tubestation/toolkit/components/uniffi-js/UniFFICallbacks.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsPrintfCString.h"
#include "nsString.h"
#include "nsThreadUtils.h"
#include "mozilla/dom/OwnedRustBuffer.h"
#include "mozilla/dom/RootedDictionary.h"
#include "mozilla/dom/UniFFIBinding.h"
#include "mozilla/dom/UniFFICallbacks.h"
#include "mozilla/Maybe.h"
#include "mozilla/Logging.h"
#include "mozilla/RefPtr.h"
#include "mozilla/UniquePtr.h"

static mozilla::LazyLogModule UNIFFI_INVOKE_CALLBACK_LOGGER("uniffi");

namespace mozilla::uniffi {

using dom::ArrayBuffer;
using dom::RootedDictionary;
using dom::UniFFICallbackHandler;
using dom::UniFFIScaffoldingCallCode;

// Implemented in UniFFIGeneratedScaffolding.cpp
Maybe<CallbackInterfaceInfo> GetCallbackInterfaceInfo(uint64_t aInterfaceId);

void RegisterCallbackHandler(uint64_t aInterfaceId,
                             UniFFICallbackHandler& aCallbackHandler,
                             ErrorResult& aError) {
  // We should only be mutating mHandler on the main thread
  MOZ_ASSERT(NS_IsMainThread());

  Maybe<CallbackInterfaceInfo> cbiInfo = GetCallbackInterfaceInfo(aInterfaceId);
  if (!cbiInfo.isSome()) {
    aError.ThrowUnknownError(
        nsPrintfCString("Unknown interface id: %" PRIu64, aInterfaceId));
    return;
  }

  if (*cbiInfo->mHandler) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Callback handler already registered for %s",
             cbiInfo->mName));
    return;
  }
  *cbiInfo->mHandler = &aCallbackHandler;
  RustCallStatus status = {0};
  cbiInfo->mInitForeignCallback(cbiInfo->mForeignCallback, &status);
  // Just use MOZ_DIAGNOSTIC_ASSERT to check the status, since the call should
  // always succeed. The RustCallStatus out param only exists because UniFFI
  // adds it to all FFI calls.
  MOZ_DIAGNOSTIC_ASSERT(status.code == RUST_CALL_SUCCESS);
}

void DeregisterCallbackHandler(uint64_t aInterfaceId, ErrorResult& aError) {
  // We should only be mutating mHandler on the main thread
  MOZ_ASSERT(NS_IsMainThread());

  Maybe<CallbackInterfaceInfo> cbiInfo = GetCallbackInterfaceInfo(aInterfaceId);
  if (!cbiInfo.isSome()) {
    aError.ThrowUnknownError(
        nsPrintfCString("Unknown interface id: %" PRIu64, aInterfaceId));
    return;
  }
  *cbiInfo->mHandler = nullptr;
}

MOZ_CAN_RUN_SCRIPT
static void QueueCallbackInner(uint64_t aInterfaceId, uint64_t aHandle,
                               uint32_t aMethod,
                               UniquePtr<uint8_t[], JS::FreePolicy>&& aArgsData,
                               int32_t aArgsLen) {
  MOZ_ASSERT(NS_IsMainThread());

  Maybe<CallbackInterfaceInfo> cbiInfo = GetCallbackInterfaceInfo(aInterfaceId);
  if (!cbiInfo.isSome()) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Unknown inferface id: %" PRIu64, aInterfaceId));
    return;
  }

  // Take our own reference to the callback handler to ensure that it stays
  // alive for the duration of this call
  RefPtr<UniFFICallbackHandler> ihandler = *cbiInfo->mHandler;

  if (!ihandler) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] JS handler for %s not registered", cbiInfo->mName));
    return;
  }

  JSObject* global = ihandler->CallbackGlobalOrNull();
  if (!global) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] JS handler for %s has null global", cbiInfo->mName));
    return;
  }

  dom::AutoEntryScript aes(global, cbiInfo->mName);

  JS::Rooted<JSObject*> args(
      aes.cx(),
      JS::NewArrayBufferWithContents(aes.cx(), aArgsLen, std::move(aArgsData)));
  if (!args) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Failed to allocate buffer for arguments"));
    return;
  }

  IgnoredErrorResult error;
  ihandler->Call(aHandle, aMethod, args, error);

  if (error.Failed()) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Error invoking JS handler for %s", cbiInfo->mName));
    return;
  }
}

void QueueCallback(uint64_t aInterfaceId, uint64_t aHandle, uint32_t aMethod,
                   const uint8_t* aArgsData, int32_t aArgsLen) {
  // Make a copy of aArgsData to be deserialized asynchronously on
  // the main thread.
  //
  // This copy will be allocated in the ArrayBufferContentsArena, as
  // ownership will be passed to an ArrayBuffer for deserialization.
  UniquePtr<uint8_t[], JS::FreePolicy> argsDataOwned(
      js_pod_arena_malloc<uint8_t>(js::ArrayBufferContentsArena, aArgsLen));
  if (!argsDataOwned) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Error allocating memory for arguments"));
    return;
  }
  memcpy(argsDataOwned.get(), aArgsData, aArgsLen);

  nsresult dispatchResult =
      GetMainThreadSerialEventTarget()->Dispatch(NS_NewRunnableFunction(
          "UniFFI callback", [=, argsDataOwned = std::move(argsDataOwned)]()
                                 MOZ_CAN_RUN_SCRIPT_BOUNDARY mutable {
                                   QueueCallbackInner(
                                       aInterfaceId, aHandle, aMethod,
                                       std::move(argsDataOwned), aArgsLen);
                                 }));

  if (NS_FAILED(dispatchResult)) {
    MOZ_LOG(UNIFFI_INVOKE_CALLBACK_LOGGER, LogLevel::Error,
            ("[UniFFI] Error dispatching UniFFI callback task"));
  }
}

}  // namespace mozilla::uniffi