3 unstable releases
Uses old Rust 2015
0.2.0 | Jun 6, 2016 |
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0.1.1 | May 31, 2016 |
0.1.0 | May 29, 2016 |
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bytevec: A Rust serialization library that uses byte vectors
bytevec takes advantage of Rust's concise and stable type system to
serialize data objects to a byte vector (Vec<u8>
) and back.
Read the documentation here.
What does it do?
Rust has a very powerful type system with predictable sizes for most types, starting with the primitive types, so it's fairly easy to convert any type to a collection of bytes and convert it back. This library intends to give the user the means of converting a given type instance to a byte vector and store it or send it through the wire to another device, with the possibility of getting the value back from the byte vector anytime using the library traits.
Of course, Rust isn't magical enough to implement the traits to serialize
the functions automatically, as every type has its quirks. This library
uses two traits to give a type the functionality it needs to do that:
ByteEncodable
and ByteDecodable
.
###The ByteEncodable
trait
A type that implements this trait is able to use the encode
method that
yields a Vec<u8>
byte sequence. Seems prone to failure right? Of course it is,
internally it uses unsafe
blocks to extract the bytes of a given type, so
it can be pretty unsafe. That's why it always checks for any possible error and
returns the vector wrapped around a BVEncodeResult
instance. If everything
goes Ok
, we will be able to get a byte vector value that represents the
original data structure.
bytevec doesn't actually do a 1:1 conversion of the bytes of the original type instance, as not every Rust type is stored on the stack. For any type that wraps a heap stored value, it will give a representation of the underlying value.
bytevec implements ByteEncodable
out of the box for the following types:
- The integral types:
u8
,u16
,u32
,u64
,i8
,i16
,i32
,i64
- The floating point types:
f32
andf64
char
,str
andString
Vec
&[T]
HashMap
HashSet
- Tuples with up to 12 elements
- Custom
struct
s
For collections and other structures, automatic implementation of bytevec
requires that all of its underlying elements implement the ByteEncodable
trait.
###The bytevec serialization format bytevec doesn't follow any particular serialization format. It follows simple rules when translating some type value to bytes:
- For a primitive type such as the integral types, floating points
or char that have fixed size, it will just grab the bytes and put them
on a
u8
buffer of the same length as the size of the type throughstd::mem::transmute
. These types are converted to and from little endian on serialization and deserialization respectively. - String and str don't store their byte count, it's up to their container (if any) to store the size of the byte buffer of the string.
- Complex data structures such as
struct
s, tuples and collections need to store the sizes of their underlying data fields. These sizes are stored as values of a generic integral type parameterSize
that should be provided in every call of the methods of theByteEncodable
andByteDecodable
traits. This type parameter is propagated to the serialization and deserialization operations of the contained data fields. The type parameterSize
is constrained by theBVSize
trait. Currently the types that implement this trait areu8
,u16
,u32
andu64
. Users should select the type for theSize
type parameter according to the expected size of the byte buffer. If the expected size exceeds the 232 byte length limit ofu32
, useu64
instead. - For structures with defined fields such as a custom
struct
or a tuple, it will store the size of each field on a sequence ofSize
values at the start of the slice segment for the structure, followed by the actual bytes of the values of the fields. - For any collection with variable length, it will first store the length
(in elements, not byte count) on a
Size
value, followed by the byte count (yes, ofSize
) of each element, and then the actual values of the elements. All of this done in order, order is important, the same order of serialization is the order of deserialization. - All serializable values can be nested, so any structure that implements
ByteEncodable
containing aVec
,String
, or another structure that also implementsByteEncodable
will be serialized along all its fields.
###The ByteDecodable
trait
Given a byte vector retrieved from memory, a file, or maybe a TCP connection,
the user will be able to pass the vector to the decode
method of
a type that implements the ByteDecodable
trait. decode
will do a few checks
on the byte vector and if the required sizes matches, it will yield a type instance wrapped
in a BVDecodeResult
. If the size doesn't match, or if some other conversion problem
arises, it will yield a ByteVecError
detailing the failure.
Almost all of the out of the box implementations of ByteEncodable
also
implement ByteDecodable
, but some of them, particularly the slices and
the tuple references don't make sense when deserialized, as they can't
point to the original data they were referencing. This is usually a problem
that requires some tweaking, but bytevec allows data conversion from byte
buffers that were originally referenced data to a new instance of an owned data type,
as long as the size requirements are the same. This way, slice data can
be assigned to a Vec
instance for example, as long as they share the same
type of the underlying elements.
The ByteDecodable
trait also provides the decode_max
method, which like decode
, it
accepts the byte buffer to deserialize, but additionally, this method also accepts
a limit
argument. This parameter is compared to the length of the u8
buffer and
if the buffer length is greater than it, it will return a BadSizeDecodeError
,
otherwise it will return the result of decode
on the byte buffer.
###Example: Serialization and deserialization of a slice
let slice = &["Rust", "Is", "Awesome!"];
let bytes = slice.encode::<u32>().unwrap();
let vec = <Vec<String>>::decode::<u32>(&bytes).unwrap();
assert_eq!(vec, slice);
###The bytevec_decl
macro
This macro allows the user to declare an arbitrary number of structures that
automatically implement both the ByteEncodable
and ByteDecodable
traits,
as long as all of the fields also implement both traits.
#[macro_use]
extern crate bytevec;
use bytevec::{ByteEncodable, ByteDecodable};
bytevec_decl! {
#[derive(PartialEq, Eq, Debug)]
pub struct Point {
x: u32,
y: u32
}
}
fn main() {
let p1 = Point {x: 32, y: 436};
let bytes = p1.encode::<u32>().unwrap();
let p2 = Point::decode::<u32>(&bytes).unwrap();
assert_eq!(p1, p2);
}
###The bytevec_impls
macro
This macro implements both the ByteEncodable
and ByteDecodable
traits
for the given struct
definitions. This macro does not declare the struct
definitions, the user should either declare them separately or use the
bytevec_decl
trait.
This trait also allows the user to create a partial implementation of the
serialization operations for a select number of the fields of the
structure. If the actual definition of the struct
has more fields than
the one provided to the macro, only the listed fields in the macro invocation
will be serialized and deserialized. In the deserialization process, the
rest of the fields of the struct
will be initialized using the value
returned from the Default::default()
method, so the struct
must
implement Default
.
#[macro_use]
extern crate bytevec;
use bytevec::{ByteEncodable, ByteDecodable};
#[derive(PartialEq, Eq, Debug, Default)]
struct Vertex3d {
x: u32,
y: u32,
z: u32
}
bytevec_impls! {
impl Vertex3d {
x: u32,
y: u32
}
}
fn main() {
let p1 = Vertex3d {x: 32, y: 436, z: 0};
let bytes = p1.encode::<u32>().unwrap();
let p2 = Vertex3d::decode::<u32>(&bytes).unwrap();
assert_eq!(p1, p2);
}
####This all sounds like your usual serialization library, but why bother with bytes? bytevec certainly isn't for everyone. It isn't a full serialization library like rustc_serialize or serde, nor is it trying to become one. This is for the people that for any reason can't handle text based serialization and just need to get some bytes fast and recreate an object out of them with low overhead through the use of a small crate with no dependencies.
##License This library is distributed under both the MIT license and the Apache License (Version 2.0). You are free to use any of them as you see fit.