Add in incremental read routine and unit test. Ref #nasa/issues/956

fsw/cfe-core/src/es/cfe_es_log.h

@@ -182,6 +182,37 @@ void CFE_ES_SysLogClear_Unsync(void);
  */
 void CFE_ES_SysLogReadStart_Unsync(CFE_ES_SysLogReadBuffer_t *Buffer);
 
+/**
+ * \brief Initialize Buffer for an incremental reading the system log
+ *
+ * This a helper function is intended to initialize the Buffer contents, assuming
+ * the Buffer was passed into CFE_ES_SysLogReadStart_Unsync at some time prior.
+ * This function supports incremental reading of the syslog buffer over time
+ * for systems that will send logs down in packets as opposed to logging to disk.
+ *
+ * This incremental reading of logs is only supported if set to OVERWRITE mode,
+ * otherwise the behavior will mimic a call to CFE_ES_SysLogReadStart_Unsync.
+ *
+ * This incremental reading of logs is only supported if CFE_ES_SysLogReadStart_Unsync
+ * has been called once previously on the Buffer, otherwise the behavior will mimic a 
+ * call to CFE_ES_SysLogReadStart_Unsync.
+ *
+ * This function uses the Buffers current (as passed in) LastOffset from a previous
+ * read log data, and the current state of the syslog log buffer to intialize the
+ * buffer to read data logged since the Buffer's LastOffset.
+ *
+ * \param Buffer  A local buffer which will be initialized based on its current LastOffset 
+ *                to read unread data from the syslog buffer.
+ *
+ * \note This function requires external thread synchronization
+ * \note This function requires Buffer has been initialized at some point by
+ *       CFE_ES_SysLogReadStart_Unsync, but only once.
+ * \note This function requires the logs be set to OVERWRITE mode.
+ * \sa CFE_ES_SysLogReadData()
+ */
+void CFE_ES_SysLogIncReadInit_Unsync(CFE_ES_SysLogReadBuffer_t *Buffer);
+
+
 
 /**
  * \brief Write a printf-style formatted string to the system log

fsw/cfe-core/src/es/cfe_es_syslog.c

@@ -134,6 +134,42 @@ void CFE_ES_SysLogReadStart_Unsync(CFE_ES_SysLogReadBuffer_t *Buffer)
     Buffer->BlockSize = 0;
 } /* End of CFE_ES_SysLogReadStart_Unsync() */
 
+
+/*
+ * -----------------------------------------------------------------
+ * CFE_ES_SysLogIncReadInit_Unsync --
+ * Initialize Buffer for an incremental reading the system log
+ * -----------------------------------------------------------------
+ */
+void CFE_ES_SysLogIncReadInit_Unsync(CFE_ES_SysLogReadBuffer_t *Buffer)
+{
+    if ( ( CFE_ES_ResetDataPtr->SystemLogMode != CFE_ES_LogMode_OVERWRITE ) ||
+         ( Buffer->LastOffset > CFE_ES_ResetDataPtr->SystemLogEndIdx ) )
+    {
+        CFE_ES_SysLogReadStart_Unsync(Buffer);
+    }
+    else
+    {
+        /* LastOffset is left at its passed in position. */
+        /* Since CFE_ES_SysLogReadStart_Unsync has been called, no new line
+         * logic added. */
+        if ( CFE_ES_ResetDataPtr->SystemLogWriteIdx < Buffer->LastOffset )
+        {
+            Buffer->SizeLeft = CFE_ES_ResetDataPtr->SystemLogEndIdx - 
+                               Buffer->LastOffset +
+                               CFE_ES_ResetDataPtr->SystemLogWriteIdx;
+        }
+        else
+        {
+            Buffer->SizeLeft = CFE_ES_ResetDataPtr->SystemLogWriteIdx - 
+                               Buffer->LastOffset;
+        }
+        Buffer->BlockSize = 0;
+        Buffer->EndIdx    = CFE_ES_ResetDataPtr->SystemLogEndIdx;
+    }
+} /* End of CFE_ES_SysLogIncReadInit_Unsync() */
+
+
 /*
  * -----------------------------------------------------------------
  * CFE_ES_SysLogAppend_Unsync() --

fsw/cfe-core/unit-test/es_UT.c

@@ -6416,6 +6416,39 @@ void TestSysLog(void)
               "CFE_ES_SysLogDump",
               "Multiple reads and writes to sys log");
 
+    /* Test Incremental Reading without wrap*/
+    ES_ResetUnitTest();
+    CFE_ES_ResetDataPtr->SystemLogMode     = CFE_ES_LogMode_OVERWRITE;
+    CFE_ES_ResetDataPtr->SystemLogEndIdx   = sizeof(CFE_ES_ResetDataPtr->SystemLog) - 1;
+    CFE_ES_ResetDataPtr->SystemLogWriteIdx = CFE_ES_ResetDataPtr->SystemLogEndIdx - 1;
+    SysLogBuffer.LastOffset = CFE_ES_ResetDataPtr->SystemLogWriteIdx - 2;;
+
+    CFE_ES_SysLogIncReadInit_Unsync(&SysLogBuffer);
+
+    UT_Report(__FILE__, __LINE__,
+              SysLogBuffer.EndIdx == (sizeof(CFE_ES_ResetDataPtr->SystemLog) - 1) &&
+              SysLogBuffer.BlockSize == 0 &&
+              SysLogBuffer.SizeLeft == 2,
+              "CFE_ES_SysLogIncReadInit_Unsync",
+              "Incremental read without wrap");
+
+    /* Test Incremental Reading with wrap*/
+    ES_ResetUnitTest();
+    CFE_ES_ResetDataPtr->SystemLogMode     = CFE_ES_LogMode_OVERWRITE;
+    CFE_ES_ResetDataPtr->SystemLogEndIdx   = sizeof(CFE_ES_ResetDataPtr->SystemLog) - 1;
+    SysLogBuffer.LastOffset                = 3;
+    CFE_ES_ResetDataPtr->SystemLogWriteIdx = 2;
+
+    CFE_ES_SysLogIncReadInit_Unsync(&SysLogBuffer);
+
+    UT_Report(__FILE__, __LINE__,
+              SysLogBuffer.EndIdx == (sizeof(CFE_ES_ResetDataPtr->SystemLog) - 1) &&
+              SysLogBuffer.LastOffset == 3 &&
+              SysLogBuffer.BlockSize == 0 &&
+              SysLogBuffer.SizeLeft == (SysLogBuffer.EndIdx - 3 + 2),
+              "CFE_ES_SysLogIncReadInit_Unsync",
+              "Incremental read with wrap");
+
     /* Test "message got truncated"  */
     ES_ResetUnitTest();
     memset(TmpString, 'a', CFE_ES_MAX_SYSLOG_MSG_SIZE);