neon/sys/
call.rs

1use std::{mem::MaybeUninit, ptr::null_mut};
2
3use smallvec::SmallVec;
4
5use super::{
6    bindings as napi,
7    raw::{Env, FunctionCallbackInfo, Local},
8};
9
10// Number of arguments to allocate on the stack. This should be large enough
11// to cover most use cases without being wasteful.
12//
13// * If the number is too large, too much space is allocated and then filled
14//   with `undefined`.
15// * If the number is too small, getting arguments frequently takes two tries
16//   and requires heap allocation.
17const ARGV_SIZE: usize = 4;
18
19#[repr(transparent)]
20/// List of JavaScript arguments to a function
21// `Arguments` is intended to be a small abstraction to hide the usage of
22// `SmallVec` allowing changes to `ARGV_SIZE` in a single location
23pub struct Arguments(SmallVec<[Local; ARGV_SIZE]>);
24
25impl Arguments {
26    #[inline]
27    /// Get an argument at a specific position
28    pub fn get(&self, i: usize) -> Option<Local> {
29        self.0.get(i).cloned()
30    }
31}
32
33pub unsafe fn is_construct(env: Env, info: FunctionCallbackInfo) -> bool {
34    let mut target: MaybeUninit<Local> = MaybeUninit::zeroed();
35
36    napi::get_new_target(env, info, target.as_mut_ptr()).unwrap();
37
38    // get_new_target is guaranteed to assign to target, so it's initialized.
39    let target: Local = target.assume_init();
40
41    // By the get_new_target contract, target will either be NULL if the current
42    // function was called without `new`, or a valid napi_value handle if the current
43    // function was called with `new`.
44    !target.is_null()
45}
46
47pub unsafe fn this(env: Env, info: FunctionCallbackInfo, out: &mut Local) {
48    napi::get_cb_info(env, info, null_mut(), null_mut(), out as *mut _, null_mut()).unwrap();
49}
50
51/// Gets the number of arguments passed to the function.
52// TODO: Remove this when `FunctionContext` is refactored to get call info upfront.
53pub unsafe fn len(env: Env, info: FunctionCallbackInfo) -> usize {
54    let mut argc = 0usize;
55    napi::get_cb_info(
56        env,
57        info,
58        &mut argc as *mut _,
59        null_mut(),
60        null_mut(),
61        null_mut(),
62    )
63    .unwrap();
64    argc
65}
66
67/// Returns the function arguments for a call
68pub unsafe fn argv(env: Env, info: FunctionCallbackInfo) -> Arguments {
69    // Allocate space on the stack for up to `ARGV_SIZE` values
70    let mut argv = MaybeUninit::<[Local; ARGV_SIZE]>::uninit();
71
72    // Starts as the size allocated; after `get_cb_info` it is the number of arguments
73    let mut argc = ARGV_SIZE;
74
75    napi::get_cb_info(
76        env,
77        info,
78        &mut argc as *mut _,
79        argv.as_mut_ptr().cast(),
80        null_mut(),
81        null_mut(),
82    )
83    .unwrap();
84
85    // We did not allocate enough space; allocate on the heap and try again
86    let argv = if argc > ARGV_SIZE {
87        // We know exactly how much space to reserve
88        let mut argv = Vec::with_capacity(argc);
89
90        napi::get_cb_info(
91            env,
92            info,
93            &mut argc as *mut _,
94            argv.as_mut_ptr(),
95            null_mut(),
96            null_mut(),
97        )
98        .unwrap();
99
100        // Set the size of `argv` to the number of initialized elements
101        argv.set_len(argc);
102        SmallVec::from_vec(argv)
103
104        // There were `ARGV_SIZE` or fewer arguments, use the stack allocated space
105    } else {
106        SmallVec::from_buf_and_len(argv.assume_init(), argc)
107    };
108
109    Arguments(argv)
110}
neon/sys/call.rs

neon/sys/
call.rs
