added code for mp3 and jpeg parsing

added interface for data sources

data/formats/DataSourcePosixFile.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <stdlib.h>
+#include <string>
+#include <stdexcept>
+
+/** file on the desktop (posix) filesystem */
+class DataSourcePosixFile {
+
+	FILE* f = nullptr;
+
+public:
+
+	DataSourcePosixFile() {
+
+	}
+
+	DataSourcePosixFile(const char* file) {
+		f = fopen(file, "rw");
+		if (!f) {
+			throw std::runtime_error(std::string("failed to open file: ") + file);
+		}
+	}
+
+	~DataSourcePosixFile() {
+		if (f) {fclose(f);}
+	}
+
+	uint32_t curPos() const {
+		return ftell(f);
+	}
+
+	void seekTo(uint32_t pos) {
+		fseek(f, pos, SEEK_SET);
+	}
+
+	uint32_t read(uint32_t bytes, uint8_t* dst) {
+		return fread(dst, bytes, 1, f) * bytes;
+	}
+
+	uint32_t write(uint32_t bytes, const uint8_t* src) {
+		return fwrite(src, bytes, 1, f) * bytes;
+	}
+	
+	/** read an entity */
+	template <typename T> void readType(T& dst) {
+		read(sizeof(T), (uint8_t*) &dst);
+	}
+
+};