Hook up custom timestamp proc for SD/SDFS

The SDFS implementation didn't include plumbing to support user-supplied
timestamp generators (for file create/write times) because the SDFat
library doesn't support a callback parameter.

Work around it by using a single, global (inside sdfs namespace) that
the static timestamp callback member can see and use.

Add a test of the feature in CI.

Fixes esp8266#7682

Author: earlephilhower

libraries/SDFS/src/SDFS.cpp

@@ -37,6 +37,8 @@ FS SDFS = FS(FSImplPtr(new sdfs::SDFSImpl()));
 
 namespace sdfs {
 
+// Required to be global because SDFAT doesn't allow a this pointer in it's own time call
+time_t (*__sdfs_timeCallback)(void) = nullptr;
 
 FileImplPtr SDFSImpl::open(const char* path, OpenMode openMode, AccessMode accessMode)
 {

libraries/SDFS/src/SDFS.h

@@ -205,12 +205,21 @@ class SDFSImpl : public FSImpl
         return mktime(&tiempo);
     }
 
+    virtual void setTimeCallback(time_t (*cb)(void)) override {
+        extern time_t (*__sdfs_timeCallback)(void);
+        __sdfs_timeCallback = cb;
+    }
+
     // Because SdFat has a single, global setting for this we can only use a
-    // static member of our class to return the time/date.  However, since
-    // this is static, we can't see the time callback variable.  Punt for now,
-    // using time(NULL) as the best we can do.
+    // static member of our class to return the time/date.
     static void dateTimeCB(uint16_t *dosYear, uint16_t *dosTime) {
-        time_t now = time(nullptr);
+        time_t now;
+	extern time_t (*__sdfs_timeCallback)(void);
+        if (__sdfs_timeCallback) {
+            now = __sdfs_timeCallback();
+        } else {
+            now = time(nullptr);
+        }
         struct tm *tiempo = localtime(&now);
         *dosYear = ((tiempo->tm_year - 80) << 9) | ((tiempo->tm_mon + 1) << 5) | tiempo->tm_mday;
         *dosTime = (tiempo->tm_hour << 11) | (tiempo->tm_min << 5) | tiempo->tm_sec;

tests/host/fs/test_fs.cpp

@@ -162,4 +162,34 @@ TEST_CASE("SD.h FILE_WRITE macro is append", "[fs]")
     REQUIRE(u == 0);
 }
 
+// SDFS timestamp setter (#7682)
+static time_t _my_time(void)
+{
+    struct tm t;
+    t.tm_year = 120;
+    t.tm_mon  = 9;
+    t.tm_mday = 22;
+    t.tm_hour = 12;
+    t.tm_min  = 13;
+    t.tm_sec  = 14;
+    return mktime(&t);
+}
+
+TEST_CASE("SDFS timeCallback")
+{
+    SDFS_MOCK_DECLARE(64, 8, 512, "");
+    REQUIRE(SDFS.begin());
+    REQUIRE(SD.begin(4));
+
+    SDFS.setTimeCallback(_my_time);
+    File f = SD.open("/file.txt", "w");
+    f.write("Had we but world enough, and time,");
+    f.close();
+    time_t expected = _my_time();
+    f = SD.open("/file.txt", "r");
+    REQUIRE(abs(f.getCreationTime() - expected) < 60);  // FAT has less precision in timestamp than time_t
+    REQUIRE(abs(f.getLastWrite() - expected) < 60);  // FAT has less precision in timestamp than time_t
+    f.close();
+}
+
 };