comment

1 files changed, 18 insertions, 0 deletions

diff --git a/src/bin/summain.rs b/src/bin/summain.rs
index 6344298..5031006 100644
--- a/src/bin/summain.rs
+++ b/src/bin/summain.rs
@@ -8,11 +8,25 @@ async fn main() -> anyhow::Result<()> {
     let mut opt = Opt::from_args();
     opt.pathnames[..].sort();
 
+    // Get metadata about all files, but don't compute checksum yet.
+    //
+    // This all runs in async worker threads, since it's theoretically
+    // I/O heavy and benefits from async task context switching. We
+    // create a task for each named file, since tasks are very cheap.
+    // We keep the JoinHandle for each task in a vector: there's not
+    // going to be so many handles that the vector becomes impossibly
+    // large: Linux only allows 128 KiB of command line arguments.
+
     let mut handles = vec![];
     for filename in opt.pathnames.iter().cloned() {
         handles.push(tokio::spawn(async move { manifest(filename) }));
     }
 
+    // Compute checksums for regular files.
+    //
+    // This runs in blocking threads, since it's CPU heavy. We create
+    // another vector of JoinHandles. Again, it won't become too large.
+
     let mut sumhandles = vec![];
     for h in handles {
         let mut m: ManifestEntry = h.await?.await?;
@@ -23,6 +37,10 @@ async fn main() -> anyhow::Result<()> {
         sumhandles.push(h)
     }
 
+    // Wait for checksums to be available and print manifest.
+    //
+    // Note how this iterates over the results in the right order.
+
     for h in sumhandles {
         let m: ManifestEntry = h.await??;
         print!("{}", serde_yaml::to_string(&m)?);