1 use crate::io::prelude::*;
4 use crate::io::{self, Error, ErrorKind, Initializer, IoSlice, IoSliceMut, SeekFrom};
6 use core::convert::TryInto;
8 /// A `Cursor` wraps an in-memory buffer and provides it with a
9 /// [`Seek`] implementation.
11 /// `Cursor`s are used with in-memory buffers, anything implementing
12 /// `AsRef<[u8]>`, to allow them to implement [`Read`] and/or [`Write`],
13 /// allowing these buffers to be used anywhere you might use a reader or writer
14 /// that does actual I/O.
16 /// The standard library implements some I/O traits on various types which
17 /// are commonly used as a buffer, like `Cursor<`[`Vec`]`<u8>>` and
18 /// `Cursor<`[`&[u8]`][bytes]`>`.
22 /// We may want to write bytes to a [`File`] in our production
23 /// code, but use an in-memory buffer in our tests. We can do this with
26 /// [`Seek`]: trait.Seek.html
27 /// [`Read`]: ../../std/io/trait.Read.html
28 /// [`Write`]: ../../std/io/trait.Write.html
29 /// [`Vec`]: ../../std/vec/struct.Vec.html
30 /// [bytes]: ../../std/primitive.slice.html
31 /// [`File`]: ../fs/struct.File.html
34 /// use std::io::prelude::*;
35 /// use std::io::{self, SeekFrom};
36 /// use std::fs::File;
38 /// // a library function we've written
39 /// fn write_ten_bytes_at_end<W: Write + Seek>(writer: &mut W) -> io::Result<()> {
40 /// writer.seek(SeekFrom::End(-10))?;
43 /// writer.write(&[i])?;
50 /// # fn foo() -> io::Result<()> {
51 /// // Here's some code that uses this library function.
53 /// // We might want to use a BufReader here for efficiency, but let's
54 /// // keep this example focused.
55 /// let mut file = File::create("foo.txt")?;
57 /// write_ten_bytes_at_end(&mut file)?;
61 /// // now let's write a test
63 /// fn test_writes_bytes() {
64 /// // setting up a real File is much slower than an in-memory buffer,
65 /// // let's use a cursor instead
66 /// use std::io::Cursor;
67 /// let mut buff = Cursor::new(vec![0; 15]);
69 /// write_ten_bytes_at_end(&mut buff).unwrap();
71 /// assert_eq!(&buff.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
74 #[stable(feature = "rust1", since = "1.0.0")]
75 #[derive(Clone, Debug, Default, Eq, PartialEq)]
76 pub struct Cursor<T> {
82 /// Creates a new cursor wrapping the provided underlying in-memory buffer.
84 /// Cursor initial position is `0` even if underlying buffer (e.g., `Vec`)
85 /// is not empty. So writing to cursor starts with overwriting `Vec`
86 /// content, not with appending to it.
91 /// use std::io::Cursor;
93 /// let buff = Cursor::new(Vec::new());
94 /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
95 /// # force_inference(&buff);
97 #[stable(feature = "rust1", since = "1.0.0")]
98 pub fn new(inner: T) -> Cursor<T> {
99 Cursor { pos: 0, inner: inner }
102 /// Consumes this cursor, returning the underlying value.
107 /// use std::io::Cursor;
109 /// let buff = Cursor::new(Vec::new());
110 /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
111 /// # force_inference(&buff);
113 /// let vec = buff.into_inner();
115 #[stable(feature = "rust1", since = "1.0.0")]
116 pub fn into_inner(self) -> T {
120 /// Gets a reference to the underlying value in this cursor.
125 /// use std::io::Cursor;
127 /// let buff = Cursor::new(Vec::new());
128 /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
129 /// # force_inference(&buff);
131 /// let reference = buff.get_ref();
133 #[stable(feature = "rust1", since = "1.0.0")]
134 pub fn get_ref(&self) -> &T {
138 /// Gets a mutable reference to the underlying value in this cursor.
140 /// Care should be taken to avoid modifying the internal I/O state of the
141 /// underlying value as it may corrupt this cursor's position.
146 /// use std::io::Cursor;
148 /// let mut buff = Cursor::new(Vec::new());
149 /// # fn force_inference(_: &Cursor<Vec<u8>>) {}
150 /// # force_inference(&buff);
152 /// let reference = buff.get_mut();
154 #[stable(feature = "rust1", since = "1.0.0")]
155 pub fn get_mut(&mut self) -> &mut T {
159 /// Returns the current position of this cursor.
164 /// use std::io::Cursor;
165 /// use std::io::prelude::*;
166 /// use std::io::SeekFrom;
168 /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
170 /// assert_eq!(buff.position(), 0);
172 /// buff.seek(SeekFrom::Current(2)).unwrap();
173 /// assert_eq!(buff.position(), 2);
175 /// buff.seek(SeekFrom::Current(-1)).unwrap();
176 /// assert_eq!(buff.position(), 1);
178 #[stable(feature = "rust1", since = "1.0.0")]
179 pub fn position(&self) -> u64 {
183 /// Sets the position of this cursor.
188 /// use std::io::Cursor;
190 /// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
192 /// assert_eq!(buff.position(), 0);
194 /// buff.set_position(2);
195 /// assert_eq!(buff.position(), 2);
197 /// buff.set_position(4);
198 /// assert_eq!(buff.position(), 4);
200 #[stable(feature = "rust1", since = "1.0.0")]
201 pub fn set_position(&mut self, pos: u64) {
206 #[stable(feature = "rust1", since = "1.0.0")]
207 impl<T> io::Seek for Cursor<T>
211 fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
212 let (base_pos, offset) = match style {
213 SeekFrom::Start(n) => {
217 SeekFrom::End(n) => (self.inner.as_ref().len() as u64, n),
218 SeekFrom::Current(n) => (self.pos, n),
220 let new_pos = if offset >= 0 {
221 base_pos.checked_add(offset as u64)
223 base_pos.checked_sub((offset.wrapping_neg()) as u64)
230 None => Err(Error::new(
231 ErrorKind::InvalidInput,
232 "invalid seek to a negative or overflowing position",
237 fn stream_len(&mut self) -> io::Result<u64> {
238 Ok(self.inner.as_ref().len() as u64)
241 fn stream_position(&mut self) -> io::Result<u64> {
246 #[stable(feature = "rust1", since = "1.0.0")]
247 impl<T> Read for Cursor<T>
251 fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
252 let n = Read::read(&mut self.fill_buf()?, buf)?;
253 self.pos += n as u64;
257 fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
260 let n = self.read(buf)?;
269 fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
271 Read::read_exact(&mut self.fill_buf()?, buf)?;
272 self.pos += n as u64;
277 unsafe fn initializer(&self) -> Initializer {
282 #[stable(feature = "rust1", since = "1.0.0")]
283 impl<T> BufRead for Cursor<T>
287 fn fill_buf(&mut self) -> io::Result<&[u8]> {
288 let amt = cmp::min(self.pos, self.inner.as_ref().len() as u64);
289 Ok(&self.inner.as_ref()[(amt as usize)..])
291 fn consume(&mut self, amt: usize) {
292 self.pos += amt as u64;
296 // Non-resizing write implementation
298 fn slice_write(pos_mut: &mut u64, slice: &mut [u8], buf: &[u8]) -> io::Result<usize> {
299 let pos = cmp::min(*pos_mut, slice.len() as u64);
300 let amt = (&mut slice[(pos as usize)..]).write(buf)?;
301 *pos_mut += amt as u64;
306 fn slice_write_vectored(
309 bufs: &[IoSlice<'_>],
310 ) -> io::Result<usize> {
311 let mut nwritten = 0;
313 let n = slice_write(pos_mut, slice, buf)?;
322 // Resizing write implementation
323 fn vec_write(pos_mut: &mut u64, vec: &mut Vec<u8>, buf: &[u8]) -> io::Result<usize> {
324 let pos: usize = (*pos_mut).try_into().map_err(|_| {
326 ErrorKind::InvalidInput,
327 "cursor position exceeds maximum possible vector length",
330 // Make sure the internal buffer is as least as big as where we
334 // use `resize` so that the zero filling is as efficient as possible
337 // Figure out what bytes will be used to overwrite what's currently
338 // there (left), and what will be appended on the end (right)
340 let space = vec.len() - pos;
341 let (left, right) = buf.split_at(cmp::min(space, buf.len()));
342 vec[pos..pos + left.len()].copy_from_slice(left);
343 vec.extend_from_slice(right);
347 *pos_mut = (pos + buf.len()) as u64;
351 fn vec_write_vectored(
354 bufs: &[IoSlice<'_>],
355 ) -> io::Result<usize> {
356 let mut nwritten = 0;
358 nwritten += vec_write(pos_mut, vec, buf)?;
363 #[stable(feature = "rust1", since = "1.0.0")]
364 impl Write for Cursor<&mut [u8]> {
366 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
367 slice_write(&mut self.pos, self.inner, buf)
371 fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
372 slice_write_vectored(&mut self.pos, self.inner, bufs)
376 fn flush(&mut self) -> io::Result<()> {
381 #[stable(feature = "cursor_mut_vec", since = "1.25.0")]
382 impl Write for Cursor<&mut Vec<u8>> {
383 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
384 vec_write(&mut self.pos, self.inner, buf)
387 fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
388 vec_write_vectored(&mut self.pos, self.inner, bufs)
392 fn flush(&mut self) -> io::Result<()> {
397 #[stable(feature = "rust1", since = "1.0.0")]
398 impl Write for Cursor<Vec<u8>> {
399 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
400 vec_write(&mut self.pos, &mut self.inner, buf)
403 fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
404 vec_write_vectored(&mut self.pos, &mut self.inner, bufs)
408 fn flush(&mut self) -> io::Result<()> {
413 #[stable(feature = "cursor_box_slice", since = "1.5.0")]
414 impl Write for Cursor<Box<[u8]>> {
416 fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
417 slice_write(&mut self.pos, &mut self.inner, buf)
421 fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
422 slice_write_vectored(&mut self.pos, &mut self.inner, bufs)
426 fn flush(&mut self) -> io::Result<()> {
433 use crate::io::prelude::*;
434 use crate::io::{Cursor, IoSlice, IoSliceMut, SeekFrom};
437 fn test_vec_writer() {
438 let mut writer = Vec::new();
439 assert_eq!(writer.write(&[0]).unwrap(), 1);
440 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
441 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
444 .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
448 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
449 assert_eq!(writer, b);
453 fn test_mem_writer() {
454 let mut writer = Cursor::new(Vec::new());
455 assert_eq!(writer.write(&[0]).unwrap(), 1);
456 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
457 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
460 .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
464 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
465 assert_eq!(&writer.get_ref()[..], b);
469 fn test_mem_mut_writer() {
470 let mut vec = Vec::new();
471 let mut writer = Cursor::new(&mut vec);
472 assert_eq!(writer.write(&[0]).unwrap(), 1);
473 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
474 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
477 .write_vectored(&[IoSlice::new(&[]), IoSlice::new(&[8, 9]), IoSlice::new(&[10])],)
481 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
482 assert_eq!(&writer.get_ref()[..], b);
486 fn test_box_slice_writer() {
487 let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
488 assert_eq!(writer.position(), 0);
489 assert_eq!(writer.write(&[0]).unwrap(), 1);
490 assert_eq!(writer.position(), 1);
491 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
492 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
493 assert_eq!(writer.position(), 8);
494 assert_eq!(writer.write(&[]).unwrap(), 0);
495 assert_eq!(writer.position(), 8);
497 assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
498 assert_eq!(writer.write(&[10]).unwrap(), 0);
499 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
500 assert_eq!(&**writer.get_ref(), b);
504 fn test_box_slice_writer_vectored() {
505 let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
506 assert_eq!(writer.position(), 0);
507 assert_eq!(writer.write_vectored(&[IoSlice::new(&[0])]).unwrap(), 1);
508 assert_eq!(writer.position(), 1);
511 .write_vectored(&[IoSlice::new(&[1, 2, 3]), IoSlice::new(&[4, 5, 6, 7]),])
515 assert_eq!(writer.position(), 8);
516 assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
517 assert_eq!(writer.position(), 8);
519 assert_eq!(writer.write_vectored(&[IoSlice::new(&[8, 9])]).unwrap(), 1);
520 assert_eq!(writer.write_vectored(&[IoSlice::new(&[10])]).unwrap(), 0);
521 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
522 assert_eq!(&**writer.get_ref(), b);
526 fn test_buf_writer() {
527 let mut buf = [0 as u8; 9];
529 let mut writer = Cursor::new(&mut buf[..]);
530 assert_eq!(writer.position(), 0);
531 assert_eq!(writer.write(&[0]).unwrap(), 1);
532 assert_eq!(writer.position(), 1);
533 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
534 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
535 assert_eq!(writer.position(), 8);
536 assert_eq!(writer.write(&[]).unwrap(), 0);
537 assert_eq!(writer.position(), 8);
539 assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
540 assert_eq!(writer.write(&[10]).unwrap(), 0);
542 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
547 fn test_buf_writer_vectored() {
548 let mut buf = [0 as u8; 9];
550 let mut writer = Cursor::new(&mut buf[..]);
551 assert_eq!(writer.position(), 0);
552 assert_eq!(writer.write_vectored(&[IoSlice::new(&[0])]).unwrap(), 1);
553 assert_eq!(writer.position(), 1);
556 .write_vectored(&[IoSlice::new(&[1, 2, 3]), IoSlice::new(&[4, 5, 6, 7])],)
560 assert_eq!(writer.position(), 8);
561 assert_eq!(writer.write_vectored(&[]).unwrap(), 0);
562 assert_eq!(writer.position(), 8);
564 assert_eq!(writer.write_vectored(&[IoSlice::new(&[8, 9])]).unwrap(), 1);
565 assert_eq!(writer.write_vectored(&[IoSlice::new(&[10])]).unwrap(), 0);
567 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
572 fn test_buf_writer_seek() {
573 let mut buf = [0 as u8; 8];
575 let mut writer = Cursor::new(&mut buf[..]);
576 assert_eq!(writer.position(), 0);
577 assert_eq!(writer.write(&[1]).unwrap(), 1);
578 assert_eq!(writer.position(), 1);
580 assert_eq!(writer.seek(SeekFrom::Start(2)).unwrap(), 2);
581 assert_eq!(writer.position(), 2);
582 assert_eq!(writer.write(&[2]).unwrap(), 1);
583 assert_eq!(writer.position(), 3);
585 assert_eq!(writer.seek(SeekFrom::Current(-2)).unwrap(), 1);
586 assert_eq!(writer.position(), 1);
587 assert_eq!(writer.write(&[3]).unwrap(), 1);
588 assert_eq!(writer.position(), 2);
590 assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
591 assert_eq!(writer.position(), 7);
592 assert_eq!(writer.write(&[4]).unwrap(), 1);
593 assert_eq!(writer.position(), 8);
595 let b: &[_] = &[1, 3, 2, 0, 0, 0, 0, 4];
600 fn test_buf_writer_error() {
601 let mut buf = [0 as u8; 2];
602 let mut writer = Cursor::new(&mut buf[..]);
603 assert_eq!(writer.write(&[0]).unwrap(), 1);
604 assert_eq!(writer.write(&[0, 0]).unwrap(), 1);
605 assert_eq!(writer.write(&[0, 0]).unwrap(), 0);
609 fn test_mem_reader() {
610 let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
612 assert_eq!(reader.read(&mut buf).unwrap(), 0);
613 assert_eq!(reader.position(), 0);
615 assert_eq!(reader.read(&mut buf).unwrap(), 1);
616 assert_eq!(reader.position(), 1);
619 let mut buf = [0; 4];
620 assert_eq!(reader.read(&mut buf).unwrap(), 4);
621 assert_eq!(reader.position(), 5);
622 let b: &[_] = &[1, 2, 3, 4];
624 assert_eq!(reader.read(&mut buf).unwrap(), 3);
625 let b: &[_] = &[5, 6, 7];
626 assert_eq!(&buf[..3], b);
627 assert_eq!(reader.read(&mut buf).unwrap(), 0);
631 fn test_mem_reader_vectored() {
632 let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
634 assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
635 assert_eq!(reader.position(), 0);
639 .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
643 assert_eq!(reader.position(), 1);
646 let mut buf1 = [0; 4];
647 let mut buf2 = [0; 4];
650 .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2),])
654 let b1: &[_] = &[1, 2, 3, 4];
655 let b2: &[_] = &[5, 6, 7];
656 assert_eq!(buf1, b1);
657 assert_eq!(&buf2[..3], b2);
658 assert_eq!(reader.read(&mut buf).unwrap(), 0);
662 fn test_boxed_slice_reader() {
663 let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
665 assert_eq!(reader.read(&mut buf).unwrap(), 0);
666 assert_eq!(reader.position(), 0);
668 assert_eq!(reader.read(&mut buf).unwrap(), 1);
669 assert_eq!(reader.position(), 1);
672 let mut buf = [0; 4];
673 assert_eq!(reader.read(&mut buf).unwrap(), 4);
674 assert_eq!(reader.position(), 5);
675 let b: &[_] = &[1, 2, 3, 4];
677 assert_eq!(reader.read(&mut buf).unwrap(), 3);
678 let b: &[_] = &[5, 6, 7];
679 assert_eq!(&buf[..3], b);
680 assert_eq!(reader.read(&mut buf).unwrap(), 0);
684 fn test_boxed_slice_reader_vectored() {
685 let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
687 assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
688 assert_eq!(reader.position(), 0);
692 .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
696 assert_eq!(reader.position(), 1);
699 let mut buf1 = [0; 4];
700 let mut buf2 = [0; 4];
703 .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
707 let b1: &[_] = &[1, 2, 3, 4];
708 let b2: &[_] = &[5, 6, 7];
709 assert_eq!(buf1, b1);
710 assert_eq!(&buf2[..3], b2);
711 assert_eq!(reader.read(&mut buf).unwrap(), 0);
716 let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
717 let mut v = Vec::new();
718 reader.read_to_end(&mut v).unwrap();
719 assert_eq!(v, [0, 1, 2, 3, 4, 5, 6, 7]);
723 fn test_slice_reader() {
724 let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
725 let reader = &mut &in_buf[..];
727 assert_eq!(reader.read(&mut buf).unwrap(), 0);
729 assert_eq!(reader.read(&mut buf).unwrap(), 1);
730 assert_eq!(reader.len(), 7);
732 assert_eq!(&buf[..], b);
733 let mut buf = [0; 4];
734 assert_eq!(reader.read(&mut buf).unwrap(), 4);
735 assert_eq!(reader.len(), 3);
736 let b: &[_] = &[1, 2, 3, 4];
737 assert_eq!(&buf[..], b);
738 assert_eq!(reader.read(&mut buf).unwrap(), 3);
739 let b: &[_] = &[5, 6, 7];
740 assert_eq!(&buf[..3], b);
741 assert_eq!(reader.read(&mut buf).unwrap(), 0);
745 fn test_slice_reader_vectored() {
746 let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
747 let reader = &mut &in_buf[..];
749 assert_eq!(reader.read_vectored(&mut [IoSliceMut::new(&mut buf)]).unwrap(), 0);
753 .read_vectored(&mut [IoSliceMut::new(&mut []), IoSliceMut::new(&mut buf),])
757 assert_eq!(reader.len(), 7);
760 let mut buf1 = [0; 4];
761 let mut buf2 = [0; 4];
764 .read_vectored(&mut [IoSliceMut::new(&mut buf1), IoSliceMut::new(&mut buf2)],)
768 let b1: &[_] = &[1, 2, 3, 4];
769 let b2: &[_] = &[5, 6, 7];
770 assert_eq!(buf1, b1);
771 assert_eq!(&buf2[..3], b2);
772 assert_eq!(reader.read(&mut buf).unwrap(), 0);
776 fn test_read_exact() {
777 let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
778 let reader = &mut &in_buf[..];
780 assert!(reader.read_exact(&mut buf).is_ok());
782 assert!(reader.read_exact(&mut buf).is_ok());
783 assert_eq!(buf[0], 0);
784 assert_eq!(reader.len(), 7);
785 let mut buf = [0, 0, 0, 0, 0, 0, 0];
786 assert!(reader.read_exact(&mut buf).is_ok());
787 assert_eq!(buf, [1, 2, 3, 4, 5, 6, 7]);
788 assert_eq!(reader.len(), 0);
790 assert!(reader.read_exact(&mut buf).is_err());
794 fn test_buf_reader() {
795 let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
796 let mut reader = Cursor::new(&in_buf[..]);
798 assert_eq!(reader.read(&mut buf).unwrap(), 0);
799 assert_eq!(reader.position(), 0);
801 assert_eq!(reader.read(&mut buf).unwrap(), 1);
802 assert_eq!(reader.position(), 1);
805 let mut buf = [0; 4];
806 assert_eq!(reader.read(&mut buf).unwrap(), 4);
807 assert_eq!(reader.position(), 5);
808 let b: &[_] = &[1, 2, 3, 4];
810 assert_eq!(reader.read(&mut buf).unwrap(), 3);
811 let b: &[_] = &[5, 6, 7];
812 assert_eq!(&buf[..3], b);
813 assert_eq!(reader.read(&mut buf).unwrap(), 0);
819 let mut r = Cursor::new(&buf[..]);
820 assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
821 assert_eq!(r.read(&mut [0]).unwrap(), 0);
823 let mut r = Cursor::new(vec![10]);
824 assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
825 assert_eq!(r.read(&mut [0]).unwrap(), 0);
828 let mut r = Cursor::new(&mut buf[..]);
829 assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
830 assert_eq!(r.write(&[3]).unwrap(), 0);
832 let mut r = Cursor::new(vec![10].into_boxed_slice());
833 assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
834 assert_eq!(r.write(&[3]).unwrap(), 0);
840 let mut r = Cursor::new(&buf[..]);
841 assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
842 assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
843 assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
844 assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
845 assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
846 assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
848 let mut r = Cursor::new(vec![10]);
849 assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
850 assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
851 assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
852 assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
853 assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
854 assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
857 let mut r = Cursor::new(&mut buf[..]);
858 assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
859 assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
860 assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
861 assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
862 assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
863 assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
865 let mut r = Cursor::new(vec![10].into_boxed_slice());
866 assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
867 assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
868 assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
869 assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
870 assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
871 assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
877 let mut r = Cursor::new(&buf[..]);
878 assert!(r.seek(SeekFrom::End(-2)).is_err());
880 let mut r = Cursor::new(vec![10]);
881 assert!(r.seek(SeekFrom::End(-2)).is_err());
884 let mut r = Cursor::new(&mut buf[..]);
885 assert!(r.seek(SeekFrom::End(-2)).is_err());
887 let mut r = Cursor::new(vec![10].into_boxed_slice());
888 assert!(r.seek(SeekFrom::End(-2)).is_err());
892 fn test_seekable_mem_writer() {
893 let mut writer = Cursor::new(Vec::<u8>::new());
894 assert_eq!(writer.position(), 0);
895 assert_eq!(writer.write(&[0]).unwrap(), 1);
896 assert_eq!(writer.position(), 1);
897 assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
898 assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
899 assert_eq!(writer.position(), 8);
900 let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
901 assert_eq!(&writer.get_ref()[..], b);
903 assert_eq!(writer.seek(SeekFrom::Start(0)).unwrap(), 0);
904 assert_eq!(writer.position(), 0);
905 assert_eq!(writer.write(&[3, 4]).unwrap(), 2);
906 let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
907 assert_eq!(&writer.get_ref()[..], b);
909 assert_eq!(writer.seek(SeekFrom::Current(1)).unwrap(), 3);
910 assert_eq!(writer.write(&[0, 1]).unwrap(), 2);
911 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
912 assert_eq!(&writer.get_ref()[..], b);
914 assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
915 assert_eq!(writer.write(&[1, 2]).unwrap(), 2);
916 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
917 assert_eq!(&writer.get_ref()[..], b);
919 assert_eq!(writer.seek(SeekFrom::End(1)).unwrap(), 10);
920 assert_eq!(writer.write(&[1]).unwrap(), 1);
921 let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
922 assert_eq!(&writer.get_ref()[..], b);
926 fn vec_seek_past_end() {
927 let mut r = Cursor::new(Vec::new());
928 assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
929 assert_eq!(r.write(&[3]).unwrap(), 1);
933 fn vec_seek_before_0() {
934 let mut r = Cursor::new(Vec::new());
935 assert!(r.seek(SeekFrom::End(-2)).is_err());
939 #[cfg(target_pointer_width = "32")]
940 fn vec_seek_and_write_past_usize_max() {
941 let mut c = Cursor::new(Vec::new());
942 c.set_position(<usize>::max_value() as u64 + 1);
943 assert!(c.write_all(&[1, 2, 3]).is_err());
947 fn test_partial_eq() {
948 assert_eq!(Cursor::new(Vec::<u8>::new()), Cursor::new(Vec::<u8>::new()));
953 struct AssertEq<T: Eq>(pub T);
955 let _: AssertEq<Cursor<Vec<u8>>> = AssertEq(Cursor::new(Vec::new()));