Unify time modification on SD and SPIFFS (#738)

* Add access to last write date time

add example

* rename cpp to ino orz

* wrong copy -past

* No comment orz

* Add missing space

libraries/FS/src/FS.cpp

@@ -32,6 +32,15 @@ size_t File::write(uint8_t c)
     return _p->write(&c, 1);
 }
 
+time_t File::getLastWrite()
+{
+    if (!_p) {
+        return 0;
+    }
+
+    return _p->getLastWrite();
+}
+
 size_t File::write(const uint8_t *buf, size_t size)
 {
     if (!_p) {

libraries/FS/src/FS.h

@@ -70,6 +70,7 @@ public:
     size_t size() const;
     void close();
     operator bool() const;
+    time_t getLastWrite();
     const char* name() const;
 
     boolean isDirectory(void);

libraries/FS/src/FSImpl.h

@@ -37,6 +37,7 @@ public:
     virtual size_t position() const = 0;
     virtual size_t size() const = 0;
     virtual void close() = 0;
+    virtual time_t getLastWrite() = 0;
     virtual const char* name() const = 0;
     virtual boolean isDirectory(void) = 0;
     virtual FileImplPtr openNextFile(const char* mode) = 0;

libraries/FS/src/vfs_api.cpp

@@ -295,6 +295,11 @@ VFSFileImpl::operator bool()
     return (_isDirectory && _d != NULL) || _f != NULL;
 }
 
+time_t VFSFileImpl::getLastWrite() {
+    _getStat() ;
+    return _stat.st_mtime;
+}
+
 void VFSFileImpl::_getStat() const
 {
     if(!_path) {

libraries/FS/src/vfs_api.h

@@ -67,6 +67,7 @@ public:
     size_t      size() const override;
     void        close() override;
     const char* name() const override;
+    time_t getLastWrite()  override;
     boolean     isDirectory(void) override;
     FileImplPtr openNextFile(const char* mode) override;
     void        rewindDirectory(void) override;