| 1 | /* |
| 2 | * SPDX-License-Identifier: MIT |
| 3 | * |
| 4 | * Copyright 2017-2023 Philippe Proulx <pproulx@efficios.com> |
| 5 | */ |
| 6 | |
| 7 | #include <algorithm> |
| 8 | |
| 9 | #include <glib.h> |
| 10 | |
| 11 | #include <babeltrace2/babeltrace.h> |
| 12 | |
| 13 | #include "common/common.h" |
| 14 | #include "cpp-common/bt2c/call.hpp" |
| 15 | #include "cpp-common/bt2c/fmt.hpp" |
| 16 | #include "cpp-common/bt2s/make-unique.hpp" |
| 17 | #include "cpp-common/vendor/fmt/format.h" |
| 18 | |
| 19 | #include "plugins/common/muxing/muxing.h" |
| 20 | |
| 21 | #include "comp.hpp" |
| 22 | #include "msg-iter.hpp" |
| 23 | |
| 24 | namespace bt2mux { |
| 25 | |
| 26 | MsgIter::MsgIter(const bt2::SelfMessageIterator selfMsgIter, |
| 27 | const bt2::SelfMessageIteratorConfiguration cfg, bt2::SelfComponentOutputPort) : |
| 28 | bt2::UserMessageIterator<MsgIter, Comp> {selfMsgIter, "MSG-ITER"}, |
| 29 | _mHeap {_HeapComparator {_mLogger}} |
| 30 | { |
| 31 | /* |
| 32 | * Create one upstream message iterator for each connected |
| 33 | * input port. |
| 34 | */ |
| 35 | auto canSeekForward = true; |
| 36 | |
| 37 | for (const auto inputPort : this->_component()._inputPorts()) { |
| 38 | if (!inputPort.isConnected()) { |
| 39 | BT_CPPLOGI("Ignoring disconnected port: name={}", inputPort.name()); |
| 40 | continue; |
| 41 | } |
| 42 | |
| 43 | /* |
| 44 | * Create new upstream message iterator and immediately make it |
| 45 | * part of `_mUpstreamMsgItersToReload` (_ensureFullHeap() will |
| 46 | * deal with it when downstream calls next()). |
| 47 | */ |
| 48 | auto upstreamMsgIter = bt2s::make_unique<UpstreamMsgIter>( |
| 49 | this->_createMessageIterator(inputPort), inputPort.name(), _mLogger); |
| 50 | |
| 51 | canSeekForward = canSeekForward && upstreamMsgIter->canSeekForward(); |
| 52 | _mUpstreamMsgItersToReload.emplace_back(upstreamMsgIter.get()); |
| 53 | _mUpstreamMsgIters.push_back(std::move(upstreamMsgIter)); |
| 54 | } |
| 55 | |
| 56 | /* Set the "can seek forward" configuration */ |
| 57 | cfg.canSeekForward(canSeekForward); |
| 58 | } |
| 59 | |
| 60 | namespace { |
| 61 | |
| 62 | std::string optMsgTsStr(const bt2s::optional<std::int64_t>& ts) |
| 63 | { |
| 64 | if (ts) { |
| 65 | return fmt::to_string(*ts); |
| 66 | } |
| 67 | |
| 68 | return "none"; |
| 69 | } |
| 70 | |
| 71 | } /* namespace */ |
| 72 | |
| 73 | void MsgIter::_next(bt2::ConstMessageArray& msgs) |
| 74 | { |
| 75 | /* Make sure all upstream message iterators are part of the heap */ |
| 76 | this->_ensureFullHeap(); |
| 77 | |
| 78 | while (msgs.length() < msgs.capacity()) { |
| 79 | /* Empty heap? */ |
| 80 | if (G_UNLIKELY(_mHeap.isEmpty())) { |
| 81 | /* No more upstream messages! */ |
| 82 | return; |
| 83 | } |
| 84 | |
| 85 | /* |
| 86 | * Retrieve the upstream message iterator having the oldest message. |
| 87 | */ |
| 88 | auto& oldestUpstreamMsgIter = *_mHeap.top(); |
| 89 | |
| 90 | /* Validate the clock class of the oldest message */ |
| 91 | this->_validateMsgClkCls(oldestUpstreamMsgIter.msg()); |
| 92 | |
| 93 | /* Append the oldest message and discard it */ |
| 94 | msgs.append(oldestUpstreamMsgIter.msg().shared()); |
| 95 | |
| 96 | if (_mLogger.wouldLogD()) { |
| 97 | BT_CPPLOGD("Appended message to array: port-name={}, ts={}", |
| 98 | oldestUpstreamMsgIter.portName(), |
| 99 | optMsgTsStr(oldestUpstreamMsgIter.msgTs())); |
| 100 | } |
| 101 | |
| 102 | oldestUpstreamMsgIter.discard(); |
| 103 | |
| 104 | /* |
| 105 | * Immediately try to reload `oldestUpstreamMsgIter`. |
| 106 | * |
| 107 | * The possible outcomes are: |
| 108 | * |
| 109 | * There's an available message: |
| 110 | * Call `_mHeap.replaceTop()` to bring |
| 111 | * `oldestUpstreamMsgIter` back to the heap, performing a |
| 112 | * single heap rebalance. |
| 113 | * |
| 114 | * There isn't an available message (ended): |
| 115 | * Remove `oldestUpstreamMsgIter` from the heap. |
| 116 | * |
| 117 | * `bt2::TryAgain` is thrown: |
| 118 | * Remove `oldestUpstreamMsgIter` from the heap. |
| 119 | * |
| 120 | * Add `oldestUpstreamMsgIter` to the set of upstream |
| 121 | * message iterators to reload. The next call to _next() |
| 122 | * will move it to the heap again (if not ended) after |
| 123 | * having successfully called reload(). |
| 124 | */ |
| 125 | BT_CPPLOGD( |
| 126 | "Trying to reload upstream message iterator having the oldest message: port-name={}", |
| 127 | oldestUpstreamMsgIter.portName()); |
| 128 | |
| 129 | try { |
| 130 | if (G_LIKELY(oldestUpstreamMsgIter.reload() == UpstreamMsgIter::ReloadStatus::MORE)) { |
| 131 | /* New current message: update heap */ |
| 132 | _mHeap.replaceTop(&oldestUpstreamMsgIter); |
| 133 | BT_CPPLOGD("More messages available; updated heap: port-name={}, heap-len={}", |
| 134 | oldestUpstreamMsgIter.portName(), _mHeap.len()); |
| 135 | } else { |
| 136 | _mHeap.removeTop(); |
| 137 | BT_CPPLOGD("Upstream message iterator has no more messages; removed from heap: " |
| 138 | "port-name{}, heap-len={}", |
| 139 | oldestUpstreamMsgIter.portName(), _mHeap.len()); |
| 140 | } |
| 141 | } catch (const bt2::TryAgain&) { |
| 142 | _mHeap.removeTop(); |
| 143 | _mUpstreamMsgItersToReload.push_back(&oldestUpstreamMsgIter); |
| 144 | BT_CPPLOGD("Moved upstream message iterator from heap to \"to reload\" set: " |
| 145 | "port-name={}, heap-len={}, to-reload-len={}", |
| 146 | oldestUpstreamMsgIter.portName(), _mHeap.len(), |
| 147 | _mUpstreamMsgItersToReload.size()); |
| 148 | throw; |
| 149 | } |
| 150 | } |
| 151 | } |
| 152 | |
| 153 | void MsgIter::_ensureFullHeap() |
| 154 | { |
| 155 | /* |
| 156 | * Always remove from `_mUpstreamMsgItersToReload` when reload() |
| 157 | * doesn't throw. |
| 158 | * |
| 159 | * If reload() returns `UpstreamMsgIter::ReloadStatus::NO_MORE`, |
| 160 | * then we don't need it anymore (remains alive in |
| 161 | * `_mUpstreamMsgIters`). |
| 162 | */ |
| 163 | for (auto it = _mUpstreamMsgItersToReload.begin(); it != _mUpstreamMsgItersToReload.end(); |
| 164 | it = _mUpstreamMsgItersToReload.erase(it)) { |
| 165 | auto& upstreamMsgIter = **it; |
| 166 | |
| 167 | BT_CPPLOGD("Handling upstream message iterator to reload: " |
| 168 | "port-name={}, heap-len={}, to-reload-len={}", |
| 169 | upstreamMsgIter.portName(), _mHeap.len(), _mUpstreamMsgItersToReload.size()); |
| 170 | |
| 171 | if (G_LIKELY(upstreamMsgIter.reload() == UpstreamMsgIter::ReloadStatus::MORE)) { |
| 172 | /* New current message: move to heap */ |
| 173 | _mHeap.insert(&upstreamMsgIter); |
| 174 | BT_CPPLOGD("More messages available; " |
| 175 | "inserted upstream message iterator into heap from \"to reload\" set: " |
| 176 | "port-name={}, heap-len={}", |
| 177 | upstreamMsgIter.portName(), _mHeap.len()); |
| 178 | } else { |
| 179 | BT_CPPLOGD("Not inserting upstream message iterator into heap (no more messages): " |
| 180 | "port-name={}", |
| 181 | upstreamMsgIter.portName()); |
| 182 | } |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | bool MsgIter::_canSeekBeginning() |
| 187 | { |
| 188 | /* |
| 189 | * We can only seek our beginning if all our upstream message |
| 190 | * iterators also can. |
| 191 | */ |
| 192 | return std::all_of(_mUpstreamMsgIters.begin(), _mUpstreamMsgIters.end(), |
| 193 | [](UpstreamMsgIter::UP& upstreamMsgIter) { |
| 194 | return upstreamMsgIter->canSeekBeginning(); |
| 195 | }); |
| 196 | } |
| 197 | |
| 198 | void MsgIter::_seekBeginning() |
| 199 | { |
| 200 | /* |
| 201 | * The current approach is that this operation is either successful |
| 202 | * (all upstream message iterators seek) or not. If it's not, then |
| 203 | * we don't keep any state that some sought and some didn't: we'll |
| 204 | * restart the whole process when the user tries to seek again. |
| 205 | * |
| 206 | * The first step is to clear all the containers of upstream message |
| 207 | * iterator pointers so that we can process what's in |
| 208 | * `_mUpstreamMsgIters` only. This is irreversible, but it's okay: |
| 209 | * if any seeking fails below, the downstream user is required to |
| 210 | * try the "seek beginning" operation again and only call |
| 211 | * bt_message_iterator_next() if it was successful. |
| 212 | * |
| 213 | * This means if the first four upstream message iterators seek, and |
| 214 | * then the fifth one throws `bt2::TryAgain`, then the next time |
| 215 | * this method executes, the first four upstream message iterators |
| 216 | * will seek again. That being said, it's such an unlikely scenario |
| 217 | * that the simplicity outweighs performance concerns here. |
| 218 | */ |
| 219 | _mHeap.clear(); |
| 220 | _mUpstreamMsgItersToReload.clear(); |
| 221 | |
| 222 | /* Also reset clock class expectation */ |
| 223 | _mClkClsExpectation = _ClkClsExpectation::ANY; |
| 224 | _mExpectedClkClsUuid.reset(); |
| 225 | |
| 226 | /* Make each upstream message iterator seek */ |
| 227 | for (auto& upstreamMsgIter : _mUpstreamMsgIters) { |
| 228 | /* This may throw! */ |
| 229 | upstreamMsgIter->seekBeginning(); |
| 230 | } |
| 231 | |
| 232 | /* |
| 233 | * All sought successfully: fill `_mUpstreamMsgItersToReload`; the |
| 234 | * next call to _next() will deal with those. |
| 235 | */ |
| 236 | for (auto& upstreamMsgIter : _mUpstreamMsgIters) { |
| 237 | _mUpstreamMsgItersToReload.push_back(upstreamMsgIter.get()); |
| 238 | } |
| 239 | } |
| 240 | |
| 241 | namespace { |
| 242 | |
| 243 | std::string optLogStr(const char * const str) noexcept |
| 244 | { |
| 245 | return str ? fmt::format("\"{}\"", str) : "(none)"; |
| 246 | } |
| 247 | |
| 248 | } /* namespace */ |
| 249 | |
| 250 | void MsgIter::_setClkClsExpectation( |
| 251 | const bt2::OptionalBorrowedObject<bt2::ConstClockClass> clkCls) noexcept |
| 252 | { |
| 253 | BT_ASSERT_DBG(_mClkClsExpectation == _ClkClsExpectation::ANY); |
| 254 | |
| 255 | /* No initial clock class: also expect none afterwards */ |
| 256 | if (!clkCls) { |
| 257 | _mClkClsExpectation = _ClkClsExpectation::NONE; |
| 258 | return; |
| 259 | } |
| 260 | |
| 261 | /* |
| 262 | * This is the first clock class that this message iterator |
| 263 | * encounters. Its properties determine what to expect for the whole |
| 264 | * lifetime of the iterator. |
| 265 | */ |
| 266 | if (clkCls->originIsUnixEpoch()) { |
| 267 | /* Expect clock classes having a Unix epoch origin*/ |
| 268 | _mClkClsExpectation = _ClkClsExpectation::ORIG_IS_UNIX_EPOCH; |
| 269 | } else { |
| 270 | if (clkCls->uuid()) { |
| 271 | /* |
| 272 | * Expect clock classes not having a Unix epoch origin and |
| 273 | * with a specific UUID. |
| 274 | */ |
| 275 | _mClkClsExpectation = _ClkClsExpectation::ORIG_ISNT_UNIX_EPOCH_AND_SPEC_UUID; |
| 276 | _mExpectedClkClsUuid = *clkCls->uuid(); |
| 277 | } else { |
| 278 | /* |
| 279 | * Expect clock classes not having a Unix epoch origin and |
| 280 | * without a UUID. |
| 281 | */ |
| 282 | _mClkClsExpectation = _ClkClsExpectation::ORIG_ISNT_UNIX_EPOCH_AND_NO_UUID; |
| 283 | } |
| 284 | } |
| 285 | } |
| 286 | |
| 287 | void MsgIter::_makeSureClkClsIsExpected( |
| 288 | const bt2::ConstMessage msg, |
| 289 | const bt2::OptionalBorrowedObject<bt2::ConstClockClass> clkCls) const |
| 290 | { |
| 291 | BT_ASSERT_DBG(_mClkClsExpectation != _ClkClsExpectation::ANY); |
| 292 | |
| 293 | if (!clkCls) { |
| 294 | if (_mClkClsExpectation != _ClkClsExpectation::NONE) { |
| 295 | /* |
| 296 | * `msg` is a stream beginning message because a message |
| 297 | * iterator inactivity message always has a clock class. |
| 298 | */ |
| 299 | const auto streamCls = msg.asStreamBeginning().stream().cls(); |
| 300 | |
| 301 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW(bt2::Error, |
| 302 | "Expecting a clock class, but got none: " |
| 303 | "stream-class-addr={}, stream-class-name=\"{}\", " |
| 304 | "stream-class-id={}", |
| 305 | static_cast<const void *>(streamCls.libObjPtr()), |
| 306 | optLogStr(streamCls.name()), streamCls.id()); |
| 307 | } |
| 308 | |
| 309 | return; |
| 310 | } |
| 311 | |
| 312 | const auto clkClsAddr = static_cast<const void *>(clkCls->libObjPtr()); |
| 313 | |
| 314 | switch (_mClkClsExpectation) { |
| 315 | case _ClkClsExpectation::ORIG_IS_UNIX_EPOCH: |
| 316 | if (!clkCls->originIsUnixEpoch()) { |
| 317 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW(bt2::Error, |
| 318 | "Expecting a clock class having a Unix epoch origin, " |
| 319 | "but got one not having a Unix epoch origin: " |
| 320 | "clock-class-addr={}, clock-class-name={}", |
| 321 | clkClsAddr, optLogStr(clkCls->name())); |
| 322 | } |
| 323 | |
| 324 | break; |
| 325 | case _ClkClsExpectation::ORIG_ISNT_UNIX_EPOCH_AND_NO_UUID: |
| 326 | BT_ASSERT_DBG(!_mExpectedClkClsUuid); |
| 327 | |
| 328 | if (clkCls->originIsUnixEpoch()) { |
| 329 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW( |
| 330 | bt2::Error, |
| 331 | "Expecting a clock class not having a Unix epoch origin, " |
| 332 | "but got one having a Unix epoch origin: " |
| 333 | "clock-class-addr={}, clock-class-name={}", |
| 334 | clkClsAddr, optLogStr(clkCls->name())); |
| 335 | } |
| 336 | |
| 337 | if (clkCls->uuid()) { |
| 338 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW( |
| 339 | bt2::Error, |
| 340 | "Expecting a clock class without a UUID, but got one with a UUID: " |
| 341 | "clock-class-addr={}, clock-class-name={}, uuid={}", |
| 342 | clkClsAddr, optLogStr(clkCls->name()), clkCls->uuid()->str()); |
| 343 | } |
| 344 | |
| 345 | break; |
| 346 | case _ClkClsExpectation::ORIG_ISNT_UNIX_EPOCH_AND_SPEC_UUID: |
| 347 | BT_ASSERT_DBG(_mExpectedClkClsUuid); |
| 348 | |
| 349 | if (clkCls->originIsUnixEpoch()) { |
| 350 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW( |
| 351 | bt2::Error, |
| 352 | "Expecting a clock class not having a Unix epoch origin, " |
| 353 | "but got one having a Unix epoch origin: " |
| 354 | "clock-class-addr={}, clock-class-name={}", |
| 355 | clkClsAddr, optLogStr(clkCls->name())); |
| 356 | } |
| 357 | |
| 358 | if (!clkCls->uuid()) { |
| 359 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW( |
| 360 | bt2::Error, |
| 361 | "Expecting a clock class with a UUID, but got one without a UUID: " |
| 362 | "clock-class-addr={}, clock-class-name={}", |
| 363 | clkClsAddr, optLogStr(clkCls->name())); |
| 364 | } |
| 365 | |
| 366 | if (*clkCls->uuid() != bt2c::UuidView {*_mExpectedClkClsUuid}) { |
| 367 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW(bt2::Error, |
| 368 | "Expecting a clock class with a specific UUID, " |
| 369 | "but got one with a different UUID: " |
| 370 | "clock-class-addr={}, clock-class-name={}, " |
| 371 | "expected-uuid=\"{}\", uuid=\"{}\"", |
| 372 | clkClsAddr, optLogStr(clkCls->name()), |
| 373 | _mExpectedClkClsUuid->str(), clkCls->uuid()->str()); |
| 374 | } |
| 375 | |
| 376 | break; |
| 377 | case _ClkClsExpectation::NONE: |
| 378 | BT_CPPLOGE_APPEND_CAUSE_AND_THROW(bt2::Error, |
| 379 | "Expecting no clock class, but got one: " |
| 380 | "clock-class-addr={}, clock-class-name={}", |
| 381 | clkClsAddr, optLogStr(clkCls->name())); |
| 382 | break; |
| 383 | default: |
| 384 | bt_common_abort(); |
| 385 | } |
| 386 | } |
| 387 | |
| 388 | void MsgIter::_validateMsgClkCls(const bt2::ConstMessage msg) |
| 389 | { |
| 390 | if (G_LIKELY(!msg.isStreamBeginning() && !msg.isMessageIteratorInactivity())) { |
| 391 | /* |
| 392 | * We don't care about the other types: all the messages related |
| 393 | * to a given stream shared the same default clock class, if |
| 394 | * any. |
| 395 | */ |
| 396 | return; |
| 397 | } |
| 398 | |
| 399 | BT_CPPLOGD("Validating the clock class of a message: msg-type={}", msg.type()); |
| 400 | |
| 401 | /* Get the clock class, if any, of `msg` */ |
| 402 | const auto clkCls = bt2c::call([msg]() -> bt2::OptionalBorrowedObject<bt2::ConstClockClass> { |
| 403 | if (msg.isStreamBeginning()) { |
| 404 | return msg.asStreamBeginning().stream().cls().defaultClockClass(); |
| 405 | } else { |
| 406 | BT_ASSERT(msg.isMessageIteratorInactivity()); |
| 407 | return msg.asMessageIteratorInactivity().clockSnapshot().clockClass(); |
| 408 | } |
| 409 | }); |
| 410 | |
| 411 | /* Set the expectation or check it */ |
| 412 | if (_mClkClsExpectation == _ClkClsExpectation::ANY) { |
| 413 | /* First message: set the expectation */ |
| 414 | this->_setClkClsExpectation(clkCls); |
| 415 | } else { |
| 416 | /* Make sure clock class is expected */ |
| 417 | this->_makeSureClkClsIsExpected(msg, clkCls); |
| 418 | } |
| 419 | } |
| 420 | |
| 421 | MsgIter::_HeapComparator::_HeapComparator(const bt2c::Logger& logger) : _mLogger {logger} |
| 422 | { |
| 423 | } |
| 424 | |
| 425 | bool MsgIter::_HeapComparator::operator()( |
| 426 | const UpstreamMsgIter * const upstreamMsgIterA, |
| 427 | const UpstreamMsgIter * const upstreamMsgIterB) const noexcept |
| 428 | { |
| 429 | /* The two messages to compare */ |
| 430 | const auto msgA = upstreamMsgIterA->msg(); |
| 431 | const auto msgB = upstreamMsgIterB->msg(); |
| 432 | auto& msgTsA = upstreamMsgIterA->msgTs(); |
| 433 | auto& msgTsB = upstreamMsgIterB->msgTs(); |
| 434 | |
| 435 | if (_mLogger.wouldLogT()) { |
| 436 | BT_CPPLOGT("Comparing two messages: " |
| 437 | "port-name-a={}, msg-a-type={}, msg-a-ts={}, " |
| 438 | "port-name-b={}, msg-b-type={}, msg-b-ts={}", |
| 439 | upstreamMsgIterA->portName(), msgA.type(), optMsgTsStr(msgTsA), |
| 440 | upstreamMsgIterB->portName(), msgB.type(), optMsgTsStr(msgTsB)); |
| 441 | } |
| 442 | |
| 443 | /* |
| 444 | * Try to compare using timestamps. |
| 445 | * |
| 446 | * If both timestamps are set and their values are different, then |
| 447 | * use this to establish the ordering of the two messages. |
| 448 | * |
| 449 | * If one timestamp is set, but not the other, the latter always |
| 450 | * wins. This is because, for a given upstream message iterator, we |
| 451 | * need to consume all the messages having no timestamp so that we |
| 452 | * can reach a message with a timestamp to compare it. |
| 453 | * |
| 454 | * Otherwise, we'll fall back to using |
| 455 | * common_muxing_compare_messages(). |
| 456 | */ |
| 457 | if (G_LIKELY(msgTsA && msgTsB)) { |
| 458 | if (*msgTsA < *msgTsB) { |
| 459 | /* |
| 460 | * Return `true` because `_mHeap.top()` provides the |
| 461 | * "greatest" element. For us, the "greatest" message is |
| 462 | * the oldest one, that is, the one having the smallest |
| 463 | * timestamp. |
| 464 | */ |
| 465 | BT_CPPLOGT_STR("Timestamp of message A is less than timestamp of message B: oldest=A"); |
| 466 | return true; |
| 467 | } else if (*msgTsA > *msgTsB) { |
| 468 | BT_CPPLOGT_STR( |
| 469 | "Timestamp of message A is greater than timestamp of message B: oldest=B"); |
| 470 | return false; |
| 471 | } |
| 472 | } else if (msgTsA && !msgTsB) { |
| 473 | BT_CPPLOGT_STR("Message A has a timestamp, but message B has none: oldest=B"); |
| 474 | return false; |
| 475 | } else if (!msgTsA && msgTsB) { |
| 476 | BT_CPPLOGT_STR("Message B has a timestamp, but message A has none: oldest=A"); |
| 477 | return true; |
| 478 | } |
| 479 | |
| 480 | /* |
| 481 | * Comparison failed using timestamps: determine an ordering using |
| 482 | * arbitrary properties, but in a deterministic way. |
| 483 | * |
| 484 | * common_muxing_compare_messages() returns less than 0 if the first |
| 485 | * message is considered older than the second, which corresponds to |
| 486 | * this comparator returning `true`. |
| 487 | */ |
| 488 | const auto res = common_muxing_compare_messages(msgA.libObjPtr(), msgB.libObjPtr()) < 0; |
| 489 | |
| 490 | BT_CPPLOGT("Timestamps are considered equal; comparing other properties: oldest={}", |
| 491 | res ? "A" : "B"); |
| 492 | return res; |
| 493 | } |
| 494 | |
| 495 | } /* namespace bt2mux */ |