refactor(tvix/nix-compat): absorb nar writer r/5793

Expose it at `nix_compat::nar::writer`.

Change-Id: I98a8acfa6277074f24608d64fb6c0082b41d10f5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7969
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

4 files changed, 0 insertions, 261 deletions

diff --git a/tvix/nar/Cargo.toml b/tvix/nar/Cargo.toml
deleted file mode 100644
index 6ec8072c3abc..000000000000
--- a/tvix/nar/Cargo.toml
+++ /dev/null
@@ -1,4 +0,0 @@
-[package]
-name = "tvix-nar"
-version = "0.0.0"
-edition = "2021"
diff --git a/tvix/nar/default.nix b/tvix/nar/default.nix
deleted file mode 100644
index 4d62add05982..000000000000
--- a/tvix/nar/default.nix
+++ /dev/null
@@ -1,5 +0,0 @@
-{ depot, ... }:
-
-depot.tvix.crates.workspaceMembers.tvix-nar.build.override {
-  runTests = true;
-}
diff --git a/tvix/nar/src/lib.rs b/tvix/nar/src/lib.rs
deleted file mode 100644
index 62d2be50140e..000000000000
--- a/tvix/nar/src/lib.rs
+++ /dev/null
@@ -1,206 +0,0 @@
-//! Implements an interface for writing the Nix archive format (NAR).
-//!
-//! NAR files (and their hashed representations) are used in C++ Nix for
-//! addressing fixed-output derivations and a variety of other things.
-//!
-//! NAR files can be output to any type that implements [`Write`], and content
-//! can be read from any type that implementes [`BufRead`].
-//!
-//! Writing a single file might look like this:
-//!
-//! ```rust
-//! # use std::io::BufReader;
-//! # let some_file: Vec<u8> = vec![0, 1, 2, 3, 4];
-//!
-//! // Output location to write the NAR to.
-//! let mut sink: Vec<u8> = Vec::new();
-//!
-//! // Instantiate writer for this output location.
-//! let mut nar = tvix_nar::open(&mut sink)?;
-//!
-//! // Acquire metadata for the single file to output, and pass it in a
-//! // `BufRead`-implementing type.
-//!
-//! let executable = false;
-//! let size = some_file.len() as u64;
-//! let mut reader = BufReader::new(some_file.as_slice());
-//! nar.file(executable, size, &mut reader)?;
-//! # Ok::<(), std::io::Error>(())
-//! ```
-
-use std::io::{self, BufRead, ErrorKind::UnexpectedEof, Write};
-
-mod wire;
-
-/// Convenience type alias for types implementing [`Write`].
-pub type Writer<'a> = dyn Write + 'a;
-
-/// Create a new NAR, writing the output to the specified writer.
-pub fn open<'a, 'w: 'a>(writer: &'a mut Writer<'w>) -> io::Result<Node<'a, 'w>> {
-    let mut node = Node { writer };
-    node.write(&wire::TOK_NAR)?;
-    Ok(node)
-}
-
-/// Single node in a NAR file.
-///
-/// A NAR can be thought of as a tree of nodes represented by this type. Each
-/// node can be a file, a symlink or a directory containing other nodes.
-pub struct Node<'a, 'w: 'a> {
-    writer: &'a mut Writer<'w>,
-}
-
-impl<'a, 'w> Node<'a, 'w> {
-    fn write(&mut self, data: &[u8]) -> io::Result<()> {
-        self.writer.write_all(data)
-    }
-
-    fn pad(&mut self, n: u64) -> io::Result<()> {
-        match (n & 7) as usize {
-            0 => Ok(()),
-            n => self.write(&[0; 8][n..]),
-        }
-    }
-
-    /// Make this node a symlink.
-    pub fn symlink(mut self, target: &str) -> io::Result<()> {
-        debug_assert!(
-            target.len() <= wire::MAX_TARGET_LEN,
-            "target.len() > {}",
-            wire::MAX_TARGET_LEN
-        );
-        debug_assert!(
-            !target.contains('\0'),
-            "invalid target characters: {target:?}"
-        );
-        debug_assert!(!target.is_empty(), "empty target");
-
-        self.write(&wire::TOK_SYM)?;
-        self.write(&target.len().to_le_bytes())?;
-        self.write(target.as_bytes())?;
-        self.pad(target.len() as u64)?;
-        self.write(&wire::TOK_PAR)?;
-        Ok(())
-    }
-
-    /// Make this node a single file.
-    pub fn file(mut self, executable: bool, size: u64, reader: &mut dyn BufRead) -> io::Result<()> {
-        self.write(if executable {
-            &wire::TOK_EXE
-        } else {
-            &wire::TOK_REG
-        })?;
-
-        self.write(&size.to_le_bytes())?;
-
-        let mut need = size;
-        while need != 0 {
-            let data = reader.fill_buf()?;
-
-            if data.is_empty() {
-                return Err(UnexpectedEof.into());
-            }
-
-            let n = need.min(data.len() as u64) as usize;
-            self.write(&data[..n])?;
-
-            need -= n as u64;
-            reader.consume(n);
-        }
-
-        self.pad(size)?;
-        self.write(&wire::TOK_PAR)?;
-
-        Ok(())
-    }
-
-    /// Make this node a directory, the content of which is set using the
-    /// resulting [`Directory`] value.
-    pub fn directory(mut self) -> io::Result<Directory<'a, 'w>> {
-        self.write(&wire::TOK_DIR)?;
-        Ok(Directory::new(self))
-    }
-}
-
-#[cfg(debug_assertions)]
-type Name = String;
-#[cfg(not(debug_assertions))]
-type Name = ();
-
-fn into_name(_name: &str) -> Name {
-    #[cfg(debug_assertions)]
-    _name.to_owned()
-}
-
-/// Content of a NAR node that represents a directory.
-pub struct Directory<'a, 'w> {
-    node: Node<'a, 'w>,
-    prev_name: Option<Name>,
-}
-
-impl<'a, 'w> Directory<'a, 'w> {
-    fn new(node: Node<'a, 'w>) -> Self {
-        Self {
-            node,
-            prev_name: None,
-        }
-    }
-
-    /// Add an entry to the directory.
-    ///
-    /// The entry is simply another [`Node`], which can then be filled like the
-    /// root of a NAR (including, of course, by nesting directories).
-    pub fn entry(&mut self, name: &str) -> io::Result<Node<'_, 'w>> {
-        debug_assert!(
-            name.len() <= wire::MAX_NAME_LEN,
-            "name.len() > {}",
-            wire::MAX_NAME_LEN
-        );
-        debug_assert!(!["", ".", ".."].contains(&name), "invalid name: {name:?}");
-        debug_assert!(
-            !name.contains(['/', '\0']),
-            "invalid name characters: {name:?}"
-        );
-
-        match self.prev_name {
-            None => {
-                self.prev_name = Some(into_name(name));
-            }
-            Some(ref mut _prev_name) => {
-                #[cfg(debug_assertions)]
-                {
-                    assert!(
-                        &**_prev_name < name,
-                        "misordered names: {_prev_name:?} >= {name:?}"
-                    );
-                    _prev_name.clear();
-                    _prev_name.push_str(name);
-                }
-                self.node.write(&wire::TOK_PAR)?;
-            }
-        }
-
-        self.node.write(&wire::TOK_ENT)?;
-        self.node.write(&name.len().to_le_bytes())?;
-        self.node.write(name.as_bytes())?;
-        self.node.pad(name.len() as u64)?;
-        self.node.write(&wire::TOK_NOD)?;
-
-        Ok(Node {
-            writer: &mut *self.node.writer,
-        })
-    }
-
-    /// Close a directory and write terminators for the directory to the NAR.
-    ///
-    /// **Important:** This *must* be called when all entries have been written
-    /// in a directory, otherwise the resulting NAR file will be invalid.
-    pub fn close(mut self) -> io::Result<()> {
-        if self.prev_name.is_some() {
-            self.node.write(&wire::TOK_PAR)?;
-        }
-
-        self.node.write(&wire::TOK_PAR)?;
-        Ok(())
-    }
-}
diff --git a/tvix/nar/src/wire.rs b/tvix/nar/src/wire.rs
deleted file mode 100644
index 98581ae3aa7c..000000000000
--- a/tvix/nar/src/wire.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-pub const MAX_NAME_LEN: usize = 255;
-pub const MAX_TARGET_LEN: usize = 4095;
-
-#[cfg(test)]
-fn token(xs: &[&str]) -> Vec<u8> {
-    let mut out = vec![];
-    for x in xs {
-        let len = x.len() as u64;
-        out.extend_from_slice(&len.to_le_bytes());
-        out.extend_from_slice(x.as_bytes());
-
-        let n = x.len() & 7;
-        if n != 0 {
-            const ZERO: [u8; 8] = [0; 8];
-            out.extend_from_slice(&ZERO[n..]);
-        }
-    }
-    out
-}
-
-pub const TOK_NAR: [u8; 56] = *b"\x0d\0\0\0\0\0\0\0nix-archive-1\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
-pub const TOK_REG: [u8; 32] = *b"\x07\0\0\0\0\0\0\0regular\0\x08\0\0\0\0\0\0\0contents";
-pub const TOK_EXE: [u8; 64] = *b"\x07\0\0\0\0\0\0\0regular\0\x0a\0\0\0\0\0\0\0executable\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x08\0\0\0\0\0\0\0contents";
-pub const TOK_SYM: [u8; 32] = *b"\x07\0\0\0\0\0\0\0symlink\0\x06\0\0\0\0\0\0\0target\0\0";
-pub const TOK_DIR: [u8; 24] = *b"\x09\0\0\0\0\0\0\0directory\0\0\0\0\0\0\0";
-pub const TOK_ENT: [u8; 48] = *b"\x05\0\0\0\0\0\0\0entry\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0name\0\0\0\0";
-pub const TOK_NOD: [u8; 48] = *b"\x04\0\0\0\0\0\0\0node\0\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
-pub const TOK_PAR: [u8; 16] = *b"\x01\0\0\0\0\0\0\0)\0\0\0\0\0\0\0";
-
-#[test]
-fn tokens() {
-    let cases: &[(&[u8], &[&str])] = &[
-        (&TOK_NAR, &["nix-archive-1", "(", "type"]),
-        (&TOK_REG, &["regular", "contents"]),
-        (&TOK_EXE, &["regular", "executable", "", "contents"]),
-        (&TOK_SYM, &["symlink", "target"]),
-        (&TOK_DIR, &["directory"]),
-        (&TOK_ENT, &["entry", "(", "name"]),
-        (&TOK_NOD, &["node", "(", "type"]),
-        (&TOK_PAR, &[")"]),
-    ];
-
-    for &(tok, xs) in cases {
-        assert_eq!(tok, token(xs));
-    }
-}