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ecbb896b9eb2acadefde57be493e4298c1aa04a3
rust/src/libstd/io/cursor.rs
Steven Fackler ecbb896b9e Add Read::initializer. 
This is an API that allows types to indicate that they can be passed
buffers of uninitialized memory which can improve performance.
2017-06-20 20:26:22 -07:00

649 lines
22 KiB
Rust
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use io::prelude::*;
use core::convert::TryInto;
use cmp;
use io::{self, Initializer, SeekFrom, Error, ErrorKind};
/// A `Cursor` wraps another type and provides it with a
/// [`Seek`] implementation.
///
/// `Cursor`s are typically used with in-memory buffers to allow them to
/// implement [`Read`] and/or [`Write`], allowing these buffers to be used
/// anywhere you might use a reader or writer that does actual I/O.
///
/// The standard library implements some I/O traits on various types which
/// are commonly used as a buffer, like `Cursor<`[`Vec`]`<u8>>` and
/// `Cursor<`[`&[u8]`][bytes]`>`.
///
/// # Examples
///
/// We may want to write bytes to a [`File`] in our production
/// code, but use an in-memory buffer in our tests. We can do this with
/// `Cursor`:
///
/// [`Seek`]: trait.Seek.html
/// [`Read`]: ../../std/io/trait.Read.html
/// [`Write`]: ../../std/io/trait.Write.html
/// [`Vec`]: ../../std/vec/struct.Vec.html
/// [bytes]: ../../std/primitive.slice.html
/// [`File`]: ../fs/struct.File.html
///
/// ```no_run
/// use std::io::prelude::*;
/// use std::io::{self, SeekFrom};
/// use std::fs::File;
///
/// // a library function we've written
/// fn write_ten_bytes_at_end<W: Write + Seek>(writer: &mut W) -> io::Result<()> {
/// writer.seek(SeekFrom::End(-10))?;
///
/// for i in 0..10 {
/// writer.write(&[i])?;
/// }
///
/// // all went well
/// Ok(())
/// }
///
/// # fn foo() -> io::Result<()> {
/// // Here's some code that uses this library function.
/// //
/// // We might want to use a BufReader here for efficiency, but let's
/// // keep this example focused.
/// let mut file = File::create("foo.txt")?;
///
/// write_ten_bytes_at_end(&mut file)?;
/// # Ok(())
/// # }
///
/// // now let's write a test
/// #[test]
/// fn test_writes_bytes() {
/// // setting up a real File is much more slow than an in-memory buffer,
/// // let's use a cursor instead
/// use std::io::Cursor;
/// let mut buff = Cursor::new(vec![0; 15]);
///
/// write_ten_bytes_at_end(&mut buff).unwrap();
///
/// assert_eq!(&buff.get_ref()[5..15], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone, Debug)]
pub struct Cursor<T> {
inner: T,
pos: u64,
}
impl<T> Cursor<T> {
/// Creates a new cursor wrapping the provided underlying I/O object.
///
/// Cursor initial position is `0` even if underlying object (e.
/// g. `Vec`) is not empty. So writing to cursor starts with
/// overwriting `Vec` content, not with appending to it.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn new(inner: T) -> Cursor<T> {
Cursor { pos: 0, inner: inner }
}
/// Consumes this cursor, returning the underlying value.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let vec = buff.into_inner();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_inner(self) -> T { self.inner }
/// Gets a reference to the underlying value in this cursor.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
///
/// let buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_ref();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_ref(&self) -> &T { &self.inner }
/// Gets a mutable reference to the underlying value in this cursor.
///
/// Care should be taken to avoid modifying the internal I/O state of the
/// underlying value as it may corrupt this cursor's position.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
///
/// let mut buff = Cursor::new(Vec::new());
/// # fn force_inference(_: &Cursor<Vec<u8>>) {}
/// # force_inference(&buff);
///
/// let reference = buff.get_mut();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn get_mut(&mut self) -> &mut T { &mut self.inner }
/// Returns the current position of this cursor.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
/// use std::io::prelude::*;
/// use std::io::SeekFrom;
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.seek(SeekFrom::Current(2)).unwrap();
/// assert_eq!(buff.position(), 2);
///
/// buff.seek(SeekFrom::Current(-1)).unwrap();
/// assert_eq!(buff.position(), 1);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn position(&self) -> u64 { self.pos }
/// Sets the position of this cursor.
///
/// # Examples
///
/// ```
/// use std::io::Cursor;
///
/// let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);
///
/// assert_eq!(buff.position(), 0);
///
/// buff.set_position(2);
/// assert_eq!(buff.position(), 2);
///
/// buff.set_position(4);
/// assert_eq!(buff.position(), 4);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn set_position(&mut self, pos: u64) { self.pos = pos; }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> io::Seek for Cursor<T> where T: AsRef<[u8]> {
fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
let (base_pos, offset) = match style {
SeekFrom::Start(n) => { self.pos = n; return Ok(n); }
SeekFrom::End(n) => (self.inner.as_ref().len() as u64, n),
SeekFrom::Current(n) => (self.pos, n),
};
let new_pos = if offset >= 0 {
base_pos.checked_add(offset as u64)
} else {
base_pos.checked_sub((offset.wrapping_neg()) as u64)
};
match new_pos {
Some(n) => {self.pos = n; Ok(self.pos)}
None => Err(Error::new(ErrorKind::InvalidInput,
"invalid seek to a negative or overflowing position"))
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Read for Cursor<T> where T: AsRef<[u8]> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let n = Read::read(&mut self.fill_buf()?, buf)?;
self.pos += n as u64;
Ok(n)
}
#[inline]
unsafe fn initializer(&self) -> Initializer {
Initializer::nop()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> BufRead for Cursor<T> where T: AsRef<[u8]> {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
let amt = cmp::min(self.pos, self.inner.as_ref().len() as u64);
Ok(&self.inner.as_ref()[(amt as usize)..])
}
fn consume(&mut self, amt: usize) { self.pos += amt as u64; }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> Write for Cursor<&'a mut [u8]> {
#[inline]
fn write(&mut self, data: &[u8]) -> io::Result<usize> {
let pos = cmp::min(self.pos, self.inner.len() as u64);
let amt = (&mut self.inner[(pos as usize)..]).write(data)?;
self.pos += amt as u64;
Ok(amt)
}
fn flush(&mut self) -> io::Result<()> { Ok(()) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl Write for Cursor<Vec<u8>> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let pos: usize = self.position().try_into().map_err(|_| {
Error::new(ErrorKind::InvalidInput,
"cursor position exceeds maximum possible vector length")
})?;
// Make sure the internal buffer is as least as big as where we
// currently are
let len = self.inner.len();
if len < pos {
// use `resize` so that the zero filling is as efficient as possible
self.inner.resize(pos, 0);
}
// Figure out what bytes will be used to overwrite what's currently
// there (left), and what will be appended on the end (right)
{
let space = self.inner.len() - pos;
let (left, right) = buf.split_at(cmp::min(space, buf.len()));
self.inner[pos..pos + left.len()].copy_from_slice(left);
self.inner.extend_from_slice(right);
}
// Bump us forward
self.set_position((pos + buf.len()) as u64);
Ok(buf.len())
}
fn flush(&mut self) -> io::Result<()> { Ok(()) }
}
#[stable(feature = "cursor_box_slice", since = "1.5.0")]
impl Write for Cursor<Box<[u8]>> {
#[inline]
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
let pos = cmp::min(self.pos, self.inner.len() as u64);
let amt = (&mut self.inner[(pos as usize)..]).write(buf)?;
self.pos += amt as u64;
Ok(amt)
}
fn flush(&mut self) -> io::Result<()> { Ok(()) }
}
#[cfg(test)]
mod tests {
use io::prelude::*;
use io::{Cursor, SeekFrom};
#[test]
fn test_vec_writer() {
let mut writer = Vec::new();
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
assert_eq!(writer, b);
}
#[test]
fn test_mem_writer() {
let mut writer = Cursor::new(Vec::new());
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
}
#[test]
fn test_box_slice_writer() {
let mut writer = Cursor::new(vec![0u8; 9].into_boxed_slice());
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[]).unwrap(), 0);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
assert_eq!(writer.write(&[10]).unwrap(), 0);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
assert_eq!(&**writer.get_ref(), b);
}
#[test]
fn test_buf_writer() {
let mut buf = [0 as u8; 9];
{
let mut writer = Cursor::new(&mut buf[..]);
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[]).unwrap(), 0);
assert_eq!(writer.position(), 8);
assert_eq!(writer.write(&[8, 9]).unwrap(), 1);
assert_eq!(writer.write(&[10]).unwrap(), 0);
}
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7, 8];
assert_eq!(buf, b);
}
#[test]
fn test_buf_writer_seek() {
let mut buf = [0 as u8; 8];
{
let mut writer = Cursor::new(&mut buf[..]);
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[1]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.seek(SeekFrom::Start(2)).unwrap(), 2);
assert_eq!(writer.position(), 2);
assert_eq!(writer.write(&[2]).unwrap(), 1);
assert_eq!(writer.position(), 3);
assert_eq!(writer.seek(SeekFrom::Current(-2)).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[3]).unwrap(), 1);
assert_eq!(writer.position(), 2);
assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
assert_eq!(writer.position(), 7);
assert_eq!(writer.write(&[4]).unwrap(), 1);
assert_eq!(writer.position(), 8);
}
let b: &[_] = &[1, 3, 2, 0, 0, 0, 0, 4];
assert_eq!(buf, b);
}
#[test]
fn test_buf_writer_error() {
let mut buf = [0 as u8; 2];
let mut writer = Cursor::new(&mut buf[..]);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.write(&[0, 0]).unwrap(), 1);
assert_eq!(writer.write(&[0, 0]).unwrap(), 0);
}
#[test]
fn test_mem_reader() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_boxed_slice_reader() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7].into_boxed_slice());
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn read_to_end() {
let mut reader = Cursor::new(vec![0, 1, 2, 3, 4, 5, 6, 7]);
let mut v = Vec::new();
reader.read_to_end(&mut v).unwrap();
assert_eq!(v, [0, 1, 2, 3, 4, 5, 6, 7]);
}
#[test]
fn test_slice_reader() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let mut reader = &mut &in_buf[..];
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.len(), 7);
let b: &[_] = &[0];
assert_eq!(&buf[..], b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.len(), 3);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(&buf[..], b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_buf_reader() {
let in_buf = vec![0, 1, 2, 3, 4, 5, 6, 7];
let mut reader = Cursor::new(&in_buf[..]);
let mut buf = [];
assert_eq!(reader.read(&mut buf).unwrap(), 0);
assert_eq!(reader.position(), 0);
let mut buf = [0];
assert_eq!(reader.read(&mut buf).unwrap(), 1);
assert_eq!(reader.position(), 1);
let b: &[_] = &[0];
assert_eq!(buf, b);
let mut buf = [0; 4];
assert_eq!(reader.read(&mut buf).unwrap(), 4);
assert_eq!(reader.position(), 5);
let b: &[_] = &[1, 2, 3, 4];
assert_eq!(buf, b);
assert_eq!(reader.read(&mut buf).unwrap(), 3);
let b: &[_] = &[5, 6, 7];
assert_eq!(&buf[..3], b);
assert_eq!(reader.read(&mut buf).unwrap(), 0);
}
#[test]
fn test_read_char() {
let b = &b"Vi\xE1\xBB\x87t"[..];
let mut c = Cursor::new(b).chars();
assert_eq!(c.next().unwrap().unwrap(), 'V');
assert_eq!(c.next().unwrap().unwrap(), 'i');
assert_eq!(c.next().unwrap().unwrap(), 'ệ');
assert_eq!(c.next().unwrap().unwrap(), 't');
assert!(c.next().is_none());
}
#[test]
fn test_read_bad_char() {
let b = &b"\x80"[..];
let mut c = Cursor::new(b).chars();
assert!(c.next().unwrap().is_err());
}
#[test]
fn seek_past_end() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.read(&mut [0]).unwrap(), 0);
let mut r = Cursor::new(vec![10]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.read(&mut [0]).unwrap(), 0);
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 0);
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 0);
}
#[test]
fn seek_past_i64() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut r = Cursor::new(vec![10]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
}
#[test]
fn seek_before_0() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut r = Cursor::new(vec![10]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert!(r.seek(SeekFrom::End(-2)).is_err());
let mut r = Cursor::new(vec![10].into_boxed_slice());
assert!(r.seek(SeekFrom::End(-2)).is_err());
}
#[test]
fn test_seekable_mem_writer() {
let mut writer = Cursor::new(Vec::<u8>::new());
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[0]).unwrap(), 1);
assert_eq!(writer.position(), 1);
assert_eq!(writer.write(&[1, 2, 3]).unwrap(), 3);
assert_eq!(writer.write(&[4, 5, 6, 7]).unwrap(), 4);
assert_eq!(writer.position(), 8);
let b: &[_] = &[0, 1, 2, 3, 4, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::Start(0)).unwrap(), 0);
assert_eq!(writer.position(), 0);
assert_eq!(writer.write(&[3, 4]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 3, 4, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::Current(1)).unwrap(), 3);
assert_eq!(writer.write(&[0, 1]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 7];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::End(-1)).unwrap(), 7);
assert_eq!(writer.write(&[1, 2]).unwrap(), 2);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2];
assert_eq!(&writer.get_ref()[..], b);
assert_eq!(writer.seek(SeekFrom::End(1)).unwrap(), 10);
assert_eq!(writer.write(&[1]).unwrap(), 1);
let b: &[_] = &[3, 4, 2, 0, 1, 5, 6, 1, 2, 0, 1];
assert_eq!(&writer.get_ref()[..], b);
}
#[test]
fn vec_seek_past_end() {
let mut r = Cursor::new(Vec::new());
assert_eq!(r.seek(SeekFrom::Start(10)).unwrap(), 10);
assert_eq!(r.write(&[3]).unwrap(), 1);
}
#[test]
fn vec_seek_before_0() {
let mut r = Cursor::new(Vec::new());
assert!(r.seek(SeekFrom::End(-2)).is_err());
}
#[test]
#[cfg(target_pointer_width = "32")]
fn vec_seek_and_write_past_usize_max() {
let mut c = Cursor::new(Vec::new());
c.set_position(<usize>::max_value() as u64 + 1);
assert!(c.write_all(&[1, 2, 3]).is_err());
}
}
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