add addressing context structure with read functions for CPU memory access

src/addressing.h

@@ -0,0 +1,18 @@
+#ifndef ADDRESSING_H
+#define ADDRESSING_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+typedef struct
+{
+    uint8_t (*read8)(uint16_t addr, void *userdata);
+    void (*read16)(uint16_t addr, void *userdata);
+
+    void *userdata;
+
+    // cpu registers
+
+} addr_ctx_t;
+
+#endif