Trie: add partialPath parameter to trie.findPath() (ethereumjs#3305)

* trie: add optional "partialPath" parameter to findPath

* trie: use partialPath input in findPath stack

* trie: start findPath walk from end of partialPath

* trie: identify starting point in debug log

* trie: test findPath with partial

* trie: test findPath on secure trie

---------

Co-authored-by: Holger Drewes <[email protected]>

packages/trie/src/trie.ts

@@ -596,11 +596,23 @@ export class Trie {
    * @param key - the search key
    * @param throwIfMissing - if true, throws if any nodes are missing. Used for verifying proofs. (default: false)
    */
-  async findPath(key: Uint8Array, throwIfMissing = false): Promise<Path> {
+  async findPath(
+    key: Uint8Array,
+    throwIfMissing = false,
+    partialPath: {
+      stack: TrieNode[]
+    } = {
+      stack: [],
+    }
+  ): Promise<Path> {
     const targetKey = bytesToNibbles(key)
     const keyLen = targetKey.length
     const stack: TrieNode[] = Array.from({ length: keyLen })
     let progress = 0
+    for (let i = 0; i < partialPath.stack.length - 1; i++) {
+      stack[i] = partialPath.stack[i]
+      progress += stack[i] instanceof BranchNode ? 1 : (<ExtensionNode>stack[i]).keyLength()
+    }
     this.DEBUG && this.debug(`Target (${targetKey.length}): [${targetKey}]`, ['FIND_PATH'])
     let result: Path | null = null
 
@@ -672,10 +684,17 @@ export class Trie {
         walkController.allChildren(node, keyProgress)
       }
     }
-
+    const startingNode = partialPath.stack[partialPath.stack.length - 1]
+    const start = startingNode !== undefined ? this.hash(startingNode?.serialize()) : this.root()
     try {
-      this.DEBUG && this.debug(`Walking trie from root: ${bytesToHex(this.root())}`, ['FIND_PATH'])
-      await this.walkTrie(this.root(), onFound)
+      this.DEBUG &&
+        this.debug(
+          `Walking trie from ${startingNode === undefined ? 'ROOT' : 'NODE'}: ${bytesToHex(
+            start as Uint8Array
+          )}`,
+          ['FIND_PATH']
+        )
+      await this.walkTrie(start, onFound)
     } catch (error: any) {
       if (error.message !== 'Missing node in DB' || throwIfMissing) {
         throw error

packages/trie/test/trie/findPath.spec.ts

@@ -0,0 +1,70 @@
+import { randomBytes } from '@ethereumjs/util'
+import { assert, describe, it } from 'vitest'
+
+import { Trie } from '../../src/index.js'
+
+describe('TRIE > findPath', async () => {
+  const keys = Array.from({ length: 200 }, () => randomBytes(8))
+  const trie = new Trie()
+  for (const [i, k] of keys.entries()) {
+    await trie.put(k, Uint8Array.from([i, i]))
+  }
+  const rootNode = await trie.lookupNode(trie.root())
+  for (const [idx, k] of keys.slice(0, 10).entries()) {
+    const val = await trie.get(k)
+    it('should find values for key', async () => {
+      assert.deepEqual(val, Uint8Array.from([idx, idx]))
+    })
+    trie['debug']('FIND PATH ORIGINAL:' + '-'.repeat(20))
+    const path = await trie.findPath(k)
+    it('should find path for key', async () => {
+      assert.isNotNull(path.node)
+      assert.deepEqual(path.stack[0], rootNode)
+      assert.deepEqual(path.node?.value(), Uint8Array.from([idx, idx]))
+    })
+    trie['debug'](`FINDING PARTIAL PATHS: ` + path.stack.length + '-'.repeat(20))
+    for (let i = 1; i <= path.stack.length - 1; i++) {
+      trie['debug']('FIND PATH PARTIAL: ' + i + '-'.repeat(20))
+      const pathFromPartial = await trie.findPath(k, false, { stack: path.stack.slice(0, i) })
+      it(`should find path for key from partial stack (${i}/${path.stack.length})`, async () => {
+        assert.deepEqual(path, pathFromPartial)
+        assert.isNotNull(pathFromPartial.node)
+        assert.deepEqual(pathFromPartial.stack[0], rootNode)
+        assert.deepEqual(pathFromPartial.node?.value(), Uint8Array.from([idx, idx]))
+        assert.equal(path.stack.length, pathFromPartial.stack.length)
+      })
+    }
+  }
+})
+describe('TRIE (secure) > findPath', async () => {
+  const keys = Array.from({ length: 1000 }, () => randomBytes(20))
+  const trie = new Trie({ useKeyHashing: true })
+  for (const [i, k] of keys.entries()) {
+    await trie.put(k, Uint8Array.from([i, i]))
+  }
+  const rootNode = await trie.lookupNode(trie.root())
+  for (const [idx, k] of keys.slice(0, 10).entries()) {
+    const val = await trie.get(k)
+    it('should find value for key', async () => {
+      assert.deepEqual(val, Uint8Array.from([idx, idx]))
+    })
+    const path = await trie.findPath(trie['hash'](k))
+    it('should find path for key', async () => {
+      assert.isNotNull(path.node)
+      assert.deepEqual(path.stack[0], rootNode)
+      assert.deepEqual(path.node?.value(), Uint8Array.from([idx, idx]))
+    })
+    for (let i = 2; i <= path.stack.length - 1; i++) {
+      const pathFromPartial = await trie.findPath(trie['hash'](k), false, {
+        stack: path.stack.slice(0, i),
+      })
+      it(`should find path for key from partial stack (${i}/${path.stack.length})`, async () => {
+        assert.deepEqual(path, pathFromPartial)
+        assert.isNotNull(pathFromPartial.node)
+        assert.deepEqual(pathFromPartial.stack[0], rootNode)
+        assert.deepEqual(pathFromPartial.node?.value(), Uint8Array.from([idx, idx]))
+        assert.equal(path.stack.length, pathFromPartial.stack.length)
+      })
+    }
+  }
+})