AK: Add load64 and load_pointer to AK::ByteReader

This lets us load misaligned 64 bit integers, and misaligned pointers
in a platform agnostic way.

AK/ByteReader.h

@@ -49,6 +49,27 @@ struct ByteReader {
  value = v._32;
  }
 
+ static void load(const u8* address, u64& value)
+ {
+ union {
+ u64 _64;
+ u8 _8[8];
+ } v { ._64 = 0 };
+ __builtin_memcpy(&v._8, address, 8);
+ value = v._64;
+ }
+
+ template<typename T>
+ static T* load_pointer(const u8* address)
+ {
+ if constexpr (sizeof(T*) == 4) {
+ return reinterpret_cast<T*>(load32(address));
+ } else {
+ static_assert(sizeof(T*) == 8, "sizeof(T*) must be either 4 or 8");
+ return reinterpret_cast<T*>(load64(address));
+ }
+ }
+
  static u16 load16(const u8* address)
  {
  u16 value;
@@ -62,6 +83,13 @@ struct ByteReader {
  load(address, value);
  return value;
  }
+
+ static u64 load64(const u8* address)
+ {
+ u64 value;
+ load(address, value);
+ return value;
+ }
 };
 
 }