// Copyright 2001 - 2003 Google Inc. All Rights Reserved

#ifndef BASE_BASICTYPES_H__
#define BASE_BASICTYPES_H__

typedef unsigned short uint16;

// The arraysize(arr) macro returns the # of elements in an array arr.
// The expression is a compile-time constant, and therefore can be
// used in defining new arrays, for example.  If you use arraysize on
// a pointer by mistake, you will get a compile-time error.
//
// One caveat is that arraysize() doesn't accept any array of an
// anonymous type or a type defined inside a function.  In these rare
// cases, you have to use the unsafe ARRAYSIZE() macro below.  This is
// due to a limitation in C++'s template system.  The limitation might
// eventually be removed, but it hasn't happened yet.

// This template function declaration is used in defining arraysize.
// Note that the function doesn't need an implementation, as we only
// use its type.
template <typename T, size_t N>
char (&ArraySizeHelper(T (&array)[N]))[N];

// That gcc wants both of these prototypes seems mysterious. VC, for
// its part, can't decide which to use (another mystery). Matching of
// template overloads: the final frontier.
#ifndef _MSC_VER
template <typename T, size_t N>
char (&ArraySizeHelper(const T (&array)[N]))[N];
#endif

#define arraysize(array) (sizeof(ArraySizeHelper(array)))

// ARRAYSIZE performs essentially the same calculation as arraysize,
// but can be used on anonymous types or types defined inside
// functions.  It's less safe than arraysize as it accepts some
// (although not all) pointers.  Therefore, you should use arraysize
// whenever possible.
//
// The expression ARRAYSIZE(a) is a compile-time constant of type
// size_t.
//
// ARRAYSIZE catches a few type errors.  If you see a compiler error
//
//   "warning: division by zero in ..."
//
// when using ARRAYSIZE, you are (wrongfully) giving it a pointer.
// You should only use ARRAYSIZE on statically allocated arrays.
//
// The following comments are on the implementation details, and can
// be ignored by the users.
//
// ARRAYSIZE(arr) works by inspecting sizeof(arr) (the # of bytes in
// the array) and sizeof(*(arr)) (the # of bytes in one array
// element).  If the former is divisible by the latter, perhaps arr is
// indeed an array, in which case the division result is the # of
// elements in the array.  Otherwise, arr cannot possibly be an array,
// and we generate a compiler error to prevent the code from
// compiling.
//
// Since the size of bool is implementation-defined, we need to cast
// !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final
// result has type size_t.
//
// This macro is not perfect as it wrongfully accepts certain
// pointers, namely where the pointer size is divisible by the pointee
// size.  Since all our code has to go through a 32-bit compiler,
// where a pointer is 4 bytes, this means all pointers to a type whose
// size is 3 or greater than 4 will be (righteously) rejected.
//
// Starting with Visual C++ 2005, WinNT.h includes ARRAYSIZE.
#define ARRAYSIZE_UNSAFE(a) \
  ((sizeof(a) / sizeof(*(a))) / \
   static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))
#endif

#endif  // BASE_BASICTYPES_H__