# Borsh [](https://github.com/alexfilatov/borsh/actions?query=workflow%3ACI) [](https://hex.pm/packages/borsh) [](https://hex.pm/packages/borsh)
BORSH, binary serializer for security-critical projects.
**IMPORTANT! Implemented only `Serialization`. `Deserialization` will be implemented by the end of the March.**
Borsh stands for `Binary` `Object` `Representation` `Serializer` for `Hashing`. It is meant to be used in
security-critical projects as it prioritizes consistency, safety, speed; and comes with a strict specification.
In short, Borsh is a non self-describing binary serialization format. It is designed to serialize any objects to
canonical and deterministic set of bytes.
General principles:
- integers are little endian;
- sizes of dynamic containers are written before values as u32;
- all unordered containers (hashmap/hashset) are ordered in lexicographic order by key (in tie breaker case on value);
- structs are serialized in the order of fields in the struct;
- enums are serialized with using u8 for the enum ordinal and then storing data inside the enum value (if present).
This is Elixir implementation of the serializer. Official specification: https://github.com/near/borsh#specification
## Installation
If [available in Hex](https://hex.pm/docs/publish), the package can be installed by adding `borsh` to your list of
dependencies in `mix.exs`:
```elixir
def deps do
[
{:borsh, "~> 0.1"}
]
end
```
## Usage
```elixir
use Borsh,
schema: [
signer_id: :string,
public_key: {:borsh, PublicKey},
nonce: :u64,
receiver_id: :string,
block_hash: [32],
actions: [
{:borsh, ActionOne},
{:borsh, ActionTwo}
]
]
```
### Options
`schema`:
Borsh schema itself, structure of fields for serialisation with serialisation formats.
### Borsh literal formats
#### String literals
`:string` - string, encoded as utf-8 bytes
`[32]` and `[64]` - A string with 32/64 chars length.
#### Number literals
`:u8` - unsigned 8-bit integer
`:u16` - unsigned 16-bit integer
`:u32` - unsigned 32-bit integer
`:u64` - unsigned 64-bit integer
`:i8` - signed 8-bit integer
`:i16` - signed 16-bit integer
`:i32` - signed 32-bit integer
`:i64` - signed 64-bit integer
`:f32` - 32-bit float
`:f64` - 64-bit float
#### Borsh-typed literals
To define custom types for serialization, we can use the syntax `{:borsh, StructModule}` in a parent struct, when we
want to serialize another struct within it. There are single and arrays of borsh types.
`{:borsh, Module}` - The syntax represents a single struct of a borsh-encoded module. When this struct is passed to the
serializer, the serializer will execute the `.borsh_encode` method of the struct's module on the struct.
`:borsh` - has the same effect as `{:borsh, Module}`, but the resulting serialized data cannot be decoded back into the
original struct. Using `:borsh` for serialization is safe for sending transactions to the NEAR blockchain, as the main
concern is just the serialization itself.
`[{:borsh, Module}]` - represents an enumeration of borsh-encoded structs, where each element of the list must have a
Borsh schema.
`[:borsh]` - has the same effect as [{:borsh, Module}], but the resulting serialized data cannot be decoded back into
the original structs. It can only be used for encoding, not decoding.
`[{:borsh, Module1}, {:borsh, Module2}]` - represents an enumeration of borsh-encoded structs, where each element
of the list must have a Borsh schema. Each element in the list can belong to a different module, and the sequence of
elements is important. This syntax can be used for both encoding and decoding.
## License
Copyright © 2021-present Alex Filatov <alex@alexfilatov.com>
This work is free. You can redistribute it and/or modify it under the
terms of the MIT License. See the LICENSE file for more details.
