Moved DirWriterLister to it's own module.

Removed currently superfluous `DirList` associated type, as it cannot be used without creating an infinite type.

dcb-io/src/drv.rs

@@ -30,9 +30,7 @@ pub struct DrvFsWriter;
 
 impl DrvFsWriter {
 	/// Creates a `.DRV` filesystem
-	pub fn write_fs<W: io::Write + io::Seek, L: DirWriterLister>(
-		writer: &mut W, root_entries: L,
-	) -> Result<(), WriteFsError<L::Error>> {
+	pub fn write_fs<W: io::Write + io::Seek, L: DirWriterLister>(writer: &mut W, root_entries: L) -> Result<(), WriteFsError<L::Error>> {
 		// Get the root and write it
 		let root = DirWriter::new(root_entries);
 		root.write_entries(writer).map_err(WriteFsError::RootDir)?;

dcb-io/src/drv/dir/writer.rs

@@ -2,35 +2,19 @@
 
 // Modules
 pub mod error;
+pub mod lister;
 
 // Exports
 pub use error::WriteEntriesError;
+pub use lister::DirWriterLister;
 
 // Imports
-use super::{entry::DirEntryWriterKind, DirEntryWriter};
+use super::entry::DirEntryWriterKind;
 use std::{
 	convert::TryFrom,
 	io::{self, SeekFrom},
 };
 
-/// Directory lister
-pub trait DirWriterLister: Sized + std::fmt::Debug
-where
-	Self: IntoIterator<Item = Result<DirEntryWriter<Self>, <Self as DirWriterLister>::Error>>,
-{
-	/// Reader used for the files in this directory
-	type FileReader: std::fmt::Debug + io::Read;
-
-	/// Directory lister for each directory in this directory
-	type DirList: DirWriterLister;
-
-	/// Error type for each entry
-	type Error: std::error::Error + 'static;
-
-	/// Returns the number of entries in this lister
-	fn entries_len(&self) -> u32;
-}
-
 /// Directory writer
 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 pub struct DirWriter<L: DirWriterLister> {

dcb-io/src/drv/dir/writer/lister.rs

@@ -0,0 +1,39 @@
+//! Directory writer lister
+
+// Imports
+use crate::drv::DirEntryWriter;
+use std::io;
+
+/// Directory lister
+///
+/// This trait serves to provide an interface for the caller
+/// to list all files and directories they want to write to
+/// the drv file without requiring them all to be read before
+/// hand.
+///
+/// It is similar to a visitor, but with the roles reversed,
+/// it is the writer that visits the entries provided by the
+/// user by means of the [`IntoIterator`] implementation.
+///
+/// It is required to know the size before-hand to know how
+/// much space to allocate for each directory. It would be
+/// possible to write the children first and then the directory
+/// to avoid this problem, but the root directory would still
+/// need to report it's size, and by putting the directories first
+/// readers don't have to seek across the file to read the full
+/// directory tree as much.
+/// This is, of course, provided the implementor supplies directories
+/// before the files, else they will not be placed at the start.
+pub trait DirWriterLister: Sized + std::fmt::Debug
+where
+	Self: IntoIterator<Item = Result<DirEntryWriter<Self>, <Self as DirWriterLister>::Error>>,
+{
+	/// Type used to read all files in this directory tree
+	type FileReader: std::fmt::Debug + io::Read;
+
+	/// Error type for each entry
+	type Error: std::error::Error + 'static;
+
+	/// Returns the number of entries in this lister
+	fn entries_len(&self) -> u32;
+}

dcb-tools/drv-packer/src/dir_lister.rs

@@ -43,7 +43,6 @@ impl DirLister {
 }
 
 impl DirWriterLister for DirLister {
-	type DirList = Self;
 	type Error = NextError;
 	type FileReader = fs::File;
 
@@ -53,7 +52,7 @@ impl DirWriterLister for DirLister {
 }
 
 impl Iterator for DirLister {
-	type Item = Result<DirEntryWriter<<Self as DirWriterLister>::DirList>, <Self as DirWriterLister>::Error>;
+	type Item = Result<DirEntryWriter<Self>, <Self as DirWriterLister>::Error>;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		// Get the next entry