corrected using fieldIndex in Message::decodeLastData(bool, ...), corrected finding field in DataFieldSet::read() with index and without name, added optional partType and fieldName to DataField::getCount()

src/lib/ebus/data.cpp

@@ -657,6 +657,10 @@ bool SingleDataField::hasFullByteOffset(bool after) const {
   || (after && firstBit + (m_dataType->getBitCount() % 8) >= 8);
 }
 
+size_t SingleDataField::getCount(PartType partType, const char* fieldName) const {
+	return isIgnored() || (partType != pt_any && partType != m_partType) || (fieldName != NULL && m_name != fieldName) ? 0 : 1;
+}
+
 
 const ValueListDataField* ValueListDataField::clone() const {
   return new ValueListDataField(*this);
@@ -925,6 +929,17 @@ size_t DataFieldSet::getLength(PartType partType, size_t maxLength) const {
   return length;
 }
 
+size_t DataFieldSet::getCount(PartType partType, const char* fieldName) const {
+  if (partType == pt_any && fieldName == NULL) {
+    return m_fields.size() - m_ignoredCount;
+  }
+  size_t count = 0;
+  for (auto field : m_fields) {
+    count += field->getCount(partType, fieldName);
+  }
+  return count;
+}
+
 string DataFieldSet::getName(ssize_t fieldIndex) const {
   if (fieldIndex < (ssize_t)m_ignoredCount) {
     return m_name;
@@ -988,7 +1003,7 @@ void DataFieldSet::dump(bool prependFieldSeparator, bool asJson, ostream* output
 
 result_t DataFieldSet::read(const SymbolString& data, size_t offset,
     const char* fieldName, ssize_t fieldIndex, unsigned int* output) const {
-  bool previousFullByteOffset = true, found = false, findFieldIndex = fieldName != NULL && fieldIndex >= 0;
+  bool previousFullByteOffset = true, found = false, findFieldIndex = fieldIndex >= 0;
   PartType partType = data.isMaster() ? pt_masterData : pt_slaveData;
   for (const auto field : m_fields) {
     if (field->getPartType() != partType) {

src/lib/ebus/data.h

@@ -251,9 +251,11 @@ class DataField : public AttributedItem {
 
   /**
    * Get the field count (excluding ignored fields).
+   * @param partType the optional part to count, or @ pt_any.
+   * @param fieldName the optional field name to count, or NULL.
    * @return the field count (excluding ignored fields).
    */
-  virtual size_t getCount() const = 0;
+  virtual size_t getCount(PartType partType = pt_any, const char* fieldName = NULL) const = 0;
 
   /**
    * Get the specified field name.
@@ -399,7 +401,7 @@ class SingleDataField : public DataField {
   bool hasFullByteOffset(bool after) const;
 
   // @copydoc
-  size_t getCount() const override { return isIgnored() ? 0 : 1; }
+  size_t getCount(PartType partType = pt_any, const char* fieldName = NULL) const override;
 
   // @copydoc
   virtual string getName(ssize_t fieldIndex) const {
@@ -638,7 +640,7 @@ class DataFieldSet : public DataField {
   size_t getLength(PartType partType, size_t maxLength) const override;
 
   // @copydoc
-  size_t getCount() const override { return m_fields.size() - m_ignoredCount; }
+  size_t getCount(PartType partType = pt_any, const char* fieldName = NULL) const override;
 
   // @copydoc
   string getName(ssize_t fieldIndex) const override;

src/lib/ebus/message.cpp

@@ -727,7 +727,7 @@ result_t Message::decodeLastData(bool master, bool leadingSeparator, const char*
   if (result < RESULT_OK) {
     return result;
   }
-  if (result == RESULT_EMPTY && fieldName != NULL) {
+  if (result == RESULT_EMPTY && (fieldName != NULL || fieldIndex >= 0)) {
     return RESULT_ERR_NOTFOUND;
   }
   return result;
@@ -742,14 +742,25 @@ result_t Message::decodeLastData(bool leadingSeparator, const char* fieldName,
     return result;
   }
   bool empty = result == RESULT_EMPTY;
-  bool useLeadingSeparator = leadingSeparator || output->tellp() > startPos;
-  result = m_data->read(m_lastSlaveData, 0, useLeadingSeparator, fieldName, fieldIndex, outputFormat, -1, output);
-  if (result < RESULT_OK) {
-    return result;
+  bool skipSlaveData = false;
+  if (fieldIndex >= 0) {
+    fieldIndex -= m_data->getCount(pt_masterData, fieldName);
+    if (fieldIndex < 0) {
+      skipSlaveData = true;
+	  fieldIndex = 0;
+    }
   }
-  if (result == RESULT_EMPTY && !empty) {
-    result = RESULT_OK;  // OK if at least one part was non-empty
-  } else if (result == RESULT_EMPTY && fieldName != NULL) {
+  if (!skipSlaveData) {
+    bool useLeadingSeparator = leadingSeparator || output->tellp() > startPos;
+    result = m_data->read(m_lastSlaveData, 0, useLeadingSeparator, fieldName, fieldIndex, outputFormat, -1, output);
+    if (result < RESULT_OK) {
+      return result;
+    }
+    if (result == RESULT_EMPTY && !empty) {
+      result = RESULT_OK;  // OK if at least one part was non-empty
+    }
+  }
+  if (result == RESULT_EMPTY && (fieldName != NULL || fieldIndex >= 0)) {
     return RESULT_ERR_NOTFOUND;
   }
   return result;