Struct snarkvm_wasm::serialize::io::Cursor

1.0.0 · source ·
pub struct Cursor<T> { /* private fields */ }
Expand description

A Cursor wraps an in-memory buffer and provides it with a Seek implementation.

Cursors are used with in-memory buffers, anything implementing AsRef<[u8]>, 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]);
}

Implementations

Creates a new cursor wrapping the provided underlying in-memory buffer.

Cursor initial position is 0 even if underlying buffer (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());

Consumes this cursor, returning the underlying value.

Examples
use std::io::Cursor;

let buff = Cursor::new(Vec::new());

let vec = buff.into_inner();

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();

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();

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);

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);
🔬This is a nightly-only experimental API. (cursor_remaining)

Returns the remaining slice.

Examples
#![feature(cursor_remaining)]
use std::io::Cursor;

let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);

assert_eq!(buff.remaining_slice(), &[1, 2, 3, 4, 5]);

buff.set_position(2);
assert_eq!(buff.remaining_slice(), &[3, 4, 5]);

buff.set_position(4);
assert_eq!(buff.remaining_slice(), &[5]);

buff.set_position(6);
assert_eq!(buff.remaining_slice(), &[]);
🔬This is a nightly-only experimental API. (cursor_remaining)

Returns true if the remaining slice is empty.

Examples
#![feature(cursor_remaining)]
use std::io::Cursor;

let mut buff = Cursor::new(vec![1, 2, 3, 4, 5]);

buff.set_position(2);
assert!(!buff.is_empty());

buff.set_position(5);
assert!(buff.is_empty());

buff.set_position(10);
assert!(buff.is_empty());

Trait Implementations

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read. Read more
Attempts to read from the AsyncRead into buf. Read more
Attempts to seek to an offset, in bytes, in a stream. Read more
Waits for a seek operation to complete. Read more
Attempt to write bytes from buf into the object. Read more
Like poll_write, except that it writes from a slice of buffers. Read more
Determines if this writer has an efficient poll_write_vectored implementation. Read more
Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
Attempt to write bytes from buf into the object. Read more
Like poll_write, except that it writes from a slice of buffers. Read more
Determines if this writer has an efficient poll_write_vectored implementation. Read more
Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
Attempt to write bytes from buf into the object. Read more
Like poll_write, except that it writes from a slice of buffers. Read more
Determines if this writer has an efficient poll_write_vectored implementation. Read more
Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
Attempt to write bytes from buf into the object. Read more
Like poll_write, except that it writes from a slice of buffers. Read more
Determines if this writer has an efficient poll_write_vectored implementation. Read more
Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
Returns the number of bytes between the current position and the end of the buffer. Read more
Returns a slice starting at the current position and of length between 0 and Buf::remaining(). Note that this can return shorter slice (this allows non-continuous internal representation). Read more
Advance the internal cursor of the Buf Read more
Fills dst with potentially multiple slices starting at self’s current position. Read more
Returns true if there are any more bytes to consume Read more
Copies bytes from self into dst. Read more
Gets an unsigned 8 bit integer from self. Read more
Gets a signed 8 bit integer from self. Read more
Gets an unsigned 16 bit integer from self in big-endian byte order. Read more
Gets an unsigned 16 bit integer from self in little-endian byte order. Read more
Gets a signed 16 bit integer from self in big-endian byte order. Read more
Gets a signed 16 bit integer from self in little-endian byte order. Read more
Gets an unsigned 32 bit integer from self in the big-endian byte order. Read more
Gets an unsigned 32 bit integer from self in the little-endian byte order. Read more
Gets a signed 32 bit integer from self in big-endian byte order. Read more
Gets a signed 32 bit integer from self in little-endian byte order. Read more
Gets an unsigned 64 bit integer from self in big-endian byte order. Read more
Gets an unsigned 64 bit integer from self in little-endian byte order. Read more
Gets a signed 64 bit integer from self in big-endian byte order. Read more
Gets a signed 64 bit integer from self in little-endian byte order. Read more
Gets an unsigned 128 bit integer from self in big-endian byte order. Read more
Gets an unsigned 128 bit integer from self in little-endian byte order. Read more
Gets a signed 128 bit integer from self in big-endian byte order. Read more
Gets a signed 128 bit integer from self in little-endian byte order. Read more
Gets an unsigned n-byte integer from self in big-endian byte order. Read more
Gets an unsigned n-byte integer from self in little-endian byte order. Read more
Gets a signed n-byte integer from self in big-endian byte order. Read more
Gets a signed n-byte integer from self in little-endian byte order. Read more
Gets an IEEE754 single-precision (4 bytes) floating point number from self in big-endian byte order. Read more
Gets an IEEE754 single-precision (4 bytes) floating point number from self in little-endian byte order. Read more
Gets an IEEE754 double-precision (8 bytes) floating point number from self in big-endian byte order. Read more
Gets an IEEE754 double-precision (8 bytes) floating point number from self in little-endian byte order. Read more
Consumes len bytes inside self and returns new instance of Bytes with this data. Read more
Creates an adaptor which will read at most limit bytes from self. Read more
Creates an adaptor which will chain this buffer with another. Read more
Creates an adaptor which implements the Read trait for self. Read more
Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more
🔬This is a nightly-only experimental API. (buf_read_has_data_left)
Check if the underlying Read has any data left to be read. Read more
Read all bytes into buf until the delimiter byte or EOF is reached. Read more
Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. You do not need to clear the buffer before appending. Read more
Returns an iterator over the contents of this reader split on the byte byte. Read more
Returns an iterator over the lines of this reader. Read more
Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Returns the “default value” for a type. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
🔬This is a nightly-only experimental API. (read_buf)
Pull some bytes from this source into the specified buffer. Read more
Like read, except that it reads into a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Reader has an efficient read_vectored implementation. Read more
Read the exact number of bytes required to fill buf. Read more
Read all bytes until EOF in this source, placing them into buf. Read more
Read all bytes until EOF in this source, appending them to buf. Read more
🔬This is a nightly-only experimental API. (read_buf)
Read the exact number of bytes required to fill cursor. Read more
Creates a “by reference” adaptor for this instance of Read. Read more
Transforms this Read instance to an Iterator over its bytes. Read more
Creates an adapter which will chain this stream with another. Read more
Creates an adapter which will read at most limit bytes from it. Read more
Seek to an offset, in bytes, in a stream. Read more
🔬This is a nightly-only experimental API. (seek_stream_len)
Returns the length of this stream (in bytes). Read more
Returns the current seek position from the start of the stream. Read more
Rewind to the beginning of a stream. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Writer has an efficient write_vectored implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Attempts to write an entire buffer into this writer. Read more
🔬This is a nightly-only experimental API. (write_all_vectored)
Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Creates a “by reference” adapter for this instance of Write. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Writer has an efficient write_vectored implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Attempts to write an entire buffer into this writer. Read more
🔬This is a nightly-only experimental API. (write_all_vectored)
Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Creates a “by reference” adapter for this instance of Write. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Writer has an efficient write_vectored implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Attempts to write an entire buffer into this writer. Read more
🔬This is a nightly-only experimental API. (write_all_vectored)
Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Creates a “by reference” adapter for this instance of Write. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Writer has an efficient write_vectored implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Attempts to write an entire buffer into this writer. Read more
🔬This is a nightly-only experimental API. (write_all_vectored)
Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Creates a “by reference” adapter for this instance of Write. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
🔬This is a nightly-only experimental API. (can_vector)
Determines if this Writer has an efficient write_vectored implementation. Read more
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Attempts to write an entire buffer into this writer. Read more
🔬This is a nightly-only experimental API. (write_all_vectored)
Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more
Creates a “by reference” adapter for this instance of Write. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Reads all bytes into buf until the delimiter byte or EOF is reached. Read more
Reads all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. Read more
Returns a stream of the contents of this reader split on the byte byte. Read more
Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more
Returns a stream over the lines of this reader. This method is the async equivalent to BufRead::lines. Read more
Creates a new AsyncRead instance that chains this stream with next. Read more
Pulls some bytes from this source into the specified buffer, returning how many bytes were read. Read more
Pulls some bytes from this source into the specified buffer, advancing the buffer’s internal cursor. Read more
Reads the exact number of bytes required to fill buf. Read more
Reads an unsigned 8 bit integer from the underlying reader. Read more
Reads a signed 8 bit integer from the underlying reader. Read more
Reads an unsigned 16-bit integer in big-endian order from the underlying reader. Read more
Reads a signed 16-bit integer in big-endian order from the underlying reader. Read more
Reads an unsigned 32-bit integer in big-endian order from the underlying reader. Read more
Reads a signed 32-bit integer in big-endian order from the underlying reader. Read more
Reads an unsigned 64-bit integer in big-endian order from the underlying reader. Read more
Reads an signed 64-bit integer in big-endian order from the underlying reader. Read more
Reads an unsigned 128-bit integer in big-endian order from the underlying reader. Read more
Reads an signed 128-bit integer in big-endian order from the underlying reader. Read more
Reads an 32-bit floating point type in big-endian order from the underlying reader. Read more
Reads an 64-bit floating point type in big-endian order from the underlying reader. Read more
Reads an unsigned 16-bit integer in little-endian order from the underlying reader. Read more
Reads a signed 16-bit integer in little-endian order from the underlying reader. Read more
Reads an unsigned 32-bit integer in little-endian order from the underlying reader. Read more
Reads a signed 32-bit integer in little-endian order from the underlying reader. Read more
Reads an unsigned 64-bit integer in little-endian order from the underlying reader. Read more
Reads an signed 64-bit integer in little-endian order from the underlying reader. Read more
Reads an unsigned 128-bit integer in little-endian order from the underlying reader. Read more
Reads an signed 128-bit integer in little-endian order from the underlying reader. Read more
Reads an 32-bit floating point type in little-endian order from the underlying reader. Read more
Reads an 64-bit floating point type in little-endian order from the underlying reader. Read more
Reads all bytes until EOF in this source, placing them into buf. Read more
Reads all bytes until EOF in this source, appending them to buf. Read more
Creates an adaptor which reads at most limit bytes from it. Read more
Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more
Creates a future which will rewind to the beginning of the stream. Read more
Creates a future which will return the current seek position from the start of the stream. Read more
Writes a buffer into this writer, returning how many bytes were written. Read more
Like write, except that it writes from a slice of buffers. Read more
Writes a buffer into this writer, advancing the buffer’s internal cursor. Read more
Attempts to write an entire buffer into this writer. Read more
Attempts to write an entire buffer into this writer. Read more
Writes an unsigned 8-bit integer to the underlying writer. Read more
Writes an unsigned 8-bit integer to the underlying writer. Read more
Writes an unsigned 16-bit integer in big-endian order to the underlying writer. Read more
Writes a signed 16-bit integer in big-endian order to the underlying writer. Read more
Writes an unsigned 32-bit integer in big-endian order to the underlying writer. Read more
Writes a signed 32-bit integer in big-endian order to the underlying writer. Read more
Writes an unsigned 64-bit integer in big-endian order to the underlying writer. Read more
Writes an signed 64-bit integer in big-endian order to the underlying writer. Read more
Writes an unsigned 128-bit integer in big-endian order to the underlying writer. Read more
Writes an signed 128-bit integer in big-endian order to the underlying writer. Read more
Writes an 32-bit floating point type in big-endian order to the underlying writer. Read more
Writes an 64-bit floating point type in big-endian order to the underlying writer. Read more
Writes an unsigned 16-bit integer in little-endian order to the underlying writer. Read more
Writes a signed 16-bit integer in little-endian order to the underlying writer. Read more
Writes an unsigned 32-bit integer in little-endian order to the underlying writer. Read more
Writes a signed 32-bit integer in little-endian order to the underlying writer. Read more
Writes an unsigned 64-bit integer in little-endian order to the underlying writer. Read more
Writes an signed 64-bit integer in little-endian order to the underlying writer. Read more
Writes an unsigned 128-bit integer in little-endian order to the underlying writer. Read more
Writes an signed 128-bit integer in little-endian order to the underlying writer. Read more
Writes an 32-bit floating point type in little-endian order to the underlying writer. Read more
Writes an 64-bit floating point type in little-endian order to the underlying writer. Read more
Flushes this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
Shuts down the output stream, ensuring that the value can be dropped cleanly. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
Compare self to key and return true if they are equal.

Returns the argument unchanged.

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
Instruments this type with the current Span, returning an Instrumented wrapper. Read more

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The alignment of pointer.
The type for initializers.
Initializes a with the given initializer. Read more
Dereferences the given pointer. Read more
Mutably dereferences the given pointer. Read more
Drops the object pointed to by the given pointer. Read more
Reads an unsigned 8 bit integer from the underlying reader. Read more
Reads a signed 8 bit integer from the underlying reader. Read more
Reads an unsigned 16 bit integer from the underlying reader. Read more
Reads a signed 16 bit integer from the underlying reader. Read more
Reads an unsigned 24 bit integer from the underlying reader. Read more
Reads a signed 24 bit integer from the underlying reader. Read more
Reads an unsigned 32 bit integer from the underlying reader. Read more
Reads a signed 32 bit integer from the underlying reader. Read more
Reads an unsigned 48 bit integer from the underlying reader. Read more
Reads a signed 48 bit integer from the underlying reader. Read more
Reads an unsigned 64 bit integer from the underlying reader. Read more
Reads a signed 64 bit integer from the underlying reader. Read more
Reads an unsigned 128 bit integer from the underlying reader. Read more
Reads a signed 128 bit integer from the underlying reader. Read more
Reads an unsigned n-bytes integer from the underlying reader. Read more
Reads a signed n-bytes integer from the underlying reader. Read more
Reads an unsigned n-bytes integer from the underlying reader.
Reads a signed n-bytes integer from the underlying reader.
Reads a IEEE754 single-precision (4 bytes) floating point number from the underlying reader. Read more
Reads a IEEE754 double-precision (8 bytes) floating point number from the underlying reader. Read more
Reads a sequence of unsigned 16 bit integers from the underlying reader. Read more
Reads a sequence of unsigned 32 bit integers from the underlying reader. Read more
Reads a sequence of unsigned 64 bit integers from the underlying reader. Read more
Reads a sequence of unsigned 128 bit integers from the underlying reader. Read more
Reads a sequence of signed 8 bit integers from the underlying reader. Read more
Reads a sequence of signed 16 bit integers from the underlying reader. Read more
Reads a sequence of signed 32 bit integers from the underlying reader. Read more
Reads a sequence of signed 64 bit integers from the underlying reader. Read more
Reads a sequence of signed 128 bit integers from the underlying reader. Read more
Reads a sequence of IEEE754 single-precision (4 bytes) floating point numbers from the underlying reader. Read more
👎Deprecated since 1.2.0: please use read_f32_into instead
DEPRECATED. Read more
Reads a sequence of IEEE754 double-precision (8 bytes) floating point numbers from the underlying reader. Read more
👎Deprecated since 1.2.0: please use read_f64_into instead
DEPRECATED. Read more
Should always be Self
The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.
Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
Writes an unsigned 8 bit integer to the underlying writer. Read more
Writes a signed 8 bit integer to the underlying writer. Read more
Writes an unsigned 16 bit integer to the underlying writer. Read more
Writes a signed 16 bit integer to the underlying writer. Read more
Writes an unsigned 24 bit integer to the underlying writer. Read more
Writes a signed 24 bit integer to the underlying writer. Read more
Writes an unsigned 32 bit integer to the underlying writer. Read more
Writes a signed 32 bit integer to the underlying writer. Read more
Writes an unsigned 48 bit integer to the underlying writer. Read more
Writes a signed 48 bit integer to the underlying writer. Read more
Writes an unsigned 64 bit integer to the underlying writer. Read more
Writes a signed 64 bit integer to the underlying writer. Read more
Writes an unsigned 128 bit integer to the underlying writer.
Writes a signed 128 bit integer to the underlying writer.
Writes an unsigned n-bytes integer to the underlying writer. Read more
Writes a signed n-bytes integer to the underlying writer. Read more
Writes an unsigned n-bytes integer to the underlying writer. Read more
Writes a signed n-bytes integer to the underlying writer. Read more
Writes a IEEE754 single-precision (4 bytes) floating point number to the underlying writer. Read more
Writes a IEEE754 double-precision (8 bytes) floating point number to the underlying writer. Read more