From bf9facc49c0ef0a8fabdda3d1e765c2edd2e390f Mon Sep 17 00:00:00 2001
From: Jens Arnold <amiconn@rockbox.org>
Date: Sun, 16 Aug 2009 17:18:45 +0000
Subject: FAT timestamp handling improvements for non-RTC targets: - When
 writing to a file that is older than the build, file date is set to the build
 date. - Time is advanced so that the minutes are a multiple of 11, excluding
 '00', and seconds =   minutes. This is done as a hint that the time isn't
 100% correct. - Date increment uses actual month lengths (but without leap
 year handling)

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@22348 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/drivers/fat.c | 99 +++++++++++++++++++++++++++-----------------------
 1 file changed, 54 insertions(+), 45 deletions(-)

diff --git a/firmware/drivers/fat.c b/firmware/drivers/fat.c
index e319669e97..578397cbe6 100644
--- a/firmware/drivers/fat.c
+++ b/firmware/drivers/fat.c
@@ -1001,70 +1001,79 @@ static void fat_time(unsigned short* date,
 #else
     /* non-RTC version returns an increment from the supplied time, or a
      * fixed standard time/date if no time given as input */
+
+/* Macros to convert a 2-digit string to a decimal constant.
+   (YEAR), MONTH and DAY are set by the date command, which outputs
+   DAY as 00..31 and MONTH as 01..12. The leading zero would lead to
+   misinterpretation as an octal constant. */
+#define S100(x) 1 ## x
+#define C2DIG2DEC(x) (S100(x)-100)
+/* The actual build date, as FAT date constant */
+#define BUILD_DATE_FAT (((YEAR - 1980) << 9) \
+                        | (C2DIG2DEC(MONTH) << 5) \
+                        | C2DIG2DEC(DAY))
+
+    bool date_forced = false;
     bool next_day = false;
+    unsigned time2 = 0; /* double time, for CRTTIME with 1s precision */
 
+    if (date && *date < BUILD_DATE_FAT)
+    {
+        *date = BUILD_DATE_FAT;
+        date_forced = true;
+    }
+    
     if (time)
     {
-        if (0 == *time)
+        time2 = *time << 1;
+        if (time2 == 0 || date_forced)
         {
-            /* set to 00:15:00 */
-            *time = (15 << 5);
+            time2 = (11 < 6) | 11; /* set to 00:11:11 */
         }
         else
         {
-            unsigned short mins = (*time >> 5) & 0x003F;
-            unsigned short hours = (*time >> 11) & 0x001F;
-            if ((mins += 10) >= 60)
-            {
-                mins = 0;
-                hours++;
-            }
-            if ((++hours) >= 24)
+            unsigned mins  = (time2 >> 6) & 0x3f;
+            unsigned hours = (time2 >> 12) & 0x1f;
+            
+            mins = 11 * ((mins/11) + 1); /* advance to next multiple of 11 */
+            if (mins > 59)
             {
-                hours = hours - 24;
-                next_day = true;
+                mins = 11; /* 00 would be a bad marker */
+                if (++hours > 23)
+                {
+                    hours = 0;
+                    next_day = true;
+                }
             }
-            *time = (hours << 11) | (mins << 5);
+            time2 = (hours << 12) | (mins << 6) | mins; /* secs = mins */
         }
+        *time = time2 >> 1;
     }
+    
+    if (tenth)
+        *tenth = (time2 & 1) * 100;
 
-    if (date)
+    if (date && next_day)
     {
-        if (0 == *date)
-        {
-/* Macros to convert a 2-digit string to a decimal constant. 
-   (YEAR), MONTH and DAY are set by the date command, which outputs
-   DAY as 00..31 and MONTH as 01..12. The leading zero would lead to
-   misinterpretation as an octal constant. */
-#define S100(x) 1 ## x
-#define C2DIG2DEC(x) (S100(x)-100)
-            /* set to build date */
-            *date = ((YEAR - 1980) << 9) | (C2DIG2DEC(MONTH) << 5)
-                    | C2DIG2DEC(DAY);
-        }
-        else
+        static const unsigned char daysinmonth[] =
+                              {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+        unsigned day   = *date & 0x1f;
+        unsigned month = (*date >> 5) & 0x0f;
+        unsigned year  = (*date >> 9) & 0x7f;
+
+        /* simplification: ignore leap years */
+        if (++day > daysinmonth[month-1])
         {
-            unsigned short day = *date & 0x001F;
-            unsigned short month = (*date >> 5) & 0x000F;
-            unsigned short year = (*date >> 9) & 0x007F;
-            if (next_day)
+            day = 1;
+            if (++month > 12)
             {
-                /* do a very simple day increment - never go above 28 days */
-                if (++day > 28)
-                {
-                    day = 1;
-                    if (++month > 12)
-                    {
-                        month = 1;
-                        year++;
-                    }
-                }
-                *date = (year << 9) | (month << 5) | day;
+                month = 1;
+                year++;
             }
         }
+        *date = (year << 9) | (month << 5) | day;
     }
-    if (tenth)
-        *tenth = 0;
+
 #endif /* CONFIG_RTC */
 }
 
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