Struct microcrates_bytes::buf::Cursor
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pub struct Cursor<T> { /* fields omitted */ }
io::Cursor
type from std
vendored for use in no_std
environments
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]
>
.
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
:
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(()) } // 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)?; // now let's write a test #[test] fn test_writes_bytes() { // setting up a real File is much slower 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]); }
Methods
impl<T> Cursor<T>
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fn new(inner: T) -> Cursor<T>
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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 into_inner(self) -> T
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Consumes this cursor, returning the underlying value.
Examples
use std::io::Cursor; let buff = Cursor::new(Vec::new()); let vec = buff.into_inner();
fn get_ref(&self) -> &T
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Gets a reference to the underlying value in this cursor.
Examples
use std::io::Cursor; let buff = Cursor::new(Vec::new()); let reference = buff.get_ref();
fn get_mut(&mut self) -> &mut T
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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()); let reference = buff.get_mut();
fn position(&self) -> u64
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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);
fn set_position(&mut self, pos: u64)
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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);
Trait Implementations
impl<T: AsRef<[u8]>> Buf for Cursor<T>
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fn remaining(&self) -> usize
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Returns the number of bytes between the current position and the end of the buffer. Read more
fn bytes(&self) -> &[u8]
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Returns a slice starting at the current position and of length between 0 and Buf::remaining()
. Read more
fn advance(&mut self, cnt: usize)
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Advance the internal cursor of the Buf Read more
fn has_remaining(&self) -> bool
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Returns true if there are any more bytes to consume Read more
fn copy_to_slice(&mut self, dst: &mut [u8])
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Copies bytes from self
into dst
. Read more
fn get_u8(&mut self) -> u8
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Gets an unsigned 8 bit integer from self
. Read more
fn get_i8(&mut self) -> i8
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Gets a signed 8 bit integer from self
. Read more
fn get_u16<T: ByteOrder>(&mut self) -> u16
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Gets an unsigned 16 bit integer from self
in the specified byte order. Read more
fn get_i16<T: ByteOrder>(&mut self) -> i16
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Gets a signed 16 bit integer from self
in the specified byte order. Read more
fn get_u32<T: ByteOrder>(&mut self) -> u32
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Gets an unsigned 32 bit integer from self
in the specified byte order. Read more
fn get_i32<T: ByteOrder>(&mut self) -> i32
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Gets a signed 32 bit integer from self
in the specified byte order. Read more
fn get_u64<T: ByteOrder>(&mut self) -> u64
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Gets an unsigned 64 bit integer from self
in the specified byte order. Read more
fn get_i64<T: ByteOrder>(&mut self) -> i64
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Gets a signed 64 bit integer from self
in the specified byte order. Read more
fn get_uint<T: ByteOrder>(&mut self, nbytes: usize) -> u64
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Gets an unsigned n-byte integer from self
in the specified byte order. Read more
fn get_int<T: ByteOrder>(&mut self, nbytes: usize) -> i64
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Gets a signed n-byte integer from self
in the specified byte order. Read more
fn get_f32<T: ByteOrder>(&mut self) -> f32
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Gets an IEEE754 single-precision (4 bytes) floating point number from self
in the specified byte order. Read more
fn get_f64<T: ByteOrder>(&mut self) -> f64
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Gets an IEEE754 double-precision (8 bytes) floating point number from self
in the specified byte order. Read more
fn collect<B>(self) -> B where
Self: Sized,
B: FromBuf,
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Self: Sized,
B: FromBuf,
Transforms a Buf
into a concrete buffer. Read more
fn take(self, limit: usize) -> Take<Self> where
Self: Sized,
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Self: Sized,
Creates an adaptor which will read at most limit
bytes from self
. Read more
fn chain<U>(self, next: U) -> Chain<Self, U::Buf> where
U: IntoBuf,
Self: Sized,
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U: IntoBuf,
Self: Sized,
Creates an adaptor which will chain this buffer with another. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
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Self: Sized,
Creates a "by reference" adaptor for this instance of Buf
. Read more
fn reader(self) -> Reader<Self> where
Self: Sized,
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Self: Sized,
Creates an adaptor which implements the Read
trait for self
. Read more
fn iter(self) -> Iter<Self> where
Self: Sized,
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Self: Sized,
Returns an iterator over the bytes contained by the buffer. Read more
impl<T: AsMut<[u8]> + AsRef<[u8]>> BufMut for Cursor<T>
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fn remaining_mut(&self) -> usize
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Returns the number of bytes that can be written from the current position until the end of the buffer is reached. Read more
unsafe fn advance_mut(&mut self, cnt: usize)
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Advance the internal cursor of the BufMut
unsafe fn bytes_mut(&mut self) -> &mut [u8]
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Returns a mutable slice starting at the current BufMut position and of
length between 0 and BufMut::remaining()
.
The returned byte slice may represent uninitialized memory.
fn has_remaining_mut(&self) -> bool
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Returns true if there is space in self
for more bytes. Read more
fn put<T: IntoBuf>(&mut self, src: T) where
Self: Sized,
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Self: Sized,
Transfer bytes into self
from src
and advance the cursor by the number of bytes written. Read more
fn put_slice(&mut self, src: &[u8])
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Transfer bytes into self
from src
and advance the cursor by the number of bytes written. Read more
fn put_u8(&mut self, n: u8)
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Writes an unsigned 8 bit integer to self
. Read more
fn put_i8(&mut self, n: i8)
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Writes a signed 8 bit integer to self
. Read more
fn put_u16<T: ByteOrder>(&mut self, n: u16)
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Writes an unsigned 16 bit integer to self
in the specified byte order. Read more
fn put_i16<T: ByteOrder>(&mut self, n: i16)
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Writes a signed 16 bit integer to self
in the specified byte order. Read more
fn put_u32<T: ByteOrder>(&mut self, n: u32)
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Writes an unsigned 32 bit integer to self
in the specified byte order. Read more
fn put_i32<T: ByteOrder>(&mut self, n: i32)
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Writes a signed 32 bit integer to self
in the specified byte order. Read more
fn put_u64<T: ByteOrder>(&mut self, n: u64)
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Writes an unsigned 64 bit integer to self
in the specified byte order. Read more
fn put_i64<T: ByteOrder>(&mut self, n: i64)
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Writes a signed 64 bit integer to self
in the specified byte order. Read more
fn put_uint<T: ByteOrder>(&mut self, n: u64, nbytes: usize)
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Writes an unsigned n-byte integer to self
in the specified byte order. Read more
fn put_int<T: ByteOrder>(&mut self, n: i64, nbytes: usize)
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Writes a signed n-byte integer to self
in the specified byte order. Read more
fn put_f32<T: ByteOrder>(&mut self, n: f32)
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Writes an IEEE754 single-precision (4 bytes) floating point number to self
in the specified byte order. Read more
fn put_f64<T: ByteOrder>(&mut self, n: f64)
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Writes an IEEE754 double-precision (8 bytes) floating point number to self
in the specified byte order. Read more
fn by_ref(&mut self) -> &mut Self where
Self: Sized,
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Self: Sized,
Creates a "by reference" adaptor for this instance of BufMut
. Read more
fn writer(self) -> Writer<Self> where
Self: Sized,
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Self: Sized,
Creates an adaptor which implements the Write
trait for self
. Read more
impl<T: Clone> Clone for Cursor<T>
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fn clone(&self) -> Cursor<T>
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Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
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Performs copy-assignment from source
. Read more