1 files changed, 84 insertions, 0 deletions
diff --git a/core/flags.rs b/core/flags.rs
new file mode 100644
index 000000000..2da35734d
--- /dev/null
+++ b/core/flags.rs
@@ -0,0 +1,84 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+//! This module wraps libdeno::deno_set_v8_flags
+use crate::libdeno::deno_set_v8_flags;
+use libc::c_char;
+use libc::c_int;
+use std::ffi::CStr;
+use std::ffi::CString;
+use std::mem;
+use std::vec::Vec;
+
+/// Pass the command line arguments to v8.
+/// Returns a vector of command line arguments that V8 did not understand.
+/// Translates --v8-options into a --help flag for V8.
+pub fn v8_set_flags(args: Vec<String>) -> Vec<String> {
+  // deno_set_v8_flags(int* argc, char** argv) mutates argc and argv to remove
+  // flags that v8 understands.
+  // First parse core args, then convert to a vector of C strings.
+  let (args, rest) = v8_set_flags_preprocess(args);
+
+  // Make a new array, that can be modified by V8::SetFlagsFromCommandLine(),
+  // containing mutable raw pointers to the individual command line args.
+  let mut raw_argv = args
+    .iter()
+    .map(|arg| CString::new(arg.as_str()).unwrap().into_bytes_with_nul())
+    .collect::<Vec<_>>();
+  let mut c_argv = raw_argv
+    .iter_mut()
+    .map(|arg| arg.as_mut_ptr() as *mut c_char)
+    .collect::<Vec<_>>();
+
+  // Store the length of the c_argv array in a local variable. We'll pass
+  // a pointer to this local variable to deno_set_v8_flags(), which then
+  // updates its value.
+  let mut c_argv_len = c_argv.len() as c_int;
+  // Let v8 parse the arguments it recognizes and remove them from c_argv.
+  unsafe { deno_set_v8_flags(&mut c_argv_len, c_argv.as_mut_ptr()) };
+  // If c_argv_len was updated we have to change the length of c_argv to match.
+  c_argv.truncate(c_argv_len as usize);
+  // Copy the modified arguments list into a proper rust vec and return it.
+  c_argv
+    .iter()
+    .map(|ptr| unsafe {
+      let cstr = CStr::from_ptr(*ptr as *const c_char);
+      let slice = cstr.to_str().unwrap();
+      slice.to_string()
+    }).chain(rest.into_iter())
+    .collect()
+}
+
+// Returns args passed to V8, followed by args passed to JS
+fn v8_set_flags_preprocess(args: Vec<String>) -> (Vec<String>, Vec<String>) {
+  let (rest, mut v8_args) =
+    args.into_iter().partition(|ref a| a.as_str() == "--help");
+
+  // Replace args being sent to V8
+  for a in &mut v8_args {
+    if a == "--v8-options" {
+      mem::swap(a, &mut String::from("--help"));
+    }
+  }
+  (v8_args, rest)
+}
+
+#[test]
+fn test_v8_set_flags_preprocess_1() {
+  let js_args = v8_set_flags_preprocess(vec![
+    "deno".to_string(),
+    "--v8-options".to_string(),
+  ]);
+  assert_eq!(
+    js_args,
+    (vec!["deno".to_string(), "--help".to_string()], vec![])
+  );
+}
+
+#[test]
+fn test_v8_set_flags_preprocess_2() {
+  let js_args =
+    v8_set_flags_preprocess(vec!["deno".to_string(), "--help".to_string()]);
+  assert_eq!(
+    js_args,
+    (vec!["deno".to_string()], vec!["--help".to_string()])
+  );
+}