perf: don't load entire files into memory

src/resolver.rs

@@ -173,7 +173,7 @@ impl Project {
                             // specifiers in indices store the index url in this field
                             .unwrap()
                     };
-                    
+
                     PackageSources::Wally(crate::source::wally::WallyPackageSource::new(index_url))
                 }
             };

src/source/fs.rs

@@ -1,11 +1,15 @@
-use crate::util::hash;
-use relative_path::RelativePathBuf;
-use serde::{Deserialize, Serialize};
 use std::{
     collections::BTreeMap,
+    io::{BufWriter, Read, Write},
     path::{Path, PathBuf},
 };
 
+use relative_path::RelativePathBuf;
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+
+use crate::util::hash;
+
 /// A file system entry
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub enum FSEntry {
@@ -40,6 +44,43 @@ pub(crate) fn store_in_cas<P: AsRef<Path>>(
     Ok((hash, cas_path))
 }
 
+pub(crate) fn store_reader_in_cas<P: AsRef<Path>>(
+    cas_dir: P,
+    contents: &mut dyn Read,
+) -> std::io::Result<String> {
+    let tmp_dir = cas_dir.as_ref().join(".tmp");
+    std::fs::create_dir_all(&tmp_dir)?;
+    let mut hasher = Sha256::new();
+    let mut buf = [0; 8 * 1024];
+    let mut file_writer = BufWriter::new(tempfile::NamedTempFile::new_in(&tmp_dir)?);
+
+    loop {
+        let bytes_read = contents.read(&mut buf)?;
+        if bytes_read == 0 {
+            break;
+        }
+
+        let bytes = &buf[..bytes_read];
+        hasher.update(bytes);
+        file_writer.write_all(bytes)?;
+    }
+
+    let hash = format!("{:x}", hasher.finalize());
+    let (prefix, rest) = hash.split_at(2);
+
+    let folder = cas_dir.as_ref().join(prefix);
+    std::fs::create_dir_all(&folder)?;
+
+    let cas_path = folder.join(rest);
+    match file_writer.into_inner()?.persist_noclobber(cas_path) {
+        Ok(_) => {}
+        Err(e) if e.error.kind() == std::io::ErrorKind::AlreadyExists => {}
+        Err(e) => return Err(e.error),
+    };
+
+    Ok(hash)
+}
+
 impl PackageFS {
     /// Write the package to the given destination
     pub fn write_to<P: AsRef<Path>, Q: AsRef<Path>>(

src/source/pesde/mod.rs

@@ -5,7 +5,7 @@ use crate::{
     },
     names::{PackageName, PackageNames},
     source::{
-        fs::{store_in_cas, FSEntry, PackageFS},
+        fs::{store_reader_in_cas, FSEntry, PackageFS},
         git_index::GitBasedSource,
         DependencySpecifiers, PackageSource, ResolveResult, VersionId,
     },
@@ -22,7 +22,6 @@ use std::{
     collections::{BTreeMap, BTreeSet},
     fmt::Debug,
     hash::Hash,
-    io::Read,
     path::PathBuf,
 };
 
@@ -296,10 +295,7 @@ impl PackageSource for PesdePackageSource {
                 continue;
             }
 
-            let mut contents = vec![];
-            entry.read_to_end(&mut contents)?;
-
-            let hash = store_in_cas(&project.cas_dir, &contents)?.0;
+            let hash = store_reader_in_cas(project.cas_dir(), &mut entry)?;
             entries.insert(path, FSEntry::File(hash));
         }
 

src/source/wally/mod.rs

@@ -1,6 +1,5 @@
 use std::{
     collections::{BTreeMap, VecDeque},
-    io::Read,
     path::PathBuf,
 };
 
@@ -13,7 +12,7 @@ use crate::{
     manifest::target::{Target, TargetKind},
     names::PackageNames,
     source::{
-        fs::{store_in_cas, FSEntry, PackageFS},
+        fs::{store_reader_in_cas, FSEntry, PackageFS},
         git_index::GitBasedSource,
         traits::PackageSource,
         version_id::VersionId,
@@ -213,10 +212,7 @@ impl PackageSource for WallyPackageSource {
             }
 
             let mut file = std::fs::File::open(entry.path())?;
-            let mut contents = vec![];
-            file.read_to_end(&mut contents)?;
-
-            let hash = store_in_cas(&project.cas_dir, &contents)?.0;
+            let hash = store_reader_in_cas(project.cas_dir(), &mut file)?;
             entries.insert(path, FSEntry::File(hash));
         }