1 files changed, 33 insertions, 3 deletions

diff --git a/src/lib.rs b/src/lib.rs
index eacce62..9f46f54 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -32,10 +32,15 @@
 //! ~~~
 
 use serde::Serialize;
-use std::fs::Metadata;
+use sha2::{Digest, Sha256};
+use std::fs::symlink_metadata;
+use std::fs::File;
+use std::io::{BufReader, Read};
 use std::os::linux::fs::MetadataExt;
 use std::path::{Path, PathBuf};
 
+const BUF_SIZE: usize = 1024 * 1024;
+
 /// An entry in a file manifest.
 #[derive(Serialize, Debug)]
 pub struct ManifestEntry {
@@ -48,6 +53,7 @@ pub struct ManifestEntry {
     mtime_nsec: i64,
     nlink: u64,
     size: Option<u64>,
+    sha256: Option<String>,
 }
 
 impl ManifestEntry {
@@ -57,8 +63,14 @@ impl ManifestEntry {
     /// caller. This function doesn't query the system for it.
     ///
     /// The structure can be serialized using serde.
-    pub fn new(path: &Path, m: Metadata) -> Self {
-        Self {
+    pub fn new(path: &Path) -> std::io::Result<Self> {
+        let m = symlink_metadata(path)?;
+        let hash = if m.is_file() {
+            Some(file_checksum(path)?)
+        } else {
+            None
+        };
+        Ok(Self {
             path: path.to_path_buf(),
             atime: m.st_atime(),
             atime_nsec: m.st_atime_nsec(),
@@ -67,8 +79,26 @@ impl ManifestEntry {
             mtime_nsec: m.st_mtime_nsec(),
             nlink: m.st_nlink(),
             size: if m.is_dir() { None } else { Some(m.st_size()) },
+            sha256: hash,
+        })
+    }
+}
+
+fn file_checksum(path: &Path) -> std::io::Result<String> {
+    let mut hasher = Sha256::new();
+
+    let file = File::open(path)?;
+    let mut reader = BufReader::new(file);
+    let mut buf = vec![0; BUF_SIZE];
+    loop {
+        let n = reader.read(&mut buf)?;
+        if n == 0 {
+            break;
         }
+        hasher.update(&buf[..n]);
     }
+    let hash = hasher.finalize();
+    Ok(format!("{:x}", hash))
 }
 
 mod mode {