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142 lines (111 loc) · 3.93 KB
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//See: https://github.com/ethereum/wiki/wiki/RLP
var convert = require('./convert.js');
function arrayifyInteger(value) {
var result = [];
while (value) {
result.unshift(value & 0xff);
value >>= 8;
}
return result;
}
function unarrayifyInteger(data, offset, length) {
var result = 0;
for (var i = 0; i < length; i++) {
result = (result * 256) + data[offset + i];
}
return result;
}
function _encode(object) {
if (Array.isArray(object)) {
var payload = [];
object.forEach(function(child) {
payload = payload.concat(_encode(child));
});
if (payload.length <= 55) {
payload.unshift(0xc0 + payload.length)
return payload;
}
var length = arrayifyInteger(payload.length);
length.unshift(0xf7 + length.length);
return length.concat(payload);
} else {
object = [].slice.call(convert.arrayify(object));
if (object.length === 1 && object[0] <= 0x7f) {
return object;
} else if (object.length <= 55) {
object.unshift(0x80 + object.length);
return object
}
var length = arrayifyInteger(object.length);
length.unshift(0xb7 + length.length);
return length.concat(object);
}
}
function encode(object) {
return convert.hexlify(_encode(object));
}
function _decodeChildren(data, offset, childOffset, length) {
var result = [];
while (childOffset < offset + 1 + length) {
var decoded = _decode(data, childOffset);
result.push(decoded.result);
childOffset += decoded.consumed;
if (childOffset > offset + 1 + length) {
throw new Error('invalid rlp');
}
}
return {consumed: (1 + length), result: result};
}
// returns { consumed: number, result: Object }
function _decode(data, offset) {
if (data.length === 0) { throw new Error('invalid rlp data'); }
// Array with extra length prefix
if (data[offset] >= 0xf8) {
var lengthLength = data[offset] - 0xf7;
if (offset + 1 + lengthLength > data.length) {
throw new Error('too short');
}
var length = unarrayifyInteger(data, offset + 1, lengthLength);
if (offset + 1 + lengthLength + length > data.length) {
throw new Error('to short');
}
return _decodeChildren(data, offset, offset + 1 + lengthLength, lengthLength + length);
} else if (data[offset] >= 0xc0) {
var length = data[offset] - 0xc0;
if (offset + 1 + length > data.length) {
throw new Error('invalid rlp data');
}
return _decodeChildren(data, offset, offset + 1, length);
} else if (data[offset] >= 0xb8) {
var lengthLength = data[offset] - 0xb7;
if (offset + 1 + lengthLength > data.length) {
throw new Error('invalid rlp data');
}
var length = unarrayifyInteger(data, offset + 1, lengthLength);
if (offset + 1 + lengthLength + length > data.length) {
throw new Error('invalid rlp data');
}
var result = convert.hexlify(data.slice(offset + 1 + lengthLength, offset + 1 + lengthLength + length));
return { consumed: (1 + lengthLength + length), result: result }
} else if (data[offset] >= 0x80) {
var length = data[offset] - 0x80;
if (offset + 1 + length > data.offset) {
throw new Error('invlaid rlp data');
}
var result = convert.hexlify(data.slice(offset + 1, offset + 1 + length));
return { consumed: (1 + length), result: result }
}
return { consumed: 1, result: convert.hexlify(data[offset]) };
}
function decode(data) {
data = convert.arrayify(data);
var decoded = _decode(data, 0);
if (decoded.consumed !== data.length) {
throw new Error('invalid rlp data');
}
return decoded.result;
}
module.exports = {
encode: encode,
decode: decode,
}