Fix parallel archive creation, add archive streaming functions

src/lib.rs

@@ -1,7 +1,10 @@
 #![doc = include_str!("../README.md")]
+use std::{collections::HashMap, fs, io::{BufWriter, Write}, sync::Mutex};
 #[cfg(feature = "parallel")]
-use rayon::prelude::{IntoParallelRefIterator, ParallelIterator};
-use std::{collections::HashMap, fs, io::BufWriter, sync::Mutex};
+use {
+    rayon::prelude::{IntoParallelRefIterator, ParallelIterator},
+    std::ops::DerefMut,
+};
 
 mod checksum;
 mod error;
@@ -22,39 +25,55 @@ pub use {
     stream::Stream,
 };
 
+/// Creates a haggis archive from a list of files
 pub fn create_archive(path: &str, files: Vec<&str>, algorithm: Algorithm) -> Result<(), Error> {
     let fd = fs::OpenOptions::new()
         .create(true)
         .truncate(true)
         .open(path)?;
     let mut writer = BufWriter::new(fd);
+    stream_archive(&mut writer, files, algorithm)?;
+    Ok(())
+}
+
+/// Streams a haggis archive over something which implements `Write`
+pub fn stream_archive<W: Write>(
+    mut writer: W,
+    files: Vec<&str>,
+    algorithm: Algorithm,
+) -> Result<(), Error> {
     let links = Mutex::new(HashMap::new());
-    for f in files.iter() {
+    for f in &files {
         let node = Node::from_path(f, algorithm, &links)?;
         node.write(&mut writer)?;
     }
     Ok(())
 }
 
+/// Creates a Haggis archive from a list of files, processing each file in parallel
 #[cfg(feature = "parallel")]
-pub fn par_create_archive(
-    path: &str,
-    files: Vec<String>,
+pub fn par_create_archive(path: &str, files: Vec<&str>, algorithm: Algorithm) -> Result<(), Error> {
+    let fd = fs::File::create(path)?;
+    let writer = BufWriter::new(fd);
+    par_stream_archive(writer, files, algorithm)?;
+    Ok(())
+}
+
+/// Streams a Haggis archive from a list of files, processing each file in parallel
+#[cfg(feature = "parallel")]
+pub fn par_stream_archive<W: Write + Send>(
+    writer: W,
+    files: Vec<&str>,
     algorithm: Algorithm,
 ) -> Result<(), Error> {
     let links = Mutex::new(HashMap::<u64, String>::new());
-    {
-        let _fd = fs::File::create(path)?;
-    }
+    let writer = Mutex::new(writer);
     files.par_iter().try_for_each(|f| {
         let node = Node::from_path(f, algorithm, &links)?;
-        let fd = fs::OpenOptions::new()
-            .create(false)
-            .truncate(false)
-            .append(true)
-            .open(path)?;
-        let mut writer = BufWriter::new(fd);
-        node.write(&mut writer)?;
+        if let Ok(mut writer) = writer.lock() {
+            let mut writer = writer.deref_mut();
+            node.write(&mut writer)?;
+        }
         Ok::<(), Error>(())
     })?;
     Ok(())