feat: adding hash-object

src/kind.rs

@@ -1,3 +1,5 @@
+use std::fmt;
+
 use anyhow::{anyhow, Result};
 
 #[derive(Debug)]
@@ -30,13 +32,16 @@ impl Kind {
             Kind::Symlink => "120000",
         }
     }
+}
 
-    pub fn string(&self) -> &str {
-        match self {
+impl fmt::Display for Kind {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let kind = match self {
             Kind::Blob(_) => "blob",
             Kind::Commit => "commit",
             Kind::Tree => "tree",
             Kind::Symlink => "symlink",
-        }
+        };
+        write!(f, "{}", kind)
     }
 }

src/main.rs

@@ -1,4 +1,5 @@
 use anyhow::{Error, Result};
+use object::hash_object;
 use repository::default_init_path;
 use std::path::PathBuf;
 
@@ -72,6 +73,11 @@ enum Command {
         /// The pack index file to dump
         pack_id: String,
     },
+    /// Hash an object
+    HashObject {
+        /// The object to hash
+        file: PathBuf,
+    },
 }
 
 fn main() -> Result<(), Error> {
@@ -128,6 +134,10 @@ fn main() -> Result<(), Error> {
             Ok(_) => (),
             Err(e) => eprintln!("Failed to dump pack index file: {}", e),
         },
+        Command::HashObject { file } => match hash_object(&file) {
+            Ok(hash) => println!("{}", hex::encode(hash)),
+            Err(e) => eprintln!("Failed to hash object: {}", e),
+        },
     }
 
     Ok(())

src/object.rs

@@ -2,6 +2,7 @@ use crate::repository::Repository;
 use crate::{error::RuntimeError, kind::Kind};
 use anyhow::{anyhow, Context, Result};
 use flate2::{write::ZlibEncoder, Compression};
+
 use sha1::{Digest, Sha1};
 use std::io::Write;
 use std::{
@@ -82,7 +83,7 @@ impl Repository {
 
     pub fn write_object(&self, kind: Kind, content: &[u8]) -> Result<[u8; 20]> {
         let mut hasher = Sha1::new();
-        hasher.update(format!("{} {}\0", kind.string(), content.len()).as_bytes());
+        hasher.update(format!("{} {}\0", kind, content.len()).as_bytes());
         hasher.update(content);
         let hash = hasher.finalize().into();
         let hash_str = hex::encode(hash);
@@ -100,8 +101,7 @@ impl Repository {
         let file_out_fd = File::create(target_file).context("could not open target file")?;
 
         let mut zlib_out = ZlibEncoder::new(file_out_fd, Compression::default());
-        write!(zlib_out, "{} {}\0", kind.string(), content.len())
-            .context("could not write header")?;
+        write!(zlib_out, "{} {}\0", kind, content.len()).context("could not write header")?;
         zlib_out.write_all(content)?;
         zlib_out
             .finish()
@@ -111,6 +111,18 @@ impl Repository {
     }
 }
 
+pub fn hash_object(file: &Path) -> Result<[u8; 20]> {
+    let content = std::fs::read(file)?;
+
+    let kind = Kind::Blob(false);
+    let mut hasher = Sha1::new();
+    hasher.update(format!("{} {}\0", kind, content.len()).as_bytes());
+    hasher.update(content);
+    let hash = hasher.finalize().into();
+
+    Ok(hash)
+}
+
 fn is_path_in_repo(repo_path: &Path, file_path: &Path) -> Result<bool> {
     // Convert both paths to absolute paths
     let repo_canonical = repo_path.canonicalize()?;
@@ -178,7 +190,7 @@ impl<R: BufRead> Object<R> {
                         format!(
                             "{:0>6} {} {}    {:name_len$}",
                             entry.mode,
-                            entry.kind.string(),
+                            entry.kind,
                             hash,
                             entry.name,
                             name_len = max_name_len
@@ -193,3 +205,31 @@ impl<R: BufRead> Object<R> {
         Ok(res)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use hex::FromHex;
+    use std::io::Cursor;
+
+    #[test]
+    fn test_object_string() {
+        let data = b"hello";
+        let _obj = Object {
+            kind: Kind::Blob(true),
+            _size: 5,
+            data: Cursor::new(data),
+        };
+
+        let temp_file = std::env::temp_dir().join("temp_file");
+        let mut file = File::create(&temp_file).unwrap();
+        file.write_all(data).unwrap();
+
+        let res = hash_object(&temp_file);
+
+        assert_eq!(
+            res.unwrap(),
+            <[u8; 20]>::from_hex("b6fc4c620b67d95f953a5c1c1230aaab5db5a1b0").unwrap(),
+        );
+    }
+}

src/pack.rs

@@ -378,10 +378,9 @@ impl Repository {
         let mut buf = [0u8; 256 * 4];
         file.read_exact(&mut buf)?;
 
-        for idx in 0..256 {
-            let offset = idx * 4;
-            num_objects = u32::from_be_bytes(buf[offset..offset + 4].try_into().unwrap());
-            fanout_table[idx] = num_objects;
+        for (idx, fanout_record) in fanout_table.iter_mut().enumerate() {
+            num_objects = u32::from_be_bytes(buf[idx * 4..idx * 4 + 4].try_into().unwrap());
+            *fanout_record = num_objects;
         }
 
         let mut names = vec![0u8; 20 * num_objects as usize];