laconicd/utils/json.go

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