Handle compression errors in a recoverable way

In case of errors during compression, we now clear the incoming ring
buffer to allow flash logging to continue at the next iteration.

Author: ccattuto

firmware/nRF51/tag-proximity/src/log.c

@@ -196,7 +196,6 @@ static void flash_log_block_commit(void)
 void flash_log_write(uint8_t flush_buf)
 {
 	uint8_t *my_head = buf_head;
-	uint8_t *tail_copy = buf_tail;
 	uint16_t chunk_size;
 
     HSE_sink_res sres = 0;
@@ -245,12 +244,12 @@ void flash_log_write(uint8_t flush_buf)
 			buf_tail -= BUF_SIZE;
 	}
 
-	/* on error, bail out and revert buffer tail to original position */
+	/* on error, clear the ring buffer and exit */
 	if (pres < 0 || sres < 0)
 	{
 		log_compression_error++;
 		status_flags |= ERROR_LOG_COMPRESS;
-		buf_tail = tail_copy;
+		buf_tail = my_head;
 		return;
 	}
 
@@ -261,12 +260,12 @@ void flash_log_write(uint8_t flush_buf)
 		/* signal encoder that we are done */
 		fres = heatshrink_encoder_finish(&hse);
 
-		/* on error, bail out and revert buffer tail to original position */
+		/* on error, clear the ring buffer and exit */
 		if (fres < 0)
 		{
 			log_compression_error++;
 			status_flags |= ERROR_LOG_COMPRESS;
-			buf_tail = tail_copy;
+			buf_tail = my_head;
 			return;
 		}
 
@@ -282,22 +281,24 @@ void flash_log_write(uint8_t flush_buf)
 
     			/* update block length */
         		LogBlock.env.len += poll_sz;
+
+        		/* on block buffer overflow, clear the ring buffer and exit */
         		if (LogBlock.env.len >= LOG_BLOCK_DATA_SIZE)
         		{
 					log_compression_error++;
 					status_flags |= ERROR_LOG_COMPRESS;
-					buf_tail = tail_copy;
+					buf_tail = my_head;
 					return;
         		}
     		} while (pres == HSER_POLL_MORE);
     	}
 
-		/* on error, bail out and revert buffer tail to original position */
+		/* on error, clear the ring buffer and exit */
     	if (pres < 0)
 		{
 			log_compression_error++;
 			status_flags |= ERROR_LOG_COMPRESS;
-			buf_tail = tail_copy;
+			buf_tail = my_head;
 			return;
 		}