1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
use std::{
    alloc::{GlobalAlloc, Layout, System},
    cell::UnsafeCell,
    mem::MaybeUninit,
    ptr::NonNull,
};

use crate::{
    dictionary::{BuiltinEntry, Dictionary, DropDict, OwnedDict},
    input::WordStrBuf,
    output::OutputBuf,
    vm,
    word::Word,
    CallContext, Forth,
};

#[cfg(feature = "async")]
use crate::{dictionary::AsyncBuiltins, AsyncForth};

// Helper type that will un-leak the buffer once it is dropped.
pub struct LeakBox<T> {
    ptr: *mut UnsafeCell<MaybeUninit<T>>,
    len: usize,
}

impl<T> LeakBox<T> {
    pub fn new(len: usize) -> Self {
        Self {
            ptr: unsafe {
                System
                    .alloc(Layout::array::<UnsafeCell<MaybeUninit<T>>>(len).unwrap())
                    .cast()
            },
            len,
        }
    }

    pub fn ptr(&self) -> *mut T {
        self.ptr.cast()
    }

    pub fn as_non_null(&self) -> NonNull<T> {
        #[cfg(debug_assertions)]
        let res = NonNull::new(self.ptr.cast::<T>()).unwrap();
        #[cfg(not(debug_assertions))]
        let res = unsafe { NonNull::new_unchecked(self.ptr.cast::<T>()) };

        res
    }

    // an `is_empty` doesn't make a ton of sense for this...maybe `len` should
    // have been called `size`...
    #[allow(clippy::len_without_is_empty)]
    pub fn len(&self) -> usize {
        self.len
    }
}

impl<T> Drop for LeakBox<T> {
    fn drop(&mut self) {
        unsafe {
            System.dealloc(
                self.ptr.cast(),
                Layout::array::<UnsafeCell<MaybeUninit<T>>>(self.len).unwrap(),
            )
        }
    }
}

#[derive(Debug)]
pub struct LBForthParams {
    pub data_stack_elems: usize,
    pub return_stack_elems: usize,
    pub control_stack_elems: usize,
    pub input_buf_elems: usize,
    pub output_buf_elems: usize,
    pub dict_buf_elems: usize,
}

#[derive(Copy, Clone)]
pub(crate) struct LeakBoxDict;

impl Default for LBForthParams {
    fn default() -> Self {
        Self {
            data_stack_elems: 256,
            return_stack_elems: 256,
            control_stack_elems: 256,
            input_buf_elems: 256,
            output_buf_elems: 256,
            dict_buf_elems: 4096,
        }
    }
}

pub struct LBForth<T: 'static> {
    pub forth: Forth<T>,
    _payload_dstack: LeakBox<Word>,
    _payload_rstack: LeakBox<Word>,
    _payload_cstack: LeakBox<CallContext<T>>,
    _input_buf: LeakBox<u8>,
    _output_buf: LeakBox<u8>,
}

#[cfg(feature = "async")]
pub struct AsyncLBForth<T: 'static, A> {
    pub forth: AsyncForth<T, A>,
    _payload_dstack: LeakBox<Word>,
    _payload_rstack: LeakBox<Word>,
    _payload_cstack: LeakBox<CallContext<T>>,
    _input_buf: LeakBox<u8>,
    _output_buf: LeakBox<u8>,
}

impl<T: 'static> LBForth<T> {
    pub fn from_params(
        params: LBForthParams,
        host_ctxt: T,
        builtins: &'static [BuiltinEntry<T>],
    ) -> Self {
        let _payload_dstack: LeakBox<Word> = LeakBox::new(params.data_stack_elems);
        let _payload_rstack: LeakBox<Word> = LeakBox::new(params.return_stack_elems);
        let _payload_cstack: LeakBox<CallContext<T>> = LeakBox::new(params.control_stack_elems);
        let _input_buf: LeakBox<u8> = LeakBox::new(params.input_buf_elems);
        let _output_buf: LeakBox<u8> = LeakBox::new(params.output_buf_elems);

        let bufs = vm::Buffers {
            dstack_buf: (_payload_dstack.ptr(), _payload_dstack.len()),
            rstack_buf: (_payload_rstack.ptr(), _payload_rstack.len()),
            cstack_buf: (_payload_cstack.ptr(), _payload_cstack.len()),
            input: WordStrBuf::new(_input_buf.ptr(), _input_buf.len()),
            output: OutputBuf::new(_output_buf.ptr(), _output_buf.len()),
        };
        let forth = unsafe {
            Forth::<T>::new(
                bufs,
                alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems),
                host_ctxt,
                builtins,
            )
            .unwrap()
        };

        Self {
            forth,
            _payload_dstack,
            _payload_rstack,
            _payload_cstack,
            _input_buf,
            _output_buf,
        }
    }

    /// Constructs a new VM whose dictionary is a fork of this VM's dictionary.
    ///
    /// The current dictionary owned by this VM is frozen (made immutable), and
    /// a reference to it is shared with this VM and the new child VM. When both
    /// this VM and the child are dropped, the frozen dictionary is deallocated.
    ///
    /// The child VM is created with empty stacks and input and output buffers.
    pub fn fork_with_params(&mut self, params: LBForthParams, host_ctxt: T) -> Self {
        let _payload_dstack: LeakBox<Word> = LeakBox::new(params.data_stack_elems);
        let _payload_rstack: LeakBox<Word> = LeakBox::new(params.return_stack_elems);
        let _payload_cstack: LeakBox<CallContext<T>> = LeakBox::new(params.control_stack_elems);
        let _input_buf: LeakBox<u8> = LeakBox::new(params.input_buf_elems);
        let _output_buf: LeakBox<u8> = LeakBox::new(params.output_buf_elems);

        let my_new_dict = alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems);
        let new_dict = alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems);

        let bufs = vm::Buffers {
            dstack_buf: (_payload_dstack.ptr(), _payload_dstack.len()),
            rstack_buf: (_payload_rstack.ptr(), _payload_rstack.len()),
            cstack_buf: (_payload_cstack.ptr(), _payload_cstack.len()),
            input: WordStrBuf::new(_input_buf.ptr(), _input_buf.len()),
            output: OutputBuf::new(_output_buf.ptr(), _output_buf.len()),
        };
        let forth = unsafe {
            self.forth
                .fork(bufs, my_new_dict, new_dict, host_ctxt)
                .unwrap()
        };
        Self {
            forth,
            _payload_dstack,
            _payload_rstack,
            _payload_cstack,
            _input_buf,
            _output_buf,
        }
    }
}

#[cfg(feature = "async")]
impl<T, D> AsyncLBForth<T, D>
where
    T: 'static,
    D: for<'forth> AsyncBuiltins<'forth, T>,
{
    pub fn from_params(
        params: LBForthParams,
        host_ctxt: T,
        sync_builtins: &'static [BuiltinEntry<T>],
        dispatcher: D,
    ) -> Self {
        let _payload_dstack: LeakBox<Word> = LeakBox::new(params.data_stack_elems);
        let _payload_rstack: LeakBox<Word> = LeakBox::new(params.return_stack_elems);
        let _payload_cstack: LeakBox<CallContext<T>> = LeakBox::new(params.control_stack_elems);
        let _input_buf: LeakBox<u8> = LeakBox::new(params.input_buf_elems);
        let _output_buf: LeakBox<u8> = LeakBox::new(params.output_buf_elems);

        let bufs = vm::Buffers {
            dstack_buf: (_payload_dstack.ptr(), _payload_dstack.len()),
            rstack_buf: (_payload_rstack.ptr(), _payload_rstack.len()),
            cstack_buf: (_payload_cstack.ptr(), _payload_cstack.len()),
            input: WordStrBuf::new(_input_buf.ptr(), _input_buf.len()),
            output: OutputBuf::new(_output_buf.ptr(), _output_buf.len()),
        };
        let forth = unsafe {
            AsyncForth::<T, D>::new(
                bufs,
                alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems),
                host_ctxt,
                sync_builtins,
                dispatcher,
            )
            .unwrap()
        };

        Self {
            forth,
            _payload_dstack,
            _payload_rstack,
            _payload_cstack,
            _input_buf,
            _output_buf,
        }
    }

    /// Constructs a new VM whose dictionary is a fork of this VM's dictionary.
    ///
    /// The current dictionary owned by this VM is frozen (made immutable), and
    /// a reference to it is shared with this VM and the new child VM. When both
    /// this VM and the child are dropped, the frozen dictionary is deallocated.
    ///
    /// The child VM is created with empty stacks and input and output buffers.
    pub fn fork_with_params(&mut self, params: LBForthParams, host_ctxt: T) -> Self
    where
        D: Clone,
    {
        let _payload_dstack: LeakBox<Word> = LeakBox::new(params.data_stack_elems);
        let _payload_rstack: LeakBox<Word> = LeakBox::new(params.return_stack_elems);
        let _payload_cstack: LeakBox<CallContext<T>> = LeakBox::new(params.control_stack_elems);
        let _input_buf: LeakBox<u8> = LeakBox::new(params.input_buf_elems);
        let _output_buf: LeakBox<u8> = LeakBox::new(params.output_buf_elems);

        let my_new_dict = alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems);
        let new_dict = alloc_dict::<T, LeakBoxDict>(params.dict_buf_elems);

        let bufs = vm::Buffers {
            dstack_buf: (_payload_dstack.ptr(), _payload_dstack.len()),
            rstack_buf: (_payload_rstack.ptr(), _payload_rstack.len()),
            cstack_buf: (_payload_cstack.ptr(), _payload_cstack.len()),
            input: WordStrBuf::new(_input_buf.ptr(), _input_buf.len()),
            output: OutputBuf::new(_output_buf.ptr(), _output_buf.len()),
        };
        let forth = unsafe {
            self.forth
                .fork(bufs, my_new_dict, new_dict, host_ctxt)
                .unwrap()
        };
        Self {
            forth,
            _payload_dstack,
            _payload_rstack,
            _payload_cstack,
            _input_buf,
            _output_buf,
        }
    }
}

impl DropDict for LeakBoxDict {
    unsafe fn drop_dict(ptr: NonNull<u8>, layout: Layout) {
        System.dealloc(ptr.cast().as_ptr(), layout)
    }
}

pub(crate) fn alloc_dict<T, D: DropDict>(size: usize) -> OwnedDict<T> {
    let layout = match Dictionary::<T>::layout(size) {
        Ok(layout) => layout,
        Err(error) => panic!("Dictionary size {size} too large to allocate: {error}"),
    };
    let ptr = unsafe { NonNull::new(System.alloc(layout)).unwrap().cast() };
    OwnedDict::new::<D>(ptr, size)
}