4 files changed, 157 insertions, 2 deletions

diff --git a/nix-rust/src/c.rs b/nix-rust/src/c.rs
index 1abd34198..542df93d2 100644
--- a/nix-rust/src/c.rs
+++ b/nix-rust/src/c.rs
@@ -1,4 +1,8 @@
-use super::{foreign::{self, CBox}, error, util, store};
+use super::{
+    error,
+    foreign::{self, CBox},
+    util,
+};
 
 #[no_mangle]
 pub extern "C" fn unpack_tarfile(
@@ -10,7 +14,8 @@ pub extern "C" fn unpack_tarfile(
 
 #[no_mangle]
 pub extern "C" fn rust_test() {
-    use crate::store::Store;
+    /*
+    use crate::store::{self, Store};
     use futures::future::{FutureExt, TryFutureExt};
     use std::path::Path;
 
@@ -39,4 +44,9 @@ pub extern "C" fn rust_test() {
     };
 
     tokio::run(fut.boxed().compat());
+     */
+
+    let file = std::fs::File::open("test.nar").unwrap();
+
+    crate::nar::parse(&mut std::io::BufReader::new(file)).unwrap();
 }
diff --git a/nix-rust/src/error.rs b/nix-rust/src/error.rs
index 5717a7a47..4defc646d 100644
--- a/nix-rust/src/error.rs
+++ b/nix-rust/src/error.rs
@@ -8,6 +8,15 @@ pub enum Error {
     BadBase32,
     StorePathNameTooLong,
     BadStorePathName,
+    NarSizeFieldTooBig,
+    BadNarString,
+    BadNarPadding,
+    BadNarVersionMagic,
+    MissingNarOpenTag,
+    MissingNarCloseTag,
+    MissingNarField,
+    BadNarField(String),
+    BadExecutableField,
     IOError(std::io::Error),
     HttpError(reqwest::Error),
     Misc(String),
@@ -37,6 +46,15 @@ impl fmt::Display for Error {
                 write!(f, "store path name is longer than 211 characters")
             }
             Error::BadStorePathName => write!(f, "store path name contains forbidden character"),
+            Error::NarSizeFieldTooBig => write!(f, "size field in NAR is too big"),
+            Error::BadNarString => write!(f, "NAR string is not valid UTF-8"),
+            Error::BadNarPadding => write!(f, "NAR padding is not zero"),
+            Error::BadNarVersionMagic => write!(f, "unsupported NAR version"),
+            Error::MissingNarOpenTag => write!(f, "NAR open tag is missing"),
+            Error::MissingNarCloseTag => write!(f, "NAR close tag is missing"),
+            Error::MissingNarField => write!(f, "expected NAR field is missing"),
+            Error::BadNarField(s) => write!(f, "unrecognized NAR field '{}'", s),
+            Error::BadExecutableField => write!(f, "bad 'executable' field in NAR"),
             Error::IOError(err) => write!(f, "I/O error: {}", err),
             Error::HttpError(err) => write!(f, "HTTP error: {}", err),
             Error::Foreign(_) => write!(f, "<C++ exception>"), // FIXME
diff --git a/nix-rust/src/lib.rs b/nix-rust/src/lib.rs
index 635c00aff..cda63d2c7 100644
--- a/nix-rust/src/lib.rs
+++ b/nix-rust/src/lib.rs
@@ -14,6 +14,7 @@ extern crate proptest;
 mod c;
 mod error;
 mod foreign;
+mod nar;
 mod store;
 mod util;
 
diff --git a/nix-rust/src/nar.rs b/nix-rust/src/nar.rs
new file mode 100644
index 000000000..aa05d815b
--- /dev/null
+++ b/nix-rust/src/nar.rs
@@ -0,0 +1,126 @@
+use crate::Error;
+use byteorder::{LittleEndian, ReadBytesExt};
+use std::convert::TryFrom;
+use std::io::Read;
+
+pub fn parse<R: Read>(input: &mut R) -> Result<(), Error> {
+    if String::read(input)? != NAR_VERSION_MAGIC {
+        return Err(Error::BadNarVersionMagic);
+    }
+
+    parse_file(input)
+}
+
+const NAR_VERSION_MAGIC: &str = "nix-archive-1";
+
+fn parse_file<R: Read>(input: &mut R) -> Result<(), Error> {
+    if String::read(input)? != "(" {
+        return Err(Error::MissingNarOpenTag);
+    }
+
+    if String::read(input)? != "type" {
+        return Err(Error::MissingNarField);
+    }
+
+    match String::read(input)?.as_ref() {
+        "regular" => {
+            let mut executable = false;
+            let mut tag = String::read(input)?;
+            if tag == "executable" {
+                executable = true;
+                if String::read(input)? != "" {
+                    return Err(Error::BadExecutableField);
+                }
+                tag = String::read(input)?;
+            }
+            if tag != "contents" {
+                return Err(Error::MissingNarField);
+            }
+            let contents = Vec::<u8>::read(input)?;
+            if String::read(input)? != ")" {
+                return Err(Error::MissingNarCloseTag);
+            }
+        }
+        "directory" => loop {
+            match String::read(input)?.as_ref() {
+                "entry" => {
+                    if String::read(input)? != "(" {
+                        return Err(Error::MissingNarOpenTag);
+                    }
+                    if String::read(input)? != "name" {
+                        return Err(Error::MissingNarField);
+                    }
+                    let name = String::read(input)?;
+                    if String::read(input)? != "node" {
+                        return Err(Error::MissingNarField);
+                    }
+                    parse_file(input)?;
+                    let tag = String::read(input)?;
+                    if tag != ")" {
+                        return Err(Error::MissingNarCloseTag);
+                    }
+                }
+                ")" => break,
+                s => return Err(Error::BadNarField(s.into())),
+            }
+        },
+        "symlink" => {
+            if String::read(input)? != "target" {
+                return Err(Error::MissingNarField);
+            }
+            let target = String::read(input)?;
+            if String::read(input)? != ")" {
+                return Err(Error::MissingNarCloseTag);
+            }
+        }
+        s => return Err(Error::BadNarField(s.into())),
+    }
+
+    Ok(())
+}
+
+trait Deserialize: Sized {
+    fn read<R: Read>(input: &mut R) -> Result<Self, Error>;
+}
+
+impl Deserialize for String {
+    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
+        let buf = Deserialize::read(input)?;
+        Ok(String::from_utf8(buf).map_err(|_| Error::BadNarString)?)
+    }
+}
+
+impl Deserialize for Vec<u8> {
+    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
+        let n: usize = Deserialize::read(input)?;
+        let mut buf = vec![0; n];
+        input.read_exact(&mut buf)?;
+        skip_padding(input, n)?;
+        Ok(buf)
+    }
+}
+
+fn skip_padding<R: Read>(input: &mut R, len: usize) -> Result<(), Error> {
+    if len % 8 != 0 {
+        let mut buf = [0; 8];
+        let buf = &mut buf[0..8 - (len % 8)];
+        input.read_exact(buf)?;
+        if !buf.iter().all(|b| *b == 0) {
+            return Err(Error::BadNarPadding);
+        }
+    }
+    Ok(())
+}
+
+impl Deserialize for u64 {
+    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
+        Ok(input.read_u64::<LittleEndian>()?)
+    }
+}
+
+impl Deserialize for usize {
+    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
+        let n: u64 = Deserialize::read(input)?;
+        Ok(usize::try_from(n).map_err(|_| Error::NarSizeFieldTooBig)?)
+    }
+}