Add time to filesystem API

Support the ESP32 File::getLastWrite() call and setting the time on
all filesystems automatically (assuming the system clock has
been set properly and time(NULL) returns the proper time!).

Adds Dir::fileTime() to get the time of a file being listed, similar to
Dir::fileName() and Dir::fileSize().

Adds ::setTimeCallback(time_t (*cb)()) to File, Dir, and FS, allowing
users to override the default timestamp on a per-file, directory, or
filesystem basis. By default, a simple callback returning time(nullptr)
is implemented.

LittleFS uses the 't' attribute and should be backwards compatible.

SD/SDFS work and include wrappers for obsolete SdFat timestamp callbacks
using the MSDOS time.

This PR does not update SPIFFS, due to compatability concerns and a
possible massive rewrite which would make it possible to determine if an
old-style ot metadata enabled FS is present at mount time.

Includes an updated SD/listfiles and LittleFS_time example.

Replaces #6315

Author: earlephilhower

cores/esp8266/FS.cpp

@@ -180,6 +180,19 @@ String File::readString()
     return ret;
 }
 
+time_t File::getLastWrite() {
+    if (!_p)
+        return 0;
+
+    return _p->getLastWrite();
+}
+
+void File::setTimeCallback(time_t (*cb)(void)) {
+    if (!_p)
+        return;
+    _p->setTimeCallback(cb);
+}
+
 File Dir::openFile(const char* mode) {
     if (!_impl) {
         return File();
@@ -192,7 +205,9 @@ File Dir::openFile(const char* mode) {
         return File();
     }
 
-    return File(_impl->openFile(om, am), _baseFS);
+    auto f = File(_impl->openFile(om, am), _baseFS);
+    f.setTimeCallback(timeCallback);
+    return f;
 }
 
 String Dir::fileName() {
@@ -203,6 +218,12 @@ String Dir::fileName() {
     return _impl->fileName();
 }
 
+time_t Dir::fileTime() {
+    if (!_impl)
+        return 0;
+    return _impl->fileTime();
+}
+
 size_t Dir::fileSize() {
     if (!_impl) {
         return 0;
@@ -241,6 +262,20 @@ bool Dir::rewind() {
     return _impl->rewind();
 }
 
+time_t Dir::getLastWrite() {
+    if (!_impl)
+        return 0;
+
+    return _impl->getLastWrite();
+}
+
+void Dir::setTimeCallback(time_t (*cb)(void)) {
+    if (!_impl)
+        return;
+    _impl->setTimeCallback(cb);
+}
+
+
 bool FS::setConfig(const FSConfig &cfg) {
     if (!_impl) {
         return false;
@@ -315,7 +350,9 @@ File FS::open(const char* path, const char* mode) {
         DEBUGV("FS::open: invalid mode `%s`\r\n", mode);
         return File();
     }
-    return File(_impl->open(path, om, am), this);
+    auto f = File(_impl->open(path, om, am), this);
+    f.setTimeCallback(timeCallback);
+    return f;
 }
 
 bool FS::exists(const char* path) {
@@ -334,7 +371,9 @@ Dir FS::openDir(const char* path) {
         return Dir();
     }
     DirImplPtr p = _impl->openDir(path);
-    return Dir(p, this);
+    auto d = Dir(p, this);
+    d.setTimeCallback(timeCallback);
+    return d;
 }
 
 Dir FS::openDir(const String& path) {
@@ -385,6 +424,11 @@ bool FS::rename(const String& pathFrom, const String& pathTo) {
     return rename(pathFrom.c_str(), pathTo.c_str());
 }
 
+void FS::setTimeCallback(time_t (*cb)(void)) {
+    if (!_impl)
+        return;
+    _impl->setTimeCallback(cb);
+}
 
 
 static bool sflags(const char* mode, OpenMode& om, AccessMode& am) {

cores/esp8266/FS.h

@@ -110,12 +110,16 @@ class File : public Stream
 
     String readString() override;
 
+    time_t getLastWrite();
+    void setTimeCallback(time_t (*cb)(void));
+
 protected:
     FileImplPtr _p;
 
     // Arduino SD class emulation
     std::shared_ptr<Dir> _fakeDir;
     FS                  *_baseFS;
+    time_t (*timeCallback)(void) = nullptr;
 };
 
 class Dir {
@@ -126,15 +130,21 @@ class Dir {
 
     String fileName();
     size_t fileSize();
+    time_t fileTime();
     bool isFile() const;
     bool isDirectory() const;
 
     bool next();
     bool rewind();
 
+    time_t getLastWrite();
+    void setTimeCallback(time_t (*cb)(void));
+
 protected:
     DirImplPtr _impl;
     FS       *_baseFS;
+    time_t (*timeCallback)(void) = nullptr;
+
 };
 
 // Backwards compatible, <4GB filesystem usage
@@ -179,17 +189,26 @@ class FSConfig
 class SPIFFSConfig : public FSConfig
 {
 public:
-    SPIFFSConfig(bool autoFormat = true) {
+    SPIFFSConfig(bool autoFormat = true, bool enableTime = true) {
         _type = SPIFFSConfig::fsid::FSId;
 	_autoFormat = autoFormat;
+	_enableTime = enableTime;
     }
     enum fsid { FSId = 0x53504946 };
+
+    SPIFFSConfig setEnableTime(bool val = true) {
+        _enableTime = val;
+        return *this;
+    }
+
+    // Inherit _type and _autoFormat
+    bool _enableTime;
 };
 
 class FS
 {
 public:
-    FS(FSImplPtr impl) : _impl(impl) { }
+    FS(FSImplPtr impl) : _impl(impl) { timeCallback = _defaultTimeCB; }
 
     bool setConfig(const FSConfig &cfg);
 
@@ -225,10 +244,14 @@ class FS
     bool gc();
     bool check();
 
+    void setTimeCallback(time_t (*cb)(void));
+
     friend class ::SDClass; // More of a frenemy, but SD needs internal implementation to get private FAT bits
 protected:
     FSImplPtr _impl;
     FSImplPtr getImpl() { return _impl; }
+    time_t (*timeCallback)(void);
+    static time_t _defaultTimeCB(void) { return time(NULL); }
 };
 
 } // namespace fs

cores/esp8266/FSImpl.h

@@ -41,6 +41,19 @@ class FileImpl {
     virtual const char* fullName() const = 0;
     virtual bool isFile() const = 0;
     virtual bool isDirectory() const = 0;
+
+    // Filesystems *may* support a timestamp per-file, so allow the user to override with
+    // their own callback for *this specific* file (as opposed to the FSImpl call of the
+    // same name.  The default implementation simply returns time(&null)
+    virtual void setTimeCallback(time_t (*cb)(void)) { timeCallback = cb; }
+
+    // Return the last written time for a file.  Undefined when called on a writable file
+    // as the FS is allowed to return either the time of the last write() operation or the
+    // time present in the filesystem metadata (often the last time the file was closed)
+    virtual time_t getLastWrite() { return 0; } // Default is to not support timestamps
+
+protected:
+    time_t (*timeCallback)(void) = nullptr;
 };
 
 enum OpenMode {
@@ -62,10 +75,24 @@ class DirImpl {
     virtual FileImplPtr openFile(OpenMode openMode, AccessMode accessMode) = 0;
     virtual const char* fileName() = 0;
     virtual size_t fileSize() = 0;
+    virtual time_t fileTime() { return 0; } // By default, FS doesn't report file times
     virtual bool isFile() const = 0;
     virtual bool isDirectory() const = 0;
     virtual bool next() = 0;
     virtual bool rewind() = 0;
+
+    // Filesystems *may* support a timestamp per-file, so allow the user to override with
+    // their own callback for *this specific* file (as opposed to the FSImpl call of the
+    // same name.  The default implementation simply returns time(&null)
+    virtual void setTimeCallback(time_t (*cb)(void)) { timeCallback = cb; }
+
+    // Return the last written time for a file.  Undefined when called on a writable file
+    // as the FS is allowed to return either the time of the last write() operation or the
+    // time present in the filesystem metadata (often the last time the file was closed)
+    virtual time_t getLastWrite() { return 0; } // Default is to not support timestamps
+
+protected:
+    time_t (*timeCallback)(void) = nullptr;
 };
 
 class FSImpl {
@@ -86,6 +113,14 @@ class FSImpl {
     virtual bool rmdir(const char* path) = 0;
     virtual bool gc() { return true; } // May not be implemented in all file systems.
     virtual bool check() { return true; } // May not be implemented in all file systems.
+
+    // Filesystems *may* support a timestamp per-file, so allow the user to override with
+    // their own callback for all files on this FS.  The default implementation simply
+    // returns the present time as reported by time(&null)
+    virtual void setTimeCallback(time_t (*cb)(void)) { timeCallback = cb; }
+
+protected:
+    time_t (*timeCallback)(void) = nullptr;
 };
 
 } // namespace fs