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fix: fix some mistakes in the spec
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David Dias
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README.md
123
README.md
@ -4,16 +4,16 @@
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[](http://github.com/multiformats/multiformats)
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[](http://webchat.freenode.net/?channels=%23ipfs)
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> self-describing codecs
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> Make data and streams self-described by prefixing them with human readable or binary packed codecs. `multicodec` offers a base table, but can also be extended with extra tables by application basis.
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## Table of Contents
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- [Motivation](#motivation)
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- [How does it work? - Protocol Description](#how-does-it-work---protocol-description)
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- [Prefix examples](#prefix-examples)
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- [prefix - codec - desc](#prefix---codec---desc)
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- [The protocol path](#the-protocol-path)
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- [How does it work? - Protocol Description](#how-does-it-work---protocol-description)
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- [The protocol path](#the-protocol-path)
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- [Multicodec table](#multicodec-table)
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- [Implementations](#implementations)
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- [Implementation details]()
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- [FAQ](#faq)
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- [Maintainers](#maintainers)
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- [Contribute](#contribute)
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@ -38,67 +38,43 @@ Moreover, this self-description allows straightforward layering of protocols wit
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`multicodec` is a _self-describing multiformat_, it wraps other formats with a tiny bit of self-description:
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```sh
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<multicodec-header><encoded-data>
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# or
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<varint-len><code>\n<encoded-data>
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<varint-len><multicodec><encoded-data>
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```
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For example, let's encode a json doc:
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```node
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> // encode some json
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> var str = JSON.stringify({"hello":"world"})
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> var buf = multicodec.encode('json', str) // prepends multistream.header('/json')
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> buf
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<Buffer 06 2f 6a 73 6f 6e 2f 7b 22 68 65 6c 6c 6f 22 3a 22 77 6f 72 6c 64 22 7d>
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> buf.toString('hex')
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062f6a736f6e2f7b2268656c6c6f223a22776f726c64227d
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> // decode, and find out what is in buf
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> multicodec.decode(buf)
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{ "codec": "json", "data": '{"hello": "world"}' }
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```JavaScript
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// encode some json
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const buf = new Buffer(JSON.stringify({ hello: 'world' }))
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const prefixedBuf = multicodec.addPrefix('json', str) // prepends multicodec ('json')
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console.log(prefixedBuf)
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// <Buffer 06 2f 6a 73 6f 6e 2f 7b 22 68 65 6c 6c 6f 22 3a 22 77 6f 72 6c 64 22 7d>
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const.log(prefixedBuf.toString('hex'))
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// 062f6a736f6e2f7b2268656c6c6f223a22776f726c64227d
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// let's get the Multicodec, and get the data back
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const codec = multicodec.getMulticodec(prefixedBuf)
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console.log(codec)
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// json
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console.log(multicodec.rmPrefix(prefixedBuf).toString())
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// "{ \"hello\": \"world\" }
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```
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So, `buf` is:
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```
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hex: 062f6a736f6e2f7b2268656c6c6f223a22776f726c64227d
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ascii: json/\n{"hello":"world"}
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ascii: /json/"{\"hello\":\"world\"}
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```
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The more you know! Let's try it again, this time with protobuf:
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Note that on the ascii version, the varint at the beginning is not being represented, you should account that.
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```
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cat proto.c
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```
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For a binary packed version of the multicodecs, see [multicodec-packed](./multicodec-packed.md).
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See also: [multicodec-packed](./multicodec-packed.md).
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## Prefix examples
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| prefix | codec | desc | type | [packed encoding](https://github.com/multiformats/multicodec/blob/master/multicodec-packed.md)|
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|----------------|-------|-------------|-------|---------------------------------------|
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|0x052f62696e2f | /bin/ |raw binary |binary | 0x00 |
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|0x042f62322f | /b2/ |ascii base2 |binary | |
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|0x052f6231362f | /b16/ |ascii base16 |hex | |
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|0x052f6233322f | /b32/ |ascii base32 | | |
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|0x052f6235382f | /b58/ |ascii base58 | | |
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|0x052f6236342f | /b64/ |ascii base64 | | |
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|0x062f6a736f6e2f |/json/ | |json | |
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|0x062f63626f722f |/cbor/ | |json | |
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|0x062f62736f6e2f |/bson/ | |json | |
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|0x072f626a736f6e2f|/bjson/| |json | |
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|0x082f75626a736f6e2f| /ubjson/| |json | |
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|0x182f6d756c7469636f6465632f | /multicodec/ | | multiformat | 0x40 |
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|0x162f6d756c7469686173682f | /multihash/ | | multiformat | 0x41 |
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|0x162f6d756c7469616464722f | /multiaddr/ | | multiformat | 0x42 |
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|0x0a2f70726f746f6275662f |/protobuf/ | Protocol Buffers |protobuf| |
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|0x072f6361706e702f | /capnp/ | Cap-n-Proto |protobuf| |
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|0x092f666c61746275662f |/flatbuf/ | FlatBuffers |protobuf| |
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|0x052f7461722f |/tar/ | | archive | |
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|0x052f7a69702f |/zip/ | | archive | |
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|0x052f706e672f | /png/ | | archive | |
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|0x052f726c702f | /rlp/ | recursive length prefix | ethereum | 0x60 |
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## The protocol path
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`multicodec` allows us to specify different protocols in a universal namespace, that way being able to recognize, multiplex, and embed them easily. We use the notion of a `path` instead of an `id` because it is meant to be a Unix-friendly URI.
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@ -115,17 +91,48 @@ An example of a _great_ path name is:
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```
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/ipfs/Qmaa4Rw81a3a1VEx4LxB7HADUAXvZFhCoRdBzsMZyZmqHD/ipfs.protocol
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/http/w3id.org/ipfs/ipfs-1.1.0.json
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/http/w3id.org/ipfs/1.1.0
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```
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These path names happen to be resolvable -- not just in a "multicodec muxer(e.g [multistream]())" but -- in the internet as a whole (provided the program (or OS) knows how to use the `/ipfs` and `/http` protocols).
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These path names happen to be resolvable -- not just in a "multicodec muxer(e.g [multistream](https://github.com/multiformats/multistream))" but -- in the internet as a whole (provided the program (or OS) knows how to use the `/ipfs` and `/http` protocols).
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## Multicodec table
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| prefix | codec | desc | type | [packed encoding](https://github.com/multiformats/multicodec/blob/master/multicodec-packed.md)|
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|----------------|-------|--------------|--------|---------------------------------------|
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|0x052f62696e2f | /bin/ | raw binary | binary | 0x00 |
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|0x042f62322f | /b2/ | ascii base2 | binary | |
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|0x052f6231362f | /b16/ | ascii base16 | hex | |
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|0x052f6233322f | /b32/ | ascii base32 | | |
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|0x052f6235382f | /b58/ | ascii base58 | | |
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|0x052f6236342f | /b64/ | ascii base64 | | |
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|0x062f6a736f6e2f |/json/ | |json | |
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|0x062f63626f722f |/cbor/ | |json | |
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|0x062f62736f6e2f |/bson/ | |json | |
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|0x072f626a736f6e2f|/bjson/| |json | |
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|0x082f75626a736f6e2f| /ubjson/| |json | |
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|0x182f6d756c7469636f6465632f | /multicodec/ | | multiformat | 0x40 |
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|0x162f6d756c7469686173682f | /multihash/ | | multiformat | 0x41 |
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|0x162f6d756c7469616464722f | /multiaddr/ | | multiformat | 0x42 |
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|0x0a2f70726f746f6275662f |/protobuf/ | Protocol Buffers |protobuf| |
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|0x072f6361706e702f | /capnp/ | Cap-n-Proto |protobuf| |
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|0x092f666c61746275662f |/flatbuf/ | FlatBuffers |protobuf| |
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|0x052f7461722f |/tar/ | | archive | |
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|0x052f7a69702f |/zip/ | | archive | |
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|0x052f706e672f | /png/ | | archive | |
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|0x052f726c702f | /rlp/ | recursive length prefix | ethereum | 0x60 |
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## Implementations
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- [go-multicodec](https://github.com/multiformats/go-multicodec)
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- [go-multistream](https://github.com/multiformats/go-multistream) - Implements multistream, which uses multicodec for stream negotiation
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- [js-multistream](https://github.com/multiformats/js-multistream-select) - Implements multistream, which uses multicodec for stream negotiation
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- [clj-multicodec](https://github.com/multiformats/clj-multicodec)
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- multicodec
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- [go-multicodec](https://github.com/multiformats/go-multicodec)
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- multicodec-packed
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- [go-multicodec-packed](https://github.com/multiformats/go-multicodec-packed)
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- [js-multicodec-packed](https://github.com/multiformats/js-multicodec-packed)
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- multistream
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- [go-multistream](https://github.com/multiformats/go-multistream) - Implements multistream, which uses multicodec for stream negotiation
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- [js-multistream](https://github.com/multiformats/js-multistream) - Implements multistream, which uses multicodec for stream negotiation
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- [clj-multicodec](https://github.com/greglook/clj-multicodec)
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## FAQ
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