Add proper error handling for uPER decoding

Rather than asserting this switches the decoder into an error state now
and invalidates the decoded result.

src/lib/asn1/uperdecoder.cpp

@@ -39,7 +39,10 @@ int64_t UPERDecoder::readConstrainedWholeNumber(int64_t minimum, int64_t maximum
 int64_t UPERDecoder::readUnconstrainedWholeNumber()
 {
     const auto len = readLengthDeterminant();
-    assert(len <= 8); // TODO
+    if (len > 8) {
+        setError("Encountered INTEGER bigger than 64bit, not implemented.");
+        return 0;
+    }
     int64_t result = m_data.valueAtMSB<int64_t>(m_idx, 8 * len);
     m_idx += 8 * len;
     return result; // TODO convert negative numbers
@@ -53,8 +56,7 @@ UPERDecoder::size_type UPERDecoder::readLengthDeterminant()
         return len;
     }
 
-    // TODO
-    assert(false);
+    setError("Encountered not implemented length determinant variant.");
     return 0;
 }
 
@@ -150,3 +152,18 @@ QList<QString> UPERDecoder::readSequenceOfUtf8String()
     }
     return result;
 }
+
+bool UPERDecoder::hasError() const
+{
+    return !m_error.isEmpty();
+}
+
+QByteArray UPERDecoder::errorMessage() const
+{
+    return m_error;
+}
+
+void UPERDecoder::setError(const char *msg)
+{
+    m_error = "uPER decoding error at offset " + QByteArray::number((qint64)m_idx) + ": " + msg;
+}

src/lib/asn1/uperdecoder.h

@@ -103,7 +103,10 @@ public:
     template <typename T>
     inline T readEnumeratedWithExtensionMarker()
     {
-        assert(!readBoolean()); // TODO
+        if (readBoolean()) {
+            setError("CHOICE with extension marker set not implemented.");
+            return {};
+        }
         return readEnumerated<T>();
     }
 
@@ -113,13 +116,29 @@ public:
     template <typename... Ts>
     inline QVariant readChoiceWithExtensionMarker()
     {
-        assert(!readBoolean()); // TODO
+        if (readBoolean()) {
+            setError("CHOICE with extension marker set not implemented.");
+            return {};
+        }
         constexpr auto count = sizeof...(Ts);
         const auto choiceIdx = readConstrainedWholeNumber(0, count - 1);
-        assert(choiceIdx < (int)count); // TODO
+        if (choiceIdx > (int)count) {
+            setError("Invalid CHOICE index.");
+            return {};
+        }
         return readChoiceElement<Ts...>(choiceIdx);
     }
 
+    /** Reading at any point encountered an error.
+     *  As uPER gives us no way to recover from that, everything
+     *  read has to be considered invalid.
+     */
+    bool hasError() const;
+    QByteArray errorMessage() const;
+
+    /** Put the decoder into the error state. */
+    void setError(const char *msg);
+
 private:
     QByteArray readIA5StringData(size_type len);
 
@@ -142,6 +161,7 @@ private:
 
     BitVectorView m_data;
     size_type m_idx = {};
+    QByteArray m_error;
 };
 
 }

src/lib/asn1/uperelement.h

@@ -75,7 +75,10 @@ private: \
     std::bitset<_uper_OptionalCount> m_optionals; \
     inline void decodeSequence(UPERDecoder &decoder) { \
         if constexpr (_uper_ExtensionMarker) { \
-            assert(!decoder.readBoolean()); /* TODO either handle this properly, or switch to an error state. */ \
+            if (decoder.readBoolean()) { \
+                decoder.setError("SEQUENCE with extension marker set not implemented."); \
+                return; \
+            } \
         } \
         m_optionals = decoder.readBitset<_uper_OptionalCount>(); \
     }

src/lib/era/fcbticket.cpp

@@ -5,10 +5,9 @@
 
 #include "fcbticket.h"
 
+#include "logging.h"
 #include "asn1/uperdecoder.h"
 
-#include <QDebug>
-
 #define FCB_READ_CONSTRAINED_INT(Name, Min, Max) \
     if (Name ## IsSet()) \
         Name = decoder.readConstrainedWholeNumber(Min, Max)
@@ -775,6 +774,10 @@ Fcb::UicRailTicketData::UicRailTicketData(const Uic9183Block &block)
 {
     UPERDecoder decoder(BitVectorView(std::string_view(block.content(), block.contentSize())));
     decode(decoder);
+    if (decoder.hasError()) {
+        qCWarning(Log) << decoder.errorMessage();
+        m_block = {};
+    }
 }
 
 void Fcb::UicRailTicketData::decode(UPERDecoder &decoder)
@@ -786,4 +789,9 @@ void Fcb::UicRailTicketData::decode(UPERDecoder &decoder)
     FCB_READ_CUSTOM(controlDetail)
 }
 
+bool Fcb::UicRailTicketData::isValid() const
+{
+    return !m_block.isNull();
+}
+
 #include "moc_fcbticket.cpp"

src/lib/era/fcbticket.h

@@ -928,6 +928,8 @@ public:
 
     static constexpr const char RecordId[] = "U_FLEX";
 
+    bool isValid() const;
+
 private:
     Uic9183Block m_block;
 };