1 files changed, 44 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..93627f1
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,44 @@
+use sha2::{Digest, Sha256};
+use std::fs::File;
+use std::io::{BufReader, Read};
+use std::path::{Path, PathBuf};
+
+const BUF_SIZE: usize = 4096;
+
+#[derive(Debug)]
+pub struct FileChecksum {
+    pub filename: PathBuf,
+    pub checksum: String,
+}
+
+impl FileChecksum {
+    pub fn new(filename: &Path, checksum: String) -> Self {
+        Self {
+            filename: filename.to_path_buf(),
+            checksum,
+        }
+    }
+
+    pub fn print(&self) {
+        println!("{} {}", self.checksum, self.filename.display());
+    }
+}
+
+pub fn checksum(filename: &Path) -> Result<FileChecksum, std::io::Error> {
+    let mut checksum = Sha256::new();
+
+    let file = File::open(filename)?;
+    let mut reader = BufReader::new(file);
+    loop {
+        let mut buf = vec![0; BUF_SIZE];
+        let n = reader.read(&mut buf)?;
+        if n == 0 {
+            break;
+        }
+        checksum.update(&buf[..n]);
+    }
+
+    let checksum = checksum.finalize();
+    let checksum = format!("{checksum:x}");
+    Ok(FileChecksum::new(filename, checksum))
+}