From 848a3fd22b5a4b8ab32b18c87229b0956c4e0336 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Tue, 2 Oct 2018 16:55:01 +0300
Subject: Change: process in chunks of 4

---
 src/main.rs | 46 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index d49266b..a4501cf 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -17,24 +17,42 @@ type Map = BTreeMap<&'static str, String>;
 
 
 fn main() -> io::Result<()> {
+    let nproc = 4;
     for dirname in env::args().skip(1) {
-        let maps: Vec<DirEntry> = WalkDir::new(&dirname)
-            .into_iter()
-            .filter_map(|e| e.ok())
-            .collect();
-        let maps: Vec<Map> = maps
-            .into_par_iter()
-            .map(mkmap)
-            .collect();
-        for map in maps {
-            println!("{}", serde_yaml::to_string(&map).unwrap());
-        }
+        summain(&dirname, nproc);
     }
     Ok(())
 }
 
 
-fn mkmap(e: DirEntry) -> Map {
+fn summain(dirname: &str, nproc: usize) {
+    let mut chunk: Vec<DirEntry> = vec![];
+    let entries = WalkDir::new(dirname)
+        .into_iter()
+        .filter_map(|e| e.ok());
+
+    for entry in entries {
+        chunk.push(entry);
+        if chunk.len() == nproc {
+            process_chunk(&chunk);
+        }
+    }
+
+    if chunk.len() > 0 {
+        process_chunk(&chunk);
+    }
+}
+
+
+fn process_chunk(chunk: &[DirEntry]) {
+    let chunk: Vec<Map> = chunk.into_par_iter().map(mkmap).collect();
+    for map in chunk {
+        print_map(map);
+    }
+}
+
+
+fn mkmap(e: &DirEntry) -> Map {
     let fields = vec![
         ("Name", format::name(&e)),
         ("Mtime", format::mtime(&e)),
@@ -58,3 +76,7 @@ fn mkmap(e: DirEntry) -> Map {
     }
     map
 }
+
+fn print_map(map: Map) {
+    println!("{}", serde_yaml::to_string(&map).unwrap());
+}
-- 
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