From 6bd433af46747345bb5b8d3d8150b9c32ae1a04f Mon Sep 17 00:00:00 2001
From: john30 <ebusd@ebusd.eu>
Date: Wed, 3 Oct 2018 10:53:38 +0200
Subject: [PATCH] fix for bit combinations during write to SymbolString

---
 src/lib/ebus/datatype.cpp |  2 +-
 src/lib/ebus/symbol.h     | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/lib/ebus/datatype.cpp b/src/lib/ebus/datatype.cpp
index 2a55c61e..399cc6fd 100755
--- a/src/lib/ebus/datatype.cpp
+++ b/src/lib/ebus/datatype.cpp
@@ -781,7 +781,7 @@ result_t NumberDataType::writeRawValue(unsigned int value, size_t offset, size_t
       symbol = (value / exp) & 0xff;
       exp <<=  8;
     }
-    if (index == start && (m_bitCount % 8) != 0 && offset + index < output->getDataSize()) {
+    if (index == start && (m_bitCount % 8) != 0 && offset + index < output->getCalculatedDataSize()) {
       output->dataAt(offset + index) |= symbol;
     } else {
       output->dataAt(offset + index) = symbol;
diff --git a/src/lib/ebus/symbol.h b/src/lib/ebus/symbol.h
index e128e0f5..82c983fc 100755
--- a/src/lib/ebus/symbol.h
+++ b/src/lib/ebus/symbol.h
@@ -249,7 +249,7 @@ class SymbolString {
     } else if (m_data.size() >= lengthOffset+255) {
       return false;
     }
-    m_data[lengthOffset] = (symbol_t)(m_data.size() - 1 - lengthOffset);
+    m_data[lengthOffset] = (symbol_t)(m_data.size() - lengthOffset - 1);
     return true;
   }
 
@@ -272,6 +272,18 @@ class SymbolString {
     return m_data.size() < lengthOffset + 1 + ret ? m_data.size() - lengthOffset - 1 : ret;
   }
 
+  /**
+   * Return the calculated number of data bytes DD (nnot yet revealed in the length field).
+   * @return the calculated number of data bytes DD.
+   */
+  size_t getCalculatedDataSize() const {
+    size_t lengthOffset = (m_isMaster ? 4 : 0);
+    if (m_data.size() <= lengthOffset) {
+      return 0;
+    }
+    return m_data.size() - lengthOffset - 1;
+  }
+
   /**
    * Return the data byte at the specified index (within DD).
    * @param index the index of the data byte (within DD) to return.