109 lines
3.5 KiB
Go
109 lines
3.5 KiB
Go
//
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// Copyright 2020 Wireline, Inc.
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//
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package utils
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import (
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"bytes"
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"errors"
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"github.com/ipld/go-ipld-prime/codec/dagcbor"
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"github.com/ipld/go-ipld-prime/fluent"
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"github.com/ipld/go-ipld-prime/linking"
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cidlink "github.com/ipld/go-ipld-prime/linking/cid"
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"github.com/ipld/go-ipld-prime/multicodec"
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"github.com/ipld/go-ipld-prime/storage/memstore"
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canonicalJson "github.com/gibson042/canonicaljson-go"
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"github.com/ipfs/go-cid"
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cbor "github.com/ipfs/go-ipld-cbor"
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basicnode "github.com/ipld/go-ipld-prime/node/basic"
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mh "github.com/multiformats/go-multihash"
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)
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var store = memstore.Store{}
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func init() {
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multicodec.RegisterEncoder(0x71, dagcbor.Encode)
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multicodec.RegisterDecoder(0x71, dagcbor.Decode)
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}
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// GenerateHash returns the hash of the canonicalized JSON input.
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func GenerateHash(json map[string]interface{}) (string, []byte, error) {
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content, err := canonicalJson.Marshal(json)
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if err != nil {
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return "", nil, err
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}
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cidString, err := CIDFromJSONBytesUsingIpldPrime(content)
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if err != nil {
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return "", nil, err
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}
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return cidString, content, nil
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}
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// CIDFromJSONBytes returns CID (cbor) for json (as bytes).
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func CIDFromJSONBytes(content []byte) (string, error) {
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cid, err := cbor.FromJSON(bytes.NewReader(content), mh.SHA2_256, -1)
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if err != nil {
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return "", err
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}
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return cid.String(), nil
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}
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// GetAttributeAsString returns a map attribute as string, if possible.
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func GetAttributeAsString(obj map[string]interface{}, attr string) (string, error) {
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if value, ok := obj[attr]; ok {
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if valueStr, ok := value.(string); ok {
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return valueStr, nil
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}
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return "", errors.New("attribute not of string type")
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}
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return "", errors.New("attribute not found")
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}
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// CIDFromJSONBytesUsingIpldPrime returns CID (dagcbor) for json (as bytes).
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func CIDFromJSONBytesUsingIpldPrime(content []byte) (string, error) {
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lsys := cidlink.DefaultLinkSystem()
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// We want to store the serialized data somewhere.
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// We'll use an in-memory store for this. (It's a package scoped variable.)
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// You can use any kind of storage system here;
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// or if you need even more control, you could also write a function that conforms to the linking.BlockWriteOpener interface.
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lsys.SetWriteStorage(&store)
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// To create any links, first we need a LinkPrototype.
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// This gathers together any parameters that might be needed when making a link.
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// (For CIDs, the version, the codec, and the multihash type are all parameters we'll need.)
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// Often, you can probably make this a constant for your whole application.
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lp := cidlink.LinkPrototype{Prefix: cid.Prefix{ //nolint:golint
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Version: 1, // Usually '1'.
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Codec: 0x71, // 0x71 means "dag-cbor" -- See the multicodecs table: https://github.com/multiformats/multicodec/
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MhType: 0x12, // 0x12 means "sha2-256" -- See the multicodecs table: https://github.com/multiformats/multicodec/
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MhLength: 32, // sha2-256 hash has a 32-byte sum.
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}}
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// And we need some data to link to! Here's a quick piece of example data:
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n, err := fluent.Build(basicnode.Prototype.Any, func(na fluent.NodeAssembler) {
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na.AssignBytes(content)
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})
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if err != nil {
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return "", err
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}
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// Now: time to apply the LinkSystem, and do the actual store operation!
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lnk, err := lsys.Store(
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linking.LinkContext{}, // The zero value is fine. Configure it it you want cancellability or other features.
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lp, // The LinkPrototype says what codec and hashing to use.
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n, // And here's our data.
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)
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if err != nil {
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return "", err
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}
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return lnk.String(), nil
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}
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