Crate positioned_io [] [src]

This crate allows you to specify an offset for reads and writes, without changing the current position in a file. This is similar to pread() and pwrite() in C.

The major advantages of this type of I/O are:

The repository is at https://github.com/vasi/positioned-io

Examples

Read the fifth 512-byte sector of a file:

use positioned_io::ReadAt;

// Note that file does not need to be mut!
let file = try!(File::open("foo.data"));
let mut buf = vec![0; 512];
let bytes_read = try!(file.read_at(2048, &mut buf));

Write an integer to the middle of a file:

use positioned_io::WriteAt;
use byteorder::{ByteOrder, LittleEndian};

// Put the integer in a buffer.
let mut buf = vec![0; 4];
LittleEndian::write_u32(&mut buf, 1234);

// Write it to the file.
let mut file = try!(OpenOptions::new().write(true).open("foo.data"));
try!(file.write_all_at(1 << 20, &buf));

Or, more simply:

// Extend files with writing integers at offsets.
use positioned_io::WriteBytesExt;

let mut file = try!(OpenOptions::new().write(true).open("foo.data"));
try!(file.write_u32_at::<LittleEndian>(1 << 20, 1234));

Read from anything else that supports ReadAt, like a byte array:

use positioned_io::ReadBytesExt;

let buf = [0, 5, 254, 212, 0, 3];
let n = try!(buf.as_ref().read_i16_at::<BigEndian>(2));
assert_eq!(n, -300);

Structs

ByteIo

Read or write with a given inherent byte-order.

Cursor

Adapts a ReadAt or WriteAt into a Read or Write.

SizeCursor

Adapts a ReadAt or WriteAt into a Read or Write, with better seeking.

Slice

A window into another ReatAt or WriteAt.

Traits

ReadAt

Trait for reading at an offset.

ReadBytesExt

Extends ReadAt with methods for reading numbers at offsets.

ReadInt

Trait for reading integers.

ReadIntAt

Trait for reading positioned integers.

Size

Trait to get the size of an I/O object.

WriteAt

Trait for writing at an offset.

WriteBytesExt

Extends WriteAt with methods for writing numbers at offsets.

WriteInt

Trait for writing integers.

WriteIntAt

Trait for writing positioned integers.