added code for mp3 and jpeg parsing

added interface for data sources

data/formats/DataSourceMemory.h

@@ -0,0 +1,38 @@
+#pragma once
+
+/** data source wrapping the memory */
+template <typename File> class DataSourceMemory {
+	
+	const uint8_t* src;
+	const uint32_t len;
+	uint32_t pos;
+	
+public:
+
+	/** ctor with the memory region */
+	DataSourceMemory(const uint8_t* src, const uint32_t len) : src(src), len(len) {
+		
+	}
+	
+	/** get the current position */
+	uint32_t curPos() const {
+		return pos;
+	}
+
+	/** seek to the given position */
+	void seekTo(uint32_t newPos) {
+		pos = newPos;
+	}
+
+	/** read an entity */
+	template <typename T> void readType(T& dst) {
+		read(sizeof(T), &dst);
+	}
+
+	/** read x bytes from the input into dst */
+	template <typename T> void read(uint32_t size, T* dst) {
+		memcpy(dst, &src[pos], size);
+		pos += size;
+	}
+	
+};