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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749
use std::ptr::NonNull; use crate::{ alloc, bytes::{Bytes, Deallocation}, datatypes::{ArrowNativeType, ToByteSlice}, util::bit_util, }; use super::Buffer; // Licensed to the Apache Software Foundation (ASF) under one // or more contributor license agreements. See the NOTICE file // distributed with this work for additional information // regarding copyright ownership. The ASF licenses this file // to you under the Apache License, Version 2.0 (the // "License"); you may not use this file except in compliance // with the License. You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, // software distributed under the License is distributed on an // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY // KIND, either express or implied. See the License for the // specific language governing permissions and limitations // under the License. /// A [`MutableBuffer`] is Arrow's interface to build a [`Buffer`] out of items or slices of items. /// [`Buffer`]s created from [`MutableBuffer`] (via `into`) are guaranteed to have its pointer aligned /// along cache lines and in multiple of 64 bytes. /// Use [MutableBuffer::push] to insert an item, [MutableBuffer::extend_from_slice] /// to insert many items, and `into` to convert it to [`Buffer`]. /// # Example /// ``` /// # use arrow::buffer::{Buffer, MutableBuffer}; /// let mut buffer = MutableBuffer::new(0); /// buffer.push(256u32); /// buffer.extend_from_slice(&[1u32]); /// let buffer: Buffer = buffer.into(); /// assert_eq!(buffer.as_slice(), &[0u8, 1, 0, 0, 1, 0, 0, 0]) /// ``` #[derive(Debug)] pub struct MutableBuffer { // dangling iff capacity = 0 data: NonNull<u8>, // invariant: len <= capacity len: usize, capacity: usize, } impl MutableBuffer { /// Allocate a new [MutableBuffer] with initial capacity to be at least `capacity`. #[inline] pub fn new(capacity: usize) -> Self { Self::with_capacity(capacity) } /// Allocate a new [MutableBuffer] with initial capacity to be at least `capacity`. #[inline] pub fn with_capacity(capacity: usize) -> Self { let capacity = bit_util::round_upto_multiple_of_64(capacity); let ptr = alloc::allocate_aligned(capacity); Self { data: ptr, len: 0, capacity, } } /// Allocates a new [MutableBuffer] with `len` and capacity to be at least `len` where /// all bytes are guaranteed to be `0u8`. /// # Example /// ``` /// # use arrow::buffer::{Buffer, MutableBuffer}; /// let mut buffer = MutableBuffer::from_len_zeroed(127); /// assert_eq!(buffer.len(), 127); /// assert!(buffer.capacity() >= 127); /// let data = buffer.as_slice_mut(); /// assert_eq!(data[126], 0u8); /// ``` pub fn from_len_zeroed(len: usize) -> Self { let new_capacity = bit_util::round_upto_multiple_of_64(len); let ptr = alloc::allocate_aligned_zeroed(new_capacity); Self { data: ptr, len, capacity: new_capacity, } } /// creates a new [MutableBuffer] with capacity and length capable of holding `len` bits. /// This is useful to create a buffer for packed bitmaps. pub fn new_null(len: usize) -> Self { let num_bytes = bit_util::ceil(len, 8); MutableBuffer::from_len_zeroed(num_bytes) } /// Set the bits in the range of `[0, end)` to 0 (if `val` is false), or 1 (if `val` /// is true). Also extend the length of this buffer to be `end`. /// /// This is useful when one wants to clear (or set) the bits and then manipulate /// the buffer directly (e.g., modifying the buffer by holding a mutable reference /// from `data_mut()`). pub fn with_bitset(mut self, end: usize, val: bool) -> Self { assert!(end <= self.capacity); let v = if val { 255 } else { 0 }; unsafe { std::ptr::write_bytes(self.data.as_ptr(), v, end); self.len = end; } self } /// Ensure that `count` bytes from `start` contain zero bits /// /// This is used to initialize the bits in a buffer, however, it has no impact on the /// `len` of the buffer and so can be used to initialize the memory region from /// `len` to `capacity`. pub fn set_null_bits(&mut self, start: usize, count: usize) { assert!(start + count <= self.capacity); unsafe { std::ptr::write_bytes(self.data.as_ptr().add(start), 0, count); } } /// Ensures that this buffer has at least `self.len + additional` bytes. This re-allocates iff /// `self.len + additional > capacity`. /// # Example /// ``` /// # use arrow::buffer::{Buffer, MutableBuffer}; /// let mut buffer = MutableBuffer::new(0); /// buffer.reserve(253); // allocates for the first time /// (0..253u8).for_each(|i| buffer.push(i)); // no reallocation /// let buffer: Buffer = buffer.into(); /// assert_eq!(buffer.len(), 253); /// ``` // For performance reasons, this must be inlined so that the `if` is executed inside the caller, and not as an extra call that just // exits. #[inline(always)] pub fn reserve(&mut self, additional: usize) { let required_cap = self.len + additional; if required_cap > self.capacity { // JUSTIFICATION // Benefit // necessity // Soundness // `self.data` is valid for `self.capacity`. let (ptr, new_capacity) = unsafe { reallocate(self.data, self.capacity, required_cap) }; self.data = ptr; self.capacity = new_capacity; } } /// Resizes the buffer, either truncating its contents (with no change in capacity), or /// growing it (potentially reallocating it) and writing `value` in the newly available bytes. /// # Example /// ``` /// # use arrow::buffer::{Buffer, MutableBuffer}; /// let mut buffer = MutableBuffer::new(0); /// buffer.resize(253, 2); // allocates for the first time /// assert_eq!(buffer.as_slice()[252], 2u8); /// ``` // For performance reasons, this must be inlined so that the `if` is executed inside the caller, and not as an extra call that just // exits. #[inline(always)] pub fn resize(&mut self, new_len: usize, value: u8) { if new_len > self.len { let diff = new_len - self.len; self.reserve(diff); // write the value unsafe { self.data.as_ptr().add(self.len).write_bytes(value, diff) }; } // this truncates the buffer when new_len < self.len self.len = new_len; } /// Returns whether this buffer is empty or not. #[inline] pub const fn is_empty(&self) -> bool { self.len == 0 } /// Returns the length (the number of bytes written) in this buffer. /// The invariant `buffer.len() <= buffer.capacity()` is always upheld. #[inline] pub const fn len(&self) -> usize { self.len } /// Returns the total capacity in this buffer. /// The invariant `buffer.len() <= buffer.capacity()` is always upheld. #[inline] pub const fn capacity(&self) -> usize { self.capacity } /// Clear all existing data from this buffer. pub fn clear(&mut self) { self.len = 0 } /// Returns the data stored in this buffer as a slice. pub fn as_slice(&self) -> &[u8] { self } /// Returns the data stored in this buffer as a mutable slice. pub fn as_slice_mut(&mut self) -> &mut [u8] { self } /// Returns a raw pointer to this buffer's internal memory /// This pointer is guaranteed to be aligned along cache-lines. #[inline] pub const fn as_ptr(&self) -> *const u8 { self.data.as_ptr() } /// Returns a mutable raw pointer to this buffer's internal memory /// This pointer is guaranteed to be aligned along cache-lines. #[inline] pub fn as_mut_ptr(&mut self) -> *mut u8 { self.data.as_ptr() } #[deprecated( since = "2.0.0", note = "This method is deprecated in favour of `into` from the trait `Into`." )] /// Freezes this buffer and return an immutable version of it. pub fn freeze(self) -> Buffer { self.into_buffer() } #[inline] pub(super) fn into_buffer(self) -> Buffer { let bytes = unsafe { Bytes::new(self.data, self.len, Deallocation::Native(self.capacity)) }; std::mem::forget(self); Buffer::from_bytes(bytes) } /// View this buffer asa slice of a specific type. /// # Safety /// This function must only be used when this buffer was extended with items of type `T`. /// Failure to do so results in undefined behavior. pub fn typed_data_mut<T: ArrowNativeType>(&mut self) -> &mut [T] { unsafe { let (prefix, offsets, suffix) = self.as_slice_mut().align_to_mut::<T>(); assert!(prefix.is_empty() && suffix.is_empty()); offsets } } /// Extends this buffer from a slice of items that can be represented in bytes, increasing its capacity if needed. /// # Example /// ``` /// # use arrow::buffer::MutableBuffer; /// let mut buffer = MutableBuffer::new(0); /// buffer.extend_from_slice(&[2u32, 0]); /// assert_eq!(buffer.len(), 8) // u32 has 4 bytes /// ``` #[inline] pub fn extend_from_slice<T: ToByteSlice>(&mut self, items: &[T]) { let len = items.len(); let additional = len * std::mem::size_of::<T>(); self.reserve(additional); unsafe { let dst = self.data.as_ptr().add(self.len); let src = items.as_ptr() as *const u8; std::ptr::copy_nonoverlapping(src, dst, additional) } self.len += additional; } /// Extends the buffer with a new item, increasing its capacity if needed. /// # Example /// ``` /// # use arrow::buffer::MutableBuffer; /// let mut buffer = MutableBuffer::new(0); /// buffer.push(256u32); /// assert_eq!(buffer.len(), 4) // u32 has 4 bytes /// ``` #[inline] pub fn push<T: ToByteSlice>(&mut self, item: T) { let additional = std::mem::size_of::<T>(); self.reserve(additional); unsafe { let dst = self.data.as_ptr().add(self.len) as *mut T; std::ptr::write(dst, item); } self.len += additional; } /// Extends the buffer with a new item, without checking for sufficient capacity /// Safety /// Caller must ensure that the capacity()-len()>=size_of<T>() #[inline] unsafe fn push_unchecked<T: ToByteSlice>(&mut self, item: T) { let additional = std::mem::size_of::<T>(); let dst = self.data.as_ptr().add(self.len) as *mut T; std::ptr::write(dst, item); self.len += additional; } /// Extends the buffer by `additional` bytes equal to `0u8`, incrementing its capacity if needed. #[inline] pub fn extend_zeros(&mut self, additional: usize) { self.resize(self.len + additional, 0); } /// # Safety /// The caller must ensure that the buffer was properly initialized up to `len`. #[inline] pub(crate) unsafe fn set_len(&mut self, len: usize) { assert!(len <= self.capacity()); self.len = len; } } /// # Safety /// `ptr` must be allocated for `old_capacity`. #[inline] unsafe fn reallocate( ptr: NonNull<u8>, old_capacity: usize, new_capacity: usize, ) -> (NonNull<u8>, usize) { let new_capacity = bit_util::round_upto_multiple_of_64(new_capacity); let new_capacity = std::cmp::max(new_capacity, old_capacity * 2); let ptr = alloc::reallocate(ptr, old_capacity, new_capacity); (ptr, new_capacity) } impl<A: ArrowNativeType> Extend<A> for MutableBuffer { #[inline] fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T) { let iterator = iter.into_iter(); self.extend_from_iter(iterator) } } impl MutableBuffer { #[inline] pub(super) fn extend_from_iter<T: ArrowNativeType, I: Iterator<Item = T>>( &mut self, mut iterator: I, ) { let size = std::mem::size_of::<T>(); let (lower, _) = iterator.size_hint(); let additional = lower * size; self.reserve(additional); // this is necessary because of https://github.com/rust-lang/rust/issues/32155 let mut len = SetLenOnDrop::new(&mut self.len); let mut dst = unsafe { self.data.as_ptr().add(len.local_len) as *mut T }; let capacity = self.capacity; while len.local_len + size <= capacity { if let Some(item) = iterator.next() { unsafe { std::ptr::write(dst, item); dst = dst.add(1); } len.local_len += size; } else { break; } } drop(len); iterator.for_each(|item| self.push(item)); } /// Creates a [`MutableBuffer`] from an [`Iterator`] with a trusted (upper) length. /// Prefer this to `collect` whenever possible, as it is faster ~60% faster. /// # Example /// ``` /// # use arrow::buffer::MutableBuffer; /// let v = vec![1u32]; /// let iter = v.iter().map(|x| x * 2); /// let buffer = unsafe { MutableBuffer::from_trusted_len_iter(iter) }; /// assert_eq!(buffer.len(), 4) // u32 has 4 bytes /// ``` /// # Safety /// This method assumes that the iterator's size is correct and is undefined behavior /// to use it on an iterator that reports an incorrect length. // This implementation is required for two reasons: // 1. there is no trait `TrustedLen` in stable rust and therefore // we can't specialize `extend` for `TrustedLen` like `Vec` does. // 2. `from_trusted_len_iter` is faster. #[inline] pub unsafe fn from_trusted_len_iter<T: ArrowNativeType, I: Iterator<Item = T>>( iterator: I, ) -> Self { let (_, upper) = iterator.size_hint(); let upper = upper.expect("from_trusted_len_iter requires an upper limit"); let len = upper * std::mem::size_of::<T>(); let mut buffer = MutableBuffer::new(len); let mut dst = buffer.data.as_ptr() as *mut T; for item in iterator { // note how there is no reserve here (compared with `extend_from_iter`) std::ptr::write(dst, item); dst = dst.add(1); } assert_eq!( dst.offset_from(buffer.data.as_ptr() as *mut T) as usize, upper, "Trusted iterator length was not accurately reported" ); buffer.len = len; buffer } /// Creates a [`MutableBuffer`] from a boolean [`Iterator`] with a trusted (upper) length. /// # use arrow::buffer::MutableBuffer; /// # Example /// ``` /// # use arrow::buffer::MutableBuffer; /// let v = vec![false, true, false]; /// let iter = v.iter().map(|x| *x || true); /// let buffer = unsafe { MutableBuffer::from_trusted_len_iter_bool(iter) }; /// assert_eq!(buffer.len(), 1) // 3 booleans have 1 byte /// ``` /// # Safety /// This method assumes that the iterator's size is correct and is undefined behavior /// to use it on an iterator that reports an incorrect length. // This implementation is required for two reasons: // 1. there is no trait `TrustedLen` in stable rust and therefore // we can't specialize `extend` for `TrustedLen` like `Vec` does. // 2. `from_trusted_len_iter_bool` is faster. #[inline] pub unsafe fn from_trusted_len_iter_bool<I: Iterator<Item = bool>>( mut iterator: I, ) -> Self { let (_, upper) = iterator.size_hint(); let upper = upper.expect("from_trusted_len_iter requires an upper limit"); let mut result = { let byte_capacity: usize = upper.saturating_add(7) / 8; MutableBuffer::new(byte_capacity) }; 'a: loop { let mut byte_accum: u8 = 0; let mut mask: u8 = 1; //collect (up to) 8 bits into a byte while mask != 0 { if let Some(value) = iterator.next() { byte_accum |= match value { true => mask, false => 0, }; mask <<= 1; } else { if mask != 1 { // Add last byte result.push_unchecked(byte_accum); } break 'a; } } // Soundness: from_trusted_len result.push_unchecked(byte_accum); } result } /// Creates a [`MutableBuffer`] from an [`Iterator`] with a trusted (upper) length or errors /// if any of the items of the iterator is an error. /// Prefer this to `collect` whenever possible, as it is faster ~60% faster. /// # Safety /// This method assumes that the iterator's size is correct and is undefined behavior /// to use it on an iterator that reports an incorrect length. #[inline] pub unsafe fn try_from_trusted_len_iter< E, T: ArrowNativeType, I: Iterator<Item = std::result::Result<T, E>>, >( iterator: I, ) -> std::result::Result<Self, E> { let (_, upper) = iterator.size_hint(); let upper = upper.expect("try_from_trusted_len_iter requires an upper limit"); let len = upper * std::mem::size_of::<T>(); let mut buffer = MutableBuffer::new(len); let mut dst = buffer.data.as_ptr() as *mut T; for item in iterator { // note how there is no reserve here (compared with `extend_from_iter`) std::ptr::write(dst, item?); dst = dst.add(1); } assert_eq!( dst.offset_from(buffer.data.as_ptr() as *mut T) as usize, upper, "Trusted iterator length was not accurately reported" ); buffer.len = len; Ok(buffer) } } impl std::ops::Deref for MutableBuffer { type Target = [u8]; fn deref(&self) -> &[u8] { unsafe { std::slice::from_raw_parts(self.as_ptr(), self.len) } } } impl std::ops::DerefMut for MutableBuffer { fn deref_mut(&mut self) -> &mut [u8] { unsafe { std::slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) } } } impl Drop for MutableBuffer { fn drop(&mut self) { unsafe { alloc::free_aligned(self.data, self.capacity) }; } } impl PartialEq for MutableBuffer { fn eq(&self, other: &MutableBuffer) -> bool { if self.len != other.len { return false; } if self.capacity != other.capacity { return false; } self.as_slice() == other.as_slice() } } unsafe impl Sync for MutableBuffer {} unsafe impl Send for MutableBuffer {} struct SetLenOnDrop<'a> { len: &'a mut usize, local_len: usize, } impl<'a> SetLenOnDrop<'a> { #[inline] fn new(len: &'a mut usize) -> Self { SetLenOnDrop { local_len: *len, len, } } } impl Drop for SetLenOnDrop<'_> { #[inline] fn drop(&mut self) { *self.len = self.local_len; } } /// Creating a `MutableBuffer` instance by setting bits according to the boolean values impl std::iter::FromIterator<bool> for MutableBuffer { fn from_iter<I>(iter: I) -> Self where I: IntoIterator<Item = bool>, { let mut iterator = iter.into_iter(); let mut result = { let byte_capacity: usize = iterator.size_hint().0.saturating_add(7) / 8; MutableBuffer::new(byte_capacity) }; loop { let mut exhausted = false; let mut byte_accum: u8 = 0; let mut mask: u8 = 1; //collect (up to) 8 bits into a byte while mask != 0 { if let Some(value) = iterator.next() { byte_accum |= match value { true => mask, false => 0, }; mask <<= 1; } else { exhausted = true; break; } } // break if the iterator was exhausted before it provided a bool for this byte if exhausted && mask == 1 { break; } //ensure we have capacity to write the byte if result.len() == result.capacity() { //no capacity for new byte, allocate 1 byte more (plus however many more the iterator advertises) let additional_byte_capacity = 1usize.saturating_add( iterator.size_hint().0.saturating_add(7) / 8, //convert bit count to byte count, rounding up ); result.reserve(additional_byte_capacity) } // Soundness: capacity was allocated above unsafe { result.push_unchecked(byte_accum) }; if exhausted { break; } } result } } #[cfg(test)] mod tests { use super::*; #[test] fn test_mutable_new() { let buf = MutableBuffer::new(63); assert_eq!(64, buf.capacity()); assert_eq!(0, buf.len()); assert!(buf.is_empty()); } #[test] fn test_mutable_extend_from_slice() { let mut buf = MutableBuffer::new(100); buf.extend_from_slice(b"hello"); assert_eq!(5, buf.len()); assert_eq!(b"hello", buf.as_slice()); buf.extend_from_slice(b" world"); assert_eq!(11, buf.len()); assert_eq!(b"hello world", buf.as_slice()); buf.clear(); assert_eq!(0, buf.len()); buf.extend_from_slice(b"hello arrow"); assert_eq!(11, buf.len()); assert_eq!(b"hello arrow", buf.as_slice()); } #[test] fn mutable_extend_from_iter() { let mut buf = MutableBuffer::new(0); buf.extend(vec![1u32, 2]); assert_eq!(8, buf.len()); assert_eq!(&[1u8, 0, 0, 0, 2, 0, 0, 0], buf.as_slice()); buf.extend(vec![3u32, 4]); assert_eq!(16, buf.len()); assert_eq!( &[1u8, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0], buf.as_slice() ); } #[test] fn test_from_trusted_len_iter() { let iter = vec![1u32, 2].into_iter(); let buf = unsafe { Buffer::from_trusted_len_iter(iter) }; assert_eq!(8, buf.len()); assert_eq!(&[1u8, 0, 0, 0, 2, 0, 0, 0], buf.as_slice()); } #[test] fn test_mutable_reserve() { let mut buf = MutableBuffer::new(1); assert_eq!(64, buf.capacity()); // Reserving a smaller capacity should have no effect. buf.reserve(10); assert_eq!(64, buf.capacity()); buf.reserve(80); assert_eq!(128, buf.capacity()); buf.reserve(129); assert_eq!(256, buf.capacity()); } #[test] fn test_mutable_resize() { let mut buf = MutableBuffer::new(1); assert_eq!(64, buf.capacity()); assert_eq!(0, buf.len()); buf.resize(20, 0); assert_eq!(64, buf.capacity()); assert_eq!(20, buf.len()); buf.resize(10, 0); assert_eq!(64, buf.capacity()); assert_eq!(10, buf.len()); buf.resize(100, 0); assert_eq!(128, buf.capacity()); assert_eq!(100, buf.len()); buf.resize(30, 0); assert_eq!(128, buf.capacity()); assert_eq!(30, buf.len()); buf.resize(0, 0); assert_eq!(128, buf.capacity()); assert_eq!(0, buf.len()); } #[test] fn test_mutable_into() { let mut buf = MutableBuffer::new(1); buf.extend_from_slice(b"aaaa bbbb cccc dddd"); assert_eq!(19, buf.len()); assert_eq!(64, buf.capacity()); assert_eq!(b"aaaa bbbb cccc dddd", buf.as_slice()); let immutable_buf: Buffer = buf.into(); assert_eq!(19, immutable_buf.len()); assert_eq!(64, immutable_buf.capacity()); assert_eq!(b"aaaa bbbb cccc dddd", immutable_buf.as_slice()); } #[test] fn test_mutable_equal() { let mut buf = MutableBuffer::new(1); let mut buf2 = MutableBuffer::new(1); buf.extend_from_slice(&[0xaa]); buf2.extend_from_slice(&[0xaa, 0xbb]); assert!(buf != buf2); buf.extend_from_slice(&[0xbb]); assert_eq!(buf, buf2); buf2.reserve(65); assert!(buf != buf2); } }