1 files changed, 185 insertions, 0 deletions
diff --git a/libcurl/rest.cpp b/libcurl/rest.cpp
new file mode 100644
index 00000000..22583483
--- /dev/null
+++ b/libcurl/rest.cpp
@@ -0,0 +1,185 @@
+// *****************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under    *
+// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
+// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
+// *****************************************************************************
+
+#include "rest.h"
+#include <zen/system.h>
+#include <zen/http.h>
+
+using namespace zen;
+
+
+HttpSession::HttpSession(const Zstring& server, const Zstring& caCertFilePath, std::chrono::seconds timeOut) : //throw SysError
+    server_(utfTo<std::string>(server)),
+    caCertFilePath_(utfTo<std::string>(caCertFilePath)),
+    timeOutSec_(timeOut) {}
+
+
+HttpSession::~HttpSession()
+{
+    if (easyHandle_)
+        ::curl_easy_cleanup(easyHandle_);
+}
+
+
+HttpSession::Result HttpSession::perform(const std::string& serverRelPath,
+                                         const std::vector<std::string>& extraHeaders, const std::vector<CurlOption>& extraOptions, //throw SysError
+                                         const std::function<void  (const void* buffer, size_t bytesToWrite)>& writeResponse /*throw X*/, //optional
+                                         const std::function<size_t(      void* buffer, size_t bytesToRead )>& readRequest   /*throw X*/) //
+{
+    if (!easyHandle_)
+    {
+        easyHandle_ = ::curl_easy_init();
+        if (!easyHandle_)
+            throw SysError(formatSystemError(L"curl_easy_init", formatCurlStatusCode(CURLE_OUT_OF_MEMORY), std::wstring()));
+    }
+    else
+        ::curl_easy_reset(easyHandle_);
+
+
+    std::vector<CurlOption> options;
+
+    char curlErrorBuf[CURL_ERROR_SIZE] = {};
+    options.emplace_back(CURLOPT_ERRORBUFFER, curlErrorBuf);
+
+    options.emplace_back(CURLOPT_USERAGENT, "FreeFileSync"); //default value; may be overwritten by caller
+
+    //lifetime: keep alive until after curl_easy_setopt() below
+    std::string curlPath = "https://" + server_ + serverRelPath;
+    options.emplace_back(CURLOPT_URL, curlPath.c_str());
+
+    options.emplace_back(CURLOPT_ACCEPT_ENCODING, "gzip"); //won't hurt + used by Google Drive
+
+    options.emplace_back(CURLOPT_NOSIGNAL, 1L); //thread-safety: https://curl.haxx.se/libcurl/c/threadsafe.html
+
+    options.emplace_back(CURLOPT_CONNECTTIMEOUT, timeOutSec_.count());
+
+    //CURLOPT_TIMEOUT: "Since this puts a hard limit for how long time a request is allowed to take, it has limited use in dynamic use cases with varying transfer times."
+    options.emplace_back(CURLOPT_LOW_SPEED_TIME, timeOutSec_.count());
+    options.emplace_back(CURLOPT_LOW_SPEED_LIMIT, 1L); //[bytes], can't use "0" which means "inactive", so use some low number
+
+
+    //libcurl forwards this char-string to OpenSSL as is, which - thank god - accepts UTF8
+    options.emplace_back(CURLOPT_CAINFO, caCertFilePath_.c_str()); //hopefully latest version from https://curl.haxx.se/docs/caextract.html
+    //CURLOPT_SSL_VERIFYPEER => already active by default
+    //CURLOPT_SSL_VERIFYHOST =>
+
+    //---------------------------------------------------
+    std::exception_ptr userCallbackException;
+
+    auto onBytesReceived = [&](const void* buffer, size_t len)
+    {
+        try
+        {
+            writeResponse(buffer, len); //throw X
+            return len;
+        }
+        catch (...)
+        {
+            userCallbackException = std::current_exception();
+            return len + 1; //signal error condition => CURLE_WRITE_ERROR
+        }
+    };
+    using ReadCbType = decltype(onBytesReceived);
+    using ReadCbWrapperType =          size_t (*)(const void* buffer, size_t size, size_t nitems, ReadCbType* callbackData); //needed for cdecl function pointer cast
+    ReadCbWrapperType onBytesReceivedWrapper = [](const void* buffer, size_t size, size_t nitems, ReadCbType* callbackData)
+    {
+        return (*callbackData)(buffer, size * nitems); //free this poor little C-API from its shackles and redirect to a proper lambda
+    };
+    //---------------------------------------------------
+    auto getBytesToSend = [&](void* buffer, size_t len) -> size_t
+    {
+        try
+        {
+            //libcurl calls back until 0 bytes are returned (Posix read() semantics), or,
+            //if CURLOPT_INFILESIZE_LARGE was set, after exactly this amount of bytes
+            const size_t bytesRead = readRequest(buffer, len);//throw X; return "bytesToRead" bytes unless end of stream!
+            return bytesRead;
+        }
+        catch (...)
+        {
+            userCallbackException = std::current_exception();
+            return CURL_READFUNC_ABORT; //signal error condition => CURLE_ABORTED_BY_CALLBACK
+        }
+    };
+    using WriteCbType = decltype(getBytesToSend);
+    using WriteCbWrapperType =         size_t (*)(void* buffer, size_t size, size_t nitems, WriteCbType* callbackData);
+    WriteCbWrapperType getBytesToSendWrapper = [](void* buffer, size_t size, size_t nitems, WriteCbType* callbackData)
+    {
+        return (*callbackData)(buffer, size * nitems); //free this poor little C-API from its shackles and redirect to a proper lambda
+    };
+    //---------------------------------------------------
+    if (writeResponse)
+    {
+        options.emplace_back(CURLOPT_WRITEDATA, &onBytesReceived);
+        options.emplace_back(CURLOPT_WRITEFUNCTION, onBytesReceivedWrapper);
+    }
+    if (readRequest)
+    {
+        if (std::all_of(extraOptions.begin(), extraOptions.end(), [](const CurlOption& o) { return o.option != CURLOPT_POST; }))
+        options.emplace_back(CURLOPT_UPLOAD, 1L); //issues HTTP PUT
+        options.emplace_back(CURLOPT_READDATA, &getBytesToSend);
+        options.emplace_back(CURLOPT_READFUNCTION, getBytesToSendWrapper);
+    }
+
+    if (std::any_of(extraOptions.begin(), extraOptions.end(), [](const CurlOption& o) { return o.option == CURLOPT_WRITEFUNCTION || o.option == CURLOPT_READFUNCTION; }))
+    throw std::logic_error("Contract violation! " + std::string(__FILE__) + ":" + numberTo<std::string>(__LINE__)); //Option already used here!
+
+    if (readRequest && std::any_of(extraOptions.begin(), extraOptions.end(), [](const CurlOption& o) { return o.option == CURLOPT_POSTFIELDS; }))
+    throw std::logic_error("Contract violation! " + std::string(__FILE__) + ":" + numberTo<std::string>(__LINE__)); //Contradicting options: CURLOPT_READFUNCTION, CURLOPT_POSTFIELDS
+
+    //---------------------------------------------------
+    curl_slist* headers = nullptr; //"libcurl will not copy the entire list so you must keep it!"
+    ZEN_ON_SCOPE_EXIT(::curl_slist_free_all(headers));
+
+    for (const std::string& headerLine : extraHeaders)
+        headers = ::curl_slist_append(headers, headerLine.c_str());
+
+    //WTF!!! 1 sec delay when server doesn't support "Expect: 100-continue!! https://stackoverflow.com/questions/49670008/how-to-disable-expect-100-continue-in-libcurl
+    headers = ::curl_slist_append(headers, "Expect:"); //guess, what: www.googleapis.com doesn't support it! e.g. gdriveUploadFile()
+
+    if (headers)
+        options.emplace_back(CURLOPT_HTTPHEADER, headers);
+    //---------------------------------------------------
+
+    append(options, extraOptions);
+
+    applyCurlOptions(easyHandle_, options); //throw SysError
+
+    //=======================================================================================================
+    const CURLcode rcPerf = ::curl_easy_perform(easyHandle_);
+    //WTF: curl_easy_perform() considers FTP response codes 4XX, 5XX as failure, but for HTTP response codes 4XX are considered success!! CONSISTENCY, people!!!
+    //=> at least libcurl is aware: CURLOPT_FAILONERROR: "request failure on HTTP response >= 400"; default: "0, do not fail on error"
+    //https://curl.haxx.se/docs/faq.html#curl_doesn_t_return_error_for_HT
+    //=> Curiously Google also screws up in their REST API design and returns HTTP 4XX status for domain-level errors!
+    //=> let caller handle HTTP status to work around this mess!
+
+    if (userCallbackException)
+        std::rethrow_exception(userCallbackException); //throw X
+    //=======================================================================================================
+
+    long httpStatusCode = 0; //optional
+    /*const CURLcode rc = */ ::curl_easy_getinfo(easyHandle_, CURLINFO_RESPONSE_CODE, &httpStatusCode);
+
+    if (rcPerf != CURLE_OK)
+    {
+        std::wstring errorMsg = trimCpy(utfTo<std::wstring>(curlErrorBuf)); //optional
+
+        if (httpStatusCode != 0) //optional
+            errorMsg += (errorMsg.empty() ? L"" : L"\n") + formatHttpStatusCode(httpStatusCode);
+#if 0
+        //utfTo<std::wstring>(::curl_easy_strerror(ec)) is uninteresting
+        //use CURLINFO_OS_ERRNO ?? https://curl.haxx.se/libcurl/c/CURLINFO_OS_ERRNO.html
+        long nativeErrorCode = 0;
+        if (::curl_easy_getinfo(easyHandle, CURLINFO_OS_ERRNO, &nativeErrorCode) == CURLE_OK)
+            if (nativeErrorCode != 0)
+                errorMsg += (errorMsg.empty() ? L"" : L"\n") + std::wstring(L"Native error code: ") + numberTo<std::wstring>(nativeErrorCode);
+#endif
+        throw SysError(formatSystemError(L"curl_easy_perform", formatCurlStatusCode(rcPerf), errorMsg));
+    }
+
+    lastSuccessfulUseTime_ = std::chrono::steady_clock::now();
+    return { static_cast<int>(httpStatusCode) /*, contentType ? contentType : ""*/ };
+}