Add deno.truncate (#805)

2 files changed, 29 insertions, 0 deletions

diff --git a/src/handlers.rs b/src/handlers.rs
index b1ef67d94..c615f5669 100644
--- a/src/handlers.rs
+++ b/src/handlers.rs
@@ -77,6 +77,7 @@ pub fn msg_from_js(
     msg::Any::Symlink => handle_symlink,
     msg::Any::SetEnv => handle_set_env,
     msg::Any::Stat => handle_stat,
+    msg::Any::Truncate => handle_truncate,
     msg::Any::WriteFile => handle_write_file,
     msg::Any::Exit => handle_exit,
     _ => panic!(format!(
@@ -977,3 +978,25 @@ fn handle_read_link(
     ))
   })
 }
+
+fn handle_truncate(
+  state: Arc<IsolateState>,
+  base: &msg::Base,
+  data: &'static mut [u8],
+) -> Box<Op> {
+  assert_eq!(data.len(), 0);
+
+  if !state.flags.allow_write {
+    return odd_future(permission_denied());
+  }
+
+  let msg = base.msg_as_truncate().unwrap();
+  let filename = String::from(msg.name().unwrap());
+  let len = msg.len();
+  blocking!(base.sync(), || {
+    debug!("handle_truncate {} {}", filename, len);
+    let f = fs::OpenOptions::new().write(true).open(&filename)?;
+    f.set_len(len as u64)?;
+    Ok(empty_buf())
+  })
+}
diff --git a/src/msg.fbs b/src/msg.fbs
index 7f42cd637..6b2e920e8 100644
--- a/src/msg.fbs
+++ b/src/msg.fbs
@@ -27,6 +27,7 @@ union Any {
   Stat,
   StatRes,
   SetEnv,
+  Truncate,
   Open,
   OpenRes,
   Read,
@@ -247,6 +248,11 @@ table StatRes {
   has_mode: bool; // false on windows
 }
 
+table Truncate {
+  name: string;
+  len: uint;
+}
+
 table WriteFileSync {
   filename: string;
   data: [ubyte];