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Simplify the callback mechanism

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This commit is contained in:
Eelco Dolstra 2018-03-27 22:16:01 +02:00
parent 1672bcd230
commit 81ea8bd5ce
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GPG key ID: 8170B4726D7198DE
16 changed files with 152 additions and 180 deletions
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37
src/libstore/download.cc
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@ -81,8 +81,7 @@ struct CurlDownloader : public Downloader
DownloadResult result;
Activity act;
bool done = false; // whether either the success or failure function has been called
std::function<void(const DownloadResult &)> success;
std::function<void(std::exception_ptr exc)> failure;
Callback<DownloadResult> callback;
CURL * req = 0;
bool active = false; // whether the handle has been added to the multi object
std::string status;
@ -97,10 +96,13 @@ struct CurlDownloader : public Downloader
std::string encoding;
DownloadItem(CurlDownloader & downloader, const DownloadRequest & request)
DownloadItem(CurlDownloader & downloader,
const DownloadRequest & request,
Callback<DownloadResult> callback)
: downloader(downloader)
, request(request)
, act(*logger, lvlTalkative, actDownload, fmt("downloading '%s'", request.uri), {request.uri}, request.parentAct)
, callback(callback)
{
if (!request.expectedETag.empty())
requestHeaders = curl_slist_append(requestHeaders, ("If-None-Match: " + request.expectedETag).c_str());
@ -129,7 +131,7 @@ struct CurlDownloader : public Downloader
{
assert(!done);
done = true;
callFailure(failure, std::make_exception_ptr(e));
callback.rethrow(std::make_exception_ptr(e));
}
size_t writeCallback(void * contents, size_t size, size_t nmemb)
@ -316,11 +318,11 @@ struct CurlDownloader : public Downloader
try {
if (request.decompress)
result.data = decodeContent(encoding, ref<std::string>(result.data));
callSuccess(success, failure, const_cast<const DownloadResult &>(result));
act.progress(result.data->size(), result.data->size());
callback(std::move(result));
} catch (...) {
done = true;
callFailure(failure, std::current_exception());
callback.rethrow();
}
} else {
// We treat most errors as transient, but won't retry when hopeless
@ -570,13 +572,12 @@ struct CurlDownloader : public Downloader
}
void enqueueDownload(const DownloadRequest & request,
std::function<void(const DownloadResult &)> success,
std::function<void(std::exception_ptr exc)> failure) override
Callback<DownloadResult> callback) override
{
/* Ugly hack to support s3:// URIs. */
if (hasPrefix(request.uri, "s3://")) {
// FIXME: do this on a worker thread
sync2async<DownloadResult>(success, failure, [&]() -> DownloadResult {
try {
#ifdef ENABLE_S3
S3Helper s3Helper("", Aws::Region::US_EAST_1); // FIXME: make configurable
auto slash = request.uri.find('/', 5);
@ -590,18 +591,15 @@ struct CurlDownloader : public Downloader
if (!s3Res.data)
throw DownloadError(NotFound, fmt("S3 object '%s' does not exist", request.uri));
res.data = s3Res.data;
return res;
callback(std::move(res));
#else
throw nix::Error("cannot download '%s' because Nix is not built with S3 support", request.uri);
#endif
});
} catch (...) { callback.rethrow(); }
return;
}
auto item = std::make_shared<DownloadItem>(*this, request);
item->success = success;
item->failure = failure;
enqueueItem(item);
enqueueItem(std::make_shared<DownloadItem>(*this, request, callback));
}
};
@ -622,8 +620,13 @@ std::future<DownloadResult> Downloader::enqueueDownload(const DownloadRequest &
{
auto promise = std::make_shared<std::promise<DownloadResult>>();
enqueueDownload(request,
[promise](const DownloadResult & result) { promise->set_value(result); },
[promise](std::exception_ptr exc) { promise->set_exception(exc); });
{[promise](std::future<DownloadResult> fut) {
try {
promise->set_value(fut.get());
} catch (...) {
promise->set_exception(std::current_exception());
}
}});
return promise->get_future();
}