Preserve hardlinks in native tar archives

1 files changed, 31 insertions, 5 deletions

diff --git a/src/archive.rs b/src/archive.rs
index 0076364..70392fa 100644
--- a/src/archive.rs
+++ b/src/archive.rs
@@ -1,4 +1,6 @@
+use std::collections::BTreeMap;
 use std::fs::{self, File};
+use std::os::unix::fs::MetadataExt;
 use std::path::Path;
 
 use anyhow::{bail, Context, Result};
@@ -26,7 +28,7 @@ impl NativeTarWriter {
         let output = output.as_ref();
         let file = File::create(output).with_context(|| format!("create archive {}", output.display()))?;
         let mut archive = Builder::new(file);
-        append_tree(&mut archive, rootfs, Path::new(""))?;
+        append_tree(&mut archive, rootfs, Path::new(""), &mut BTreeMap::new())?;
         archive
             .finish()
             .with_context(|| format!("finish archive {}", output.display()))?;
@@ -34,7 +36,12 @@ impl NativeTarWriter {
     }
 }
 
-fn append_tree(archive: &mut Builder<File>, rootfs: &Path, relative: &Path) -> Result<()> {
+fn append_tree(
+    archive: &mut Builder<File>,
+    rootfs: &Path,
+    relative: &Path,
+    hardlink_targets: &mut BTreeMap<(u64, u64), std::path::PathBuf>,
+) -> Result<()> {
     let directory = rootfs.join(relative);
     let mut entries = fs::read_dir(&directory)
         .with_context(|| format!("read rootfs directory {}", directory.display()))?
@@ -54,9 +61,9 @@ fn append_tree(archive: &mut Builder<File>, rootfs: &Path, relative: &Path) -> R
 
         if file_type.is_dir() {
             append_directory(archive, &archive_path, &metadata)?;
-            append_tree(archive, rootfs, &archive_path)?;
+            append_tree(archive, rootfs, &archive_path, hardlink_targets)?;
         } else if file_type.is_file() {
-            append_file(archive, &path, &archive_path, &metadata)?;
+            append_file(archive, &path, &archive_path, &metadata, hardlink_targets)?;
         } else if file_type.is_symlink() {
             append_symlink(archive, &path, &archive_path, &metadata)?;
         } else {
@@ -91,12 +98,31 @@ fn append_file(
     source: &Path,
     path: &Path,
     metadata: &fs::Metadata,
+    hardlink_targets: &mut BTreeMap<(u64, u64), std::path::PathBuf>,
 ) -> Result<()> {
+    let key = (metadata.dev(), metadata.ino());
+    if let Some(target) = hardlink_targets.get(&key) {
+        return append_hardlink(archive, path, target, metadata);
+    }
     let mut header = deterministic_header(metadata, EntryType::Regular, metadata.len());
     let input = File::open(source).with_context(|| format!("open rootfs file {}", source.display()))?;
     archive
         .append_data(&mut header, path, input)
-        .with_context(|| format!("append file {}", path.display()))
+        .with_context(|| format!("append file {}", path.display()))?;
+    hardlink_targets.insert(key, path.to_path_buf());
+    Ok(())
+}
+
+fn append_hardlink(
+    archive: &mut Builder<File>,
+    path: &Path,
+    target: &Path,
+    metadata: &fs::Metadata,
+) -> Result<()> {
+    let mut header = deterministic_header(metadata, EntryType::Link, 0);
+    archive
+        .append_link(&mut header, path, target)
+        .with_context(|| format!("append hardlink {}", path.display()))
 }
 
 fn append_symlink(