File base class for Teensy 2.0

teensy/FS.h

+/* Teensyduino Core Library - File base class
+ * http://www.pjrc.com/teensy/
+ * Copyright (c) 2020 PJRC.COM, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * 1. The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * 2. If the Software is incorporated into a build system that allows
+ * selection among a list of target devices, then similar target
+ * devices manufactured by PJRC.COM must be included in the list of
+ * target devices and selectable in the same manner.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef FS_H
+#define FS_H
+#ifdef __cplusplus
+
+#include <Arduino.h>
+
+#define FILE_READ  0
+#define FILE_WRITE 1
+
+enum SeekMode {
+	SeekSet = 0,
+	SeekCur = 1,
+	SeekEnd = 2
+};
+
+//#define FILE_WHOAMI
+
+class File : public Stream {
+public:
+	File() : f(nullptr) { }
+	File(File *file) {
+		// "file" must only be a class derived from File
+		// can we use is_same or is_polymorphic with static_assert?
+		// or is_base_of
+		//static_assert(std::is_same<decltype(*file),File>::value,
+			//"File(File *file) constructor only accepts pointers "
+			//"to derived classes, not File itself");
+		f = file;
+		if (f) f->refcount++;
+	}
+	File(const File &file) {
+		//Serial.println("File copy constructor");
+		//static int copycount=0;
+		//if (++copycount > 20) while (1) ;
+		f = file.f;
+		if (f) f->refcount++;
+	}
+	File& operator = (const File &file) {
+		//Serial.println("File assignment");
+		//static int assigncount=0;
+		//if (++assigncount > 20) while (1) ;
+		invalidate();
+		f = file.f;
+		if (f) f->refcount++;
+		return *this;
+	}
+	virtual ~File() {
+		invalidate();
+	}
+#ifdef FILE_WHOAMI
+	virtual void whoami() { // testing only
+		Serial.printf("  File    this=%x, f=%x\n", (int)this, (int)f);
+		if (f) f->whoami();
+	}
+	unsigned int getRefcount() { // testing only
+		return refcount;
+	}
+#endif
+	virtual size_t read(void *buf, size_t nbyte) {
+		return (f) ? f->read(buf, nbyte) : 0;
+	}
+	virtual size_t write(const void *buf, size_t size) {
+		return (f) ? f->write(buf, size) : 0;
+	}
+	virtual int available() {
+		return (f) ? f->available() : 0;
+	}
+	virtual int peek() {
+		return (f) ? f->peek() : -1;
+	}
+	virtual void flush() {
+		if (f) f->flush();
+	}
+	virtual bool seek(uint32_t pos, int mode) {
+		return (f) ? f->seek(pos, mode) : false;
+	}
+	virtual uint32_t position() {
+		return (f) ? f->position() : 0;
+	}
+	virtual uint32_t size() {
+		return (f) ? f->size() : 0;
+	}
+	virtual void close() {
+		if (f) f->close();
+	}
+	virtual operator bool() {
+		return (f) ? (bool)*f : false;
+	}
+	virtual const char* name() {
+		return (f) ? f->name() : "";
+	}
+	virtual bool isDirectory() {
+		return (f) ? f->isDirectory() : false;
+	}
+	virtual File openNextFile(uint8_t mode=0) {
+		return (f) ? f->openNextFile(mode) : *this;
+	}
+	virtual void rewindDirectory(void) {
+		if (f) f->rewindDirectory();
+	}
+	bool seek(uint32_t pos) {
+		return seek(pos, SeekSet);
+	}
+	int read() {
+		if (!f) return -1;
+		unsigned char b;
+		if (f->read(&b, 1) < 1) return -1;
+		return b;
+	}
+	size_t write(uint8_t b) {
+		return write(&b, 1);
+	}
+	size_t write(const char *str) {
+		return write(str, strlen(str));
+	}
+	size_t readBytes(char *buffer, size_t length) {
+		return read(buffer, length);
+	}
+private:
+	void invalidate() {
+		if (f && --(f->refcount) == 0) delete f;
+	}
+	union {
+		// instances of base File class use this pointer
+		File *f;
+		// instances of derived classes (which actually access media)
+		// use this reference count which is managed by the base class
+		unsigned int refcount;
+	};
+};
+
+
+class FS
+{
+public:
+	FS() {}
+	File open(const char *filename, uint8_t mode = FILE_READ);
+	bool exists(const char *filepath);
+	bool mkdir(const char *filepath);
+	bool remove(const char *filepath);
+	bool rmdir(const char *filepath);
+};
+
+
+#endif // __cplusplus
+#endif // FS_H