Add Real-World Util Blob Example (#4192)

* Expand util blob example

* Fix getBlobs() in Util, remove size limitation in example

* revert change to getBlob

* fix blob example

* Commented out blobs example file reading and make it optional again

---------

Co-authored-by: ScottyPoi <[email protected]>

Author: holgerd77

packages/util/examples/blobs.ts

@@ -1,12 +1,37 @@
-import { bytesToHex, computeVersionedHash, getBlobs } from '@ethereumjs/util'
+//import * as fs from 'fs'
+import {
+  type PrefixedHexString,
+  blobsToCellProofs,
+  blobsToProofs,
+  computeVersionedHash,
+  hexToBytes,
+} from '@ethereumjs/util'
+import { trustedSetup } from '@paulmillr/trusted-setups/fast-peerdas.js'
+import { KZG as microEthKZG } from 'micro-eth-signer/kzg.js'
 
-const blobs = getBlobs('test input')
+const kzg = new microEthKZG(trustedSetup)
 
-console.log('Created the following blobs:')
-console.log(blobs)
+/**
+ *  Uncomment for a more realistic example using a real blob, e.g. from https://blobscan.com/
+ *  Use with node ./examples/blobs.ts <file path>
+ */
+// const filePath = process.argv[2]
+//const blob: PrefixedHexString = `0x${fs.readFileSync(filePath, 'ascii')}`
+const blob: PrefixedHexString = `0x${'11'.repeat(131072)}` // 128 KiB
+console.log(blob)
+
+const commitment = kzg.blobToKzgCommitment(blob)
 
-const commitment = bytesToHex(new Uint8Array([1, 2, 3]))
 const blobCommitmentVersion = 0x01
-const versionedHash = computeVersionedHash(commitment, blobCommitmentVersion)
+const versionedHash = computeVersionedHash(commitment as PrefixedHexString, blobCommitmentVersion)
+
+// EIP-4844 only
+const blobProof = blobsToProofs(kzg, [blob], [commitment as PrefixedHexString])
+const cellProofs = blobsToCellProofs(kzg, [blob])
 
-console.log(`Versioned hash ${versionedHash} computed`)
+console.log(`Blob size                   : ${hexToBytes(blob).length / 1024}KiB`)
+console.log(`Commitment                  : ${commitment}`)
+console.log(`Versioned hash              : ${versionedHash}`)
+console.log(`Blob proof (EIP-4844)       : ${blobProof}`)
+console.log(`First cell proof (EIP-7594) : ${cellProofs[0]}`)
+console.log(`Num cell proofs (EIP-7594)  : ${cellProofs.length}`)

packages/util/src/blobs.ts

@@ -36,7 +36,7 @@ function getPadded(data: Uint8Array, blobs_len: number): Uint8Array {
  * @param data Input data (must be exactly BLOB_SIZE bytes)
  * @returns Hex-prefixed blob string
  */
-function getBlob(data: Uint8Array): PrefixedHexString {
+export function getBlob(data: Uint8Array): PrefixedHexString {
   const blob = new Uint8Array(BLOB_SIZE)
   for (let i = 0; i < FIELD_ELEMENTS_PER_BLOB; i++) {
     const chunk = new Uint8Array(32)