      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
    485
    486
    487
    488
    489
    490
    491
    492
    493
    494
    495
    496
    497
    498
    499
    500
    501
    502
    503
    504
    505
    506
    507
    508
    509
    510
    511
    512
    513
    514
    515
    516
    517
    518
    519
    520
    521
    522
    523
    524
    525
    526
    527
    528
    529
    530
    531
    532
    533
    534
    535
    536
    537
    538
    539
    540
    541
    542
    543
    544
    545
    546
    547
    548
    549
    550
    551
    552
    553
    554
    555
    556
    557
    558
    559
    560
    561
    562
    563
    564
    565
    566
    567
    568
    569
    570
    571
    572
    573
    574
    575
    576
    577
    578
    579
    580
    581
    582
    583
    584
    585
    586
    587
    588
    589
    590
    591
    592
    593
    594
    595
    596
    597
    598
    599
    600
    601
    602
    603
    604
    605
    606
    607
    608
    609
    610
    611
    612
    613
    614
    615
    616
    617
    618
    619
    620
    621
    622
    623
    624
    625
    626
    627
    628
    629
    630
    631
    632
    633
    634
    635
    636
    637
    638
    639
    640
    641
    642
    643
    644
    645
    646
    647
    648
    649
    650
    651
    652
    653
    654
    655
    656
    657
    658
    659
    660
    661
    662
    663
    664
    665
    666
    667
    668
    669
    670
    671
    672
    673
    674
    675
    676
    677
    678
    679
    680
    681
    682
    683
    684
    685
    686
    687
    688
    689
    690
    691
    692
    693
    694
    695
    696
    697
    698
    699
    700
    701
    702
    703
    704
    705
    706
    707
    708
    709
    710
    711
    712
    713
    714
    715
    716
    717
    718
    719
    720
    721
    722
    723
    724
    725
    726
    727
    728
    729
    730
    731
    732
    733
    734
    735
    736
    737
    738
    739
    740

    use alloc::{rc::Rc, string::ToString, vec::Vec};
    use core::{
        cell::{Cell, RefCell},
        cmp, fmt,
        ops::Range,
        u32,
    };
    use memory_units::{Bytes, Pages, RoundUpTo};
    use parity_wasm::elements::ResizableLimits;
    use value::LittleEndianConvert;
    use Error;

    #[cfg(all(unix, not(feature = "vec_memory")))]
    #[path = "mmap_bytebuf.rs"]
    mod bytebuf;

    #[cfg(any(not(unix), feature = "vec_memory"))]
    #[path = "vec_bytebuf.rs"]
    mod bytebuf;

    use self::bytebuf::ByteBuf;

    /// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
    ///
    /// The size of a memory is always a integer multiple of a page size.
    ///
    /// [`MemoryInstance`]: struct.MemoryInstance.html
    pub const LINEAR_MEMORY_PAGE_SIZE: Bytes = Bytes(65536);

    /// Reference to a memory (See [`MemoryInstance`] for details).
    ///
    /// This reference has a reference-counting semantics.
    ///
    /// [`MemoryInstance`]: struct.MemoryInstance.html
    ///
    #[derive(Clone, Debug)]
    pub struct MemoryRef(Rc<MemoryInstance>);

    impl ::core::ops::Deref for MemoryRef {
        type Target = MemoryInstance;
        fn deref(&self) -> &MemoryInstance {
            &self.0
        }
    }

    /// Runtime representation of a linear memory (or `memory` for short).
    ///
    /// A memory is a contiguous, mutable array of raw bytes. Wasm code can load and store values
    /// from/to a linear memory at any byte address.
    /// A trap occurs if an access is not within the bounds of the current memory size.
    ///
    /// A memory is created with an initial size but can be grown dynamically.
    /// The growth can be limited by specifying maximum size.
    /// The size of a memory is always a integer multiple of a [page size][`LINEAR_MEMORY_PAGE_SIZE`] - 64KiB.
    ///
    /// At the moment, wasm doesn't provide any way to shrink the memory.
    ///
    /// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
    pub struct MemoryInstance {
        /// Memory limits.
        limits: ResizableLimits,
        /// Linear memory buffer with lazy allocation.
        buffer: RefCell<ByteBuf>,
        initial: Pages,
        current_size: Cell<usize>,
        maximum: Option<Pages>,
    }

    impl fmt::Debug for MemoryInstance {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.debug_struct("MemoryInstance")
                .field("limits", &self.limits)
                .field("buffer.len", &self.buffer.borrow().len())
                .field("maximum", &self.maximum)
                .field("initial", &self.initial)
                .finish()
        }
    }

    struct CheckedRegion {
        offset: usize,
        size: usize,
    }

    impl CheckedRegion {
        fn range(&self) -> Range<usize> {
            self.offset..self.offset + self.size
        }

        fn intersects(&self, other: &Self) -> bool {
            let low = cmp::max(self.offset, other.offset);
            let high = cmp::min(self.offset + self.size, other.offset + other.size);

            low < high
        }
    }

    impl MemoryInstance {
        /// Allocate a memory instance.
        ///
        /// The memory allocated with initial number of pages specified by `initial`.
        /// Minimal possible value for `initial` is 0 and maximum possible is `65536`.
        /// (Since maximum addressible memory is 2<sup>32</sup> = 4GiB = 65536 * [64KiB][`LINEAR_MEMORY_PAGE_SIZE`]).
        ///
        /// It is possible to limit maximum number of pages this memory instance can have by specifying
        /// `maximum`. If not specified, this memory instance would be able to allocate up to 4GiB.
        ///
        /// Allocated memory is always zeroed.
        ///
        /// # Errors
        ///
        /// Returns `Err` if:
        ///
        /// - `initial` is greater than `maximum`
        /// - either `initial` or `maximum` is greater than `65536`.
        ///
        /// [`LINEAR_MEMORY_PAGE_SIZE`]: constant.LINEAR_MEMORY_PAGE_SIZE.html
        pub fn alloc(initial: Pages, maximum: Option<Pages>) -> Result<MemoryRef, Error> {
            {
                use core::convert::TryInto;
                let initial_u32: u32 = initial.0.try_into().map_err(|_| {
                    Error::Memory(format!("initial ({}) can't be coerced to u32", initial.0))
                })?;
                let maximum_u32: Option<u32> = match maximum {
                    Some(maximum_pages) => Some(maximum_pages.0.try_into().map_err(|_| {
                        Error::Memory(format!(
                            "maximum ({}) can't be coerced to u32",
                            maximum_pages.0
                        ))
                    })?),
                    None => None,
                };
                validation::validate_memory(initial_u32, maximum_u32).map_err(Error::Memory)?;
            }

            let memory = MemoryInstance::new(initial, maximum)?;
            Ok(MemoryRef(Rc::new(memory)))
        }

        /// Create new linear memory instance.
        fn new(initial: Pages, maximum: Option<Pages>) -> Result<Self, Error> {
            let limits = ResizableLimits::new(initial.0 as u32, maximum.map(|p| p.0 as u32));

            let initial_size: Bytes = initial.into();
            Ok(MemoryInstance {
                limits: limits,
                buffer: RefCell::new(
                    ByteBuf::new(initial_size.0).map_err(|err| Error::Memory(err.to_string()))?,
                ),
                initial: initial,
                current_size: Cell::new(initial_size.0),
                maximum: maximum,
            })
        }

        /// Return linear memory limits.
        pub(crate) fn limits(&self) -> &ResizableLimits {
            &self.limits
        }

        /// Returns number of pages this `MemoryInstance` was created with.
        pub fn initial(&self) -> Pages {
            self.initial
        }

        /// Returns maximum amount of pages this `MemoryInstance` can grow to.
        ///
        /// Returns `None` if there is no limit set.
        /// Maximum memory size cannot exceed `65536` pages or 4GiB.
        pub fn maximum(&self) -> Option<Pages> {
            self.maximum
        }

        /// Returns current linear memory size.
        ///
        /// Maximum memory size cannot exceed `65536` pages or 4GiB.
        ///
        /// # Example
        ///
        /// To convert number of pages to number of bytes you can use the following code:
        ///
        /// ```rust
        /// use wasmi::MemoryInstance;
        /// use wasmi::memory_units::*;
        ///
        /// let memory = MemoryInstance::alloc(Pages(1), None).unwrap();
        /// let byte_size: Bytes = memory.current_size().into();
        /// assert_eq!(
        ///     byte_size,
        ///     Bytes(65536),
        /// );
        /// ```
        pub fn current_size(&self) -> Pages {
            Bytes(self.buffer.borrow().len()).round_up_to()
        }

        /// Get value from memory at given offset.
        pub fn get_value<T: LittleEndianConvert>(&self, offset: u32) -> Result<T, Error> {
            let mut buffer = self.buffer.borrow_mut();
            let region =
                self.checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?;
            Ok(
                T::from_little_endian(&buffer.as_slice_mut()[region.range()])
                    .expect("Slice size is checked"),
            )
        }

        /// Copy data from memory at given offset.
        ///
        /// This will allocate vector for you.
        /// If you can provide a mutable slice you can use [`get_into`].
        ///
        /// [`get_into`]: #method.get_into
        pub fn get(&self, offset: u32, size: usize) -> Result<Vec<u8>, Error> {
            let mut buffer = self.buffer.borrow_mut();
            let region = self.checked_region(&mut buffer, offset as usize, size)?;

            Ok(buffer.as_slice_mut()[region.range()].to_vec())
        }

        /// Copy data from given offset in the memory into `target` slice.
        ///
        /// # Errors
        ///
        /// Returns `Err` if the specified region is out of bounds.
        pub fn get_into(&self, offset: u32, target: &mut [u8]) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();
            let region = self.checked_region(&mut buffer, offset as usize, target.len())?;

            target.copy_from_slice(&buffer.as_slice_mut()[region.range()]);

            Ok(())
        }

        /// Copy data in the memory at given offset.
        pub fn set(&self, offset: u32, value: &[u8]) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();
            let range = self
                .checked_region(&mut buffer, offset as usize, value.len())?
                .range();

            buffer.as_slice_mut()[range].copy_from_slice(value);

            Ok(())
        }

        /// Copy value in the memory at given offset.
        pub fn set_value<T: LittleEndianConvert>(&self, offset: u32, value: T) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();
            let range = self
                .checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?
                .range();
            value.into_little_endian(&mut buffer.as_slice_mut()[range]);
            Ok(())
        }

        /// Increases the size of the linear memory by given number of pages.
        /// Returns previous memory size if succeeds.
        ///
        /// # Errors
        ///
        /// Returns `Err` if attempted to allocate more memory than permited by the limit.
        pub fn grow(&self, additional: Pages) -> Result<Pages, Error> {
            let size_before_grow: Pages = self.current_size();

            if additional == Pages(0) {
                return Ok(size_before_grow);
            }
            if additional > Pages(65536) {
                return Err(Error::Memory(format!(
                    "Trying to grow memory by more than 65536 pages"
                )));
            }

            let new_size: Pages = size_before_grow + additional;
            let maximum = self
                .maximum
                .unwrap_or(Pages(validation::LINEAR_MEMORY_MAX_PAGES as usize));
            if new_size > maximum {
                return Err(Error::Memory(format!(
                    "Trying to grow memory by {} pages when already have {}",
                    additional.0, size_before_grow.0,
                )));
            }

            let new_buffer_length: Bytes = new_size.into();
            self.buffer
                .borrow_mut()
                .realloc(new_buffer_length.0)
                .map_err(|err| Error::Memory(err.to_string()))?;

            self.current_size.set(new_buffer_length.0);

            Ok(size_before_grow)
        }

        fn checked_region(
            &self,
            buffer: &mut ByteBuf,
            offset: usize,
            size: usize,
        ) -> Result<CheckedRegion, Error> {
            let end = offset.checked_add(size).ok_or_else(|| {
                Error::Memory(format!(
                    "trying to access memory block of size {} from offset {}",
                    size, offset
                ))
            })?;

            if end > buffer.len() {
                return Err(Error::Memory(format!(
                    "trying to access region [{}..{}] in memory [0..{}]",
                    offset,
                    end,
                    buffer.len()
                )));
            }

            Ok(CheckedRegion {
                offset: offset,
                size: size,
            })
        }

        fn checked_region_pair(
            &self,
            buffer: &mut ByteBuf,
            offset1: usize,
            size1: usize,
            offset2: usize,
            size2: usize,
        ) -> Result<(CheckedRegion, CheckedRegion), Error> {
            let end1 = offset1.checked_add(size1).ok_or_else(|| {
                Error::Memory(format!(
                    "trying to access memory block of size {} from offset {}",
                    size1, offset1
                ))
            })?;

            let end2 = offset2.checked_add(size2).ok_or_else(|| {
                Error::Memory(format!(
                    "trying to access memory block of size {} from offset {}",
                    size2, offset2
                ))
            })?;

            if end1 > buffer.len() {
                return Err(Error::Memory(format!(
                    "trying to access region [{}..{}] in memory [0..{}]",
                    offset1,
                    end1,
                    buffer.len()
                )));
            }

            if end2 > buffer.len() {
                return Err(Error::Memory(format!(
                    "trying to access region [{}..{}] in memory [0..{}]",
                    offset2,
                    end2,
                    buffer.len()
                )));
            }

            Ok((
                CheckedRegion {
                    offset: offset1,
                    size: size1,
                },
                CheckedRegion {
                    offset: offset2,
                    size: size2,
                },
            ))
        }

        /// Copy contents of one memory region to another.
        ///
        /// Semantically equivalent to `memmove`.
        ///
        /// # Errors
        ///
        /// Returns `Err` if either of specified regions is out of bounds.
        pub fn copy(&self, src_offset: usize, dst_offset: usize, len: usize) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();

            let (read_region, write_region) =
                self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;

            unsafe {
                ::core::ptr::copy(
                    buffer.as_slice()[read_region.range()].as_ptr(),
                    buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
                    len,
                )
            }

            Ok(())
        }

        /// Copy contents of one memory region to another (non-overlapping version).
        ///
        /// Semantically equivalent to `memcpy`.
        /// but returns Error if source overlaping with destination.
        ///
        /// # Errors
        ///
        /// Returns `Err` if:
        ///
        /// - either of specified regions is out of bounds,
        /// - these regions overlaps.
        pub fn copy_nonoverlapping(
            &self,
            src_offset: usize,
            dst_offset: usize,
            len: usize,
        ) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();

            let (read_region, write_region) =
                self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;

            if read_region.intersects(&write_region) {
                return Err(Error::Memory(format!(
                    "non-overlapping copy is used for overlapping regions"
                )));
            }

            unsafe {
                ::core::ptr::copy_nonoverlapping(
                    buffer.as_slice()[read_region.range()].as_ptr(),
                    buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
                    len,
                )
            }

            Ok(())
        }

        /// Copy memory between two (possibly distinct) memory instances.
        ///
        /// If the same memory instance passed as `src` and `dst` then usual `copy` will be used.
        pub fn transfer(
            src: &MemoryRef,
            src_offset: usize,
            dst: &MemoryRef,
            dst_offset: usize,
            len: usize,
        ) -> Result<(), Error> {
            if Rc::ptr_eq(&src.0, &dst.0) {
                // `transfer` is invoked with with same source and destination. Let's assume that regions may
                // overlap and use `copy`.
                return src.copy(src_offset, dst_offset, len);
            }

            // Because memory references point to different memory instances, it is safe to `borrow_mut`
            // both buffers at once (modulo `with_direct_access_mut`).
            let mut src_buffer = src.buffer.borrow_mut();
            let mut dst_buffer = dst.buffer.borrow_mut();

            let src_range = src
                .checked_region(&mut src_buffer, src_offset, len)?
                .range();
            let dst_range = dst
                .checked_region(&mut dst_buffer, dst_offset, len)?
                .range();

            dst_buffer.as_slice_mut()[dst_range].copy_from_slice(&src_buffer.as_slice()[src_range]);

            Ok(())
        }

        /// Fill the memory region with the specified value.
        ///
        /// Semantically equivalent to `memset`.
        ///
        /// # Errors
        ///
        /// Returns `Err` if the specified region is out of bounds.
        pub fn clear(&self, offset: usize, new_val: u8, len: usize) -> Result<(), Error> {
            let mut buffer = self.buffer.borrow_mut();

            let range = self.checked_region(&mut buffer, offset, len)?.range();

            for val in &mut buffer.as_slice_mut()[range] {
                *val = new_val
            }
            Ok(())
        }

        /// Fill the specified memory region with zeroes.
        ///
        /// # Errors
        ///
        /// Returns `Err` if the specified region is out of bounds.
        pub fn zero(&self, offset: usize, len: usize) -> Result<(), Error> {
            self.clear(offset, 0, len)
        }

        /// Set every byte in the entire linear memory to 0, preserving its size.
        ///
        /// Might be useful for some optimization shenanigans.
        pub fn erase(&self) -> Result<(), Error> {
            self.buffer
                .borrow_mut()
                .erase()
                .map_err(|err| Error::Memory(err.to_string()))
        }

        /// Provides direct access to the underlying memory buffer.
        ///
        /// # Panics
        ///
        /// Any call that requires write access to memory (such as [`set`], [`clear`], etc) made within
        /// the closure will panic.
        ///
        /// [`set`]: #method.get
        /// [`clear`]: #method.set
        pub fn with_direct_access<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
            let buf = self.buffer.borrow();
            f(buf.as_slice())
        }

        /// Provides direct mutable access to the underlying memory buffer.
        ///
        /// # Panics
        ///
        /// Any calls that requires either read or write access to memory (such as [`get`], [`set`], [`copy`], etc) made
        /// within the closure will panic. Proceed with caution.
        ///
        /// [`get`]: #method.get
        /// [`set`]: #method.set
        pub fn with_direct_access_mut<R, F: FnOnce(&mut [u8]) -> R>(&self, f: F) -> R {
            let mut buf = self.buffer.borrow_mut();
            f(buf.as_slice_mut())
        }
    }

    #[cfg(test)]
    mod tests {

        use super::{MemoryInstance, MemoryRef, LINEAR_MEMORY_PAGE_SIZE};
        use memory_units::Pages;
        use std::rc::Rc;
        use Error;

        #[test]
        fn alloc() {
            let mut fixtures = vec![
                (0, None, true),
                (0, Some(0), true),
                (1, None, true),
                (1, Some(1), true),
                (0, Some(1), true),
                (1, Some(0), false),
            ];

            #[cfg(target_pointer_width = "64")]
            fixtures.extend(&[
                (65536, Some(65536), true),
                (65536, Some(0), false),
                (65536, None, true),
            ]);

            for (index, &(initial, maybe_max, expected_ok)) in fixtures.iter().enumerate() {
                let initial: Pages = Pages(initial);
                let maximum: Option<Pages> = maybe_max.map(|m| Pages(m));
                let result = MemoryInstance::alloc(initial, maximum);
                if result.is_ok() != expected_ok {
                    panic!(
                        "unexpected error at {}, initial={:?}, max={:?}, expected={}, result={:?}",
                        index, initial, maybe_max, expected_ok, result,
                    );
                }
            }
        }

        #[test]
        fn ensure_page_size() {
            use memory_units::ByteSize;
            assert_eq!(LINEAR_MEMORY_PAGE_SIZE, Pages::byte_size());
        }

        fn create_memory(initial_content: &[u8]) -> MemoryInstance {
            let mem = MemoryInstance::new(Pages(1), Some(Pages(1))).unwrap();
            mem.set(0, initial_content)
                .expect("Successful initialize the memory");
            mem
        }

        #[test]
        fn copy_overlaps_1() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            mem.copy(0, 4, 6).expect("Successfully copy the elements");
            let result = mem.get(0, 10).expect("Successfully retrieve the result");
            assert_eq!(result, &[0, 1, 2, 3, 0, 1, 2, 3, 4, 5]);
        }

        #[test]
        fn copy_overlaps_2() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            mem.copy(4, 0, 6).expect("Successfully copy the elements");
            let result = mem.get(0, 10).expect("Successfully retrieve the result");
            assert_eq!(result, &[4, 5, 6, 7, 8, 9, 6, 7, 8, 9]);
        }

        #[test]
        fn copy_nonoverlapping() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            mem.copy_nonoverlapping(0, 10, 10)
                .expect("Successfully copy the elements");
            let result = mem.get(10, 10).expect("Successfully retrieve the result");
            assert_eq!(result, &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
        }

        #[test]
        fn copy_nonoverlapping_overlaps_1() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            let result = mem.copy_nonoverlapping(0, 4, 6);
            match result {
                Err(Error::Memory(_)) => {}
                _ => panic!("Expected Error::Memory(_) result, but got {:?}", result),
            }
        }

        #[test]
        fn copy_nonoverlapping_overlaps_2() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            let result = mem.copy_nonoverlapping(4, 0, 6);
            match result {
                Err(Error::Memory(_)) => {}
                _ => panic!("Expected Error::Memory(_), but got {:?}", result),
            }
        }

        #[test]
        fn transfer_works() {
            let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
            let dst = MemoryRef(Rc::new(create_memory(&[
                10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
            ])));

            MemoryInstance::transfer(&src, 4, &dst, 0, 3).unwrap();

            assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            assert_eq!(
                dst.get(0, 10).unwrap(),
                &[4, 5, 6, 13, 14, 15, 16, 17, 18, 19]
            );
        }

        #[test]
        fn transfer_still_works_with_same_memory() {
            let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));

            MemoryInstance::transfer(&src, 4, &src, 0, 3).unwrap();

            assert_eq!(src.get(0, 10).unwrap(), &[4, 5, 6, 3, 4, 5, 6, 7, 8, 9]);
        }

        #[test]
        fn transfer_oob_with_same_memory_errors() {
            let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
            assert!(MemoryInstance::transfer(&src, 65535, &src, 0, 3).is_err());

            // Check that memories content left untouched
            assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
        }

        #[test]
        fn transfer_oob_errors() {
            let src = MemoryRef(Rc::new(create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9])));
            let dst = MemoryRef(Rc::new(create_memory(&[
                10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
            ])));

            assert!(MemoryInstance::transfer(&src, 65535, &dst, 0, 3).is_err());

            // Check that memories content left untouched
            assert_eq!(src.get(0, 10).unwrap(), &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            assert_eq!(
                dst.get(0, 10).unwrap(),
                &[10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
            );
        }

        #[test]
        fn clear() {
            let mem = create_memory(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            mem.clear(0, 0x4A, 10)
                .expect("To successfully clear the memory");
            let result = mem.get(0, 10).expect("To successfully retrieve the result");
            assert_eq!(result, &[0x4A; 10]);
        }

        #[test]
        fn get_into() {
            let mem = MemoryInstance::new(Pages(1), None).unwrap();
            mem.set(6, &[13, 17, 129])
                .expect("memory set should not fail");

            let mut data = [0u8; 2];
            mem.get_into(7, &mut data[..])
                .expect("get_into should not fail");

            assert_eq!(data, [17, 129]);
        }

        #[test]
        fn zero_copy() {
            let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
            mem.set(100, &[0]).expect("memory set should not fail");
            mem.with_direct_access_mut(|buf| {
                assert_eq!(
                    buf.len(),
                    65536,
                    "the buffer length is expected to be 1 page long"
                );
                buf[..10].copy_from_slice(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            });
            mem.with_direct_access(|buf| {
                assert_eq!(
                    buf.len(),
                    65536,
                    "the buffer length is expected to be 1 page long"
                );
                assert_eq!(&buf[..10], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
            });
        }

        #[should_panic]
        #[test]
        fn zero_copy_panics_on_nested_access() {
            let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
            let mem_inner = mem.clone();
            mem.with_direct_access(move |_| {
                let _ = mem_inner.set(0, &[11, 12, 13]);
            });
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)