From 5287f1b4933e8d7f056636b792e6b9048241619e Mon Sep 17 00:00:00 2001
From: Pyry Kontio <pyry.kontio@drasa.eu>
Date: Tue, 31 Jan 2023 04:54:26 +0900
Subject: [PATCH] Refactored rsc and nrsc into their own implementations,
 started implementing explode functionality.

---
 README.md                    |  21 ++
 src/{abi.rs => abi_utils.rs} |   0
 src/audio.rs                 | 279 +++++--------------
 src/{main.rs => bin/cli.rs}  | 183 ++++++------
 src/bin/explode.rs           |  49 ++++
 src/dict.rs                  |  53 ++--
 src/error.rs                 |  16 +-
 src/key.rs                   |  72 +++--
 src/lib.rs                   |  56 +---
 src/pages.rs                 | 447 ++----------------------------
 src/resource.rs              |  56 ++++
 src/resource/nrsc.rs         | 269 ++++++++++++++++++
 src/resource/rsc.rs          | 521 +++++++++++++++++++++++++++++++++++
 13 files changed, 1182 insertions(+), 840 deletions(-)
 rename src/{abi.rs => abi_utils.rs} (100%)
 rename src/{main.rs => bin/cli.rs} (55%)
 create mode 100644 src/bin/explode.rs
 create mode 100644 src/resource.rs
 create mode 100644 src/resource/nrsc.rs
 create mode 100644 src/resource/rsc.rs

diff --git a/README.md b/README.md
index d156826..ea6881c 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,24 @@
 # monokakido.rs
 
 A Rust library for parsing and interpreting the [Monokakido](https://www.monokakido.jp/en/dictionaries/app/) dictionary format. Aiming for full test coverage and efficient implementation with minimal dependencies.
+
+## TODO:
+- Refactor code for generic "rsc" and "nrsc" support
+- Audio using "rsc" (CCCAD, WISDOM3)
+- Audio using "nrsc" (DAIJISEN2, NHKACCENT2, OALD10, OLDAE, OLEX, OLT, RHEJ, SMK8)
+- Multiple contents (WISDOM3, OLEX)
+- Document the rsc, nrsc and keystore formats
+- Split main.rs into "dict exploder" and "dict cli"
+
+## Planned to support:
+- WISDOM3
+- SMK8
+- RHEJ
+- OLT
+- OLEX
+- OLDAE
+- OCD
+- OALD10
+- NHKACCENT2
+- DAIJISEN2
+- CCCAD
diff --git a/src/abi.rs b/src/abi_utils.rs
similarity index 100%
rename from src/abi.rs
rename to src/abi_utils.rs
diff --git a/src/audio.rs b/src/audio.rs
index 1e8f272..1e34b8a 100644
--- a/src/audio.rs
+++ b/src/audio.rs
@@ -1,226 +1,85 @@
-use core::{mem::size_of, ops::Not};
-use std::{
-    ffi::OsStr,
-    fs::{self, File},
-    io::{Read, Seek, SeekFrom},
+use std::{path::PathBuf, ops::Range};
+
+use crate::{
+    dict::Paths,
+    resource::{Nrsc, Rsc},
+    Error,
 };
 
-use miniz_oxide::inflate::core as zlib;
-
-use crate::{abi::TransmuteSafe, decompress, dict::Paths, ContentsFile, Error};
-
-#[derive(Debug, Clone)]
-pub(crate) struct AudioIndex {
-    idx: Vec<AudioIdxRecord>,
-    ids: String, // contains null bytes as substring separators
-}
-
-mod abi {
-    use std::mem::size_of;
-
-    use crate::{audio::AudioFormat, Error};
-
-    #[repr(C)]
-    #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
-    pub(crate) struct AudioIdxRecord {
-        format: u16,
-        fileseq: u16,
-        id_str_offset: u32,
-        file_offset: u32,
-        len: u32,
-    }
-
-    impl AudioIdxRecord {
-        pub fn id_str_offset(&self) -> usize {
-            u32::from_le(self.id_str_offset) as usize
-        }
-
-        pub(super) fn format(&self) -> Result<AudioFormat, Error> {
-            match u16::from_le(self.format) {
-                0 => Ok(AudioFormat::Acc),
-                1 => Ok(AudioFormat::ZlibAcc),
-                _ => Err(Error::InvalidAudioFormat),
-            }
-        }
-
-        pub fn fileseq(&self) -> usize {
-            u16::from_le(self.fileseq) as usize
-        }
-
-        pub fn file_offset(&self) -> u64 {
-            u32::from_le(self.file_offset) as u64
-        }
-
-        pub fn len(&self) -> usize {
-            u32::from_le(self.len) as usize
-        }
-    }
-
-    #[test]
-    fn test_audio_index() {
-        use crate::audio::AudioIndex;
-        let air = |id_str_offset| AudioIdxRecord {
-            format: 0,
-            fileseq: 0,
-            id_str_offset,
-            file_offset: 0,
-            len: 0,
-        };
-        let mut audio_idx = AudioIndex {
-            idx: vec![air(0), air(1), air(3), air(6), air(10)],
-            ids: "\0a\0bb\0ccc\0dddd".to_owned(),
-        };
-
-        let diff = 8 + audio_idx.idx.len() * size_of::<AudioIdxRecord>();
-        // Fix offsets now that they are known
-        for air in audio_idx.idx.iter_mut() {
-            air.id_str_offset += diff as u32;
-        }
-
-        dbg!(&audio_idx);
-        assert_eq!(audio_idx.get_id_at(diff + 0).unwrap(), "");
-        assert_eq!(audio_idx.get_id_at(diff + 1).unwrap(), "a");
-        assert_eq!(audio_idx.get_id_at(diff + 3).unwrap(), "bb");
-        assert_eq!(audio_idx.get_id_at(diff + 4), Err(Error::InvalidIndex));
-        assert_eq!(audio_idx.get_id_at(diff + 6).unwrap(), "ccc");
-        assert_eq!(audio_idx.get_id_at(diff + 10), Err(Error::InvalidIndex));
-
-        audio_idx.ids = "\0a\0bb\0ccc\0dddd\0".to_owned();
-        let diff = diff as u32;
-        assert_eq!(audio_idx.get_by_id("").unwrap(), air(diff + 0));
-        assert_eq!(audio_idx.get_by_id("a").unwrap(), air(diff + 1));
-        assert_eq!(audio_idx.get_by_id("bb").unwrap(), air(diff + 3));
-        assert_eq!(audio_idx.get_by_id("ccc").unwrap(), air(diff + 6));
-        assert_eq!(audio_idx.get_by_id("dddd").unwrap(), air(diff + 10));
-        assert_eq!(audio_idx.get_by_id("ddd"), Err(Error::NotFound));
-    }
-}
-
-pub(crate) use abi::AudioIdxRecord;
-
-enum AudioFormat {
-    Acc,
-    ZlibAcc,
-}
-
-unsafe impl TransmuteSafe for AudioIdxRecord {}
-
-impl AudioIndex {
-    pub(crate) fn new(paths: &Paths) -> Result<Self, Error> {
-        let mut file = File::open(paths.audio_idx_path()).map_err(|_| Error::FopenError)?;
-        let mut len = [0; 8];
-        file.read_exact(&mut len).map_err(|_| Error::IOError)?;
-        let len = u32::from_le_bytes(len[4..8].try_into().unwrap()) as usize;
-        let file_size = file.metadata().map_err(|_| Error::IOError)?.len() as usize;
-        let idx_expected_size = size_of::<AudioIdxRecord>() * len + 8;
-        let mut idx = vec![AudioIdxRecord::default(); len];
-        let mut ids = String::with_capacity(file_size - idx_expected_size);
-        file.read_exact(AudioIdxRecord::slice_as_bytes_mut(idx.as_mut_slice()))
-            .map_err(|_| Error::IOError)?;
-        file.read_to_string(&mut ids).map_err(|_| Error::IOError)?;
-        Ok(Self { idx, ids })
-    }
-
-    fn get_id_at(&self, offset: usize) -> Result<&str, Error> {
-        let offset = offset - (size_of::<AudioIdxRecord>() * self.idx.len() + 8);
-        if offset > 0 && &self.ids[offset - 1..offset] != "\0" {
-            return Err(Error::InvalidIndex);
-        }
-        let tail = &self.ids[offset..];
-        let len = tail.find('\0').ok_or(Error::InvalidIndex)?;
-        Ok(&tail[..len])
-    }
-
-    pub fn get_by_id(&self, id: &str) -> Result<AudioIdxRecord, Error> {
-        let mut idx_err = Ok(());
-        let i = self
-            .idx
-            .binary_search_by_key(&id, |idx| match self.get_id_at(idx.id_str_offset()) {
-                Ok(ok) => ok,
-                Err(err) => {
-                    idx_err = Err(err);
-                    ""
-                }
-            })
-            .map_err(|_| Error::NotFound)?;
-        idx_err?;
-
-        Ok(self.idx[i])
-    }
-}
+const RSC_NAME: &str = "audio";
 
 pub struct Audio {
-    index: AudioIndex,
-    audio: Vec<ContentsFile>,
-    read_buf: Vec<u8>,
-    decomp_buf: Vec<u8>,
-    zlib_state: zlib::DecompressorOxide,
+    path: PathBuf,
+    res: Option<AudioResource>,
+}
+
+enum AudioResource {
+    Rsc(Rsc),
+    Nrsc(Nrsc),
 }
 
 impl Audio {
-    fn parse_fname(fname: &OsStr) -> Option<u32> {
-        let fname = fname.to_str()?;
-        if fname.ends_with(".nrsc").not() {
-            return None;
-        }
-        u32::from_str_radix(&fname[..5], 10).ok()
-    }
-
-    pub(crate) fn new(paths: &Paths) -> Result<Self, Error> {
-        let mut audio = Vec::new();
-        for entry in fs::read_dir(&paths.audio_path()).map_err(|_| Error::IOError)? {
-            let entry = entry.map_err(|_| Error::IOError)?;
-            let seqnum = Audio::parse_fname(&entry.file_name());
-            if let Some(seqnum) = seqnum {
-                audio.push(ContentsFile {
-                    seqnum,
-                    len: entry.metadata().map_err(|_| Error::IOError)?.len() as usize,
-                    offset: 0,
-                    file: File::open(entry.path()).map_err(|_| Error::IOError)?,
-                });
-            }
-        }
-        audio.sort_by_key(|f| f.seqnum);
-        if Some(audio.len()) != audio.last().map(|a| a.seqnum as usize + 1) {
-            return Err(Error::NoContentFilesFound);
-        }
-        let index = AudioIndex::new(&paths)?;
-        Ok(Audio {
-            index,
-            audio,
-            read_buf: Vec::new(),
-            decomp_buf: Vec::new(),
-            zlib_state: zlib::DecompressorOxide::new(),
+    pub fn new(paths: &Paths) -> Result<Option<Self>, Error> {
+        let mut path = paths.contents_path();
+        path.push(RSC_NAME);
+        Ok(if path.exists() {
+            Some(Audio { path, res: None })
+        } else {
+            None
         })
     }
 
-    fn get_by_idx(&mut self, idx: AudioIdxRecord) -> Result<&[u8], Error> {
-        let file = &mut self.audio[idx.fileseq() as usize];
-
-        file.file
-            .seek(SeekFrom::Start(idx.file_offset()))
-            .map_err(|_| Error::IOError)?;
-        if self.read_buf.len() < idx.len() {
-            self.read_buf.resize(idx.len(), 0);
-        }
-        file.file
-            .read_exact(&mut self.read_buf[..idx.len()])
-            .map_err(|_| Error::IOError)?;
-
-        match idx.format()? {
-            AudioFormat::Acc => Ok(&self.read_buf[..idx.len()]),
-            AudioFormat::ZlibAcc => {
-                let n_out = decompress(
-                    &mut self.zlib_state,
-                    &self.read_buf[..idx.len()],
-                    &mut self.decomp_buf,
-                )?;
-                Ok(&self.decomp_buf[..n_out])
-            }
+    pub fn init(&mut self) -> Result<(), Error> {
+        if self.res.is_none() {
+            self.path.push("index.nidx");
+            let nrsc_index_exists = self.path.exists();
+            self.path.pop();
+            self.res = Some(if nrsc_index_exists {
+                AudioResource::Nrsc(Nrsc::new(&self.path)?)
+            } else {
+                AudioResource::Rsc(Rsc::new(&self.path, RSC_NAME)?)
+            });
         }
+        Ok(())
     }
 
     pub fn get(&mut self, id: &str) -> Result<&[u8], Error> {
-        self.get_by_idx(self.index.get_by_id(id)?)
+        self.init()?;
+        let Some(res) = self.res.as_mut() else { unreachable!() };
+        match res {
+            AudioResource::Rsc(rsc) => {
+                rsc.get(u32::from_str_radix(id, 10).map_err(|_| Error::InvalidIndex)?)
+            }
+            AudioResource::Nrsc(nrsc) => nrsc.get(id),
+        }
+    }
+
+    pub fn get_by_idx(&mut self, idx: usize) -> Result<(AudioId, &[u8]), Error> {
+        self.init()?;
+        let Some(res) = self.res.as_mut() else { unreachable!() };
+        Ok(match res {
+            AudioResource::Rsc(rsc) => {
+                let (id, page) = rsc.get_by_idx(idx)?;
+                (AudioId::Num(id), page)
+            },
+            AudioResource::Nrsc(nrsc) => {
+                let (id, page) = nrsc.get_by_idx(idx)?;
+                (AudioId::Str(id), page)
+            },
+        })
+    }
+
+    pub fn idx_iter(&mut self) -> Result<Range<usize>, Error> {
+        self.init()?;
+        let Some(res) = self.res.as_ref() else { unreachable!() };
+        Ok(0..match res {
+            AudioResource::Rsc(rsc) => rsc.len(),
+            AudioResource::Nrsc(nrsc) => nrsc.len(),
+        })
     }
 }
+
+pub enum AudioId<'a> {
+    Str(&'a str),
+    Num(u32)
+}
diff --git a/src/main.rs b/src/bin/cli.rs
similarity index 55%
rename from src/main.rs
rename to src/bin/cli.rs
index e185327..560e184 100644
--- a/src/main.rs
+++ b/src/bin/cli.rs
@@ -1,6 +1,9 @@
-use std::{io::{stdout, Write}, ops::Neg};
+use std::{
+    io::{stdout, Write},
+    ops::Neg,
+};
 
-use monokakido::{MonokakidoDict, Error};
+use monokakido::{Error, MonokakidoDict};
 
 fn get_first_audio_id(page: &str) -> Result<&str, Error> {
     if let Some((_, sound_tail)) = page.split_once("<sound>") {
@@ -19,13 +22,16 @@ fn get_first_accent(page: &str) -> Result<i8, Error> {
     if let Some((_, accent_tail)) = page.split_once("<accent_text>") {
         if let Some((mut accent, _)) = accent_tail.split_once("</accent_text>") {
             if let Some((a, _)) = accent.split_once("<sound>") {
-                    accent = a;
+                accent = a;
             }
             if let Some(pos) = accent.find("<symbol_backslash>＼</symbol_backslash>") {
                 let endpos = pos + "<symbol_backslash>＼</symbol_backslash>".len();
                 let before = &accent[..pos];
                 let after = &accent[endpos..];
-                let is_mora = |&c: &char| (matches!(c, 'ぁ'..='ん' | 'ァ'..='ン' | 'ー') && !matches!(c, 'ゃ'..='ょ' | 'ャ'..='ョ'));
+                let is_mora = |&c: &char| {
+                    (matches!(c, 'ぁ'..='ん' | 'ァ'..='ン' | 'ー')
+                        && !matches!(c, 'ゃ'..='ょ' | 'ャ'..='ョ'))
+                };
                 return Ok((before.chars().filter(is_mora).count() as i8));
             }
             if let Some(_) = accent.find("<symbol_macron>━</symbol_macron>") {
@@ -44,25 +50,27 @@ fn get_accents(page: &str) -> Result<(i8, Option<i8>), Error> {
 }
 
 fn main() {
-
     let Some(key) = std::env::args().nth(1) else {
         return;
     };
-    /*
-       for dict in MonokakidoDict::list().unwrap() {
-           dbg!(dict.unwrap());
-       }
-    */
+
+    for dict in MonokakidoDict::list().unwrap() {
+        dbg!(dict.unwrap());
+    }
+
     let mut dict = MonokakidoDict::open("NHKACCENT2").unwrap();
-    let mut accents = vec![];
+    // let mut accents = vec![];
     let result = dict.keys.search_exact(&key);
+
     match result {
         Ok((_, pages)) => {
-            for id in pages{
+            for id in pages {
                 let page = dict.pages.get(id).unwrap();
+                println!("{page}");
+                /*
                 if let Ok(accent) = get_accents(page) {
                     accents.push(accent);
-                }
+                } */
                 /*
                 let id = get_first_audio_id(page).unwrap();
                 let audio = dict.audio.get(id).unwrap();
@@ -70,12 +78,13 @@ fn main() {
                 stdout.write_all(audio).unwrap();
                 */
             }
-        },
+        }
         Err(e) => {
             println!("{:?}", e);
             return;
-        },
+        }
     }
+    /*
     print!("{key}\t");
     accents.sort();
     accents.dedup();
@@ -91,84 +100,84 @@ fn main() {
             }
             print!(" ");
         }
-    }
+    } */
     println!()
 
-/*
-    let idx_list = [
-        0,
-        1,
-        2,
-        3,
-        4,
-        5,
-        6,
-        7,
-        8,
-        9,
-        10,
-        11,
-        12,
-        13,
-        14,
-        15,
-        16,
-        17,
-        18,
-        19,
-        20,
-        46200,
-        46201,
-        46202,
-        46203,
-        46204,
-        46205,
-        46206,
-        46207,
-        46208,
-        46209,
-        46210,
-        46211,
-        70000,
-        dict.keys.count() - 1,
-    ];
+    /*
+       let idx_list = [
+           0,
+           1,
+           2,
+           3,
+           4,
+           5,
+           6,
+           7,
+           8,
+           9,
+           10,
+           11,
+           12,
+           13,
+           14,
+           15,
+           16,
+           17,
+           18,
+           19,
+           20,
+           46200,
+           46201,
+           46202,
+           46203,
+           46204,
+           46205,
+           46206,
+           46207,
+           46208,
+           46209,
+           46210,
+           46211,
+           70000,
+           dict.keys.count() - 1,
+       ];
 
-    println!("Index: length order");
-    for idx in idx_list {
-        let (word, pages) = dict.keys.get_index_len(idx).unwrap();
-        println!("\n{}", word);
-        for id in pages {
-            println!("{}", dict.pages.get(id).unwrap());
-        }
-    }
+       println!("Index: length order");
+       for idx in idx_list {
+           let (word, pages) = dict.keys.get_index_len(idx).unwrap();
+           println!("\n{}", word);
+           for id in pages {
+               println!("{}", dict.pages.get(id).unwrap());
+           }
+       }
 
-    println!("Index: prefix order");
-    for idx in idx_list {
-        let (word, pages) = dict.keys.get_index_prefix(idx).unwrap();
-        println!("\n{}", word);
-        for id in pages {
-            println!("{}", dict.pages.get(id).unwrap());
-        }
-    }
+       println!("Index: prefix order");
+       for idx in idx_list {
+           let (word, pages) = dict.keys.get_index_prefix(idx).unwrap();
+           println!("\n{}", word);
+           for id in pages {
+               println!("{}", dict.pages.get(id).unwrap());
+           }
+       }
 
-    println!("Index: suffix order");
-    for idx in idx_list {
-        let (word, pages) = dict.keys.get_index_suffix(idx).unwrap();
-        println!("\n{}", word);
-        for id in pages {
-            println!("{}", dict.pages.get(id).unwrap());
-        }
-    }
+       println!("Index: suffix order");
+       for idx in idx_list {
+           let (word, pages) = dict.keys.get_index_suffix(idx).unwrap();
+           println!("\n{}", word);
+           for id in pages {
+               println!("{}", dict.pages.get(id).unwrap());
+           }
+       }
 
-    println!("Index: ?");
-    for idx in idx_list {
-        let (word, pages) = dict.keys.get_index_d(idx).unwrap();
-        println!("\n{}", word);
-        for id in pages {
-            println!("{}", dict.pages.get(id).unwrap());
-        }
-    }
- */
+       println!("Index: ?");
+       for idx in idx_list {
+           let (word, pages) = dict.keys.get_index_d(idx).unwrap();
+           println!("\n{}", word);
+           for id in pages {
+               println!("{}", dict.pages.get(id).unwrap());
+           }
+       }
+    */
     //let mut stdout = stdout().lock();
     //stdout.write_all(audio).unwrap();
 }
diff --git a/src/bin/explode.rs b/src/bin/explode.rs
new file mode 100644
index 0000000..fa6e67d
--- /dev/null
+++ b/src/bin/explode.rs
@@ -0,0 +1,49 @@
+use std::{
+    fmt::Write as _,
+    fs::{create_dir_all, File},
+    io::Write,
+    path::Path,
+};
+
+use monokakido::{Error, MonokakidoDict};
+
+fn explode() -> Result<(), Error> {
+    let arg = std::env::args().nth(1).ok_or(Error::InvalidArg)?;
+
+    let mut dict = if Path::new(&arg).exists() {
+        MonokakidoDict::open_with_path(Path::new(&arg))
+    } else {
+        MonokakidoDict::open(&arg)
+    }?;
+    let pages_dir = "./pages/";
+    create_dir_all(pages_dir)?;
+    let mut path = String::from(pages_dir);
+    for idx in dict.pages.idx_iter()? {
+        let (id, page) = dict.pages.get_by_idx(idx)?;
+        write!(&mut path, "{id:0>10}.xml")?;
+        let mut file = File::create(&path)?;
+        path.truncate(pages_dir.len());
+        file.write_all(page.as_bytes())?;
+    }
+
+    if let Some(audio) = &mut dict.audio {
+        let audio_dir = "./audio/";
+        create_dir_all(audio_dir)?;
+        let mut path = String::from(audio_dir);
+        for idx in audio.idx_iter()? {
+            let (id, page) = dict.pages.get_by_idx(idx)?;
+            write!(&mut path, "{id:0>10}.aac")?;
+            let mut file = File::create(&path)?;
+            path.truncate(pages_dir.len());
+            file.write_all(page.as_bytes())?;
+        }
+    }
+    Ok(())
+}
+
+fn main() {
+    if let Err(err) = explode() {
+        eprintln!("{err:?}");
+        return;
+    };
+}
diff --git a/src/dict.rs b/src/dict.rs
index b2fdb28..061e8aa 100644
--- a/src/dict.rs
+++ b/src/dict.rs
@@ -2,7 +2,6 @@ use miniserde::{json, Deserialize};
 use std::{
     ffi::OsStr,
     fs,
-    ops::Not,
     path::{Path, PathBuf},
 };
 
@@ -11,7 +10,7 @@ use crate::{audio::Audio, key::Keys, pages::Pages, Error};
 pub struct MonokakidoDict {
     paths: Paths,
     pub pages: Pages,
-    pub audio: Audio,
+    pub audio: Option<Audio>,
     pub keys: Keys,
 }
 
@@ -27,7 +26,7 @@ struct DSProductContents {
     dir: String,
 }
 
-pub(crate) struct Paths {
+pub struct Paths {
     base_path: PathBuf,
     name: String,
     contents_dir: String,
@@ -57,33 +56,6 @@ impl Paths {
         let mut pb = PathBuf::from(&self.base_path);
         pb.push("Contents");
         pb.push(&self.contents_dir);
-        pb.push("contents");
-        pb
-    }
-
-    pub(crate) fn audio_path(&self) -> PathBuf {
-        let mut pb = PathBuf::from(&self.base_path);
-        pb.push("Contents");
-        pb.push(&self.contents_dir);
-        pb.push("audio");
-        pb
-    }
-
-    pub(crate) fn contents_idx_path(&self) -> PathBuf {
-        let mut pb = self.contents_path();
-        pb.push("contents.idx");
-        pb
-    }
-
-    pub(crate) fn contents_map_path(&self) -> PathBuf {
-        let mut pb = self.contents_path();
-        pb.push("contents.map");
-        pb
-    }
-
-    pub(crate) fn audio_idx_path(&self) -> PathBuf {
-        let mut pb = self.audio_path();
-        pb.push("index.nidx");
         pb
     }
 
@@ -104,10 +76,12 @@ impl Paths {
 
 fn parse_dict_name(fname: &OsStr) -> Option<&str> {
     let fname = fname.to_str()?;
-    if fname.starts_with("jp.monokakido.Dictionaries.").not() {
-        return None;
+    let dict_prefix = "jp.monokakido.Dictionaries.";
+    if fname.starts_with(dict_prefix) {
+        Some(&fname[dict_prefix.len()..])
+    } else {
+        None
     }
-    Some(&fname[27..])
 }
 
 impl MonokakidoDict {
@@ -123,14 +97,23 @@ impl MonokakidoDict {
 
     pub fn open(name: &str) -> Result<Self, Error> {
         let std_path = Paths::std_dict_path(name);
-        Self::open_with_path(&std_path, name)
+        Self::open_with_path_name(&std_path, name)
     }
 
     pub fn name(&self) -> &str {
         &self.paths.name
     }
 
-    pub fn open_with_path(path: impl Into<PathBuf>, name: &str) -> Result<Self, Error> {
+    pub fn open_with_path(path: impl Into<PathBuf>) -> Result<Self, Error> {
+        let path: PathBuf = path.into();
+        let dir_name = path.file_name().ok_or(Error::FopenError)?.to_string_lossy();
+
+        let dict_name = dir_name.rsplit_once(".").ok_or(Error::FopenError)?.0;
+
+        Self::open_with_path_name(&path, dict_name)
+    }
+
+    fn open_with_path_name(path: impl Into<PathBuf>, name: &str) -> Result<Self, Error> {
         let base_path = path.into();
         let json_path = Paths::json_path(&base_path, name);
         let json = fs::read_to_string(json_path).map_err(|_| Error::NoDictJsonFound)?;
diff --git a/src/error.rs b/src/error.rs
index ec93675..cede223 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,9 +1,10 @@
-use std::{io::Error as IoError, str::Utf8Error};
+use std::{fmt::Error as FmtError, io::Error as IoError, str::Utf8Error};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Error {
     Transmute,
-    Validate,
+    KeyIndexHeaderValidate,
+    KeyFileHeaderValidate,
     FopenError,
     FstatError,
     MmapError,
@@ -17,9 +18,12 @@ pub enum Error {
     NoDictJsonFound,
     InvalidDictJson,
     IOError,
-    NoContentFilesFound,
+    MissingResourceFile,
     InvalidIndex,
     InvalidAudioFormat,
+    InvalidArg,
+    FmtError,
+    IndexDoesntExist,
 }
 
 impl From<IoError> for Error {
@@ -33,3 +37,9 @@ impl From<Utf8Error> for Error {
         Error::Utf8Error
     }
 }
+
+impl From<FmtError> for Error {
+    fn from(_: FmtError) -> Self {
+        Error::FmtError
+    }
+}
diff --git a/src/key.rs b/src/key.rs
index 0a383b0..556da0d 100644
--- a/src/key.rs
+++ b/src/key.rs
@@ -1,13 +1,14 @@
 use std::{
+    borrow::Cow,
+    cmp::Ordering,
     fs::File,
     io::{Read, Seek},
     mem::size_of,
     str::from_utf8,
-    cmp::Ordering, borrow::Cow,
 };
 
 use crate::{
-    abi::{TransmuteSafe, LE32},
+    abi_utils::{TransmuteSafe, LE32},
     dict::Paths,
     Error,
 };
@@ -40,7 +41,7 @@ mod abi {
             {
                 Ok(())
             } else {
-                Err(Error::Validate)
+                Err(Error::KeyFileHeaderValidate)
             }
         }
     }
@@ -59,15 +60,20 @@ mod abi {
 
     impl IndexHeader {
         pub(super) fn validate(&self, file_end: usize) -> Result<(), Error> {
+            let a = self.index_a_offset.us();
+            let b = self.index_b_offset.us();
+            let c = self.index_c_offset.us();
+            let d = self.index_d_offset.us();
+            let check_order = |l, r| l < r || r == 0;
             if self.magic1.read() == 0x04
-                && self.index_a_offset.us() < self.index_b_offset.us()
-                && self.index_b_offset.us() < self.index_c_offset.us()
-                && self.index_c_offset.us() < self.index_d_offset.us()
-                && self.index_d_offset.us() < file_end
+                && check_order(a, b)
+                && check_order(b, c)
+                && check_order(c, d)
+                && check_order(d, file_end)
             {
                 Ok(())
             } else {
-                Err(Error::Validate)
+                Err(Error::KeyIndexHeaderValidate)
             }
         }
     }
@@ -78,21 +84,26 @@ use abi::{FileHeader, IndexHeader};
 
 pub struct Keys {
     words: Vec<LE32>,
-    index_len: Vec<LE32>,
-    index_prefix: Vec<LE32>,
-    index_suffix: Vec<LE32>,
-    index_d: Vec<LE32>,
+    index_len: Option<Vec<LE32>>,
+    index_prefix: Option<Vec<LE32>>,
+    index_suffix: Option<Vec<LE32>>,
+    index_d: Option<Vec<LE32>>,
 }
 
 impl Keys {
-    fn read_vec(file: &mut File, start: usize, end: usize) -> Result<Vec<LE32>, Error> {
+    fn read_vec(file: &mut File, start: usize, end: usize) -> Result<Option<Vec<LE32>>, Error> {
+        if start == 0 || end == 0 {
+            return Ok(None);
+        }
+        // Replace this with div_ceil once it stabilizes
         let size = (end - start + size_of::<LE32>() - 1) / size_of::<LE32>();
         let mut buf = vec![LE32::default(); size];
         file.read_exact(LE32::slice_as_bytes_mut(&mut buf))?;
-        Ok(buf)
+        Ok(Some(buf))
     }
 
-    fn check_vec_len(buf: &Vec<LE32>) -> Result<(), Error> {
+    fn check_vec_len(buf: &Option<Vec<LE32>>) -> Result<(), Error> {
+        let Some(buf) = buf else { return Ok(()) };
         if buf.get(0).ok_or(Error::InvalidIndex)?.us() + 1 != buf.len() {
             return Err(Error::InvalidIndex);
         }
@@ -108,10 +119,7 @@ impl Keys {
 
         file.seek(std::io::SeekFrom::Start(hdr.words_offset.read() as u64))?;
         let words = Self::read_vec(&mut file, hdr.words_offset.us(), hdr.idx_offset.us())?;
-
-        if words.get(0).ok_or(Error::InvalidIndex)?.us() + 1 >= words.len() {
-            return Err(Error::InvalidIndex);
-        }
+        let Some(words) = words else { return Err(Error::InvalidIndex); };
 
         let file_end = file_size - hdr.idx_offset.us();
         let mut ihdr = IndexHeader::default();
@@ -177,26 +185,26 @@ impl Keys {
     }
 
     pub(crate) fn cmp_key(&self, target: &str, idx: usize) -> Result<Ordering, Error> {
-        let offset = self.index_prefix[idx + 1].us() + size_of::<LE32>() + 1;
+        let Some(index) = &self.index_len else { return Err(Error::IndexDoesntExist) };
+        let offset = index[idx + 1].us() + size_of::<LE32>() + 1;
         let words_bytes = LE32::slice_as_bytes(&self.words);
         if words_bytes.len() < offset + target.len() + 1 {
-
             return Err(Error::InvalidIndex); // Maybe just return Ordering::Less instead?
         }
         let found_tail = &words_bytes[offset..];
         let found = &found_tail[..target.len()];
         Ok(match found.cmp(target.as_bytes()) {
-            Ordering::Equal => if found_tail[target.len()] == b'\0'
-                {
+            Ordering::Equal => {
+                if found_tail[target.len()] == b'\0' {
                     Ordering::Equal
                 } else {
                     Ordering::Greater
-                },
+                }
+            }
             ord => ord,
         })
     }
 
-
     fn get_inner(&self, index: &[LE32], idx: usize) -> Result<(&str, PageIter<'_>), Error> {
         if idx >= self.count() {
             return Err(Error::NotFound);
@@ -208,19 +216,23 @@ impl Keys {
     }
 
     pub fn get_index_len(&self, idx: usize) -> Result<(&str, PageIter<'_>), Error> {
-        self.get_inner(&self.index_len, idx)
+        let Some(index) = &self.index_len else { return Err(Error::IndexDoesntExist) };
+        self.get_inner(index, idx)
     }
 
     pub fn get_index_prefix(&self, idx: usize) -> Result<(&str, PageIter<'_>), Error> {
-        self.get_inner(&self.index_prefix, idx)
+        let Some(index) = &self.index_prefix else { return Err(Error::IndexDoesntExist) };
+        self.get_inner(index, idx)
     }
 
     pub fn get_index_suffix(&self, idx: usize) -> Result<(&str, PageIter<'_>), Error> {
-        self.get_inner(&self.index_suffix, idx)
+        let Some(index) = &self.index_suffix else { return Err(Error::IndexDoesntExist) };
+        self.get_inner(index, idx)
     }
 
     pub fn get_index_d(&self, idx: usize) -> Result<(&str, PageIter<'_>), Error> {
-        self.get_inner(&self.index_d, idx)
+        let Some(index) = &self.index_d else { return Err(Error::IndexDoesntExist) };
+        self.get_inner(index, idx)
     }
 
     pub fn search_exact(&self, target_key: &str) -> Result<(usize, PageIter<'_>), Error> {
@@ -300,7 +312,7 @@ impl<'a> PageIter<'a> {
                 e => {
                     dbg!("hmm", &e[..100]);
                     return Err(Error::InvalidIndex);
-                },
+                }
             }
         }
         let span_len = pages.len() - tail.len();
diff --git a/src/lib.rs b/src/lib.rs
index 2ecaf0a..46ddd93 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,61 +1,13 @@
-use std::fs;
-
-use miniz_oxide::inflate::{core as zlib, TINFLStatus as ZStatus};
-
-mod abi;
+mod abi_utils;
 mod audio;
 mod dict;
 mod error;
 mod key;
 mod pages;
+mod resource;
 
+pub use audio::Audio;
 pub use dict::MonokakidoDict;
 pub use error::Error;
-pub use pages::Pages;
-pub use audio::Audio;
 pub use key::Keys;
-
-fn decompress(
-    zlib_state: &mut zlib::DecompressorOxide,
-    in_buf: &[u8],
-    out_buf: &mut Vec<u8>,
-) -> Result<usize, Error> {
-    use zlib::inflate_flags as flg;
-    use ZStatus::{Done, HasMoreOutput};
-
-    let flags = flg::TINFL_FLAG_PARSE_ZLIB_HEADER | flg::TINFL_FLAG_USING_NON_WRAPPING_OUTPUT_BUF;
-    let mut n_in_total = 0;
-    let mut n_out_total = 0;
-    zlib_state.init();
-    loop {
-        let (status, n_in, n_out) = zlib::decompress(
-            zlib_state,
-            &in_buf[n_in_total..],
-            out_buf,
-            n_out_total,
-            flags,
-        );
-        n_out_total += n_out;
-        n_in_total += n_in;
-        match status {
-            HasMoreOutput => {
-                out_buf.resize(out_buf.len() * 2 + 1, 0);
-                continue;
-            }
-            Done => break,
-            _ => return Err(Error::ZlibError),
-        }
-    }
-    if n_in_total != in_buf.len() {
-        return Err(Error::IncorrectStreamLength);
-    }
-    Ok(n_out_total)
-}
-
-#[derive(Debug)]
-struct ContentsFile {
-    seqnum: u32,
-    len: usize,
-    offset: usize,
-    file: fs::File,
-}
+pub use pages::Pages;
diff --git a/src/pages.rs b/src/pages.rs
index 5498dbd..e4ecabc 100644
--- a/src/pages.rs
+++ b/src/pages.rs
@@ -1,444 +1,45 @@
-use core::{cmp::min, mem::size_of, ops::Not};
-use miniz_oxide::inflate::core as zlib;
-use std::{
-    ffi::OsStr,
-    fs::{self, File},
-    io::{Read, Seek, SeekFrom},
-};
+use std::{ops::Range, path::PathBuf};
 
-use crate::{
-    abi::{TransmuteSafe, LE32},
-    decompress,
-    dict::Paths,
-    ContentsFile, Error,
-};
+use crate::{dict::Paths, resource::Rsc, Error};
 
-mod abi {
-    use crate::abi::LE32;
-
-    #[repr(C)]
-    #[derive(Debug, Clone, Copy, Default)]
-    pub(crate) struct TextIdxRecord {
-        pub dic_item_id: LE32,
-        pub map_idx: LE32,
-    }
-
-    #[repr(C)]
-    #[derive(Debug, Clone, Copy, Default, PartialEq, Eq, PartialOrd, Ord)]
-    pub(crate) struct TextMapRecord {
-        pub zoffset: LE32,
-        pub ioffset: LE32,
-    }
-
-    #[test]
-    fn test_get_by_id() {
-        use crate::{pages::PageIndex, Error};
-
-        fn idx(id: u32, idx: u32) -> TextIdxRecord {
-            TextIdxRecord {
-                dic_item_id: id.into(),
-                map_idx: idx.into(),
-            }
-        }
-        fn map(z: u32, i: u32) -> TextMapRecord {
-            TextMapRecord {
-                zoffset: z.into(),
-                ioffset: i.into(),
-            }
-        }
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![],
-                map: vec![],
-            }
-            .get_by_id(500),
-            Err(Error::NotFound)
-        );
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![idx(1, 0)],
-                map: vec![map(0, 0)],
-            }
-            .get_by_id(500),
-            Err(Error::NotFound)
-        );
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![idx(1, 0), idx(2, 1)],
-                map: vec![map(0, 0), map(0, 10)],
-            }
-            .get_by_id(500),
-            Err(Error::NotFound)
-        );
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![idx(1, 0), idx(2, 1), idx(1000, 2)],
-                map: vec![map(0, 0), map(0, 10), map(0, 20)],
-            }
-            .get_by_id(500),
-            Err(Error::NotFound)
-        );
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![idx(1, 0), idx(2, 1), idx(500, 2), idx(1000, 3)],
-                map: vec![map(0, 0), map(0, 10), map(0, 20), map(10, 0)],
-            }
-            .get_by_id(500),
-            Ok(map(0, 20))
-        );
-
-        assert_eq!(
-            PageIndex {
-                idx: vec![
-                    idx(1, 0),
-                    idx(2, 1),
-                    idx(499, 2),
-                    idx(500, 3),
-                    idx(501, 4),
-                    idx(1000, 5)
-                ],
-                map: vec![
-                    map(0, 0),
-                    map(0, 10),
-                    map(0, 20),
-                    map(10, 0),
-                    map(10, 0),
-                    map(10, 0)
-                ],
-            }
-            .get_by_id(500),
-            Ok(map(10, 0))
-        );
-    }
-}
-pub(crate) use abi::{TextIdxRecord, TextMapRecord};
-
-#[derive(Debug, Clone)]
-pub(crate) struct PageIndex {
-    idx: Vec<TextIdxRecord>,
-    map: Vec<TextMapRecord>,
-}
-
-unsafe impl TransmuteSafe for TextMapRecord {}
-unsafe impl TransmuteSafe for TextIdxRecord {}
-
-impl PageIndex {
-    pub(crate) fn new(paths: &Paths) -> Result<Self, Error> {
-        let mut idx_file = File::open(paths.contents_idx_path())?;
-        let mut map_file = File::open(paths.contents_map_path())?;
-        let mut len = [0; 4];
-        idx_file.read_exact(&mut len)?;
-        let len = u32::from_le_bytes(len) as usize;
-        idx_file.seek(SeekFrom::Start(8))?;
-        map_file.seek(SeekFrom::Start(8))?;
-        let idx_size = idx_file.metadata().map_err(|_| Error::IOError)?.len();
-        let map_size = map_file.metadata().map_err(|_| Error::IOError)?.len();
-        let idx_expected_size = (size_of::<TextIdxRecord>() * len + 8) as u64;
-        let map_expected_size = (size_of::<TextMapRecord>() * len + 8) as u64;
-        if idx_size != idx_expected_size || map_size != map_expected_size {
-            return Err(Error::IncorrectStreamLength);
-        }
-        let mut idx = vec![TextIdxRecord::default(); len];
-        let mut map = vec![TextMapRecord::default(); len];
-        idx_file
-            .read_exact(TextIdxRecord::slice_as_bytes_mut(idx.as_mut_slice()))
-            .map_err(|_| Error::IOError)?;
-        map_file
-            .read_exact(TextMapRecord::slice_as_bytes_mut(map.as_mut_slice()))
-            .map_err(|_| Error::IOError)?;
-        Ok(PageIndex { idx, map })
-    }
-
-    fn get_idx_by_id(&self, id: u32) -> Option<usize> {
-        if self.idx.is_empty() {
-            return None;
-        }
-        // Let's guess first, since usually the IDs are completely predictable, without gaps.
-        let idx_list = self.idx.as_slice();
-        let idx = min(id as usize, idx_list.len() - 1);
-        let guess = idx_list[idx].dic_item_id.read();
-        if id == guess {
-            return Some(idx);
-        }
-        let idx = min(id.saturating_sub(1) as usize, idx_list.len() - 1);
-        let guess = idx_list[idx].dic_item_id.read();
-        if id == guess {
-            return Some(idx);
-        }
-        return idx_list
-            .binary_search_by_key(&id, |r| r.dic_item_id.read())
-            .ok();
-    }
-
-    pub fn get_by_id(&self, id: u32) -> Result<TextMapRecord, Error> {
-        if let Some(idx) = self.get_idx_by_id(id) {
-            let record = self.map[self.idx[idx].map_idx.us()];
-            Ok(record)
-        } else {
-            Err(Error::NotFound)
-        }
-    }
-}
+const RSC_NAME: &str = "contents";
 
 pub struct Pages {
-    index: PageIndex,
-    contents: Vec<ContentsFile>,
-    zlib_buf: Vec<u8>,
-    zlib_state: zlib::DecompressorOxide,
-    contents_buf: Vec<u8>,
-    current_offset: usize,
-    current_len: usize,
+    path: PathBuf,
+    res: Option<Rsc>,
 }
 
 impl Pages {
-    fn parse_fname(fname: &OsStr) -> Option<u32> {
-        let fname = fname.to_str()?;
-        if (fname.starts_with("contents-") && fname.ends_with(".rsc")).not() {
-            return None;
-        }
-        u32::from_str_radix(&fname[9..13], 10).ok()
-    }
-
-    pub(crate) fn new(paths: &Paths) -> Result<Self, Error> {
-        let mut contents = Vec::new();
-        for entry in fs::read_dir(&paths.contents_path()).map_err(|_| Error::IOError)? {
-            let entry = entry.map_err(|_| Error::IOError)?;
-            let seqnum = Pages::parse_fname(&entry.file_name());
-            if let Some(seqnum) = seqnum {
-                contents.push(ContentsFile {
-                    seqnum,
-                    len: entry.metadata().map_err(|_| Error::IOError)?.len() as usize,
-                    offset: 0,
-                    file: File::open(entry.path()).map_err(|_| Error::IOError)?,
-                });
-            }
-        }
-        contents.sort_by_key(|f| f.seqnum);
-        let mut offset = 0;
-        for (i, cf) in contents.iter_mut().enumerate() {
-            if cf.seqnum != i as u32 + 1 {
-                return Err(Error::NoContentFilesFound);
-            }
-            cf.offset = offset;
-            offset += cf.len;
-        }
-        let index = PageIndex::new(&paths)?;
+    pub fn new(paths: &Paths) -> Result<Self, Error> {
         Ok(Pages {
-            index,
-            contents,
-            zlib_buf: Vec::new(),
-            zlib_state: zlib::DecompressorOxide::new(),
-            contents_buf: Vec::new(),
-            current_offset: 0,
-            current_len: 0,
+            path: paths.contents_path().join(RSC_NAME),
+            res: None,
         })
     }
 
-    fn load_contents(&mut self, zoffset: usize) -> Result<(), Error> {
-        let (file, file_offset) = file_offset(&mut self.contents, zoffset)?;
-
-        let mut len = [0_u8; 4];
-        file.seek(SeekFrom::Start(file_offset))
-            .map_err(|_| Error::IOError)?;
-        file.read_exact(&mut len).map_err(|_| Error::IOError)?;
-        let len = u32::from_le_bytes(len) as usize;
-        if self.zlib_buf.len() < len {
-            self.zlib_buf.resize(len, 0);
+    pub fn init(&mut self) -> Result<(), Error> {
+        if self.res.is_none() {
+            self.res = Some(Rsc::new(&self.path, RSC_NAME)?);
         }
-        file.read_exact(&mut self.zlib_buf[..len])
-            .map_err(|_| Error::IOError)?;
-
-        let n_out = decompress(
-            &mut self.zlib_state,
-            &self.zlib_buf[..len],
-            &mut self.contents_buf,
-        )?;
-
-        self.current_len = n_out;
-        self.current_offset = zoffset;
-
         Ok(())
     }
 
     pub fn get(&mut self, id: u32) -> Result<&str, Error> {
-        self.get_by_idx(self.index.get_by_id(id)?)
+        self.init()?;
+        let Some(res) = self.res.as_mut() else { unreachable!() };
+        Ok(std::str::from_utf8(res.get(id)?).map_err(|_| Error::Utf8Error)?)
     }
 
-    fn get_by_idx(&mut self, idx: TextMapRecord) -> Result<&str, Error> {
-        if self.contents_buf.is_empty() || idx.zoffset.us() != self.current_offset {
-            self.load_contents(idx.zoffset.us())?;
-        }
+    pub fn get_by_idx(&mut self, idx: usize) -> Result<(u32, &str), Error> {
+        self.init()?;
+        let Some(res) = self.res.as_mut() else { unreachable!() };
+        let (id, page) = res.get_by_idx(idx)?;
+        Ok((id, std::str::from_utf8(page).map_err(|_| Error::Utf8Error)?))
+    }
 
-        let contents = &self.contents_buf[idx.ioffset.us()..self.current_len];
-        let (len, contents_tail) = LE32::from(contents)?;
-        Ok(std::str::from_utf8(&contents_tail[..len.us()]).map_err(|_| Error::Utf8Error)?)
+    pub fn idx_iter(&mut self) -> Result<Range<usize>, Error> {
+        self.init()?;
+        let Some(res) = self.res.as_ref() else { unreachable!() };
+        Ok(0..res.len())
     }
 }
-
-fn file_offset(contents: &mut [ContentsFile], offset: usize) -> Result<(&mut File, u64), Error> {
-    let file_idx = contents
-        .binary_search_by(|cf| cmp_range(offset, cf.offset..cf.offset + cf.len).reverse())
-        .map_err(|_| Error::InvalidIndex)?;
-    let cf = &mut contents[file_idx];
-    let file = &mut cf.file;
-    let file_offset = (offset - cf.offset) as u64;
-    Ok((file, file_offset))
-}
-
-#[test]
-fn test_file_offset() {
-    use std::os::unix::prelude::AsRawFd;
-
-    assert_eq!(file_offset(&mut [], 0).err(), Some(Error::InvalidIndex));
-
-    let mock_file = || {
-        let f = File::open("/dev/zero").unwrap();
-        let fd = f.as_raw_fd();
-        (f, fd)
-    };
-    let (f1, f1_fd) = mock_file();
-    let one_file = &mut vec![ContentsFile {
-        seqnum: 1,
-        len: 100,
-        offset: 0,
-        file: f1,
-    }];
-
-    let result = file_offset(one_file, 101);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(one_file, 100);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(one_file, 0);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(one_file, 99);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
-
-    let (f1, f1_fd) = mock_file();
-    let (f2, f2_fd) = mock_file();
-    let two_files = &mut vec![
-        ContentsFile {
-            seqnum: 1,
-            len: 100,
-            offset: 0,
-            file: f1,
-        },
-        ContentsFile {
-            seqnum: 2,
-            len: 200,
-            offset: 100,
-            file: f2,
-        },
-    ];
-
-    let result = file_offset(two_files, 301);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(two_files, 300);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(two_files, 0);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(two_files, 99);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
-
-    let result = file_offset(two_files, 100);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(two_files, 299);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(199));
-
-    let (f1, f1_fd) = mock_file();
-    let (f2, f2_fd) = mock_file();
-    let (f3, f3_fd) = mock_file();
-    let three_files = &mut vec![
-        ContentsFile {
-            seqnum: 1,
-            len: 100,
-            offset: 0,
-            file: f1,
-        },
-        ContentsFile {
-            seqnum: 2,
-            len: 200,
-            offset: 100,
-            file: f2,
-        },
-        ContentsFile {
-            seqnum: 3,
-            len: 100,
-            offset: 300,
-            file: f3,
-        },
-    ];
-
-    let result = file_offset(three_files, 401);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(three_files, 400);
-    assert_eq!(result.err(), Some(Error::InvalidIndex));
-
-    let result = file_offset(three_files, 0);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(three_files, 99);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
-
-    let result = file_offset(three_files, 100);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(three_files, 299);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(199));
-
-    let result = file_offset(three_files, 300);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f3_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
-
-    let result = file_offset(three_files, 399);
-    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f3_fd));
-    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
-}
-
-fn cmp_range(num: usize, range: core::ops::Range<usize>) -> core::cmp::Ordering {
-    use core::cmp::Ordering;
-    if num < range.start {
-        Ordering::Less
-    } else if range.end <= num {
-        Ordering::Greater
-    } else {
-        Ordering::Equal
-    }
-}
-
-#[test]
-fn test_cmp_to_range() {
-    use core::cmp::Ordering;
-    assert_eq!(cmp_range(0, 0..0), Ordering::Greater);
-    assert_eq!(cmp_range(0, 0..1), Ordering::Equal);
-    assert_eq!(cmp_range(0, 0..100), Ordering::Equal);
-    assert_eq!(cmp_range(1, 0..100), Ordering::Equal);
-    assert_eq!(cmp_range(99, 0..100), Ordering::Equal);
-    assert_eq!(cmp_range(100, 0..100), Ordering::Greater);
-    assert_eq!(cmp_range(101, 0..100), Ordering::Greater);
-    assert_eq!(cmp_range(0, 1..100), Ordering::Less);
-    assert_eq!(cmp_range(99, 100..100), Ordering::Less);
-    assert_eq!(cmp_range(100, 100..100), Ordering::Greater);
-}
diff --git a/src/resource.rs b/src/resource.rs
new file mode 100644
index 0000000..ebacda1
--- /dev/null
+++ b/src/resource.rs
@@ -0,0 +1,56 @@
+mod nrsc;
+mod rsc;
+
+use std::fs;
+
+pub use nrsc::Nrsc;
+pub use rsc::Rsc;
+
+use crate::Error;
+
+use miniz_oxide::inflate::{core as zlib, TINFLStatus as ZStatus};
+
+#[derive(Debug)]
+struct ResourceFile {
+    seqnum: u32,
+    len: usize,
+    offset: usize,
+    file: fs::File,
+}
+
+fn decompress(
+    zlib_state: &mut zlib::DecompressorOxide,
+    in_buf: &[u8],
+    out_buf: &mut Vec<u8>,
+) -> Result<usize, Error> {
+    use zlib::inflate_flags as flg;
+    use ZStatus::{Done, HasMoreOutput};
+
+    let flags = flg::TINFL_FLAG_PARSE_ZLIB_HEADER | flg::TINFL_FLAG_USING_NON_WRAPPING_OUTPUT_BUF;
+    let mut n_in_total = 0;
+    let mut n_out_total = 0;
+    zlib_state.init();
+    loop {
+        let (status, n_in, n_out) = zlib::decompress(
+            zlib_state,
+            &in_buf[n_in_total..],
+            out_buf,
+            n_out_total,
+            flags,
+        );
+        n_out_total += n_out;
+        n_in_total += n_in;
+        match status {
+            HasMoreOutput => {
+                out_buf.resize(out_buf.len() * 2 + 1, 0);
+                continue;
+            }
+            Done => break,
+            _ => return Err(Error::ZlibError),
+        }
+    }
+    if n_in_total != in_buf.len() {
+        return Err(Error::IncorrectStreamLength);
+    }
+    Ok(n_out_total)
+}
diff --git a/src/resource/nrsc.rs b/src/resource/nrsc.rs
new file mode 100644
index 0000000..919e386
--- /dev/null
+++ b/src/resource/nrsc.rs
@@ -0,0 +1,269 @@
+use core::mem::size_of;
+use std::{
+    ffi::OsStr,
+    fs::{self, File},
+    io::{Read, Seek, SeekFrom},
+    path::Path,
+};
+
+use miniz_oxide::inflate::core as zlib;
+
+use crate::{abi_utils::TransmuteSafe, resource::decompress, Error};
+
+#[derive(Debug, Clone)]
+pub(crate) struct NrscIndex {
+    idx: Vec<NrscIdxRecord>,
+    ids: String, // contains null bytes as substring separators
+}
+
+mod abi {
+
+    use super::Format;
+    use crate::Error;
+
+    // TODO: Use LE16 & LE32?
+    #[repr(C)]
+    #[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
+    pub(crate) struct NrscIdxRecord {
+        format: u16,
+        fileseq: u16,
+        id_str_offset: u32,
+        file_offset: u32,
+        len: u32,
+    }
+
+    impl NrscIdxRecord {
+        pub fn id_str_offset(&self) -> usize {
+            u32::from_le(self.id_str_offset) as usize
+        }
+
+        pub(super) fn format(&self) -> Result<Format, Error> {
+            match u16::from_le(self.format) {
+                0 => Ok(Format::Uncompressed),
+                1 => Ok(Format::Zlib),
+                _ => Err(Error::InvalidAudioFormat),
+            }
+        }
+
+        pub fn fileseq(&self) -> usize {
+            u16::from_le(self.fileseq) as usize
+        }
+
+        pub fn file_offset(&self) -> u64 {
+            u32::from_le(self.file_offset) as u64
+        }
+
+        pub fn len(&self) -> usize {
+            u32::from_le(self.len) as usize
+        }
+    }
+
+    #[test]
+    fn test_audio_index() {
+        use super::NrscIndex;
+        use std::mem::size_of;
+        let air = |id_str_offset| NrscIdxRecord {
+            format: 0,
+            fileseq: 0,
+            id_str_offset,
+            file_offset: 0,
+            len: 0,
+        };
+        let mut audio_idx = NrscIndex {
+            idx: vec![air(0), air(1), air(3), air(6), air(10)],
+            ids: "\0a\0bb\0ccc\0dddd".to_owned(),
+        };
+
+        let diff = 8 + audio_idx.idx.len() * size_of::<NrscIdxRecord>();
+        // Fix offsets now that they are known
+        for air in audio_idx.idx.iter_mut() {
+            air.id_str_offset += diff as u32;
+        }
+
+        assert_eq!(audio_idx.get_id_at(diff + 0).unwrap(), "");
+        assert_eq!(audio_idx.get_id_at(diff + 1).unwrap(), "a");
+        assert_eq!(audio_idx.get_id_at(diff + 3).unwrap(), "bb");
+        assert_eq!(audio_idx.get_id_at(diff + 4), Err(Error::InvalidIndex));
+        assert_eq!(audio_idx.get_id_at(diff + 6).unwrap(), "ccc");
+        assert_eq!(audio_idx.get_id_at(diff + 10), Err(Error::InvalidIndex));
+
+        audio_idx.ids = "\0a\0bb\0ccc\0dddd\0".to_owned();
+        let diff = diff as u32;
+        assert_eq!(audio_idx.get_by_id("").unwrap(), air(diff + 0));
+        assert_eq!(audio_idx.get_by_id("a").unwrap(), air(diff + 1));
+        assert_eq!(audio_idx.get_by_id("bb").unwrap(), air(diff + 3));
+        assert_eq!(audio_idx.get_by_id("ccc").unwrap(), air(diff + 6));
+        assert_eq!(audio_idx.get_by_id("dddd").unwrap(), air(diff + 10));
+        assert_eq!(audio_idx.get_by_id("ddd"), Err(Error::NotFound));
+    }
+}
+
+pub(crate) use abi::NrscIdxRecord;
+
+use super::ResourceFile;
+
+enum Format {
+    Uncompressed,
+    Zlib,
+}
+
+unsafe impl TransmuteSafe for NrscIdxRecord {}
+
+impl NrscIndex {
+    pub(crate) fn new(path: &Path) -> Result<Self, Error> {
+        let path = path.join("index.nidx");
+        let mut file = File::open(path).map_err(|_| Error::FopenError)?;
+        let mut len = [0; 8];
+        file.read_exact(&mut len).map_err(|_| Error::IOError)?;
+        let len = u32::from_le_bytes(len[4..8].try_into().unwrap()) as usize;
+        let file_size = file.metadata().map_err(|_| Error::IOError)?.len() as usize;
+        let idx_expected_size = size_of::<NrscIdxRecord>() * len + 8;
+        let mut idx = vec![NrscIdxRecord::default(); len];
+        let mut ids = String::with_capacity(file_size - idx_expected_size);
+        file.read_exact(NrscIdxRecord::slice_as_bytes_mut(idx.as_mut_slice()))
+            .map_err(|_| Error::IOError)?;
+        file.read_to_string(&mut ids).map_err(|_| Error::IOError)?;
+        Ok(Self { idx, ids })
+    }
+
+    fn get_id_at(&self, offset: usize) -> Result<&str, Error> {
+        let offset = offset - (size_of::<NrscIdxRecord>() * self.idx.len() + 8);
+        if offset > 0 && &self.ids[offset - 1..offset] != "\0" {
+            return Err(Error::InvalidIndex);
+        }
+        let tail = &self.ids[offset..];
+        let len = tail.find('\0').ok_or(Error::InvalidIndex)?;
+        Ok(&tail[..len])
+    }
+
+    pub fn get_by_id(&self, id: &str) -> Result<NrscIdxRecord, Error> {
+        let mut idx_err = Ok(());
+        let i = self
+            .idx
+            .binary_search_by_key(&id, |idx| match self.get_id_at(idx.id_str_offset()) {
+                Ok(ok) => ok,
+                Err(err) => {
+                    idx_err = Err(err);
+                    ""
+                }
+            })
+            .map_err(|_| Error::NotFound)?;
+        idx_err?;
+
+        Ok(self.idx[i])
+    }
+
+    pub fn get_by_idx(&self, idx: usize) -> Result<(&str, NrscIdxRecord), Error> {
+        let idx_rec = self.idx.get(idx).copied().ok_or(Error::InvalidIndex)?;
+        let item_id = self.get_id_at(idx_rec.id_str_offset())?;
+        Ok((item_id, idx_rec))
+    }
+}
+
+pub struct Nrsc {
+    index: NrscIndex,
+    data: NrscData,
+}
+
+struct NrscData {
+    files: Vec<ResourceFile>,
+    read_buf: Vec<u8>,
+    decomp_buf: Vec<u8>,
+    zlib_state: zlib::DecompressorOxide,
+}
+
+impl Nrsc {
+    fn parse_fname(fname: &OsStr) -> Option<u32> {
+        let fname = fname.to_str()?;
+        if fname.ends_with(".nrsc") {
+            let secnum_end = fname.len() - ".nrsc".len();
+            u32::from_str_radix(&fname[..secnum_end], 10).ok()
+        } else {
+            None
+        }
+    }
+
+    fn files(path: &Path) -> Result<Vec<ResourceFile>, Error> {
+        let mut files = Vec::new();
+
+        for entry in fs::read_dir(path).map_err(|_| Error::IOError)? {
+            let entry = entry.map_err(|_| Error::IOError)?;
+            let seqnum = Nrsc::parse_fname(&entry.file_name());
+            if let Some(seqnum) = seqnum {
+                files.push(ResourceFile {
+                    seqnum,
+                    len: entry.metadata().map_err(|_| Error::IOError)?.len() as usize,
+                    offset: 0,
+                    file: File::open(entry.path()).map_err(|_| Error::IOError)?,
+                });
+            }
+        }
+        let mut offset = 0;
+        files.sort_by_key(|f| f.seqnum);
+        for (i, cf) in files.iter_mut().enumerate() {
+            if cf.seqnum != i as u32 {
+                return Err(Error::MissingResourceFile);
+            }
+            cf.offset = offset;
+            offset += cf.len;
+        }
+        Ok(files)
+    }
+
+    pub(crate) fn new(path: &Path) -> Result<Self, Error> {
+        let files = Nrsc::files(path)?;
+        let index = NrscIndex::new(path)?;
+        Ok(Nrsc {
+            index,
+            data: NrscData {
+                files,
+                read_buf: Vec::new(),
+                decomp_buf: Vec::new(),
+                zlib_state: zlib::DecompressorOxide::new(),
+            },
+        })
+    }
+
+    pub fn get_by_idx(&mut self, idx: usize) -> Result<(&str, &[u8]), Error> {
+        let (id, nidx_rec) = self.index.get_by_idx(idx)?;
+        let item = self.data.get_by_nidx_rec(nidx_rec)?;
+        Ok((id, item))
+    }
+
+    pub fn get(&mut self, id: &str) -> Result<&[u8], Error> {
+        self.data.get_by_nidx_rec(self.index.get_by_id(id)?)
+    }
+
+    pub fn len(&self) -> usize {
+        self.index.idx.len()
+    }
+}
+
+impl NrscData {
+    fn get_by_nidx_rec(&mut self, idx: NrscIdxRecord) -> Result<&[u8], Error> {
+        let file = &mut self.files[idx.fileseq() as usize];
+
+        file.file
+            .seek(SeekFrom::Start(idx.file_offset()))
+            .map_err(|_| Error::IOError)?;
+        if self.read_buf.len() < idx.len() {
+            self.read_buf.resize(idx.len(), 0);
+        }
+        file.file
+            .read_exact(&mut self.read_buf[..idx.len()])
+            .map_err(|_| Error::IOError)?;
+
+        match idx.format()? {
+            Format::Uncompressed => Ok(&self.read_buf[..idx.len()]),
+            Format::Zlib => {
+                let n_out = decompress(
+                    &mut self.zlib_state,
+                    &self.read_buf[..idx.len()],
+                    &mut self.decomp_buf,
+                )?;
+                Ok(&self.decomp_buf[..n_out])
+            }
+        }
+    }
+
+}
diff --git a/src/resource/rsc.rs b/src/resource/rsc.rs
new file mode 100644
index 0000000..ceaae98
--- /dev/null
+++ b/src/resource/rsc.rs
@@ -0,0 +1,521 @@
+use core::{cmp::min, mem::size_of, ops::Not, slice};
+use miniz_oxide::inflate::core as zlib;
+use std::{
+    ffi::OsStr,
+    fs::{self, File},
+    io::{Read, Seek, SeekFrom},
+    path::Path,
+};
+
+use crate::{
+    abi_utils::{TransmuteSafe, LE32},
+    resource::decompress,
+    Error,
+};
+
+mod abi {
+    use crate::abi_utils::LE32;
+
+    #[repr(C)]
+    #[derive(Debug, Clone, Copy, Default)]
+    pub(crate) struct IdxRecord {
+        pub item_id: LE32,
+        pub map_idx: LE32,
+    }
+
+    #[repr(C)]
+    #[derive(Debug, Clone, Copy, Default, PartialEq, Eq, PartialOrd, Ord)]
+    pub struct MapRecord {
+        pub(crate) zoffset: LE32,
+        pub(crate) ioffset: LE32,
+    }
+
+    #[test]
+    fn test_get_by_id() {
+        use super::RscIndex;
+        use crate::Error;
+
+        fn idx(id: u32, idx: u32) -> IdxRecord {
+            IdxRecord {
+                item_id: id.into(),
+                map_idx: idx.into(),
+            }
+        }
+        fn map(z: u32, i: u32) -> MapRecord {
+            MapRecord {
+                zoffset: z.into(),
+                ioffset: i.into(),
+            }
+        }
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![]),
+                map: vec![],
+            }
+            .get_by_id(500),
+            Err(Error::NotFound)
+        );
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![idx(1, 0)]),
+                map: vec![map(0, 0)],
+            }
+            .get_by_id(500),
+            Err(Error::NotFound)
+        );
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![idx(1, 0), idx(2, 1)]),
+                map: vec![map(0, 0), map(0, 10)],
+            }
+            .get_by_id(500),
+            Err(Error::NotFound)
+        );
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![idx(1, 0), idx(2, 1), idx(1000, 2)]),
+                map: vec![map(0, 0), map(0, 10), map(0, 20)],
+            }
+            .get_by_id(500),
+            Err(Error::NotFound)
+        );
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![idx(1, 0), idx(2, 1), idx(500, 2), idx(1000, 3)]),
+                map: vec![map(0, 0), map(0, 10), map(0, 20), map(10, 0)],
+            }
+            .get_by_id(500),
+            Ok(map(0, 20))
+        );
+
+        assert_eq!(
+            RscIndex {
+                idx: Some(vec![
+                    idx(1, 0),
+                    idx(2, 1),
+                    idx(499, 2),
+                    idx(500, 3),
+                    idx(501, 4),
+                    idx(1000, 5)
+                ]),
+                map: vec![
+                    map(0, 0),
+                    map(0, 10),
+                    map(0, 20),
+                    map(10, 0),
+                    map(10, 0),
+                    map(10, 0)
+                ],
+            }
+            .get_by_id(500),
+            Ok(map(10, 0))
+        );
+    }
+}
+pub(crate) use abi::{IdxRecord, MapRecord};
+
+use super::ResourceFile;
+
+#[derive(Debug, Clone)]
+pub(crate) struct RscIndex {
+    idx: Option<Vec<IdxRecord>>,
+    map: Vec<MapRecord>,
+}
+
+unsafe impl TransmuteSafe for MapRecord {}
+unsafe impl TransmuteSafe for IdxRecord {}
+
+impl RscIndex {
+    fn load_idx(path: &Path) -> Result<Option<Vec<IdxRecord>>, Error> {
+        let path = path.with_extension("idx");
+        if path.exists().not() {
+            return Ok(None);
+        };
+        let mut idx_file = File::open(path)?;
+        let mut len = [0; 4];
+        idx_file.read_exact(&mut len)?;
+        let len = u32::from_le_bytes(len) as usize;
+        idx_file.seek(SeekFrom::Start(8))?;
+        let idx_size = idx_file.metadata().map_err(|_| Error::IOError)?.len();
+        let idx_expected_size = (size_of::<IdxRecord>() * len + 8) as u64;
+        if idx_size != idx_expected_size {
+            return Err(Error::IncorrectStreamLength);
+        }
+        let mut idx = vec![IdxRecord::default(); len];
+        idx_file
+            .read_exact(IdxRecord::slice_as_bytes_mut(idx.as_mut_slice()))
+            .map_err(|_| Error::IOError)?;
+        Ok(Some(idx))
+    }
+
+    fn load_map(path: &Path) -> Result<Vec<MapRecord>, Error> {
+        let path = path.with_extension("map");
+        let mut map_file = File::open(path)?;
+        let mut len = [0; 4];
+        map_file.seek(SeekFrom::Start(4))?;
+        map_file.read_exact(&mut len)?;
+        let len = u32::from_le_bytes(len) as usize;
+        map_file.seek(SeekFrom::Start(8))?;
+        let map_size = map_file.metadata().map_err(|_| Error::IOError)?.len();
+        let map_expected_size = (size_of::<MapRecord>() * len + 8) as u64;
+        if map_size != map_expected_size {
+            return Err(Error::IncorrectStreamLength);
+        }
+        let mut map = vec![MapRecord::default(); len];
+        map_file
+            .read_exact(MapRecord::slice_as_bytes_mut(map.as_mut_slice()))
+            .map_err(|_| Error::IOError)?;
+        Ok(map)
+    }
+    pub(crate) fn new(path: &Path, rsc_name: &str) -> Result<Self, Error> {
+        let path = path.join(rsc_name); // filename stem
+        let idx = Self::load_idx(&path)?;
+        let map = Self::load_map(&path)?;
+        Ok(RscIndex { idx, map })
+    }
+
+    fn get_map_idx_by_id(&self, id: u32) -> Result<usize, Error> {
+        let Some(idx_list) = &self.idx else {
+            return Ok(id as usize);
+        };
+        if idx_list.is_empty() {
+            return Err(Error::NotFound);
+        }
+
+        // Let's guess first, since usually the IDs are completely predictable, without gaps.
+        let idx = min(id as usize, idx_list.len() - 1);
+        let guess = idx_list[idx].item_id.read();
+        if id == guess {
+            return Ok(idx);
+        }
+        let idx = min(id.saturating_sub(1) as usize, idx_list.len() - 1);
+        let guess = idx_list[idx].item_id.read();
+        if id == guess {
+            return Ok(idx);
+        }
+        let map_idx = idx_list
+            .binary_search_by_key(&id, |r| r.item_id.read())
+            .map(|idx| idx_list[idx].map_idx.us())
+            .map_err(|_| Error::NotFound)?;
+        if map_idx >= self.map.len() {
+            return Err(Error::IndexMismach);
+        }
+        Ok(map_idx)
+    }
+
+    pub fn get_by_id(&self, id: u32) -> Result<MapRecord, Error> {
+        let idx = self.get_map_idx_by_id(id)?;
+        let record = self.map[idx];
+        Ok(record)
+    }
+
+    pub fn get_by_idx(&self, idx: usize) -> Result<(u32, MapRecord), Error> {
+        let item_id = if let Some(indexes) = &self.idx {
+            let idx_rec = indexes.get(idx).copied().ok_or(Error::InvalidIndex)?;
+            if idx_rec.map_idx.us() != idx {
+                return Err(Error::InvalidIndex);
+            };
+            idx_rec.item_id.read()
+        } else {
+            idx as u32
+        };
+        let map_rec = self.map.get(idx).copied().ok_or(Error::InvalidIndex)?;
+        Ok((item_id, map_rec))
+    }
+}
+
+pub struct Rsc {
+    index: RscIndex,
+    files: Vec<ResourceFile>,
+    zlib_buf: Vec<u8>,
+    zlib_state: zlib::DecompressorOxide,
+    contents_buf: Vec<u8>,
+    current_offset: usize,
+    current_len: usize,
+}
+
+impl Rsc {
+    fn parse_fname(rsc_name: &str, fname: &OsStr) -> Option<u32> {
+        let fname = fname.to_str()?;
+        let ext = ".rsc";
+        let min_len = rsc_name.len() + 1 + ext.len();
+        if fname.starts_with(rsc_name) && fname.ends_with(ext) && fname.len() > min_len {
+            let seqnum_start = rsc_name.len() + 1;
+            let seqnum_end = fname.len() - ext.len();
+            u32::from_str_radix(&fname[seqnum_start..seqnum_end], 10).ok()
+        } else {
+            None
+        }
+    }
+
+    fn files(path: &Path, rsc_name: &str) -> Result<Vec<ResourceFile>, Error> {
+        let mut files = Vec::new();
+
+        for entry in fs::read_dir(path).map_err(|_| Error::IOError)? {
+            let entry = entry.map_err(|_| Error::IOError)?;
+            let seqnum = Self::parse_fname(rsc_name, &entry.file_name());
+            if let Some(seqnum) = seqnum {
+                files.push(ResourceFile {
+                    seqnum,
+                    len: entry.metadata().map_err(|_| Error::IOError)?.len() as usize,
+                    offset: 0,
+                    file: File::open(entry.path()).map_err(|_| Error::IOError)?,
+                });
+            }
+        }
+        files.sort_by_key(|f| f.seqnum);
+        let mut offset = 0;
+        for (i, cf) in files.iter_mut().enumerate() {
+            if cf.seqnum != i as u32 + 1 {
+                return Err(Error::MissingResourceFile);
+            }
+            cf.offset = offset;
+            offset += cf.len;
+        }
+        Ok(files)
+    }
+
+    pub(crate) fn new(path: &Path, rsc_name: &str) -> Result<Self, Error> {
+        let files = Rsc::files(path, rsc_name)?;
+        let index = RscIndex::new(path, rsc_name)?;
+        Ok(Self {
+            index,
+            files,
+            zlib_buf: Vec::new(),
+            zlib_state: zlib::DecompressorOxide::new(),
+            contents_buf: Vec::new(),
+            current_offset: 0,
+            current_len: 0,
+        })
+    }
+
+    fn load_contents(&mut self, zoffset: usize) -> Result<(), Error> {
+        let (file, file_offset) = file_offset(&mut self.files, zoffset)?;
+
+        let mut len = [0_u8; 4];
+        file.seek(SeekFrom::Start(file_offset))
+            .map_err(|_| Error::IOError)?;
+        file.read_exact(&mut len).map_err(|_| Error::IOError)?;
+        let len = u32::from_le_bytes(len) as usize;
+        if self.zlib_buf.len() < len {
+            self.zlib_buf.resize(len, 0);
+        }
+        file.read_exact(&mut self.zlib_buf[..len])
+            .map_err(|_| Error::IOError)?;
+
+        let n_out = decompress(
+            &mut self.zlib_state,
+            &self.zlib_buf[..len],
+            &mut self.contents_buf,
+        )?;
+
+        self.current_len = n_out;
+        self.current_offset = zoffset;
+
+        Ok(())
+    }
+
+    pub fn get(&mut self, id: u32) -> Result<&[u8], Error> {
+        self.get_by_map(self.index.get_by_id(id)?)
+    }
+
+    pub fn get_by_idx(&mut self, idx: usize) -> Result<(u32, &[u8]), Error> {
+        let (id, map_rec) = self.index.get_by_idx(idx)?;
+        let item = self.get_by_map(map_rec)?;
+        Ok((id, item))
+    }
+
+    fn get_by_map(&mut self, idx: MapRecord) -> Result<&[u8], Error> {
+        if self.contents_buf.is_empty() || idx.zoffset.us() != self.current_offset {
+            self.load_contents(idx.zoffset.us())?;
+        }
+
+        let contents = &self.contents_buf[idx.ioffset.us()..self.current_len];
+        let (len, contents_tail) = LE32::from(contents)?;
+        Ok(&contents_tail[..len.us()])
+    }
+
+    pub fn len(&self) -> usize {
+        self.index.map.len()
+    }
+}
+
+fn file_offset(contents: &mut [ResourceFile], offset: usize) -> Result<(&mut File, u64), Error> {
+    let file_idx = contents
+        .binary_search_by(|cf| cmp_range(offset, cf.offset..cf.offset + cf.len).reverse())
+        .map_err(|_| Error::InvalidIndex)?;
+    let cf = &mut contents[file_idx];
+    let file = &mut cf.file;
+    let file_offset = (offset - cf.offset) as u64;
+    Ok((file, file_offset))
+}
+
+#[test]
+fn test_file_offset() {
+    use std::os::unix::prelude::AsRawFd;
+
+    assert_eq!(file_offset(&mut [], 0).err(), Some(Error::InvalidIndex));
+
+    let mock_file = || {
+        let f = File::open("/dev/zero").unwrap();
+        let fd = f.as_raw_fd();
+        (f, fd)
+    };
+    let (f1, f1_fd) = mock_file();
+    let one_file = &mut vec![ResourceFile {
+        seqnum: 1,
+        len: 100,
+        offset: 0,
+        file: f1,
+    }];
+
+    let result = file_offset(one_file, 101);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(one_file, 100);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(one_file, 0);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(one_file, 99);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
+
+    let (f1, f1_fd) = mock_file();
+    let (f2, f2_fd) = mock_file();
+    let two_files = &mut vec![
+        ResourceFile {
+            seqnum: 1,
+            len: 100,
+            offset: 0,
+            file: f1,
+        },
+        ResourceFile {
+            seqnum: 2,
+            len: 200,
+            offset: 100,
+            file: f2,
+        },
+    ];
+
+    let result = file_offset(two_files, 301);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(two_files, 300);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(two_files, 0);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(two_files, 99);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
+
+    let result = file_offset(two_files, 100);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(two_files, 299);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(199));
+
+    let (f1, f1_fd) = mock_file();
+    let (f2, f2_fd) = mock_file();
+    let (f3, f3_fd) = mock_file();
+    let three_files = &mut vec![
+        ResourceFile {
+            seqnum: 1,
+            len: 100,
+            offset: 0,
+            file: f1,
+        },
+        ResourceFile {
+            seqnum: 2,
+            len: 200,
+            offset: 100,
+            file: f2,
+        },
+        ResourceFile {
+            seqnum: 3,
+            len: 100,
+            offset: 300,
+            file: f3,
+        },
+    ];
+
+    let result = file_offset(three_files, 401);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(three_files, 400);
+    assert_eq!(result.err(), Some(Error::InvalidIndex));
+
+    let result = file_offset(three_files, 0);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(three_files, 99);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f1_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
+
+    let result = file_offset(three_files, 100);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(three_files, 299);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f2_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(199));
+
+    let result = file_offset(three_files, 300);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f3_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(0));
+
+    let result = file_offset(three_files, 399);
+    assert_eq!(result.as_ref().map(|f| f.0.as_raw_fd()), Ok(f3_fd));
+    assert_eq!(result.as_ref().map(|f| f.1), Ok(99));
+}
+
+fn cmp_range(num: usize, range: core::ops::Range<usize>) -> core::cmp::Ordering {
+    use core::cmp::Ordering;
+    if num < range.start {
+        Ordering::Less
+    } else if range.end <= num {
+        Ordering::Greater
+    } else {
+        Ordering::Equal
+    }
+}
+
+#[test]
+fn test_cmp_to_range() {
+    use core::cmp::Ordering;
+    assert_eq!(cmp_range(0, 0..0), Ordering::Greater);
+    assert_eq!(cmp_range(0, 0..1), Ordering::Equal);
+    assert_eq!(cmp_range(0, 0..100), Ordering::Equal);
+    assert_eq!(cmp_range(1, 0..100), Ordering::Equal);
+    assert_eq!(cmp_range(99, 0..100), Ordering::Equal);
+    assert_eq!(cmp_range(100, 0..100), Ordering::Greater);
+    assert_eq!(cmp_range(101, 0..100), Ordering::Greater);
+    assert_eq!(cmp_range(0, 1..100), Ordering::Less);
+    assert_eq!(cmp_range(99, 100..100), Ordering::Less);
+    assert_eq!(cmp_range(100, 100..100), Ordering::Greater);
+}
+
+pub struct RscIter<'a> {
+    map: slice::Iter<'a, MapRecord>,
+}
+
+impl<'a> Iterator for RscIter<'a> {
+    type Item = MapRecord;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.map.next().copied()
+    }
+}