ethers.js/lib.esm/utils/rlp-decode.js
2022-09-05 16:57:11 -04:00

83 lines
3.1 KiB
JavaScript

//See: https://github.com/ethereum/wiki/wiki/RLP
import { hexlify } from "./data.js";
import { logger } from "./logger.js";
function hexlifyByte(value) {
let result = value.toString(16);
while (result.length < 2) {
result = "0" + result;
}
return "0x" + result;
}
function unarrayifyInteger(data, offset, length) {
let result = 0;
for (let i = 0; i < length; i++) {
result = (result * 256) + data[offset + i];
}
return result;
}
function _decodeChildren(data, offset, childOffset, length) {
const result = [];
while (childOffset < offset + 1 + length) {
const decoded = _decode(data, childOffset);
result.push(decoded.result);
childOffset += decoded.consumed;
if (childOffset > offset + 1 + length) {
logger.throwError("child data too short", "BUFFER_OVERRUN", {
buffer: data, length, offset
});
}
}
return { consumed: (1 + length), result: result };
}
// returns { consumed: number, result: Object }
function _decode(data, offset) {
if (data.length === 0) {
logger.throwError("data too short", "BUFFER_OVERRUN", {
buffer: data, length: 0, offset: 1
});
}
const checkOffset = (offset) => {
if (offset > data.length) {
logger.throwError("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]) };
}
export function decodeRlp(_data) {
const data = logger.getBytes(_data, "data");
const decoded = _decode(data, 0);
if (decoded.consumed !== data.length) {
logger.throwArgumentError("unexpected junk after rlp payload", "data", _data);
}
return decoded.result;
}
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