merkle-patricia-tree

constructor

constructor(db?: any, root?: Buffer, deleteFromDB?: boolean);

• test

  Parameter db

  A [levelup](https://github.com/Level/levelup) instance. By default (if the db is null or left undefined) creates an in-memory [memdown](https://github.com/Level/memdown) instance.

  Parameter root

  A Buffer for the root of a previously stored trie

  Parameter deleteFromDB

  Delete nodes from DB on delete operations (disallows switching to an older state root) (default: false)

property db

db: DB;

• The backend DB

property EMPTY_TRIE_ROOT

EMPTY_TRIE_ROOT: Buffer;

• The root for an empty trie

property isCheckpoint

readonly isCheckpoint: boolean;

• BaseTrie has no checkpointing so return false

property lock

protected lock: Semaphore;

property root

root: Buffer;

• Gets the current root of the trie

method batch

batch: (ops: BatchDBOp[]) => Promise<void>;

• The given hash of operations (key additions or deletions) are executed on the trie (delete operations are only executed on DB with deleteFromDB set to true)

  Parameter ops

  Example 1

  const ops = [ { type: 'del', key: Buffer.from('father') } , { type: 'put', key: Buffer.from('name'), value: Buffer.from('Yuri Irsenovich Kim') } , { type: 'put', key: Buffer.from('dob'), value: Buffer.from('16 February 1941') } , { type: 'put', key: Buffer.from('spouse'), value: Buffer.from('Kim Young-sook') } , { type: 'put', key: Buffer.from('occupation'), value: Buffer.from('Clown') } ] await trie.batch(ops)

method checkRoot

checkRoot: (root: Buffer) => Promise<boolean>;

• Checks if a given root exists.

method copy

copy: () => Trie;

• Creates a new trie backed by the same db.

method createProof

static createProof: (trie: Trie, key: Buffer) => Promise<Proof>;

• Creates a proof from a trie and key that can be verified using Trie.verifyProof.

  Parameter trie

  Parameter key

method createReadStream

createReadStream: () => ReadStream;

• The data event is given an Object that has two properties; the key and the value. Both should be Buffers. Returns a [stream](https://nodejs.org/dist/latest-v12.x/docs/api/stream.html#stream_class_stream_readable) of the contents of the trie

method del

del: (key: Buffer) => Promise<void>;

• Deletes a value given a key from the trie (delete operations are only executed on DB with deleteFromDB set to true)

  Parameter key

  Returns

  A Promise that resolves once value is deleted.

method findPath

findPath: (key: Buffer, throwIfMissing?: boolean) => Promise<Path>;

• Tries to find a path to the node for the given key. It returns a stack of nodes to the closest node.

  Parameter key

  the search key

  Parameter throwIfMissing

  if true, throws if any nodes are missing. Used for verifying proofs. (default: false)

method fromProof

static fromProof: (proof: Proof, trie?: Trie) => Promise<Trie>;

• Saves the nodes from a proof into the trie. If no trie is provided a new one wil be instantiated.

  Parameter proof

  Parameter trie

method get

get: (key: Buffer, throwIfMissing?: boolean) => Promise<Buffer | null>;

• Gets a value given a key

  Parameter key

  the key to search for

  Parameter throwIfMissing

  if true, throws if any nodes are missing. Used for verifying proofs. (default: false)

  Returns

  A Promise that resolves to Buffer if a value was found or null if no value was found.

method lookupNode

lookupNode: (node: Buffer | Buffer[]) => Promise<TrieNode | null>;

• Retrieves a node from db by hash.

method prove

static prove: (trie: Trie, key: Buffer) => Promise<Proof>;

• prove has been renamed to Trie.createProof.

  Parameter trie

  Parameter key

  Deprecated

method put

put: (key: Buffer, value: Buffer) => Promise<void>;

• Stores a given value at the given key or do a delete if value is empty (delete operations are only executed on DB with deleteFromDB set to true)

  Parameter key

  Parameter value

  Returns

  A Promise that resolves once value is stored.

method setRoot

setRoot: (value?: Buffer) => void;

• This method is deprecated. Please use Trie.root instead.

  Parameter value

  Deprecated

method verifyProof

static verifyProof: (
    rootHash: Buffer,
    key: Buffer,
    proof: Proof
) => Promise<Buffer | null>;

• Verifies a proof.

  Parameter rootHash

  Parameter key

  Parameter proof

  Returns

  The value from the key, or null if valid proof of non-existence.

  Throws

  If proof is found to be invalid.

method verifyRangeProof

static verifyRangeProof: (
    rootHash: Buffer,
    firstKey: Buffer | null,
    lastKey: Buffer | null,
    keys: Buffer[],
    values: Buffer[],
    proof: Buffer[] | null
) => Promise<boolean>;

• verifyRangeProof

method walkTrie

walkTrie: (root: Buffer, onFound: FoundNodeFunction) => Promise<void>;

• Walks a trie until finished.

  Parameter root

  Parameter onFound

  callback to call when a node is found. This schedules new tasks. If no tasks are available, the Promise resolves.

  Returns

  Resolves when finished walking trie.

constructor

constructor(...args: any);

property db

db: CheckpointDB;

property isCheckpoint

readonly isCheckpoint: boolean;

• Is the trie during a checkpoint phase?

method checkpoint

checkpoint: () => void;

• Creates a checkpoint that can later be reverted to or committed. After this is called, all changes can be reverted until commit is called.

method commit

commit: () => Promise<void>;

• Commits a checkpoint to disk, if current checkpoint is not nested. If nested, only sets the parent checkpoint as current checkpoint.

  Throws

  If not during a checkpoint phase

method copy

copy: (includeCheckpoints?: boolean) => CheckpointTrie;

• Returns a copy of the underlying trie with the interface of CheckpointTrie.

  Parameter includeCheckpoints

  If true and during a checkpoint, the copy will contain the checkpointing metadata and will use the same scratch as underlying db.

method revert

revert: () => Promise<void>;

• Reverts the trie to the state it was at when checkpoint was first called. If during a nested checkpoint, sets root to most recent checkpoint, and sets parent checkpoint as current.

constructor

constructor(...args: any);

method copy

copy: (includeCheckpoints?: boolean) => SecureTrie;

• Returns a copy of the underlying trie with the interface of SecureTrie.

  Parameter includeCheckpoints

  If true and during a checkpoint, the copy will contain the checkpointing metadata and will use the same scratch as underlying db.

method createProof

static createProof: (trie: SecureTrie, key: Buffer) => Promise<Proof>;

• Creates a proof that can be verified using SecureTrie.verifyProof.

  Parameter trie

  Parameter key

method del

del: (key: Buffer) => Promise<void>;

• Deletes a value given a key.

  Parameter key

method get

get: (key: Buffer) => Promise<Buffer | null>;

• Gets a value given a key

  Parameter key

  the key to search for

  Returns

  A Promise that resolves to Buffer if a value was found or null if no value was found.

method prove

static prove: (trie: SecureTrie, key: Buffer) => Promise<Proof>;

• prove has been renamed to SecureTrie.createProof.

  Parameter trie

  Parameter key

  Deprecated

method put

put: (key: Buffer, val: Buffer) => Promise<void>;

• Stores a given value at the given key. For a falsey value, use the original key to avoid double hashing the key.

  Parameter key

  Parameter value

method verifyProof

static verifyProof: (
    rootHash: Buffer,
    key: Buffer,
    proof: Proof
) => Promise<Buffer | null>;

• Verifies a proof.

  Parameter rootHash

  Parameter key

  Parameter proof

  Returns

  The value from the key.

  Throws

  If proof is found to be invalid.

method verifyRangeProof

static verifyRangeProof: (
    rootHash: Buffer,
    firstKey: Buffer | null,
    lastKey: Buffer | null,
    keys: Buffer[],
    values: Buffer[],
    proof: Buffer[] | null
) => Promise<boolean>;

• Verifies a range proof.

property onNode

readonly onNode: FoundNodeFunction;

property taskExecutor

readonly taskExecutor: PrioritizedTaskExecutor;

property trie

readonly trie: BaseTrie;

method allChildren

allChildren: (node: TrieNode, key?: Nibbles) => void;

• Run all children of a node. Priority of these nodes are the key length of the children.

  Parameter node

  Node to get all children of and call onNode on.

  Parameter key

  The current key which would yield the node when trying to get this node with a get operation.

method newWalk

static newWalk: (
    onNode: FoundNodeFunction,
    trie: BaseTrie,
    root: Buffer,
    poolSize?: number
) => Promise<void>;

• Async function to create and start a new walk over a trie.

  Parameter onNode

  The `FoundNodeFunction to call if a node is found.

  Parameter trie

  The trie to walk on.

  Parameter root

  The root key to walk on.

  Parameter poolSize

  Task execution pool size to prevent OOM errors. Defaults to 500.

method onlyBranchIndex

onlyBranchIndex: (
    node: BranchNode,
    key: Nibbles | undefined,
    childIndex: number,
    priority?: number
) => void;

• Push a branch of a certain BranchNode to the event queue.

  Parameter node

  The node to select a branch on. Should be a BranchNode.

  Parameter key

  The current key which leads to the corresponding node.

  Parameter childIndex

  The child index to add to the event queue.

  Parameter priority

  Optional priority of the event, defaults to the total key length.

method pushNodeToQueue

pushNodeToQueue: (nodeRef: Buffer, key?: Nibbles, priority?: number) => void;

• Push a node to the queue. If the queue has places left for tasks, the node is executed immediately, otherwise it is queued.

  Parameter nodeRef

  Push a node reference to the event queue. This reference is a 32-byte keccak hash of the value corresponding to the key.

  Parameter key

  The current key.

  Parameter priority

  Optional priority, defaults to key length