Ensure that Callback is called only once
Also, make Callback movable but uncopyable.
This commit is contained in:
parent
8c4ea7a451
commit
7348653ff4
5 changed files with 36 additions and 17 deletions
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@ -249,21 +249,23 @@ void BinaryCacheStore::queryPathInfoUncached(const Path & storePath,
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auto narInfoFile = narInfoFileFor(storePath);
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auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
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getFile(narInfoFile,
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{[=](std::future<std::shared_ptr<std::string>> fut) {
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try {
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auto data = fut.get();
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if (!data) return callback(nullptr);
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if (!data) return (*callbackPtr)(nullptr);
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stats.narInfoRead++;
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callback((std::shared_ptr<ValidPathInfo>)
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(*callbackPtr)((std::shared_ptr<ValidPathInfo>)
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std::make_shared<NarInfo>(*this, *data, narInfoFile));
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(void) act; // force Activity into this lambda to ensure it stays alive
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} catch (...) {
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callback.rethrow();
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callbackPtr->rethrow();
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}
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}});
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}
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@ -77,13 +77,13 @@ struct CurlDownloader : public Downloader
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DownloadItem(CurlDownloader & downloader,
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const DownloadRequest & request,
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Callback<DownloadResult> callback)
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Callback<DownloadResult> && callback)
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: downloader(downloader)
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, request(request)
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, act(*logger, lvlTalkative, actDownload,
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fmt(request.data ? "uploading '%s'" : "downloading '%s'", request.uri),
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{request.uri}, request.parentAct)
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, callback(callback)
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, callback(std::move(callback))
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, finalSink([this](const unsigned char * data, size_t len) {
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if (this->request.dataCallback) {
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writtenToSink += len;
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@ -665,7 +665,7 @@ struct CurlDownloader : public Downloader
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return;
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}
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enqueueItem(std::make_shared<DownloadItem>(*this, request, callback));
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enqueueItem(std::make_shared<DownloadItem>(*this, request, std::move(callback)));
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}
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};
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@ -137,17 +137,19 @@ protected:
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auto request(makeRequest(path));
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auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
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getDownloader()->enqueueDownload(request,
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{[callback, this](std::future<DownloadResult> result) {
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{[callbackPtr, this](std::future<DownloadResult> result) {
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try {
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callback(result.get().data);
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(*callbackPtr)(result.get().data);
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} catch (DownloadError & e) {
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if (e.error == Downloader::NotFound || e.error == Downloader::Forbidden)
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return callback(std::shared_ptr<std::string>());
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return (*callbackPtr)(std::shared_ptr<std::string>());
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maybeDisable();
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callback.rethrow();
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callbackPtr->rethrow();
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} catch (...) {
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callback.rethrow();
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callbackPtr->rethrow();
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}
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}});
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}
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@ -365,8 +365,10 @@ void Store::queryPathInfo(const Path & storePath,
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} catch (...) { return callback.rethrow(); }
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auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
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queryPathInfoUncached(storePath,
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{[this, storePath, hashPart, callback](std::future<std::shared_ptr<ValidPathInfo>> fut) {
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{[this, storePath, hashPart, callbackPtr](std::future<std::shared_ptr<ValidPathInfo>> fut) {
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try {
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auto info = fut.get();
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@ -386,8 +388,8 @@ void Store::queryPathInfo(const Path & storePath,
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throw InvalidPath("path '%s' is not valid", storePath);
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}
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callback(ref<ValidPathInfo>(info));
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} catch (...) { callback.rethrow(); }
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(*callbackPtr)(ref<ValidPathInfo>(info));
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} catch (...) { callbackPtr->rethrow(); }
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}});
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}
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@ -445,21 +445,34 @@ string get(const T & map, const string & key, const string & def = "")
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type T or an exception. (We abuse std::future<T> to pass the value or
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exception.) */
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template<typename T>
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struct Callback
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class Callback
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{
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std::function<void(std::future<T>)> fun;
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std::atomic_flag done = ATOMIC_FLAG_INIT;
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public:
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Callback(std::function<void(std::future<T>)> fun) : fun(fun) { }
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void operator()(T && t) const
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Callback(Callback && callback) : fun(std::move(callback.fun))
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{
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auto prev = callback.done.test_and_set();
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if (prev) done.test_and_set();
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}
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void operator()(T && t)
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{
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auto prev = done.test_and_set();
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assert(!prev);
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std::promise<T> promise;
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promise.set_value(std::move(t));
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fun(promise.get_future());
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}
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void rethrow(const std::exception_ptr & exc = std::current_exception()) const
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void rethrow(const std::exception_ptr & exc = std::current_exception())
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{
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auto prev = done.test_and_set();
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assert(!prev);
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std::promise<T> promise;
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promise.set_exception(exc);
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fun(promise.get_future());
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