diff options
Diffstat (limited to 'tvix/nix-compat/src/nar/writer')
| -rw-r--r-- | tvix/nix-compat/src/nar/writer/mod.rs | 225 | ||||
| -rw-r--r-- | tvix/nix-compat/src/nar/writer/sync.rs | 225 |
2 files changed, 227 insertions, 223 deletions
diff --git a/tvix/nix-compat/src/nar/writer/mod.rs b/tvix/nix-compat/src/nar/writer/mod.rs index 9abc2510d149..9d87ed6a9747 100644 --- a/tvix/nix-compat/src/nar/writer/mod.rs +++ b/tvix/nix-compat/src/nar/writer/mod.rs @@ -1,226 +1,5 @@ -//! 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 = nix_compat::nar::writer::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 bstr::ByteSlice; -use std::io::{ - self, BufRead, - ErrorKind::{InvalidInput, UnexpectedEof}, - Write, -}; +pub use sync::*; mod wire; -/// Convenience type alias for types implementing [`Write`]. -pub type Writer<'a> = dyn Write + Send + '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: &[u8]) -> io::Result<()> { - debug_assert!( - target.len() <= wire::MAX_TARGET_LEN, - "target.len() > {}", - wire::MAX_TARGET_LEN - ); - debug_assert!(!target.is_empty(), "target is empty"); - debug_assert!(!target.contains(&0), "target contains null byte"); - - self.write(&wire::TOK_SYM)?; - self.write(&target.len().to_le_bytes())?; - self.write(target)?; - 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); - } - - // bail if there's still data left in the passed reader. - // This uses the same code as [BufRead::has_data_left] (unstable). - if reader.fill_buf().map(|b| !b.is_empty())? { - return Err(io::Error::new( - InvalidInput, - "reader contained more data than specified size", - )); - } - - 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. - /// - /// It is the caller's responsibility to invoke [`Directory::close`], - /// or invalid archives will be produced silently. - pub fn directory(mut self) -> io::Result<Directory<'a, 'w>> { - self.write(&wire::TOK_DIR)?; - Ok(Directory::new(self)) - } -} - -#[cfg(debug_assertions)] -type Name = Vec<u8>; -#[cfg(not(debug_assertions))] -type Name = (); - -fn into_name(_name: &[u8]) -> 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). - /// - /// It is the caller's responsibility to ensure that directory entries are - /// written in order of ascending name. If this is not ensured, this method - /// may panic or silently produce invalid archives. - pub fn entry(&mut self, name: &[u8]) -> io::Result<Node<'_, 'w>> { - debug_assert!( - name.len() <= wire::MAX_NAME_LEN, - "name.len() > {}", - wire::MAX_NAME_LEN - ); - debug_assert!(!name.is_empty(), "name is empty"); - debug_assert!(!name.contains(&0), "name contains null byte"); - debug_assert!(!name.contains(&b'/'), "name contains {:?}", '/'); - debug_assert!(name != b".", "name == {:?}", "."); - debug_assert!(name != b"..", "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.as_bstr(), - name.as_bstr() - ); - _prev_name.clear(); - _prev_name.extend_from_slice(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)?; - 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(()) - } -} +pub mod sync; diff --git a/tvix/nix-compat/src/nar/writer/sync.rs b/tvix/nix-compat/src/nar/writer/sync.rs new file mode 100644 index 000000000000..996815149dd6 --- /dev/null +++ b/tvix/nix-compat/src/nar/writer/sync.rs @@ -0,0 +1,225 @@ +//! 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 = nix_compat::nar::writer::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 super::wire; +use bstr::ByteSlice; +use std::io::{ + self, BufRead, + ErrorKind::{InvalidInput, UnexpectedEof}, + Write, +}; + +/// Convenience type alias for types implementing [`Write`]. +pub type Writer<'a> = dyn Write + Send + '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: &[u8]) -> io::Result<()> { + debug_assert!( + target.len() <= wire::MAX_TARGET_LEN, + "target.len() > {}", + wire::MAX_TARGET_LEN + ); + debug_assert!(!target.is_empty(), "target is empty"); + debug_assert!(!target.contains(&0), "target contains null byte"); + + self.write(&wire::TOK_SYM)?; + self.write(&target.len().to_le_bytes())?; + self.write(target)?; + 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); + } + + // bail if there's still data left in the passed reader. + // This uses the same code as [BufRead::has_data_left] (unstable). + if reader.fill_buf().map(|b| !b.is_empty())? { + return Err(io::Error::new( + InvalidInput, + "reader contained more data than specified size", + )); + } + + 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. + /// + /// It is the caller's responsibility to invoke [`Directory::close`], + /// or invalid archives will be produced silently. + pub fn directory(mut self) -> io::Result<Directory<'a, 'w>> { + self.write(&wire::TOK_DIR)?; + Ok(Directory::new(self)) + } +} + +#[cfg(debug_assertions)] +type Name = Vec<u8>; +#[cfg(not(debug_assertions))] +type Name = (); + +fn into_name(_name: &[u8]) -> 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). + /// + /// It is the caller's responsibility to ensure that directory entries are + /// written in order of ascending name. If this is not ensured, this method + /// may panic or silently produce invalid archives. + pub fn entry(&mut self, name: &[u8]) -> io::Result<Node<'_, 'w>> { + debug_assert!( + name.len() <= wire::MAX_NAME_LEN, + "name.len() > {}", + wire::MAX_NAME_LEN + ); + debug_assert!(!name.is_empty(), "name is empty"); + debug_assert!(!name.contains(&0), "name contains null byte"); + debug_assert!(!name.contains(&b'/'), "name contains {:?}", '/'); + debug_assert!(name != b".", "name == {:?}", "."); + debug_assert!(name != b"..", "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.as_bstr(), + name.as_bstr() + ); + _prev_name.clear(); + _prev_name.extend_from_slice(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)?; + 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(()) + } +} |