102 lines
3.0 KiB
TypeScript
102 lines
3.0 KiB
TypeScript
// Copyright 2017-2019 @polkadot/trie-codec authors & contributors
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// This software may be modified and distributed under the terms
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// of the Apache-2.0 license. See the LICENSE file for details.
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import { compactStripLength, logger } from '@polkadot/util';
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import NodeHeader, { BranchHeader, NibbleHeader } from './NodeHeader';
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import { NODE_TYPE_NULL, NODE_TYPE_BRANCH, NODE_TYPE_EXT, NODE_TYPE_LEAF } from './constants';
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import { addNibblesTerminator, encodeNibbles } from './nibbles';
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import { toNibbles } from './util';
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const EMPTY_BRANCH: Array<Uint8Array | null> = [
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null, null, null, null,
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null, null, null, null,
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null, null, null, null,
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null, null, null, null
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];
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const l = logger('trie/codec');
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l.noop();
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function _decodeBranch (header: NodeHeader, input: Uint8Array): Array<null | Uint8Array | [Uint8Array, Uint8Array]> {
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let offset = header.encodedLength;
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const branch = header.value as BranchHeader;
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const bitmap = input[offset] + (input[offset + 1] * 256);
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let value: null | Uint8Array = null;
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offset += 2;
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if (branch.valueOf() === true) {
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const [length, bytes] = compactStripLength(input.subarray(offset));
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value = bytes;
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offset += length;
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}
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let cursor = 1;
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return EMPTY_BRANCH.concat(value).map((value, index) => {
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let result: null | Uint8Array | [Uint8Array, Uint8Array] = value;
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if ((index < 16) && (bitmap & cursor)) {
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const [length, bytes] = compactStripLength(input.subarray(offset));
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result = bytes.length === 32
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? bytes
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: decode(bytes) as any;
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offset += length;
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}
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cursor = cursor << 1;
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return result;
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});
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}
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function _decodeKv (header: NodeHeader, input: Uint8Array): Array<null | Uint8Array | [Uint8Array, Uint8Array]> {
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let offset = header.encodedLength;
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const nibbleCount = (header.value as NibbleHeader).toNumber();
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const nibbleLength = Math.floor((nibbleCount + 1) / 2);
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const nibbleData = input.subarray(offset, offset + nibbleLength);
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// for odd, ignore the first nibble, data starts at offset 1
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const nibbles = toNibbles(nibbleData).subarray(nibbleCount % 2);
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offset += nibbleData.length;
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const [, value] = compactStripLength(input.subarray(offset));
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return [
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encodeNibbles(
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header.nodeType === NODE_TYPE_LEAF
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? addNibblesTerminator(nibbles)
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: nibbles
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),
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value
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];
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}
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function _decode (input: null | Uint8Array): Uint8Array | null | Array<null | Uint8Array | [Uint8Array, Uint8Array]> {
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const header = new NodeHeader(input);
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const nodeType = header.nodeType;
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if (!input || nodeType === NODE_TYPE_NULL) {
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return input;
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} else if (nodeType === NODE_TYPE_BRANCH) {
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return _decodeBranch(header, input);
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} else if (nodeType === NODE_TYPE_EXT || nodeType === NODE_TYPE_LEAF) {
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return _decodeKv(header, input);
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}
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throw new Error('Unreachable');
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}
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export default function decode (input: null | Uint8Array): Uint8Array | null | Array<null | Uint8Array | Array<null | Uint8Array>> {
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const decoded = _decode(input);
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// l.debug(() => ['decode', { input, decoded }]);
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return decoded;
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}
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