huge work on FAT32, initial support for writing

ext/sd/tests/Helper.h

@@ -6,7 +6,23 @@
 
 struct TestDevice {
 
-	uint8_t buf[4096];
+	size_t size;
+	uint8_t* buf;
+
+	TestDevice(size_t size) : size(size) {
+		buf = (uint8_t*) malloc(size);
+		memset(buf, 0, size);
+	}
+
+	~TestDevice() {
+		free(buf);
+	}
+
+	void toFile(const std::string& name) {
+		FILE* f = fopen(name.c_str(), "w+");
+		fwrite(buf, size, 1, f);
+		fclose(f);
+	}
 
 	/** read a 512 byte block into dst */
 	bool readSingleBlock(LBA512 addr, uint8_t* dst) {
@@ -14,7 +30,7 @@ struct TestDevice {
 		return true;
 	}
 
-	bool writeSingleBlock(LBA512 addr, uint8_t* src) {
+	bool writeSingleBlock(LBA512 addr, const uint8_t* src) {
 		memcpy(buf+addr*512, src, 512);
 		return true;
 	}