First version

.gitignore

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+/target
+**/*.rs.bk
+Cargo.lock

.travis.yml

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+language: rust
+
+rust:
+  - beta
+  - stable

Cargo.toml

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+[package]
+name = "multicodec"
+version = "0.1.0"
+authors = ["Benjamin Kampmann <ben@gnunicorn.org>"]
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+unsigned-varint = "0.2"
+failure = "0.1"
+serde = "1.0"

Readme.md

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+# Multicodec in Rust
+
+[![](https://img.shields.io/badge/readme%20style-standard-brightgreen.svg?style=flat-square)](https://github.com/RichardLitt/standard-readme)
+
+> rust implementation of the [multicodec specs](https://github.com/multiformats/multicodec)
+
+
+
+## ToDo's
+
+
+### Coding
+
+ - [ ] automatic deserialisation through external serdes (JSON, CBOR, ...)
+ - [ ] Integrate with Multihash & Multiaddr 
+ - [ ] no-std/Wasm-support
+
+### Mgmnt
+ - [ ] Publish on crates.io
+ - [ ] Add proper License Files
+ - [ ] Activate travis-ci

src/lib.rs

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+extern crate unsigned_varint;
+#[macro_use] extern crate failure;
+extern crate serde;
+
+
+use unsigned_varint::{decode::u16 as decode_varint,
+                      encode::u16 as encode_varint,
+                      decode::Error as VarintError};
+
+use serde::{Serialize, Serializer, ser::SerializeSeq};
+
+#[derive(Debug, Fail)]
+pub enum Error {
+    #[fail(display = "Codec {} unknown", _0)]
+    InvalidCodec(u16),
+    #[fail(display = "Can't parse varint: {}", _0)]
+    VarintFailed(VarintError)
+
+}
+
+macro_rules! build_codec_enum {
+    {$( $val:expr => $var:ident, )*} => {
+        #[allow(non_camel_case_types)]
+        #[derive(PartialEq, Eq, Clone, Copy, Debug)]
+        pub enum Codec {
+            $( $var, )*
+        }
+
+        use Codec::*;
+
+        impl Codec {
+            /// Get the base code.
+            pub fn code(&self) -> u16 {
+                match *self {
+                    $( $var => $val, )*
+                }
+            }
+
+            /// Convert a code to a base.
+            pub fn from_code(code: u16) -> Result<Codec, Error> {
+                match code {
+                    $( $val => Ok($var), )*
+                    _ => Err(Error::InvalidCodec(code)),
+                }
+            }
+        }
+    }
+}
+
+// SOURCE: https://github.com/multiformats/multicodec/blob/master/table.csv
+build_codec_enum! {
+	0x55 => Bin,
+    // bases encodings
+    0x01 => Base1,
+    0x07 => Base8,
+    0x09 => Base10, 
+
+    // serialization formats
+    0x51 => Cbor,
+    0x50 => Protobuf,
+    0x60 => Rlp,
+    0x63 => Bencode,
+
+    // multiformats
+    0x30 => Multicodec,
+    0x31 => Multihash,
+    0x32 => Multiaddr,
+    0x33 => Multibase,
+
+    // multihashes
+    0x11 => Sha1,
+    0x12 => Sha2_256,
+    0x13 => Sha2_512,
+    0x56 => Dbl_Sha2_256,
+    0x17 => Sha3_224,
+    0x16 => Sha3_256,
+    0x15 => Sha3_384,
+    0x14 => Sha3_512,
+    0x18 => Shake_128,
+    0x19 => Shake_256,
+    0x1A => Keccak_224,
+    0x1B => Keccak_256,
+    0x1C => Keccak_384,
+    0x1D => Keccak_512,
+    0x22 => Murmur3,
+    0xb201 => Blake2b_8,
+    0xb202 => Blake2b_16,
+    0xb203 => Blake2b_24,
+    0xb204 => Blake2b_32,
+    0xb205 => Blake2b_40,
+    0xb206 => Blake2b_48,
+    0xb207 => Blake2b_56,
+    0xb208 => Blake2b_64,
+    0xb209 => Blake2b_72,
+    0xb20a => Blake2b_80,
+    0xb20b => Blake2b_88,
+    0xb20c => Blake2b_96,
+    0xb20d => Blake2b_104,
+    0xb20e => Blake2b_112,
+    0xb20f => Blake2b_120,
+    0xb210 => Blake2b_128,
+    0xb211 => Blake2b_136,
+    0xb212 => Blake2b_144,
+    0xb213 => Blake2b_152,
+    0xb214 => Blake2b_160,
+    0xb215 => Blake2b_168,
+    0xb216 => Blake2b_176,
+    0xb217 => Blake2b_184,
+    0xb218 => Blake2b_192,
+    0xb219 => Blake2b_200,
+    0xb21a => Blake2b_208,
+    0xb21b => Blake2b_216,
+    0xb21c => Blake2b_224,
+    0xb21d => Blake2b_232,
+    0xb21e => Blake2b_240,
+    0xb21f => Blake2b_248,
+    0xb220 => Blake2b_256,
+    0xb221 => Blake2b_264,
+    0xb222 => Blake2b_272,
+    0xb223 => Blake2b_280,
+    0xb224 => Blake2b_288,
+    0xb225 => Blake2b_296,
+    0xb226 => Blake2b_304,
+    0xb227 => Blake2b_312,
+    0xb228 => Blake2b_320,
+    0xb229 => Blake2b_328,
+    0xb22a => Blake2b_336,
+    0xb22b => Blake2b_344,
+    0xb22c => Blake2b_352,
+    0xb22d => Blake2b_360,
+    0xb22e => Blake2b_368,
+    0xb22f => Blake2b_376,
+    0xb230 => Blake2b_384,
+    0xb231 => Blake2b_392,
+    0xb232 => Blake2b_400,
+    0xb233 => Blake2b_408,
+    0xb234 => Blake2b_416,
+    0xb235 => Blake2b_424,
+    0xb236 => Blake2b_432,
+    0xb237 => Blake2b_440,
+    0xb238 => Blake2b_448,
+    0xb239 => Blake2b_456,
+    0xb23a => Blake2b_464,
+    0xb23b => Blake2b_472,
+    0xb23c => Blake2b_480,
+    0xb23d => Blake2b_488,
+    0xb23e => Blake2b_496,
+    0xb23f => Blake2b_504,
+    0xb240 => Blake2b_512,
+    0xb241 => Blake2s_8,
+    0xb242 => Blake2s_16,
+    0xb243 => Blake2s_24,
+    0xb244 => Blake2s_32,
+    0xb245 => Blake2s_40,
+    0xb246 => Blake2s_48,
+    0xb247 => Blake2s_56,
+    0xb248 => Blake2s_64,
+    0xb249 => Blake2s_72,
+    0xb24a => Blake2s_80,
+    0xb24b => Blake2s_88,
+    0xb24c => Blake2s_96,
+    0xb24d => Blake2s_104,
+    0xb24e => Blake2s_112,
+    0xb24f => Blake2s_120,
+    0xb250 => Blake2s_128,
+    0xb251 => Blake2s_136,
+    0xb252 => Blake2s_144,
+    0xb253 => Blake2s_152,
+    0xb254 => Blake2s_160,
+    0xb255 => Blake2s_168,
+    0xb256 => Blake2s_176,
+    0xb257 => Blake2s_184,
+    0xb258 => Blake2s_192,
+    0xb259 => Blake2s_200,
+    0xb25a => Blake2s_208,
+    0xb25b => Blake2s_216,
+    0xb25c => Blake2s_224,
+    0xb25d => Blake2s_232,
+    0xb25e => Blake2s_240,
+    0xb25f => Blake2s_248,
+    0xb260 => Blake2s_256,
+
+    // multiaddrs
+    0x04 => Ip4,
+    0x29 => Ip6,
+    0x06 => Tcp,
+    0x0111 => Udp,
+    0x21 => Dccp,
+    0x84 => Sctp,
+    0x012D => Udt,
+    0x012E => Utp,
+    0x01A5 => Ipfs,
+    0x01E0 => Http,
+    0x01BB => Https,
+    0x01CC => Quic,
+    0x01DD => Ws,
+    0x01BC => Onion,
+    0x0122 => P2p_Circuit,
+
+    // IPLD formats
+    0x70 => Dag_Pb, 
+    0x71 => Dag_Cbor,
+
+    0x78 => Git_Raw,
+
+    0x90 => Eth_Block,
+    0x91 => Eth_Block_List,
+    0x92 => Eth_Tx_Trie,
+    0x93 => Eth_Tx, 
+    0x94 => Eth_Tx_Receipt_Trie,
+    0x95 => Eth_Tx_Receipt,
+    0x96 => Eth_State_Trie,
+    0x97 => Eth_Account_Snapshot, 
+    0x98 => Eth_Storage_Trie,
+
+    0xb0 => Bitcoin_Block,
+    0xb1 => Bitcoin_Tx,
+
+    0xc0 => Zcash_Block,
+    0xc1 => Zcash_Tx,
+
+    0xd0 => Stellar_Block,
+    0xd1 => Stellar_Tx,
+
+    0x7b => Torrent_Info,
+    0x7c => Torrent_File,
+    0xed => Ed25519_Pub,
+}
+
+
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+pub struct MultiCodec<'a> {
+	codec: Codec,
+	data: &'a [u8]
+}
+
+impl<'a> MultiCodec<'a> {
+	/// create a new MultiCodec
+	pub fn new(codec: Codec, data: &'a [u8]) -> MultiCodec {
+		MultiCodec { codec, data }
+	}
+	/// try to parse a MultiCodec from a packed bytestring
+	pub fn from(packed: &'a [u8]) -> Result<MultiCodec, Error> {
+		let (code, data) = decode_varint(packed).map_err(|e| Error::VarintFailed(e))?;
+		let codec = Codec::from_code(code)?;
+		Ok(MultiCodec { codec, data })
+	}
+
+    pub fn pack(&self) -> Vec<u8> {
+        let mut buf = [0u8; 3];
+        encode_varint(self.codec.code(), &mut buf);
+        let mut v : Vec<u8> = Vec::new();
+        for b in &buf {
+            v.push(*b);
+            // varint uses first bit to indicate another byte follows, stop if not the case
+            if *b <= 127 { break }
+        }
+        v.extend(self.data);
+        v
+    }
+}
+
+impl<'a> Serialize for MultiCodec<'a> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_bytes(&self.pack())
+    }
+}
+
+
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+    #[test]
+    fn it_works() {
+        let codec = MultiCodec::new(Codec::Sha2_256, b"EiC5TSe5k00");
+        let packed = codec.pack();
+        let redo = MultiCodec::from(&packed).unwrap();
+        assert_eq!(packed, "\x12EiC5TSe5k00".as_bytes());
+        assert_eq!(redo, codec);
+    }
+}