memoverlay 0.1.0

Puts a writable layer of bytes over some byte stream
Documentation 
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# memoverlay
Puts a writable layer of bytes over some byte stream

# memoverlay


```txt
+-----------------+------------+-----------------+-------+----------------------+-------+-----------------+
|    chunk 0      |  chunk 1   |    chunk 2      |   3   |       chunk 4        |   5   |     chunk 6     |
+-----------------+------------+-----------------+-------+----------------------+-------+-----------------+

                               +-----------------+       +----------------------+
                               +-----------------+       +----------------------+
                  +-------------------+                           +---------------------+
                  +-------------------+                           +---------------------+
+---------------------------------------------------------------------------------------------------------+
+---------------------------------------------------------------------------------------------------------+
```

## Usage example

```rust
use std::io::{Cursor, Read, Seek, SeekFrom};
use memoverlay::MemOverlay;
use memoverlay::overlay;

let message1 = "hello, world!";
let mut overlay = overlay!(message1.as_bytes());
overlay.add_bytes_at(7, "peter".as_bytes()).unwrap();

let mut message2 = String::new();
let _ = overlay.read_to_string(&mut message2).unwrap();
overlay.seek(SeekFrom::Start(0)).unwrap();

assert_eq!(message2, "hello, peter!");

overlay.add_bytes_at(1, "a".as_bytes()).unwrap();
let mut message3 = String::new();
let _ = overlay.read_to_string(&mut message3).unwrap();
overlay.seek(SeekFrom::Start(0)).unwrap();
assert_eq!(message3, "hallo, peter!");

overlay.add_bytes_at(1, "o".as_bytes()).unwrap();
overlay.add_bytes_at(5, "w".as_bytes()).unwrap();
let mut message4 = String::new();
let _ = overlay.read_to_string(&mut message4).unwrap();
assert_eq!(message4, "hollow peter!");
```