fix(tvix): Avoid buffering file into memory in builtins.hashFile r/7882

Right now `builtins.hashFile` always reads the entire file into memory
before hashing, which is not ideal for large files. This replaces
`read_to_string` with `open_file` which allows calculating the hash of
the file without buffering it entirely into memory. Other callers can
continue to buffer into memory if they choose, but they still use the
`open_file` VM request and then call `read_to_string` or `read_to_end`
on the `std::io::Reader`.

Fixes b/380

Change-Id: Ifa1c8324bcee8f751604b0b449feab875c632fda
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11236
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 2 insertions, 3 deletions

diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index 8973a25927ed..cb55894b6c7e 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -773,9 +773,8 @@ mod pure_builtins {
     }
 
     #[builtin("hashString")]
-    #[allow(non_snake_case)]
-    async fn builtin_hashString(co: GenCo, algo: Value, s: Value) -> Result<Value, ErrorKind> {
-        hash_nix_string(algo.to_str()?, s.to_str()?).map(Value::from)
+    async fn builtin_hash_string(co: GenCo, algo: Value, s: Value) -> Result<Value, ErrorKind> {
+        hash_nix_string(algo.to_str()?, std::io::Cursor::new(s.to_str()?)).map(Value::from)
     }
 
     #[builtin("head")]