ethers.js/src.ts/utils/rlp-decode.ts
2022-11-04 18:08:37 -04:00

105 lines
3.3 KiB
TypeScript

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