pipe: Add pipe_chmod binding

Contributes towards luvit#410

docs.md

@@ -1663,6 +1663,20 @@ the given type, returned by `uv.pipe_pending_type()` and call
 
 **Returns:** `string`
 
+### `uv.pipe_chmod(pipe, flags)`
+
+> method form `pipe:chmod(flags)`
+
+**Parameters:**
+- `pipe`: `uv_pipe_t userdata`
+- `flags`: `string`
+
+Alters pipe permissions, allowing it to be accessed from processes run by different users.
+Makes the pipe writable or readable by all users. `flags` are: `"r"`, `"w"`, `"rw"`, or `"wr"`
+where `r` is `READABLE` and `w` is `WRITABLE`. This function is blocking.
+
+**Returns:** `0` or `fail`
+
 ## `uv_tty_t` — TTY handle
 
 [`uv_tty_t`]: #uv_tty_t--tty-handle

src/luv.c

@@ -157,6 +157,9 @@ static const luaL_Reg luv_functions[] = {
   {"new_pipe", luv_new_pipe},
   {"pipe_open", luv_pipe_open},
   {"pipe_bind", luv_pipe_bind},
+#if LUV_UV_VERSION_GEQ(1, 16, 0)
+  {"pipe_chmod", luv_pipe_chmod},
+#endif
   {"pipe_connect", luv_pipe_connect},
   {"pipe_getsockname", luv_pipe_getsockname},
 #if LUV_UV_VERSION_GEQ(1, 3, 0)
@@ -422,6 +425,9 @@ static const luaL_Reg luv_stream_methods[] = {
 static const luaL_Reg luv_pipe_methods[] = {
   {"open", luv_pipe_open},
   {"bind", luv_pipe_bind},
+#if LUV_UV_VERSION_GEQ(1, 16, 0)
+  {"chmod", luv_pipe_chmod},
+#endif
   {"connect", luv_pipe_connect},
   {"getsockname", luv_pipe_getsockname},
 #if LUV_UV_VERSION_GEQ(1, 3, 0)

src/pipe.c

@@ -111,3 +111,22 @@ static int luv_pipe_pending_type(lua_State* L) {
   lua_pushstring(L, type_name);
   return 1;
 }
+
+#if LUV_UV_VERSION_GEQ(1,16,0)
+static const char *const luv_pipe_chmod_flags[] = {
+  "r", "w", "rw", "wr", NULL
+};
+
+static int luv_pipe_chmod(lua_State* L) {
+  uv_pipe_t* handle = luv_check_pipe(L, 1);
+  int flags;
+  switch (luaL_checkoption(L, 2, NULL, luv_pipe_chmod_flags)) {
+  case 0: flags = UV_READABLE; break;
+  case 1: flags = UV_WRITABLE; break;
+  case 2: case 3: flags = UV_READABLE | UV_WRITABLE; break;
+  default: flags = 0; /* unreachable */
+  }
+  int ret = uv_pipe_chmod(handle, flags);
+  return luv_result(L, ret);
+}
+#endif

tests/test-pipe.lua

@@ -0,0 +1,23 @@
+local TEST_PIPENAME = "\\\\?\\pipe\\luv-test"
+
+return require('lib/tap')(function (test)
+  test("pipe chmod", function (print, p, expect, uv)
+    local pipe = assert(uv.new_pipe())
+    assert(pipe:bind(TEST_PIPENAME))
+    local _, err, errname = pipe:chmod("r")
+    if errname == "EPERM" then
+      print("Insufficient privileges to alter pipe fmode, skipping")
+      pipe:close()
+      return
+    end
+    assert(not err, err)
+    assert(pipe:chmod("w"))
+    assert(pipe:chmod("rw"))
+    assert(pipe:chmod("wr"))
+
+    local ok = pcall(function() uv.pipe_chmod(pipe, "bad flags") end)
+    assert(not ok)
+
+    pipe:close()
+  end, "1.16.0")
+end)