Add experiment based on Josh Triplett's gist, related to #59

experiments/object-access.rs

@@ -0,0 +1,66 @@
+#!/usr/bin/env -S cargo eval --
+//! Currently this experiment fails as `locate(…)` can't actually find objects. My guess is that
+//! it can't find objects in packs for some reason because it could find some objects there were
+//! probably loose, but failed right away after a `git gc`.
+//! Let's see if a unit test can reproduce this too, right now this functionality is entirely untested
+//! I think.
+//! ```cargo
+//! [dependencies]
+//! atty = "0.2"
+//! anyhow = "1"
+//! git-odb = "0.9"
+//! git-hash = "0.1"
+//! git2 = "0.13"
+//! ```
+use std::io::BufRead;
+use std::time::Instant;
+
+fn main() -> anyhow::Result<()> {
+    if atty::is(atty::Stream::Stdin) {
+        anyhow::bail!("Need object hashes on stdin, one per line");
+    }
+
+    let stdin = std::io::stdin();
+    let stdin = stdin.lock();
+    let hashes = stdin.lines().collect::<Result<Vec<String>, _>>()?;
+
+    println!("{} objects", hashes.len());
+
+    let start = Instant::now();
+    let bytes = do_git2(hashes.as_slice())?;
+    let elapsed = start.elapsed();
+    println!("libgit2:  confirmed {} bytes in {:?}", bytes, elapsed);
+
+    let start = Instant::now();
+    let bytes = do_gitoxide(hashes.as_slice())?;
+    let elapsed = start.elapsed();
+    println!("gitoxide: confirmed {} bytes in {:?}", bytes, elapsed);
+
+    Ok(())
+}
+
+fn do_git2(hashes: &[String]) -> anyhow::Result<u64> {
+    git2::opts::strict_hash_verification(false);
+    let repo = git2::Repository::open("../.git")?;
+    let odb = repo.odb()?;
+    let mut bytes = 0u64;
+    for hash in hashes {
+        let hash = git2::Oid::from_str(&hash)?;
+        let obj = odb.read(hash)?;
+        bytes += obj.len() as u64;
+    }
+    Ok(bytes)
+}
+
+fn do_gitoxide(hashes: &[String]) -> anyhow::Result<u64> {
+    let odb = git_odb::compound::Db::at("../.git/objects")?;
+    let mut buf = Vec::new();
+    let mut bytes = 0u64;
+    for hash in hashes {
+        dbg!(hash);
+        let hash = git_hash::owned::Digest::from_40_bytes_in_hex(hash.as_bytes())?;
+        let obj = odb.locate(hash.to_borrowed(), &mut buf).expect("object must exist")?;
+        bytes += obj.size() as u64;
+    }
+    Ok(bytes)
+}