add upstream 10.20

   It is worth noting that the send email feature is not present in the
   GPL release.

14 files changed, 389 insertions, 117 deletions

diff --git a/zen/error_log.h b/zen/error_log.h
index 5115e6ef..cc52fc6e 100644
--- a/zen/error_log.h
+++ b/zen/error_log.h
@@ -10,9 +10,10 @@
 #include <cassert>
 #include <algorithm>
 #include <vector>
-#include <string>
+//#include <string>
 #include "time.h"
 #include "i18n.h"
+#include "utf.h"
 #include "zstring.h"
 
 
@@ -30,7 +31,7 @@ struct LogEntry
 {
     time_t      time = 0;
     MessageType type = MSG_TYPE_FATAL_ERROR;
-    Zstringw    message; //std::wstring may employ small string optimization: we cannot accept bloating the "ErrorLog::entries" memory block below (think 1 million items)
+    Zstringw    message; //std::wstring may employ small string optimization: we cannot accept bloating the "ErrorLog::entries_" memory block below (think 1 million items)
 };
 
 std::wstring formatMessage(const LogEntry& entry);
@@ -71,17 +72,14 @@ void ErrorLog::logMsg(const std::wstring& msg, MessageType type)
 inline
 int ErrorLog::getItemCount(int typeFilter) const
 {
-    return static_cast<int>(std::count_if(entries_.begin(), entries_.end(), [&](const LogEntry& e) { return e.type & typeFilter; }));
+    return static_cast<int>(std::count_if(entries_.begin(), entries_.end(), [typeFilter](const LogEntry& e) { return e.type & typeFilter; }));
 }
 
 
-namespace
+inline 
+std::wstring getMessageTypeLabel(MessageType type)
 {
-std::wstring formatMessageImpl(const LogEntry& entry)
-{
-    auto getTypeName = [&]
-    {
-        switch (entry.type)
+        switch (type)
         {
             case MSG_TYPE_INFO:
                 return _("Info");
@@ -94,32 +92,33 @@ std::wstring formatMessageImpl(const LogEntry& entry)
         }
         assert(false);
         return std::wstring();
-    };
+}
+
+
+inline
+std::wstring formatMessage(const LogEntry& entry)
+{
+    std::wstring msgFmt = L"[" + formatTime<std::wstring>(FORMAT_TIME, getLocalTime(entry.time)) + L"]  " + getMessageTypeLabel(entry.type) + L":  ";
+    const size_t prefixLen = unicodeLength(msgFmt); //consider Unicode!
 
-    std::wstring msgFmt = L"[" + formatTime<std::wstring>(FORMAT_TIME, getLocalTime(entry.time)) + L"]  " + getTypeName() + L":  ";
-    const size_t prefixLen = msgFmt.size(); //considers UTF-16 only!
+    const Zstringw msg = trimCpy(entry.message);
+    static_assert(std::is_same_v<decltype(msg), const Zstringw>, "don't worry about copying as long as we're using a ref-counted string!");
 
-    for (auto it = entry.message.begin(); it != entry.message.end(); )
+    for (auto it = msg.begin(); it != msg.end(); )
         if (*it == L'\n')
         {
             msgFmt += L'\n';
             msgFmt.append(prefixLen, L' ');
-
-            do //skip duplicate newlines
-            {
-                ++it;
-            }
-            while (it != entry.message.end() && *it == L'\n');
+            ++it;
+            //skip duplicate newlines
+            for (;it != msg.end() && *it == L'\n'; ++it)
+                ;
         }
         else
             msgFmt += *it++;
 
-    return msgFmt;
-}
+    return msgFmt += L'\n';
 }
-
-inline
-std::wstring formatMessage(const LogEntry& entry) { return formatMessageImpl(entry); }
 }
 
 #endif //ERROR_LOG_H_8917590832147915
diff --git a/zen/http.cpp b/zen/http.cpp
index 4f2c5205..8cd99d7a 100644
--- a/zen/http.cpp
+++ b/zen/http.cpp
@@ -18,15 +18,19 @@ class HttpInputStream::Impl
 {
 public:
     Impl(const Zstring& url,
-         const std::vector<std::pair<std::string, std::string>>* postParams, //issue POST if bound, GET otherwise
+         const std::string* postBuf /*issue POST if bound, GET otherwise*/,
+         const Zstring& contentType, //required for POST
          bool disableGetCache /*not relevant for POST (= never cached)*/,
          const Zstring& userAgent,
          const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-         const IOCallback& notifyUnbufferedIO) : //throw SysError
+         const IOCallback& notifyUnbufferedIO) : //throw SysError, X
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
         ZEN_ON_SCOPE_FAIL(cleanup(); /*destructor call would lead to member double clean-up!!!*/);
 
+        //may be sending large POST: call back first
+        if (notifyUnbufferedIO_) notifyUnbufferedIO_(0); //throw X
+
         const Zstring urlFmt =              afterFirst(url, Zstr("://"), IF_MISSING_RETURN_NONE);
         const Zstring server =            beforeFirst(urlFmt, Zstr('/'), IF_MISSING_RETURN_ALL);
         const Zstring page   = Zstr('/') + afterFirst(urlFmt, Zstr('/'), IF_MISSING_RETURN_NONE);
@@ -40,6 +44,13 @@ public:
             throw SysError(L"URL uses unexpected protocol.");
         }();
 
+        assert(postBuf || contentType.empty());
+
+        std::map<std::string, std::string, LessAsciiNoCase> headers;
+
+        if (postBuf && !contentType.empty())
+            headers["Content-Type"] = utfTo<std::string>(contentType);
+
         if (useTls) //HTTP default port: 443, see %WINDIR%\system32\drivers\etc\services
         {
             socket_ = std::make_unique<Socket>(server, Zstr("https")); //throw SysError
@@ -49,27 +60,23 @@ public:
             socket_ = std::make_unique<Socket>(server, Zstr("http")); //throw SysError
 
         //we don't support "chunked and gzip transfer encoding" => HTTP 1.0
-        std::map<std::string, std::string, LessAsciiNoCase> headers;
         headers["Host"      ] = utfTo<std::string>(server); //only required for HTTP/1.1 but a few servers expect it even for HTTP/1.0
         headers["User-Agent"] = utfTo<std::string>(userAgent);
         headers["Accept"    ] = "*/*"; //won't hurt?
 
-        const std::string postBuf = postParams ? xWwwFormUrlEncode(*postParams) : "";
-
-        if (!postParams /*HTTP GET*/ && disableGetCache)
+        if (!postBuf /*HTTP GET*/ && disableGetCache)
             headers["Pragma"] = "no-cache"; //HTTP 1.0 only! superseeded by "Cache-Control"
-        else //HTTP POST
-        {
-            headers["Content-Type"] = "application/x-www-form-urlencoded";
-            headers["Content-Length"] = numberTo<std::string>(postBuf.size());
-        }
+
+        if (postBuf)
+            headers["Content-Length"] = numberTo<std::string>(postBuf->size());
 
         //https://www.w3.org/Protocols/HTTP/1.0/spec.html#Request-Line
-        std::string msg = (postParams ? "POST " : "GET ") + utfTo<std::string>(page) + " HTTP/1.0\r\n";
+        std::string msg = (postBuf ? "POST " : "GET ") + utfTo<std::string>(page) + " HTTP/1.0\r\n";
         for (const auto& [name, value] : headers)
             msg += name + ": " + value + "\r\n";
         msg += "\r\n";
-        msg += postBuf;
+        if (postBuf)
+            msg += *postBuf;
 
         //send request
         for (size_t bytesToSend = msg.size(); bytesToSend > 0;)
@@ -121,6 +128,9 @@ public:
         //try to get "Content-Length" header if available
         if (const std::string* value = getHeader("Content-Length"))
             contentRemaining_ = stringTo<int64_t>(*value) - (bufPosEnd_ - bufPos_);
+
+        //let's not get too finicky: at least report the logical amount of bytes sent/received (excluding HTTP headers)
+        if (notifyUnbufferedIO_) notifyUnbufferedIO_(postBuf ? postBuf->size() : 0); //throw X
     }
 
     ~Impl() { cleanup(); }
@@ -225,16 +235,17 @@ std::string HttpInputStream::readAll() { return bufferedLoad<std::string>(*pimpl
 namespace
 {
 std::unique_ptr<HttpInputStream::Impl> sendHttpRequestImpl(const Zstring& url,
-                                                           const std::vector<std::pair<std::string, std::string>>* postParams /*issue POST if bound, GET otherwise*/,
+                                                           const std::string* postBuf /*issue POST if bound, GET otherwise*/,
+                                                           const Zstring& contentType, //required for POST
                                                            const Zstring& userAgent,
                                                            const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                                                           const IOCallback& notifyUnbufferedIO) //throw SysError
+                                                           const IOCallback& notifyUnbufferedIO) //throw SysError, X
 {
     Zstring urlRed = url;
     //"A user agent should not automatically redirect a request more than five times, since such redirections usually indicate an infinite loop."
     for (int redirects = 0; redirects < 6; ++redirects)
     {
-        auto response = std::make_unique<HttpInputStream::Impl>(urlRed, postParams, false /*disableGetCache*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError
+        auto response = std::make_unique<HttpInputStream::Impl>(urlRed, postBuf, contentType, false /*disableGetCache*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 
         //https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#3xx_Redirection
         const int httpStatusCode = response->getStatusCode();
@@ -258,48 +269,48 @@ std::unique_ptr<HttpInputStream::Impl> sendHttpRequestImpl(const Zstring& url,
 }
 
 
-//encode into "application/x-www-form-urlencoded"
+//encode for "application/x-www-form-urlencoded"
 std::string urlencode(const std::string& str)
 {
-    std::string out;
-    for (const char c : str) //follow PHP spec: https://github.com/php/php-src/blob/master/ext/standard/url.c#L500
+    std::string output;
+    for (const char c : str) //follow PHP spec: https://github.com/php/php-src/blob/e99d5d39239c611e1e7304e79e88545c4e71a073/ext/standard/url.c#L455
         if (c == ' ')
-            out += '+';
+            output += '+';
         else if (('0' <= c && c <= '9') ||
                  ('A' <= c && c <= 'Z') ||
                  ('a' <= c && c <= 'z') ||
                  c == '-' || c == '.' || c == '_') //note: "~" is encoded by PHP!
-            out += c;
+            output += c;
         else
         {
             const auto [high, low] = hexify(c);
-            out += '%';
-            out += high;
-            out += low;
+            output += '%';
+            output += high;
+            output += low;
         }
-    return out;
+    return output;
 }
 
 
 std::string urldecode(const std::string& str)
 {
-    std::string out;
+    std::string output;
     for (size_t i = 0; i < str.size(); ++i)
     {
         const char c = str[i];
         if (c == '+')
-            out += ' ';
+            output += ' ';
         else if (c == '%' && str.size() - i >= 3 &&
                  isHexDigit(str[i + 1]) &&
                  isHexDigit(str[i + 2]))
         {
-            out += unhexify(str[i + 1], str[i + 2]);
+            output += unhexify(str[i + 1], str[i + 2]);
             i += 2;
         }
         else
-            out += c;
+            output += c;
     }
-    return out;
+    return output;
 }
 }
 
@@ -327,16 +338,24 @@ std::vector<std::pair<std::string, std::string>> zen::xWwwFormUrlDecode(const st
 }
 
 
+HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+{
+    return sendHttpRequestImpl(url, nullptr /*postBuf*/, Zstr("") /*contentType*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X, X
+}
+
+
 HttpInputStream zen::sendHttpPost(const Zstring& url, const std::vector<std::pair<std::string, std::string>>& postParams,
-                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
 {
-    return sendHttpRequestImpl(url, &postParams, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError
+    return sendHttpPost(url, xWwwFormUrlEncode(postParams), Zstr("application/x-www-form-urlencoded"), userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
 
 
-HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError
+
+HttpInputStream zen::sendHttpPost(const Zstring& url, const std::string& postBuf, const Zstring& contentType,
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
 {
-    return sendHttpRequestImpl(url, nullptr /*postParams*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError
+    return sendHttpRequestImpl(url, &postBuf, contentType, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
 
 
@@ -346,6 +365,7 @@ bool zen::internetIsAlive() //noexcept
     {
         auto response = std::make_unique<HttpInputStream::Impl>(Zstr("http://www.google.com/"),
                                                                 nullptr /*postParams*/,
+                                                                Zstr("") /*contentType*/,
                                                                 true /*disableGetCache*/,
                                                                 Zstr("FreeFileSync"),
                                                                 nullptr /*caCertFilePath*/,
@@ -439,4 +459,79 @@ std::wstring zen::formatHttpStatusCode(int sc)
         return trimCpy(replaceCpy<std::wstring>(L"HTTP status %x.", L"%x", numberTo<std::wstring>(sc)));
     else
         return trimCpy(replaceCpy<std::wstring>(L"HTTP status %x: ", L"%x", numberTo<std::wstring>(sc)) + statusText);
-}
\ No newline at end of file
+}
+
+
+bool zen::isValidEmail(const Zstring& email)
+{
+    //https://en.wikipedia.org/wiki/Email_address#Syntax
+    //https://tools.ietf.org/html/rfc3696 => note errata! https://www.rfc-editor.org/errata_search.php?rfc=3696
+    //https://tools.ietf.org/html/rfc5321
+    std::string local  = utfTo<std::string>(beforeLast(email, Zstr('@'), IF_MISSING_RETURN_NONE));
+    std::string domain = utfTo<std::string>( afterLast(email, Zstr('@'), IF_MISSING_RETURN_NONE));
+    //consider: "t@st"@email.com t\@st@email.com"
+
+    auto stripComments = [](std::string& part)
+    {
+        if (startsWith(part, '('))
+            part = afterFirst(part, ')', IF_MISSING_RETURN_NONE);
+
+        if (endsWith(part, ')'))
+            part = beforeLast(part, '(', IF_MISSING_RETURN_NONE);
+    };
+    stripComments(local);
+    stripComments(domain);
+
+    if (local .empty() || local .size() > 63 || // 64 octets ->  63 ASCII chars: https://devblogs.microsoft.com/oldnewthing/20120412-00/?p=7873
+        domain.empty() || domain.size() > 253)  //255 octets -> 253 ASCII chars
+        return false;
+    //---------------------------------------------------------------------
+
+    const bool quoted = (startsWith(local, '"') && endsWith(local, '"')) ||
+                        contains(local, '\\'); //e.g. "t\@st@email.com"
+    if (!quoted) //I'm not going to parse and validate this!
+        for (const std::string& comp : split(local, '.', SplitType::ALLOW_EMPTY))
+            if (comp.empty() || !std::all_of(comp.begin(), comp.end(), [](char c)
+        {
+            const char printable[] = "!#$%&'*+-/=?^_`{|}~";
+                return isAsciiAlpha(c) || isDigit(c) || makeUnsigned(c) >= 128 ||
+                       std::find(std::begin(printable), std::end(printable), c) != std::end(printable);
+            }))
+    return false;
+    //---------------------------------------------------------------------
+
+    //e.g. jsmith@[192.168.2.1]  jsmith@[IPv6:2001:db8::1]
+    const bool likelyIp = startsWith(domain, '[') && endsWith(domain, ']');
+    if (!likelyIp) //not interested in parsing IPs!
+    {
+        if (!contains(domain, '.'))
+            return false;
+
+        for (const std::string& comp : split(domain, '.', SplitType::ALLOW_EMPTY))
+            if (comp.empty() || comp.size() > 63 ||
+            !std::all_of(comp.begin(), comp.end(), [](char c) { return isAsciiAlpha(c) ||isDigit(c) || makeUnsigned(c) >= 128 || c ==  '-'; }))
+        return false;
+    }
+
+    return true;
+}
+
+
+std::string zen::htmlSpecialChars(const std::string& str)
+{
+    //mirror PHP: https://github.com/php/php-src/blob/e99d5d39239c611e1e7304e79e88545c4e71a073/ext/standard/html_tables.h#L6189
+    std::string output;
+    for (const char c : str)
+        switch (c)
+        {
+            //*INDENT-OFF*
+            case '&': output += "&amp;" ; break;
+            case '"': output += "&quot;"; break;
+            case '<': output += "&lt;"  ; break;
+            case '>': output += "&gt;"  ; break;
+            //case '\'': output += "&apos;"; break; -> not encoded by default (needs ENT_QUOTES)
+            default: output += c; break;
+            //*INDENT-ON*
+        }
+    return output;
+}
diff --git a/zen/http.h b/zen/http.h
index 42b0e279..fbaa09de 100644
--- a/zen/http.h
+++ b/zen/http.h
@@ -39,15 +39,24 @@ private:
 HttpInputStream sendHttpGet(const Zstring& url,
                             const Zstring& userAgent,
                             const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                            const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError
+                            const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 HttpInputStream sendHttpPost(const Zstring& url,
                              const std::vector<std::pair<std::string, std::string>>& postParams,
                              const Zstring& userAgent,
                              const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                             const IOCallback& notifyUnbufferedIO /*throw X*/);
+                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+
+HttpInputStream sendHttpPost(const Zstring& url,
+                             const std::string& postBuf, const Zstring& contentType,
+                             const Zstring& userAgent,
+                             const Zstring* caCertFilePath /*optional: enable certificate validation*/,
+                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+
 bool internetIsAlive(); //noexcept
 std::wstring formatHttpStatusCode(int httpStatusCode);
+bool isValidEmail(const Zstring& email);
+std::string htmlSpecialChars(const std::string& str);
 
 std::string xWwwFormUrlEncode(const std::vector<std::pair<std::string, std::string>>& paramPairs);
 std::vector<std::pair<std::string, std::string>> xWwwFormUrlDecode(const std::string& str);
diff --git a/zen/json.h b/zen/json.h
index e6464286..725874f7 100644
--- a/zen/json.h
+++ b/zen/json.h
@@ -27,16 +27,18 @@ struct JsonValue
     };
 
     explicit JsonValue() {}
-    explicit JsonValue(Type t) : type(t) {}
-    explicit JsonValue(bool b)                 : type(Type::boolean), primVal(b ? "true" : "false") {}
-    explicit JsonValue(int64_t num)            : type(Type::number),  primVal(numberTo<std::string>(num)) {}
-    explicit JsonValue(double num)             : type(Type::number),  primVal(numberTo<std::string>(num)) {}
-    explicit JsonValue(const std::string& str) : type(Type::string),  primVal(str) {}
+    explicit JsonValue(Type t)          : type(t) {}
+    explicit JsonValue(bool b)          : type(Type::boolean), primVal(b ? "true" : "false") {}
+    explicit JsonValue(int num)         : type(Type::number),  primVal(numberTo<std::string>(num)) {}
+    explicit JsonValue(int64_t num)     : type(Type::number),  primVal(numberTo<std::string>(num)) {}
+    explicit JsonValue(double num)      : type(Type::number),  primVal(numberTo<std::string>(num)) {}
+    explicit JsonValue(std::string str) : type(Type::string),  primVal(std::move(str)) {} //unifying assignment
+    explicit JsonValue(const void*) = delete; //catch usage errors e.g. const char* -> JsonValue(bool)
 
     Type type = Type::null;
-    std::string                                       primVal; //for primitive types
-    std::map<std::string, std::unique_ptr<JsonValue>> objectVal; //"[...] most implementations of JSON libraries do not accept duplicate keys [...]" => fine!
-    std::vector<std::unique_ptr<JsonValue>>           arrayVal;
+    std::string                        primVal; //for primitive types
+    std::map<std::string, JsonValue> objectVal; //"[...] most implementations of JSON libraries do not accept duplicate keys [...]" => fine!
+    std::vector<JsonValue>            arrayVal;
 };
 
 
@@ -66,7 +68,7 @@ const JsonValue* getChildFromJsonObject(const JsonValue& jvalue, const std::stri
     if (it == jvalue.objectVal.end())
         return nullptr;
 
-    return it->second.get();
+    return &it->second;
 }
 
 
@@ -240,8 +242,8 @@ void serialize(const JsonValue& jval, std::string& stream,
 
                     stream += '"' + jsonEscape(childName) + "\":";
 
-                    if ((childValue->type == JsonValue::Type::object && !childValue->objectVal.empty()) ||
-                        (childValue->type == JsonValue::Type::array  && !childValue->arrayVal .empty()))
+                    if ((childValue.type == JsonValue::Type::object && !childValue.objectVal.empty()) ||
+                        (childValue.type == JsonValue::Type::array  && !childValue.arrayVal .empty()))
                     {
                         stream += lineBreak;
                         writeIndent(indentLevel + 1);
@@ -249,7 +251,7 @@ void serialize(const JsonValue& jval, std::string& stream,
                     else if (!indent.empty())
                         stream += ' ';
 
-                    serialize(*childValue, stream, lineBreak, indent, indentLevel + 1);
+                    serialize(childValue, stream, lineBreak, indent, indentLevel + 1);
                 }
                 stream += lineBreak;
                 writeIndent(indentLevel);
@@ -263,7 +265,7 @@ void serialize(const JsonValue& jval, std::string& stream,
             {
                 for (auto it = jval.arrayVal.begin(); it != jval.arrayVal.end(); ++it)
                 {
-                    const auto& childValue = **it;
+                    const auto& childValue = *it;
 
                     if (it != jval.arrayVal.begin())
                         stream += ',';
@@ -462,7 +464,7 @@ private:
                     consumeToken(Token::Type::colon); //throw JsonParsingError
 
                     JsonValue value = parseValue(); //throw JsonParsingError
-                    jval.objectVal.emplace(std::move(name), std::make_unique<JsonValue>(std::move(value)));
+                    jval.objectVal.emplace(std::move(name), std::move(value));
 
                     if (token().type != Token::Type::comma)
                         break;
@@ -482,7 +484,7 @@ private:
                 for (;;)
                 {
                     JsonValue value = parseValue();  //throw JsonParsingError
-                    jval.arrayVal.emplace_back(std::make_unique<JsonValue>(std::move(value)));
+                    jval.arrayVal.emplace_back(std::move(value));
 
                     if (token().type != Token::Type::comma)
                         break;
diff --git a/zen/serialize.h b/zen/serialize.h
index bdeec858..dd884e3b 100644
--- a/zen/serialize.h
+++ b/zen/serialize.h
@@ -120,7 +120,7 @@ private:
 template <class BinContainer>
 struct MemoryStreamIn
 {
-    MemoryStreamIn(const BinContainer& cont) : buffer_(cont) {} //this better be cheap!
+    explicit MemoryStreamIn(const BinContainer& cont) : buffer_(cont) {} //this better be cheap!
 
     size_t read(void* buffer, size_t bytesToRead) //return "bytesToRead" bytes unless end of stream!
     {
@@ -207,11 +207,12 @@ BinContainer bufferedLoad(BufferedInputStream& streamIn) //throw X
     for (;;)
     {
         buffer.resize(buffer.size() + blockSize);
-        const size_t bytesRead = streamIn.read(&*(buffer.end() - blockSize), blockSize); //throw X; return "bytesToRead" bytes unless end of stream!
-        buffer.resize(buffer.size() - blockSize + bytesRead); //caveat: unsigned arithmetics
-
+        const size_t bytesRead = streamIn.read(&*(buffer.end() - blockSize), blockSize); //throw X; return "blockSize" bytes unless end of stream!
         if (bytesRead < blockSize) //end of file
+        {
+            buffer.resize(buffer.size() - (blockSize - bytesRead)); //caveat: unsigned arithmetics
             return buffer;
+        }
     }
 }
 
@@ -270,12 +271,11 @@ C readContainer(BufferedInputStream& stream) //throw UnexpectedEndOfStreamError
     {
         try
         {
-            cont.resize(strLength); //throw std::bad_alloc
-        }
-        catch (std::bad_alloc&) //most likely this is due to data corruption!
-        {
-            throw UnexpectedEndOfStreamError();
+            cont.resize(strLength); //throw std::length_error
         }
+        catch (std::length_error&) { throw UnexpectedEndOfStreamError(); } //most likely this is due to data corruption!
+        catch (   std::bad_alloc&) { throw UnexpectedEndOfStreamError(); } //
+
         readArray(stream, &*cont.begin(), sizeof(typename C::value_type) * strLength); //throw UnexpectedEndOfStreamError
     }
     return cont;
diff --git a/zen/shell_execute.h b/zen/shell_execute.h
index 56322236..580c4558 100644
--- a/zen/shell_execute.h
+++ b/zen/shell_execute.h
@@ -19,15 +19,15 @@ namespace zen
 //Windows: COM needs to be initialized before calling this function!
 enum class ExecutionType
 {
-    SYNC,
-    ASYNC
+    sync,
+    async
 };
 
 namespace
 {
 
 
-void shellExecute(const Zstring& command, ExecutionType type, bool hideConsole) //throw FileError
+int shellExecute(const Zstring& command, ExecutionType type, bool hideConsole) //throw FileError
 {
     /*
     we cannot use wxExecute due to various issues:
@@ -35,21 +35,23 @@ void shellExecute(const Zstring& command, ExecutionType type, bool hideConsole)
     - does not provide any reasonable error information
     - uses a zero-sized dummy window as a hack to keep focus which leaves a useless empty icon in ALT-TAB list in Windows
     */
-    if (type == ExecutionType::SYNC)
+    if (type == ExecutionType::sync)
     {
         //Posix ::system() - execute a shell command
         const int rv = ::system(command.c_str()); //do NOT use std::system as its documentation says nothing about "WEXITSTATUS(rv)", etc...
         if (rv == -1 || WEXITSTATUS(rv) == 127)
-            throw FileError(_("Incorrect command line:") + L"\n" + utfTo<std::wstring>(command));
+            throw FileError(_("Incorrect command line:") + L' ' + utfTo<std::wstring>(command));
         //https://linux.die.net/man/3/system "In case /bin/sh could not be executed, the exit status will be that of a command that does exit(127)"
         //Bonus: For an incorrect command line /bin/sh also returns with 127!
+
+        return /*int exitCode = */ WEXITSTATUS(rv);
     }
     else
     {
         //follow implemenation of ::system() except for waitpid():
         const pid_t pid = ::fork();
         if (pid < 0) //pids are never negative, empiric proof: https://linux.die.net/man/2/wait
-            THROW_LAST_FILE_ERROR(_("Incorrect command line:") + L"\n" + utfTo<std::wstring>(command), L"fork");
+            THROW_LAST_FILE_ERROR(_("Incorrect command line:") + L' ' + utfTo<std::wstring>(command), L"fork");
 
         if (pid == 0) //child process
         {
@@ -64,7 +66,39 @@ void shellExecute(const Zstring& command, ExecutionType type, bool hideConsole)
             ::_exit(127); //[!] avoid flushing I/O buffers or doing other clean up from child process like with "exit(127)"!
         }
         //else //parent process
+        return 0;
+    }
+}
+
+
+std::string getCommandOutput(const Zstring& command) //throw SysError
+{
+    //https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/popen.3.html
+    FILE* pipe = ::popen(command.c_str(), "r"); 
+    if (!pipe)
+        THROW_LAST_SYS_ERROR(L"popen");
+    ZEN_ON_SCOPE_EXIT(::pclose(pipe));
+
+    std::string output;
+    const size_t blockSize = 64 * 1024;
+    do
+    {
+        output.resize(output.size() + blockSize);
+
+        //caveat: SIGCHLD is NOT ignored under macOS debugger => EINTR inside fread() => call ::siginterrupt(SIGCHLD, false) during startup
+        const size_t bytesRead = ::fread(&*(output.end() - blockSize), 1, blockSize, pipe);
+        if (::ferror(pipe))
+            THROW_LAST_SYS_ERROR(L"fread");
+
+        if (bytesRead > blockSize)
+            throw SysError(L"fread: buffer overflow");
+
+        if (bytesRead < blockSize)
+            output.resize(output.size() - (blockSize - bytesRead)); //caveat: unsigned arithmetics
     }
+    while (!::feof(pipe));
+    
+    return output;
 }
 }
 
@@ -72,7 +106,7 @@ void shellExecute(const Zstring& command, ExecutionType type, bool hideConsole)
 inline
 void openWithDefaultApplication(const Zstring& itemPath) //throw FileError
 {
-    shellExecute("xdg-open \"" + itemPath +  '"', ExecutionType::ASYNC, false /*hideConsole*/); //throw FileError
+    shellExecute("xdg-open \"" + itemPath +  '"', ExecutionType::async, false /*hideConsole*/); //throw FileError
 }
 }
 
diff --git a/zen/shutdown.cpp b/zen/shutdown.cpp
index 5ce586f0..89da55ee 100644
--- a/zen/shutdown.cpp
+++ b/zen/shutdown.cpp
@@ -18,7 +18,7 @@ void zen::shutdownSystem() //throw FileError
     //https://linux.die.net/man/2/reboot => needs admin rights!
 
     //"systemctl" should work without admin rights:
-    shellExecute("systemctl poweroff", ExecutionType::SYNC, false/*hideConsole*/); //throw FileError
+    shellExecute("systemctl poweroff", ExecutionType::sync, false/*hideConsole*/); //throw FileError
 
 }
 
@@ -26,7 +26,7 @@ void zen::shutdownSystem() //throw FileError
 void zen::suspendSystem() //throw FileError
 {
     //"systemctl" should work without admin rights:
-    shellExecute("systemctl suspend", ExecutionType::SYNC, false/*hideConsole*/); //throw FileError
+    shellExecute("systemctl suspend", ExecutionType::sync, false/*hideConsole*/); //throw FileError
 
 }
 
diff --git a/zen/string_tools.h b/zen/string_tools.h
index 47271bc7..5c444830 100644
--- a/zen/string_tools.h
+++ b/zen/string_tools.h
@@ -27,7 +27,7 @@ template <class Char> bool isLineBreak (Char c);
 template <class Char> bool isDigit     (Char c); //not exactly the same as "std::isdigit" -> we consider '0'-'9' only!
 template <class Char> bool isHexDigit  (Char c);
 template <class Char> bool isAsciiAlpha(Char c);
-template <class Char> bool isAsciiString(const Char* str);
+template <class S   > bool isAsciiString(const S& str);
 template <class Char> Char asciiToLower(Char c);
 template <class Char> Char asciiToUpper(Char c);
 
@@ -150,14 +150,11 @@ bool isAsciiAlpha(Char c)
 }
 
 
-template <class Char> inline
-bool isAsciiString(const Char* str)
+template <class S> inline
+bool isAsciiString(const S& str)
 {
-    static_assert(std::is_same_v<Char, char> || std::is_same_v<Char, wchar_t>);
-    for (Char c = *str; c != 0; c = *++str)
-        if (zen::makeUnsigned(c) >= 128)
-            return false;
-    return true;
+    const auto* const first = strBegin(str);
+    return std::all_of(first, first + strLength(str), [](auto c) { return makeUnsigned(c) < 128; });
 }
 
 
@@ -170,8 +167,8 @@ Char asciiToLower(Char c)
 }
 
 
-    template <class Char> inline
-    Char asciiToUpper(Char c)
+template <class Char> inline
+Char asciiToUpper(Char c)
 {
     if (static_cast<Char>('a') <= c && c <= static_cast<Char>('z'))
                                     return static_cast<Char>(c - static_cast<Char>('a') + static_cast<Char>('A'));
@@ -604,7 +601,7 @@ S numberTo(const Num& number, std::integral_constant<NumberType, NumberType::FLO
 
     char buffer[128]; //zero-initialize?
     //let's give some leeway, but 24 chars should suffice: https://www.reddit.com/r/cpp/comments/dgj89g/cppcon_2019_stephan_t_lavavej_floatingpoint/f3j7d3q/
-    const char* strEnd = zen::to_chars(std::begin(buffer), std::end(buffer), number);
+    const char* strEnd = to_chars(std::begin(buffer), std::end(buffer), number);
 
     S output;
     std::for_each(static_cast<const char*>(buffer), strEnd,
@@ -703,7 +700,7 @@ inline
 double stringToFloat(const char* first, const char* last)
 {
     //don't use std::strtod(): 1. requires null-terminated string 2. SLOWER than std::from_chars()
-    return zen::from_chars(first, last);
+    return from_chars(first, last);
 }
 
 
@@ -713,7 +710,7 @@ double stringToFloat(const wchar_t* first, const wchar_t* last)
     std::string buf(last - first, '\0');
     std::transform(first, last, buf.begin(), [](wchar_t c) { return static_cast<char>(c); });
 
-    return zen::from_chars(buf.c_str(), buf.c_str() + buf.size());
+    return from_chars(buf.c_str(), buf.c_str() + buf.size());
 }
 
 
diff --git a/zen/sys_error.h b/zen/sys_error.h
index 57503732..a9347bdd 100644
--- a/zen/sys_error.h
+++ b/zen/sys_error.h
@@ -85,9 +85,8 @@ std::wstring formatSystemError(const std::wstring& functionName, long long lastE
 inline
 std::wstring formatSystemError(const std::wstring& functionName, ErrorCode ec)
 {
-    const std::wstring errorDescr = formatSystemErrorRaw(ec);
     const std::wstring errorCode = numberTo<std::wstring>(ec);
-    //const std::wstring errorCode = printNumber<std::wstring>(L"0x%08x", static_cast<int>(ec));
+    const std::wstring errorDescr = formatSystemErrorRaw(ec);
 
     return formatSystemError(functionName, replaceCpy(_("Error Code %x"), L"%x", errorCode), errorDescr);
 }
diff --git a/zen/system.cpp b/zen/system.cpp
new file mode 100644
index 00000000..5945484f
--- /dev/null
+++ b/zen/system.cpp
@@ -0,0 +1,84 @@
+// *****************************************************************************
+// * 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 "system.h"
+#include "file_access.h"
+#include "crc.h"
+
+    #include "symlink_target.h"
+    #include "file_io.h"
+    #include <ifaddrs.h>
+    #include <net/if.h> //IFF_LOOPBACK
+    #include <netpacket/packet.h> //sockaddr_ll
+
+    #include <unistd.h> //getuid()
+    #include <pwd.h>    //getpwuid_r()
+    #include "shell_execute.h"
+
+using namespace zen;
+
+
+std::wstring zen::getUserName() //throw FileError
+{
+    const uid_t userIdNo = ::getuid(); //never fails
+
+    std::vector<char> buffer(std::max<long>(10000, ::sysconf(_SC_GETPW_R_SIZE_MAX))); //::sysconf may return long(-1)
+    struct passwd buffer2 = {};
+    struct passwd* pwsEntry = nullptr;
+    if (::getpwuid_r(userIdNo, &buffer2, &buffer[0], buffer.size(), &pwsEntry) != 0) //getlogin() is deprecated and not working on Ubuntu at all!!!
+        THROW_LAST_FILE_ERROR(_("Cannot get process information."), L"getpwuid_r");
+    if (!pwsEntry)
+        throw FileError(_("Cannot get process information."), L"no login found"); //should not happen?
+
+    return utfTo<std::wstring>(pwsEntry->pw_name);
+}
+
+
+namespace
+{
+}
+
+
+ComputerModel zen::getComputerModel() //throw FileError
+{
+    try
+    {
+        auto tryGetInfo = [](const Zstring& filePath)
+        {
+            if (!fileAvailable(filePath))
+                return std::wstring();
+            try
+            {
+                const std::string stream = loadBinContainer<std::string>(filePath, nullptr /*notifyUnbufferedIO*/); //throw FileError
+                return utfTo<std::wstring>(trimCpy(stream));
+            }
+            catch (const FileError& e) { throw SysError(e.toString()); } //errors should be further enriched by context info => SysError
+        };
+        return { tryGetInfo("/sys/devices/virtual/dmi/id/product_name"), //throw SysError
+                 tryGetInfo("/sys/devices/virtual/dmi/id/sys_vendor") }; //
+
+    }
+    catch (const SysError& e) { throw FileError(_("Cannot get process information."), e.toString()); }
+}
+
+
+
+
+std::wstring zen::getOsDescription() //throw FileError
+{
+    try
+    {
+        const std::string osName    = trimCpy(getCommandOutput("lsb_release --id -s"     )); //throw SysError
+        const std::string osVersion = trimCpy(getCommandOutput("lsb_release --release -s")); //
+        return utfTo<std::wstring>(osName + " " + osVersion); //e.g. "CentOS 7.7.1908"
+
+    }
+    catch (const SysError& e) { throw FileError(_("Cannot get process information."), e.toString()); }
+}
+
+
+
+
diff --git a/zen/system.h b/zen/system.h
new file mode 100644
index 00000000..f10a6a40
--- /dev/null
+++ b/zen/system.h
@@ -0,0 +1,33 @@
+// *****************************************************************************
+// * 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 *
+// *****************************************************************************
+
+#ifndef SYSTEM_H_4189731847832147508915
+#define SYSTEM_H_4189731847832147508915
+
+#include "file_error.h"
+
+
+namespace zen
+{
+//COM needs to be initialized before calling any of these functions! CoInitializeEx/CoUninitialize
+
+std::wstring getUserName(); //throw FileError
+
+struct ComputerModel
+{
+    std::wstring model;  //best-effort: empty if not available
+    std::wstring vendor; //
+};
+ComputerModel getComputerModel(); //throw FileError
+
+
+
+std::wstring getOsDescription(); //throw FileError
+
+
+}
+
+#endif //SYSTEM_H_4189731847832147508915
diff --git a/zen/zlib_wrap.cpp b/zen/zlib_wrap.cpp
index f7418b88..57a0f33c 100644
--- a/zen/zlib_wrap.cpp
+++ b/zen/zlib_wrap.cpp
@@ -149,3 +149,23 @@ private:
 zen::InputStreamAsGzip::InputStreamAsGzip(const std::function<size_t(void* buffer, size_t bytesToRead)>& readBlock /*throw X*/) : pimpl_(std::make_unique<Impl>(readBlock)) {} //throw SysError
 zen::InputStreamAsGzip::~InputStreamAsGzip() {}
 size_t zen::InputStreamAsGzip::read(void* buffer, size_t bytesToRead) { return pimpl_->read(buffer, bytesToRead); } //throw SysError, X
+
+
+std::string zen::compressAsGzip(const void* buffer, size_t bufSize) //throw SysError
+{
+    struct MemoryStreamAsGzip : InputStreamAsGzip
+    {
+        explicit MemoryStreamAsGzip(const std::function<size_t(void* buffer, size_t bytesToRead)>& readBlock /*throw X*/) : InputStreamAsGzip(readBlock) {} //throw SysError
+        static size_t getBlockSize() { return 128 * 1024; } //InputStreamAsGzip has no idea what it's wrapping => has no getBlockSize() member!
+    };
+
+    MemoryStreamAsGzip gzipStream([&](void* bufIn, size_t bytesToRead) //throw SysError
+    {
+        const size_t bytesRead = std::min(bufSize, bytesToRead);
+        std::memcpy(bufIn, buffer, bytesRead);
+        buffer = static_cast<const char*>(buffer) + bytesRead;
+        bufSize -= bytesRead;
+        return bytesRead; //returning 0 signals EOF: Posix read() semantics
+    });
+    return bufferedLoad<std::string>(gzipStream); //throw SysError
+}
diff --git a/zen/zlib_wrap.h b/zen/zlib_wrap.h
index 9d9229ac..b820a4f8 100644
--- a/zen/zlib_wrap.h
+++ b/zen/zlib_wrap.h
@@ -27,8 +27,8 @@ BinContainer decompress(const BinContainer& stream); //throw SysError
 class InputStreamAsGzip //convert input stream into gzip on the fly
 {
 public:
-    InputStreamAsGzip( //throw SysError
-        const std::function<size_t(void* buffer, size_t bytesToRead)>& readBlock /*throw X*/); //returning 0 signals EOF: Posix read() semantics
+    explicit InputStreamAsGzip( //throw SysError
+        const std::function<size_t(void* buffer, size_t bytesToRead)>& readBlock /*throw X;  returning 0 signals EOF: Posix read() semantics*/);
     ~InputStreamAsGzip();
 
     size_t read(void* buffer, size_t bytesToRead); //throw SysError, X; return "bytesToRead" bytes unless end of stream!
@@ -38,6 +38,7 @@ private:
     const std::unique_ptr<Impl> pimpl_;
 };
 
+std::string compressAsGzip(const void* buffer, size_t bufSize); //throw SysError
 
 
 
@@ -103,10 +104,9 @@ BinContainer decompress(const BinContainer& stream) //throw SysError
         {
             contOut.resize(static_cast<size_t>(uncompressedSize)); //throw std::bad_alloc
         }
-        catch (const std::bad_alloc& e) //most likely due to data corruption!
-        {
-            throw SysError(L"zlib error: " + _("Out of memory.") + L" " + utfTo<std::wstring>(e.what()));
-        }
+        //most likely this is due to data corruption:
+        catch (const std::length_error& e) { throw SysError(L"zlib error: " + _("Out of memory.") + L" " + utfTo<std::wstring>(e.what())); }
+        catch (const    std::bad_alloc& e) { throw SysError(L"zlib error: " + _("Out of memory.") + L" " + utfTo<std::wstring>(e.what())); }
 
         const size_t bytesWritten = impl::zlib_decompress(&*stream.begin() + sizeof(uncompressedSize),
                                                           stream.size() - sizeof(uncompressedSize),
diff --git a/zen/zstring.cpp b/zen/zstring.cpp
index f018b14f..ff20b8cf 100644
--- a/zen/zstring.cpp
+++ b/zen/zstring.cpp
@@ -17,7 +17,7 @@ using namespace zen;
 Zstring makeUpperCopy(const Zstring& str)
 {
     //fast pre-check:
-    if (isAsciiString(str.c_str())) //perf: in the range of 3.5ns
+    if (isAsciiString(str)) //perf: in the range of 3.5ns
     {
         Zstring output = str;
         for (Zchar& c : output) c = asciiToUpper(c);
@@ -49,7 +49,7 @@ Zstring makeUpperCopy(const Zstring& str)
 Zstring getUnicodeNormalForm(const Zstring& str)
 {
     //fast pre-check:
-    if (isAsciiString(str.c_str())) //perf: in the range of 3.5ns
+    if (isAsciiString(str)) //perf: in the range of 3.5ns
         return str; //god bless our ref-counting! => save output string memory consumption!
 
     //Example: const char* decomposed  = "\x6f\xcc\x81";