From 844f050cf334d659cfc6b0087319977a6435ce13 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Wed, 1 Jul 2015 20:22:53 +1000
Subject: [PATCH] DataFlash: correct zero-byte-file handling in CLI

-rw-rw-r-- 1 pbarker pbarker   2105344 Jul  1 16:10 1.BIN
-rw-rw-r-- 1 pbarker pbarker         0 Jul  1 19:35 2.BIN
-rw-rw-r-- 1 pbarker pbarker   2494464 Jul  1 16:58 3.BIN
-rw-rw-r-- 1 pbarker pbarker 128503808 Jul  1 20:22 4.BIN
-rw-rw-r-- 1 pbarker pbarker         3 Jul  1 19:46 LASTLOG.TXT

Before fix:

2 logs
Log 3 in logs/3.BIN of size 2494464 2015/7/1 6:58
Log 4 in logs/4.BIN of size 128503808 2015/7/1 10:22

After Fix:

4 logs
Log 1 in logs/1.BIN of size 2105344 2015/7/1 6:10
Log 2 in logs/2.BIN of size 0 2015/7/1 9:35
Log 3 in logs/3.BIN of size 2494464 2015/7/1 6:58
Log 4 in logs/4.BIN of size 128503808 2015/7/1 10:22

If the last file was zero bytes, no files would be shown.
---
 libraries/DataFlash/DataFlash_File.cpp | 16 +++++++++++++---
 libraries/DataFlash/DataFlash_File.h   |  1 +
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/libraries/DataFlash/DataFlash_File.cpp b/libraries/DataFlash/DataFlash_File.cpp
index 9134ada8ec..fde93e0d9f 100644
--- a/libraries/DataFlash/DataFlash_File.cpp
+++ b/libraries/DataFlash/DataFlash_File.cpp
@@ -274,6 +274,18 @@ uint16_t DataFlash_File::find_last_log(void)
     return ret;
 }
 
+bool DataFlash_File::_log_exists(uint16_t log_num)
+{
+    char *fname = _log_file_name(log_num);
+    if (fname == NULL) {
+        return 0;
+    }
+    struct stat st;
+    // stat return 0 if the file exists:
+    bool ret = ::stat(fname, &st) ? false : true;
+    free(fname);
+    return ret;
+}
 
 uint32_t DataFlash_File::_get_log_size(uint16_t log_num)
 {
@@ -395,7 +407,7 @@ uint16_t DataFlash_File::get_num_logs(void)
     uint16_t ret;
     uint16_t high = find_last_log();
     for (ret=0; ret<high; ret++) {
-        if (_get_log_size(high - ret) <= 0) {
+        if (!_log_exists(high - ret)) {
             break;
         }
     }
@@ -587,7 +599,6 @@ void DataFlash_File::ListAvailableLogs(AP_HAL::BetterStream *port)
         char *filename = _log_file_name(log_num);
         if (filename != NULL) {
             size = _get_log_size(log_num);
-            if (size != 0) {
                 struct stat st;
                 if (stat(filename, &st) == 0) {
                     struct tm *tm = gmtime(&st.st_mtime);
@@ -601,7 +612,6 @@ void DataFlash_File::ListAvailableLogs(AP_HAL::BetterStream *port)
                                    (unsigned)tm->tm_hour,
                                    (unsigned)tm->tm_min);
                 }
-            }
             free(filename);
         }
     }
diff --git a/libraries/DataFlash/DataFlash_File.h b/libraries/DataFlash/DataFlash_File.h
index 6bd2521190..ac56de6851 100644
--- a/libraries/DataFlash/DataFlash_File.h
+++ b/libraries/DataFlash/DataFlash_File.h
@@ -44,6 +44,7 @@ public:
     void get_log_info(uint16_t log_num, uint32_t &size, uint32_t &time_utc);
     int16_t get_log_data(uint16_t log_num, uint16_t page, uint32_t offset, uint16_t len, uint8_t *data);
     uint16_t get_num_logs(void);
+    bool _log_exists(uint16_t log_num);
     uint16_t start_new_log(void);
     void LogReadProcess(uint16_t log_num,
                         uint16_t start_page, uint16_t end_page,