TOTPFit/lib/protobuf-decoder/protobufDecoder.js

133 lines
2.8 KiB
JavaScript

import { decodeVarint } from "./varintUtils";
export class BufferReader {
constructor(buffer) {
this.buffer = buffer;
this.offset = 0;
}
readVarInt() {
const result = decodeVarint(this.buffer, this.offset);
this.offset += result.length;
return result.value;
}
readBuffer(length) {
this.checkByte(length);
const result = this.buffer.slice(this.offset, this.offset + length);
this.offset += length;
return result;
}
// gRPC has some additional header - remove it
trySkipGrpcHeader() {
const backupOffset = this.offset;
if (this.buffer[this.offset] === 0 && this.leftBytes() >= 5) {
this.offset++;
const length = this.buffer.readInt32BE(this.offset);
this.offset += 4;
if (length > this.leftBytes()) {
// Something is wrong, revert
this.offset = backupOffset;
}
}
}
leftBytes() {
return this.buffer.length - this.offset;
}
checkByte(length) {
const bytesAvailable = this.leftBytes();
if (length > bytesAvailable) {
throw new Error(
"Not enough bytes left. Requested: " +
length +
" left: " +
bytesAvailable
);
}
}
checkpoint() {
this.savedOffset = this.offset;
}
resetToCheckpoint() {
this.offset = this.savedOffset;
}
}
export const TYPES = {
VARINT: 0,
FIXED64: 1,
LENDELIM: 2,
FIXED32: 5
};
export function decodeProto(buffer) {
const reader = new BufferReader(buffer);
const parts = [];
reader.trySkipGrpcHeader();
try {
while (reader.leftBytes() > 0) {
reader.checkpoint();
const byteRange = [reader.offset];
const indexType = parseInt(reader.readVarInt().toString());
const type = indexType & 0b111;
const index = indexType >> 3;
let value;
if (type === TYPES.VARINT) {
value = reader.readVarInt().toString();
} else if (type === TYPES.LENDELIM) {
const length = parseInt(reader.readVarInt().toString());
value = reader.readBuffer(length);
} else if (type === TYPES.FIXED32) {
value = reader.readBuffer(4);
} else if (type === TYPES.FIXED64) {
value = reader.readBuffer(8);
} else {
throw new Error("Unknown type: " + type);
}
byteRange.push(reader.offset);
parts.push({
byteRange,
index,
type,
value
});
}
} catch (err) {
reader.resetToCheckpoint();
}
return {
parts,
leftOver: reader.readBuffer(reader.leftBytes())
};
}
export function typeToString(type, subType) {
switch (type) {
case TYPES.VARINT:
return "varint";
case TYPES.LENDELIM:
return subType || "len_delim";
case TYPES.FIXED32:
return "fixed32";
case TYPES.FIXED64:
return "fixed64";
default:
return "unknown";
}
}