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
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
use crate::prelude::*;
use crate::runtime::vm::{self as runtime};
use crate::store::{AutoAssertNoGc, StoreData, StoreOpaque, Stored};
use crate::trampoline::generate_table_export;
use crate::{AnyRef, AsContext, AsContextMut, ExternRef, Func, HeapType, Ref, TableType};
use core::iter;
use core::ptr::NonNull;
use runtime::{GcRootsList, SendSyncPtr};
use wasmtime_environ::TypeTrace;

/// A WebAssembly `table`, or an array of values.
///
/// Like [`Memory`][crate::Memory] a table is an indexed array of values, but
/// unlike [`Memory`][crate::Memory] it's an array of WebAssembly reference type
/// values rather than bytes. One of the most common usages of a table is a
/// function table for wasm modules (a `funcref` table), where each element has
/// the `ValType::FuncRef` type.
///
/// A [`Table`] "belongs" to the store that it was originally created within
/// (either via [`Table::new`] or via instantiating a
/// [`Module`](crate::Module)). Operations on a [`Table`] only work with the
/// store it belongs to, and if another store is passed in by accident then
/// methods will panic.
#[derive(Copy, Clone, Debug)]
#[repr(transparent)] // here for the C API
pub struct Table(pub(super) Stored<crate::runtime::vm::ExportTable>);

impl Table {
    /// Creates a new [`Table`] with the given parameters.
    ///
    /// * `store` - the owner of the resulting [`Table`]
    /// * `ty` - the type of this table, containing both the element type as
    ///   well as the initial size and maximum size, if any.
    /// * `init` - the initial value to fill all table entries with, if the
    ///   table starts with an initial size.
    ///
    /// # Errors
    ///
    /// Returns an error if `init` does not match the element type of the table,
    /// or if `init` does not belong to the `store` provided.
    ///
    /// # Panics
    ///
    /// This function will panic when used with a [`Store`](`crate::Store`)
    /// which has a [`ResourceLimiterAsync`](`crate::ResourceLimiterAsync`)
    /// (see also: [`Store::limiter_async`](`crate::Store::limiter_async`).
    /// When using an async resource limiter, use [`Table::new_async`]
    /// instead.
    ///
    /// # Examples
    ///
    /// ```
    /// # use wasmtime::*;
    /// # fn main() -> anyhow::Result<()> {
    /// let engine = Engine::default();
    /// let mut store = Store::new(&engine, ());
    ///
    /// let ty = TableType::new(RefType::FUNCREF, 2, None);
    /// let table = Table::new(&mut store, ty, Ref::Func(None))?;
    ///
    /// let module = Module::new(
    ///     &engine,
    ///     "(module
    ///         (table (import \"\" \"\") 2 funcref)
    ///         (func $f (result i32)
    ///             i32.const 10)
    ///         (elem (i32.const 0) $f)
    ///     )"
    /// )?;
    ///
    /// let instance = Instance::new(&mut store, &module, &[table.into()])?;
    /// // ...
    /// # Ok(())
    /// # }
    /// ```
    pub fn new(mut store: impl AsContextMut, ty: TableType, init: Ref) -> Result<Table> {
        Table::_new(store.as_context_mut().0, ty, init)
    }

    /// Async variant of [`Table::new`]. You must use this variant with
    /// [`Store`](`crate::Store`)s which have a
    /// [`ResourceLimiterAsync`](`crate::ResourceLimiterAsync`).
    ///
    /// # Panics
    ///
    /// This function will panic when used with a non-async
    /// [`Store`](`crate::Store`)
    #[cfg(feature = "async")]
    pub async fn new_async<T>(
        mut store: impl AsContextMut<Data = T>,
        ty: TableType,
        init: Ref,
    ) -> Result<Table>
    where
        T: Send,
    {
        let mut store = store.as_context_mut();
        assert!(
            store.0.async_support(),
            "cannot use `new_async` without enabling async support on the config"
        );
        store
            .on_fiber(|store| Table::_new(store.0, ty, init))
            .await?
    }

    fn _new(store: &mut StoreOpaque, ty: TableType, init: Ref) -> Result<Table> {
        let wasmtime_export = generate_table_export(store, &ty)?;
        let init = init.into_table_element(store, ty.element())?;
        unsafe {
            let table = Table::from_wasmtime_table(wasmtime_export, store);
            let wasmtime_table = table.wasmtime_table(store, iter::empty());
            (*wasmtime_table)
                .fill(store.gc_store_mut()?, 0, init, ty.minimum())
                .err2anyhow()?;
            Ok(table)
        }
    }

    /// Returns the underlying type of this table, including its element type as
    /// well as the maximum/minimum lower bounds.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own this table.
    pub fn ty(&self, store: impl AsContext) -> TableType {
        self._ty(store.as_context().0)
    }

    fn _ty(&self, store: &StoreOpaque) -> TableType {
        let ty = &store[self.0].table.table;
        TableType::from_wasmtime_table(store.engine(), ty)
    }

    fn wasmtime_table(
        &self,
        store: &mut StoreOpaque,
        lazy_init_range: impl Iterator<Item = u64>,
    ) -> *mut runtime::Table {
        unsafe {
            let export = &store[self.0];
            crate::runtime::vm::Instance::from_vmctx(export.vmctx, |handle| {
                let idx = handle.table_index(&*export.definition);
                handle.get_defined_table_with_lazy_init(idx, lazy_init_range)
            })
        }
    }

    /// Returns the table element value at `index`.
    ///
    /// Returns `None` if `index` is out of bounds.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own this table.
    pub fn get(&self, mut store: impl AsContextMut, index: u64) -> Option<Ref> {
        let mut store = AutoAssertNoGc::new(store.as_context_mut().0);
        let table = self.wasmtime_table(&mut store, iter::once(index));
        unsafe {
            match (*table).get(store.unwrap_gc_store_mut(), index)? {
                runtime::TableElement::FuncRef(f) => {
                    let func = Func::from_vm_func_ref(&mut store, f);
                    Some(func.into())
                }

                runtime::TableElement::UninitFunc => {
                    unreachable!("lazy init above should have converted UninitFunc")
                }

                runtime::TableElement::GcRef(None) => {
                    Some(Ref::null(self._ty(&store).element().heap_type()))
                }

                #[cfg_attr(not(feature = "gc"), allow(unreachable_code, unused_variables))]
                runtime::TableElement::GcRef(Some(x)) => {
                    match self._ty(&store).element().heap_type().top() {
                        HeapType::Any => {
                            let x = AnyRef::from_cloned_gc_ref(&mut store, x);
                            Some(x.into())
                        }
                        HeapType::Extern => {
                            let x = ExternRef::from_cloned_gc_ref(&mut store, x);
                            Some(x.into())
                        }
                        HeapType::Func => {
                            unreachable!("never have TableElement::GcRef for func tables")
                        }
                        ty => unreachable!("not a top type: {ty:?}"),
                    }
                }
            }
        }
    }

    /// Writes the `val` provided into `index` within this table.
    ///
    /// # Errors
    ///
    /// Returns an error if `index` is out of bounds, if `val` does not have
    /// the right type to be stored in this table, or if `val` belongs to a
    /// different store.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own this table.
    pub fn set(&self, mut store: impl AsContextMut, index: u64, val: Ref) -> Result<()> {
        let store = store.as_context_mut().0;
        let ty = self.ty(&store);
        let val = val.into_table_element(store, ty.element())?;
        let table = self.wasmtime_table(store, iter::empty());
        unsafe {
            (*table)
                .set(index, val)
                .map_err(|()| anyhow!("table element index out of bounds"))
        }
    }

    /// Returns the current size of this table.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own this table.
    pub fn size(&self, store: impl AsContext) -> u64 {
        self.internal_size(store.as_context().0)
    }

    pub(crate) fn internal_size(&self, store: &StoreOpaque) -> u64 {
        // unwrap here should be ok because the runtime should always guarantee
        // that we can fit the number of elements in a 64-bit integer.
        unsafe { u64::try_from((*store[self.0].definition).current_elements).unwrap() }
    }

    /// Grows the size of this table by `delta` more elements, initialization
    /// all new elements to `init`.
    ///
    /// Returns the previous size of this table if successful.
    ///
    /// # Errors
    ///
    /// Returns an error if the table cannot be grown by `delta`, for example
    /// if it would cause the table to exceed its maximum size. Also returns an
    /// error if `init` is not of the right type or if `init` does not belong to
    /// `store`.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own this table.
    ///
    /// This function will panic when used with a [`Store`](`crate::Store`)
    /// which has a [`ResourceLimiterAsync`](`crate::ResourceLimiterAsync`)
    /// (see also: [`Store::limiter_async`](`crate::Store::limiter_async`)).
    /// When using an async resource limiter, use [`Table::grow_async`]
    /// instead.
    pub fn grow(&self, mut store: impl AsContextMut, delta: u64, init: Ref) -> Result<u64> {
        let store = store.as_context_mut().0;
        let ty = self.ty(&store);
        let init = init.into_table_element(store, ty.element())?;
        let table = self.wasmtime_table(store, iter::empty());
        unsafe {
            match (*table).grow(delta, init, store)? {
                Some(size) => {
                    let vm = (*table).vmtable();
                    *store[self.0].definition = vm;
                    // unwrap here should be ok because the runtime should always guarantee
                    // that we can fit the table size in a 64-bit integer.
                    Ok(u64::try_from(size).unwrap())
                }
                None => bail!("failed to grow table by `{}`", delta),
            }
        }
    }

    /// Async variant of [`Table::grow`]. Required when using a
    /// [`ResourceLimiterAsync`](`crate::ResourceLimiterAsync`).
    ///
    /// # Panics
    ///
    /// This function will panic when used with a non-async
    /// [`Store`](`crate::Store`).
    #[cfg(feature = "async")]
    pub async fn grow_async<T>(
        &self,
        mut store: impl AsContextMut<Data = T>,
        delta: u64,
        init: Ref,
    ) -> Result<u64>
    where
        T: Send,
    {
        let mut store = store.as_context_mut();
        assert!(
            store.0.async_support(),
            "cannot use `grow_async` without enabling async support on the config"
        );
        store
            .on_fiber(|store| self.grow(store, delta, init))
            .await?
    }

    /// Copy `len` elements from `src_table[src_index..]` into
    /// `dst_table[dst_index..]`.
    ///
    /// # Errors
    ///
    /// Returns an error if the range is out of bounds of either the source or
    /// destination tables, or if the source table's element type does not match
    /// the destination table's element type.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own either `dst_table` or `src_table`.
    pub fn copy(
        mut store: impl AsContextMut,
        dst_table: &Table,
        dst_index: u64,
        src_table: &Table,
        src_index: u64,
        len: u64,
    ) -> Result<()> {
        let store = store.as_context_mut().0;

        let dst_ty = dst_table.ty(&store);
        let src_ty = src_table.ty(&store);
        src_ty
            .element()
            .ensure_matches(store.engine(), dst_ty.element())
            .context(
                "type mismatch: source table's element type does not match \
                 destination table's element type",
            )?;

        let dst_table = dst_table.wasmtime_table(store, iter::empty());
        let src_range = src_index..(src_index.checked_add(len).unwrap_or(u64::MAX));
        let src_table = src_table.wasmtime_table(store, src_range);
        unsafe {
            runtime::Table::copy(
                store.gc_store_mut()?,
                dst_table,
                src_table,
                dst_index,
                src_index,
                len,
            )
            .err2anyhow()?;
        }
        Ok(())
    }

    /// Fill `table[dst..(dst + len)]` with the given value.
    ///
    /// # Errors
    ///
    /// Returns an error if
    ///
    /// * `val` is not of the same type as this table's
    ///   element type,
    ///
    /// * the region to be filled is out of bounds, or
    ///
    /// * `val` comes from a different `Store` from this table.
    ///
    /// # Panics
    ///
    /// Panics if `store` does not own either `dst_table` or `src_table`.
    pub fn fill(&self, mut store: impl AsContextMut, dst: u64, val: Ref, len: u64) -> Result<()> {
        let store = store.as_context_mut().0;
        let ty = self.ty(&store);
        let val = val.into_table_element(store, ty.element())?;

        let table = self.wasmtime_table(store, iter::empty());
        unsafe {
            (*table)
                .fill(store.gc_store_mut()?, dst, val, len)
                .err2anyhow()?;
        }

        Ok(())
    }

    pub(crate) fn trace_roots(&self, store: &mut StoreOpaque, gc_roots_list: &mut GcRootsList) {
        if !self
            ._ty(store)
            .element()
            .is_vmgcref_type_and_points_to_object()
        {
            return;
        }

        let table = self.wasmtime_table(store, iter::empty());
        for gc_ref in unsafe { (*table).gc_refs_mut() } {
            if let Some(gc_ref) = gc_ref {
                let gc_ref = NonNull::from(gc_ref);
                let gc_ref = SendSyncPtr::new(gc_ref);
                unsafe {
                    gc_roots_list.add_root(gc_ref, "Wasm table element");
                }
            }
        }
    }

    pub(crate) unsafe fn from_wasmtime_table(
        mut wasmtime_export: crate::runtime::vm::ExportTable,
        store: &mut StoreOpaque,
    ) -> Table {
        // Ensure that the table's type is engine-level canonicalized.
        wasmtime_export
            .table
            .table
            .ref_type
            .canonicalize_for_runtime_usage(&mut |module_index| {
                crate::runtime::vm::Instance::from_vmctx(wasmtime_export.vmctx, |instance| {
                    instance.engine_type_index(module_index)
                })
            });

        Table(store.store_data_mut().insert(wasmtime_export))
    }

    pub(crate) fn wasmtime_ty<'a>(&self, data: &'a StoreData) -> &'a wasmtime_environ::Table {
        &data[self.0].table.table
    }

    pub(crate) fn vmimport(&self, store: &StoreOpaque) -> crate::runtime::vm::VMTableImport {
        let export = &store[self.0];
        crate::runtime::vm::VMTableImport {
            from: export.definition,
            vmctx: export.vmctx,
        }
    }

    /// Get a stable hash key for this table.
    ///
    /// Even if the same underlying table definition is added to the
    /// `StoreData` multiple times and becomes multiple `wasmtime::Table`s,
    /// this hash key will be consistent across all of these tables.
    #[allow(dead_code)] // Not used yet, but added for consistency.
    pub(crate) fn hash_key(&self, store: &StoreOpaque) -> impl core::hash::Hash + Eq {
        store[self.0].definition as usize
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{Instance, Module, Store};

    #[test]
    fn hash_key_is_stable_across_duplicate_store_data_entries() -> Result<()> {
        let mut store = Store::<()>::default();
        let module = Module::new(
            store.engine(),
            r#"
                (module
                    (table (export "t") 1 1 externref)
                )
            "#,
        )?;
        let instance = Instance::new(&mut store, &module, &[])?;

        // Each time we `get_table`, we call `Table::from_wasmtime` which adds
        // a new entry to `StoreData`, so `t1` and `t2` will have different
        // indices into `StoreData`.
        let t1 = instance.get_table(&mut store, "t").unwrap();
        let t2 = instance.get_table(&mut store, "t").unwrap();

        // That said, they really point to the same table.
        assert!(t1.get(&mut store, 0).unwrap().unwrap_extern().is_none());
        assert!(t2.get(&mut store, 0).unwrap().unwrap_extern().is_none());
        let e = ExternRef::new(&mut store, 42)?;
        t1.set(&mut store, 0, e.into())?;
        assert!(t1.get(&mut store, 0).unwrap().unwrap_extern().is_some());
        assert!(t2.get(&mut store, 0).unwrap().unwrap_extern().is_some());

        // And therefore their hash keys are the same.
        assert!(t1.hash_key(&store.as_context().0) == t2.hash_key(&store.as_context().0));

        // But the hash keys are different from different tables.
        let instance2 = Instance::new(&mut store, &module, &[])?;
        let t3 = instance2.get_table(&mut store, "t").unwrap();
        assert!(t1.hash_key(&store.as_context().0) != t3.hash_key(&store.as_context().0));

        Ok(())
    }
}