113 lines
3.5 KiB
TypeScript
113 lines
3.5 KiB
TypeScript
//See: https://github.com/ethereum/wiki/wiki/RLP
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import { hexlify } from "./data.js";
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import { throwArgumentError, throwError } from "./errors.js";
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import { getBytes } from "./data.js";
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import type { BytesLike, RlpStructuredData } from "./index.js";
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function hexlifyByte(value: number): string {
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let result = value.toString(16);
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while (result.length < 2) { result = "0" + result; }
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return "0x" + result;
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}
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function unarrayifyInteger(data: Uint8Array, offset: number, length: number): number {
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let result = 0;
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for (let i = 0; i < length; i++) {
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result = (result * 256) + data[offset + i];
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}
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return result;
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}
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type Decoded = {
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result: any;
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consumed: number;
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};
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function _decodeChildren(data: Uint8Array, offset: number, childOffset: number, length: number): Decoded {
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const result = [];
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while (childOffset < offset + 1 + length) {
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const decoded = _decode(data, childOffset);
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result.push(decoded.result);
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childOffset += decoded.consumed;
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if (childOffset > offset + 1 + length) {
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throwError("child data too short", "BUFFER_OVERRUN", {
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buffer: data, length, offset
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});
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}
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}
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return {consumed: (1 + length), result: result};
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}
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// returns { consumed: number, result: Object }
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function _decode(data: Uint8Array, offset: number): { consumed: number, result: any } {
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if (data.length === 0) {
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throwError("data too short", "BUFFER_OVERRUN", {
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buffer: data, length: 0, offset: 1
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});
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}
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const checkOffset = (offset: number) => {
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if (offset > data.length) {
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throwError("data short segment too short", "BUFFER_OVERRUN", {
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buffer: data, length: data.length, offset
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});
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}
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};
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// Array with extra length prefix
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if (data[offset] >= 0xf8) {
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const lengthLength = data[offset] - 0xf7;
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checkOffset(offset + 1 + lengthLength);
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const length = unarrayifyInteger(data, offset + 1, lengthLength);
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checkOffset(offset + 1 + lengthLength + length);
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return _decodeChildren(data, offset, offset + 1 + lengthLength, lengthLength + length);
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} else if (data[offset] >= 0xc0) {
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const length = data[offset] - 0xc0;
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checkOffset(offset + 1 + length);
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return _decodeChildren(data, offset, offset + 1, length);
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} else if (data[offset] >= 0xb8) {
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const lengthLength = data[offset] - 0xb7;
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checkOffset(offset + 1 + lengthLength);
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const length = unarrayifyInteger(data, offset + 1, lengthLength);
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checkOffset(offset + 1 + lengthLength + length);
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const result = hexlify(data.slice(offset + 1 + lengthLength, offset + 1 + lengthLength + length));
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return { consumed: (1 + lengthLength + length), result: result }
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} else if (data[offset] >= 0x80) {
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const length = data[offset] - 0x80;
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checkOffset(offset + 1 + length);
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const result = hexlify(data.slice(offset + 1, offset + 1 + length));
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return { consumed: (1 + length), result: result }
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}
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return { consumed: 1, result: hexlifyByte(data[offset]) };
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}
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/**
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* Decodes %%data%% into the structured data it represents.
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*/
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export function decodeRlp(_data: BytesLike): RlpStructuredData {
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const data = getBytes(_data, "data");
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const decoded = _decode(data, 0);
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if (decoded.consumed !== data.length) {
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throwArgumentError("unexpected junk after rlp payload", "data", _data);
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}
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return decoded.result;
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}
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