Add recursive SHA256 example application

1 files changed, 55 insertions, 0 deletions

diff --git a/examples/recursive-sha256/src/main.rs b/examples/recursive-sha256/src/main.rs
new file mode 100644
index 0000000..6fcbbfa
--- /dev/null
+++ b/examples/recursive-sha256/src/main.rs
@@ -0,0 +1,55 @@
+//! Print the SHA256 sum of each regular file in the current directory recursively.
+
+use std::{fs::File, path::PathBuf};
+
+use parseq::ParallelIterator;
+use sha2::{Digest, Sha256};
+use walkdir::WalkDir;
+
+fn main() {
+    WalkDir::new(".")
+        .sort_by_file_name()
+        .into_iter()
+        .filter_map(|entry| match entry {
+            Ok(entry) if entry.file_type().is_file() => Some(Ok(entry.into_path())),
+            Ok(_) => None,
+            Err(err) => Some(Err(Error::WalkdirError(err))),
+        })
+        .map_parallel(|item| {
+            item.and_then(|path| {
+                let mut file =
+                    File::open(&path).map_err(|err| Error::IoError(path.clone(), err))?;
+                let mut hasher = Sha256::new();
+                std::io::copy(&mut file, &mut hasher)
+                    .map_err(|err| Error::IoError(path.clone(), err))?;
+                Ok((path, hasher.finalize()))
+            })
+        })
+        .for_each(|item| match item {
+            Ok((path, hash)) => println!("{:x} {}", hash, path.display()),
+            Err(err) => eprintln!("{err}"),
+        });
+}
+
+#[derive(Debug)]
+enum Error {
+    WalkdirError(walkdir::Error),
+    IoError(PathBuf, std::io::Error),
+}
+
+impl std::error::Error for Error {}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::WalkdirError(err) => {
+                if let Some(path) = err.path() {
+                    write!(f, "{}: {}", path.display(), err)
+                } else {
+                    write!(f, "{err}")
+                }
+            }
+            Error::IoError(path, err) => write!(f, "{}: {}", path.display(), err),
+        }
+    }
+}