            } else if (mode & libc::S_IFMT) == libc::S_IFLNK {
+            } else {
+                bail!("unknown item mode/type for {:?}", prefix);
+            }
+
+            prefix.pop();
+        }
+
+        Ok(())
+    }
+}