@stricahq/cardano-codec

Cardano block and transaction parser for JavaScript. It turns the CBOR of blocks, transactions, witness sets and metadata into plain JavaScript data, with parsers for every era from Byron to Conway.

Every hash it computes, from block hashes and transaction ids to script and datum hashes, covers the item's bytes as they were written on chain, never a re-encoding, so it matches the ledger's even for an item encoded in a non-canonical way. The bytes come from the annotation tree of @stricahq/cbors: you decode with cbors, and the parsers read its tree.

• Blocks and transactions of Byron, Shelley, Allegra, Mary, Alonzo, Babbage and Conway, Conway governance included
• Amounts as decimal strings and integers beyond 2^53 as bigint, so neither loses precision
• Native scripts and metadata of any depth, parsed without recursion
• TypeScript types for every result
• No Node.js builtins: runs in Node.js and in browsers, without polyfills

v3 is a breaking change

v3 is not a drop-in upgrade. It is ESM-only and needs Node >= 22.12, the parsers take a node from cbors v2's decodeAnnotated() instead of a decoded value and the block bytes, and results hold bigint and Uint8Array where 2.x had BigNumber and Buffer. Migrating from 2.x lists every change and its replacement.

Moving to v3 is the recommended path: it parses real blocks about 1.5x faster than v2.x, computes every hash over the bytes as written, and its browser bundle is a fifth of the size.

Staying on 2.x

2.x remains on npm and keeps working. Pin the major version to stay there:

yarn add @stricahq/cardano-codec@2

<script src="https://cdn.jsdelivr.net/npm/@stricahq/cardano-codec@2/dist/index.min.js"></script>

2.x is a CJS + ESM dual package, runs on Node >= 18, and uses Buffer and BigNumber. Everything below documents v3.

Installation

yarn/npm

yarn add @stricahq/cardano-codec @stricahq/cbors

The parsers take nodes from cbors' decodeAnnotated(), so cbors goes into your own dependencies, next to the codec.

The package is ESM-only. CommonJS code can require() it on Node >= 22.12:

const { conway } = require("@stricahq/cardano-codec");

A TypeScript project that compiles to CommonJS needs TypeScript >= 5.8 with module: nodenext for that.

The only dependencies are @stricahq/cbors and blakejs. Neither uses Node.js builtins, so bundlers need no polyfills or aliases.

Browser

<script src="https://cdn.jsdelivr.net/npm/@stricahq/cardano-codec/dist/index.min.js"></script>

<script>
  // the cardanoCodec global carries a copy of cbors to decode with
  const { cbors, conway } = cardanoCodec;
  const toBytes = (hex) => Uint8Array.from(hex.match(/../g), (b) => parseInt(b, 16));

  const block = conway.parseBlock(cbors.decodeAnnotated(toBytes(blockHex), { maxDepth: Infinity }));
  block.header.body.hash;
</script>

Quick start

import { decodeAnnotated } from "@stricahq/cbors";
import { conway } from "@stricahq/cardano-codec";

const block = conway.parseBlock(decodeAnnotated(blockBytes, { maxDepth: Infinity }));

block.header.body.hash;        // block hash
block.header.body.slot;        // slot
block.transactions[0].hash;    // id of the first transaction
block.witnesses[0];            // its witness set
block.auxiliaryDataMap.get(0); // its auxiliary data (metadata and scripts), if it has any

blockBytes is the block's CBOR, as a Uint8Array or a Node.js Buffer.

Decode chain data with { maxDepth: Infinity }. cbors rejects items nested deeper than 1024 levels by default, and a valid transaction can nest deeper than that. cbors decodes any depth without recursion, and so do the parsers.

Parsing

A parser takes the CborNode of the item it parses. That can be the root of a tree or any node inside one, so a message decoded once is parsed piece by piece.

Transactions

A standalone transaction is [body, witnessSet, isValid, auxiliaryData]:

const tx = decodeAnnotated(txBytes, { maxDepth: Infinity });

const transaction = conway.parseTransaction(tx.at(0)); // body, with the transaction id as `hash`
const witnesses = conway.parseWitnessMap(tx.at(1));    // witness set

const auxNode = tx.at(3); // CBOR null when the transaction has none
const auxiliaryData = auxNode.kind === "null" ? null : conway.parseAuxiliaryData(auxNode);

Shelley to Mary transactions have no isValid flag, so their auxiliary data is tx.at(2).

APIs and wallets usually hand transactions out as hex. cbors ships no hex helper: Buffer.from(hex, "hex") converts it on Node.js, and Uint8Array.fromHex(hex) on runtimes that have it.

Blocks from a node

In block-fetch, and in node-to-client chain-sync, a node sends each block as [era, block]. The inner node goes straight to a parser, and the era number says which one:

import { byron, alonzo, babbage, conway } from "@stricahq/cardano-codec";

const parsers = [
  byron.parseEbBlock, // 0: Byron epoch boundary block
  byron.parseBlock,   // 1: Byron
  alonzo.parseBlock,  // 2: Shelley
  alonzo.parseBlock,  // 3: Allegra
  alonzo.parseBlock,  // 4: Mary
  alonzo.parseBlock,  // 5: Alonzo
  babbage.parseBlock, // 6: Babbage
  conway.parseBlock,  // 7: Conway
];

const message = decodeAnnotated(payload, { maxDepth: Infinity }); // [era, block]
const block = parsers[message.at(0).value](message.at(1));

Which parser for which era

| Era | Block | Transaction | |---|---|---| | Byron epoch boundary | byron.parseEbBlock | — | | Byron | byron.parseBlock | byron.parseTransaction, on the transaction payload of the block body | | Shelley, Allegra, Mary, Alonzo | alonzo.parseBlock | alonzo.parseTransaction | | Babbage | babbage.parseBlock | babbage.parseTransaction | | Conway | conway.parseBlock | conway.parseTransaction |

Each era also exports parseHeader, and Shelley onwards parseWitnessMap and parseAuxiliaryData, for parsing those items on their own. common has the metadata and native script parsers the Shelley-based eras share: parseMetadata, parseNativeScript and parseNativeScripts.

Block parsers are not interchangeable: babbage.parseBlock and conway.parseBlock read the Babbage header format, and throw on a Shelley to Alonzo block.

Transaction parsers read the transactions of earlier eras too, except for what a later era removed. The babbage parser throws on an update proposal that sets a parameter Babbage dropped (d, entropy, minUTxOValue). The conway parser throws on any update proposal, and on genesis delegation and MIR certificates, all of which Conway removed. The parser of a transaction's own era always reads it.

What you get back

• Hashes, keys, signatures, asset names, scripts and Plutus data: lowercase hex strings.
• Addresses and reward accounts: the address bytes in hex, not bech32 or base58.
• Lovelace and token amounts: decimal strings. That covers fee, output, token and MIR amounts, withdrawals, certificate and governance proposal deposits, a pool's pledge and cost, totalCollateral, treasuryAmount, donation, and the lovelace-valued protocol parameters (minFeeA, minFeeB, stakeKeyDeposit, poolDeposit, minPoolCost, adaPerUtxoByte, govActionDeposit, dRepDeposit).
• Every other integer, such as slots, ttl, epochs, execution units and the remaining protocol parameters: a number, or a bigint beyond ±2^53.
• Rationals: a number for protocol parameters and voting thresholds, a [numerator, denominator] pair for a pool's margin and for exUnitPrices.
• Metadata values: Map, Array, number, bigint, Uint8Array or string (types.*.MetaDatum). Byte strings are copies, so a result never pins or aliases the buffer you decoded.
• Native scripts and metadata: nested as deep as they were written, which can be thousands of levels.

A Conway stake registration and delegation, as conway.parseTransaction() returns it:

{
  hash: "ac67ea37e6ad9fbadfe9210d49f8b778d35426227dada6dbc1a453e2dee40d0d",
  inputs: [{ txId: "c6270586133ca06ceacacb66de8bd21afa934ca6e51700a20f15c069e5d57a9f", index: 0 }],
  outputs: [
    {
      address: "010a05f7cc825c9a0c036db891b4597b7adcf0c454caf1f207ca7a00419ef5a37441acfbe92fffbafab7c6b30ef56abd24f450296d7b4aeb8c",
      amount: "452825303",
      // tokens, plutusDataHash, plutusData and scriptRef: undefined unless the output has them
    },
  ],
  fee: "174697",
  ttl: 192034209,
  certificates: [
    {
      type: 7, // CertificateType.STAKE_REG, a registration with a deposit
      cert: {
        stakeCredential: { key: "9ef5a37441acfbe92fffbafab7c6b30ef56abd24f450296d7b4aeb8c", type: 0 },
        deposit: "2000000",
      },
    },
    {
      type: 2, // CertificateType.STAKE_DELEGATION
      cert: {
        stakeCredential: { key: "9ef5a37441acfbe92fffbafab7c6b30ef56abd24f450296d7b4aeb8c", type: 0 },
        poolKeyHash: "153806dbcd134ddee69a8c5204e38ac80448f62342f8c23cfe4b7edf",
      },
    },
  ],
}

Every field that says what kind of thing something is comes back as the number the ledger's CDDL gives it, never a name: a certificate's type (7 and 2 above), a credential's type (0 a key hash, 1 a script), a script's type (0 native, 1 to 3 Plutus V1 to V3), a redeemer's tag, and Conway's governance actions, voters, votes and DRep delegations. The matching types.* enum turns one back into a name to print: types.ConwayTypes.HashType[0] is "ADDRESS".

Hashes

The parsers compute these hashes, over the bytes as written:

• the block hash: header.body.hash, or header.hash for Byron
• the transaction id: a transaction's hash
• the keys of a witness set's records: vKeyWitnesses and bootstrapWitness are keyed by the hash of the public key, nativeScripts, plutusScripts, plutusScriptsV2 and plutusScriptsV3 by script hash, and plutusData by datum hash
• an output's scriptRef.hash, and the plutusDataHash of an output with an inline datum

The transaction above is signed with the payment and the stake key of its output's address, so its vkey witnesses are keyed by the two key hashes in that address:

conway.parseWitnessMap(tx.at(1)).vKeyWitnesses;
// {
//   "0a05f7cc825c9a0c036db891b4597b7adcf0c454caf1f207ca7a0041": { vKey: "08e9c80e…", signature: "3cb2fa51…" },
//   "9ef5a37441acfbe92fffbafab7c6b30ef56abd24f450296d7b4aeb8c": { vKey: "e401ab0c…", signature: "4194bdbd…" },
// }

Every other hash, such as auxiliaryDataHash, scriptDataHash or a datum hash an output carries, is read from the transaction.

Serializing results

JSON.stringify throws on a bigint, and writes a Map (auxiliaryDataMap, metadata maps) as {} and a Uint8Array as an object of indexes. Give it a replacer:

const replacer = (_key, value) => {
  if (typeof value === "bigint") return value.toString();
  if (value instanceof Map) return [...value]; // [key, value] pairs: metadata keys need not be strings
  if (value instanceof Uint8Array) {
    return Array.from(value, (byte) => byte.toString(16).padStart(2, "0")).join("");
  }
  return value;
};

JSON.stringify(block, replacer);

JSON.stringify recurses, so a native script or metadata nested thousands of levels deep makes it throw a RangeError.

Types

Types for every parser result ship with the package:

import type { CborNode } from "@stricahq/cbors";
import { conway, types } from "@stricahq/cardano-codec";

// types.ByronTypes, types.AlonzoTypes, types.BabbageTypes, types.ConwayTypes, types.OuroborosTypes
const parse = (block: CborNode): types.ConwayTypes.ConwayBlock => conway.parseBlock(block);

Enums such as types.ConwayTypes.CertificateType, GovActionType and ScriptType are runtime values too, to compare results against and, indexed by number, to name them. CertificateType is shared: types.AlonzoTypes.CertificateType is the same enum.

Errors

A parser throws when the CBOR does not have the shape its era gives the item, rather than guess. An item of the wrong kind is named by its byte range in the buffer you decoded:

Error: Expected array at bytes [416, 450), got bytes

A missing item throws Expected …, got nothing. Anything else the parser does not know, such as a transaction field or certificate type from a later era, throws as well, and so does metadata holding anything but maps, arrays, integers, and byte or text strings.

Migrating from 2.x

| 2.x | 3.x | |---|---| | cbors.Decoder.decode(bytes).value before a parser | decodeAnnotated(bytes, { maxDepth: Infinity }), from your own @stricahq/cbors dependency | | parseBlock(decoded, blockCbor) | parseBlock(block), the node | | parseTransaction(decoded[0], blockCbor) | parseTransaction(tx.at(0)) | | common.parsePlutusData(datum, blockCbor) | gone: datumNode.bytes is the datum as written | | common.parseMetadata / parseNativeScript(s) on decoded values | the same, on a CborNode | | import codec from "@stricahq/cardano-codec" | import * as codec from "@stricahq/cardano-codec", or named imports | | CJS + ESM dual package, Node >= 18 | ESM only, Node >= 22.12 (require(esm)) | | Buffer: metadata byte strings, RollForward.block, LocalTxMonitorResponse.nextTx | Uint8Array | | BigNumber for integers beyond ±2^53 | bigint | | cardanoCodec.Buffer in the browser bundle | gone; cardanoCodec.cbors stays | | PlutusV3 witness scripts in witnesses.plutusScriptsV2 | witnesses.plutusScriptsV3 | | protocol parameter 33 (minFeeRefScriptCostPerByte) in govActionValidity | refScriptCostByte | | Credential type, script type and redeemer tag as names, such as "ADDRESS", "PLUTUS_V2" and "SPEND" | their CDDL numbers, the way certificate type and the conway parser's enums already read | | LocalTransactionSubmissionResponse.rejectionMessage: any | unknown: narrow it before reading from it |

Also check:

• JSON.stringify throws on a bigint. A value 2.x returned as a BigNumber, which serialized as a string, is a bigint now. Serializing results has a replacer.
• No Buffer. The codec no longer installs the buffer package. An app that imports buffer without depending on it has to add it.
• Malformed CBOR throws. A field of the wrong kind throws where 2.x returned undefined or a wrong value; see Errors.
• Lovelace-valued protocol parameters and ProposalProcedure.deposit are strings now. 2.x declared them string but returned a number; they are decimal strings, like every other amount. ProtocolParamUpdate.govActionDeposit and dRepDeposit, declared number in 2.x, are strings as well.
• Some fields are typed number now. Fields declared string that hold a count or a size, such as maxValueSize and NativeScript.n, invalidBefore and invalidAfter, are declared number. Their values did not change.

Tests

yarn test

The specs parse real blocks and transactions of every era and check them against the values the ledger records for them and against snapshots of the full output. Synthetic CBOR covers the shapes no real fixture has.

API Doc

Find the API documentation here.

License

Copyright 2023 Strica

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.