Handle multiple protobuf messages in the same grpc request

Author: pimterry

src/services/ui-worker-formatters.ts

@@ -6,7 +6,7 @@ import {
 import * as beautifyXml from 'xml-beautifier';
 
 import { bufferToHex, bufferToString, getReadableSize } from '../util/buffer';
-import { parseRawProtobuf, parseGrpcProtobuf } from '../util/protobuf';
+import { parseRawProtobuf, extractProtobufFromGrpc } from '../util/protobuf';
 
 const truncationMarker = (size: string) => `\n[-- Truncated to ${size} --]`;
 const FIVE_MB = 1024 * 1024 * 5;
@@ -94,7 +94,10 @@ const WorkerFormatters = {
         }, 2);
     },
     'grpc-proto': (content: Buffer) => {
-        const data = parseGrpcProtobuf(content);
+        const protobufMessages = extractProtobufFromGrpc(content);
+
+        let data = protobufMessages.map((msg) => parseRawProtobuf(msg, { prefix: '' }));
+        if (data.length === 1) data = data[0];
 
         return JSON.stringify(data, (_key, value) => {
             // Buffers have toJSON defined, so arrive here in JSONified form:

src/util/protobuf.ts

@@ -28,23 +28,26 @@ export function isProbablyProtobuf(input: Uint8Array) {
 
 export const parseRawProtobuf = parseRawProto;
 
+// GRPC message structure:
 // The repeated sequence of Length-Prefixed-Message items is delivered in DATA frames
-
 // Length-Prefixed-Message → Compressed-Flag Message-Length Message
 // Compressed-Flag → 0 / 1 ; encoded as 1 byte unsigned integer
 // Message-Length → {length of Message} ; encoded as 4 byte unsigned integer (big endian)
 // Message → *{binary octet}
-export const parseGrpcProtobuf = (input: Buffer) => {
-    if (input.readInt8() != 0) {
-        // TODO support compressed gRPC messages?
-        throw new Error("compressed gRPC messages not yet supported")
+export const extractProtobufFromGrpc = (input: Buffer) => {
+    const protobufMessasges: Buffer[] = [];
+
+    while (input.length > 0) {
+        if (input.readInt8() != 0) {
+            throw new Error("Compressed gRPC messages not yet supported")
+        }
+
+        const length = input.readInt32BE(1);
+        protobufMessasges.push(input.slice(5, 5 + length));
+        input = input.subarray(5 + length);
     }
-    const length = input.readInt32BE(1);
-    input = input.slice(5, 5+length);
 
-    return parseRawProtobuf(input, {
-        prefix: ''
-    });
+    return protobufMessasges;
 }
 
 export const isValidProtobuf = (input: Uint8Array) => {