/js/public/TemplateLib.h
http://github.com/zpao/v8monkey · C Header · 179 lines · 84 code · 20 blank · 75 comment · 0 complexity · 108172a2c47e21ab2cd0fc7b38bccc80 MD5 · raw file
- /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
- * vim: set ts=8 sw=4 et tw=99 ft=cpp:
- *
- * ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is Mozilla SpiderMonkey JavaScript code.
- *
- * The Initial Developer of the Original Code is
- * the Mozilla Foundation.
- * Portions created by the Initial Developer are Copyright (C) 2011
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- * Luke Wagner <luke@mozilla.com>
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- #ifndef js_template_lib_h__
- #define js_template_lib_h__
- #include "jstypes.h"
- /*
- * Library of reusable template meta-functions (that is, functions on types and
- * compile-time values). Meta-functions are placed inside the 'tl' namespace to
- * avoid conflict with non-meta functions that logically have the same name
- * (e.g., js::tl::Min vs. js::Min).
- */
- namespace js {
- namespace tl {
- /* Compute min/max/clamp. */
- template <size_t i, size_t j> struct Min {
- static const size_t result = i < j ? i : j;
- };
- template <size_t i, size_t j> struct Max {
- static const size_t result = i > j ? i : j;
- };
- template <size_t i, size_t min, size_t max> struct Clamp {
- static const size_t result = i < min ? min : (i > max ? max : i);
- };
- /* Compute x^y. */
- template <size_t x, size_t y> struct Pow {
- static const size_t result = x * Pow<x, y - 1>::result;
- };
- template <size_t x> struct Pow<x,0> {
- static const size_t result = 1;
- };
- /* Compute floor(log2(i)). */
- template <size_t i> struct FloorLog2 {
- static const size_t result = 1 + FloorLog2<i / 2>::result;
- };
- template <> struct FloorLog2<0> { /* Error */ };
- template <> struct FloorLog2<1> { static const size_t result = 0; };
- /* Compute ceiling(log2(i)). */
- template <size_t i> struct CeilingLog2 {
- static const size_t result = FloorLog2<2 * i - 1>::result;
- };
- /* Round up to the nearest power of 2. */
- template <size_t i> struct RoundUpPow2 {
- static const size_t result = size_t(1) << CeilingLog2<i>::result;
- };
- template <> struct RoundUpPow2<0> {
- static const size_t result = 1;
- };
- /* Compute the number of bits in the given unsigned type. */
- template <class T> struct BitSize {
- static const size_t result = sizeof(T) * JS_BITS_PER_BYTE;
- };
- /* Allow Assertions by only including the 'result' typedef if 'true'. */
- template <bool> struct StaticAssert {};
- template <> struct StaticAssert<true> { typedef int result; };
- /* Boolean test for whether two types are the same. */
- template <class T, class U> struct IsSameType {
- static const bool result = false;
- };
- template <class T> struct IsSameType<T,T> {
- static const bool result = true;
- };
- /*
- * Produce an N-bit mask, where N <= BitSize<size_t>::result. Handle the
- * language-undefined edge case when N = BitSize<size_t>::result.
- */
- template <size_t N> struct NBitMask {
- typedef typename StaticAssert<N < BitSize<size_t>::result>::result _;
- static const size_t result = (size_t(1) << N) - 1;
- };
- template <> struct NBitMask<BitSize<size_t>::result> {
- static const size_t result = size_t(-1);
- };
- /*
- * For the unsigned integral type size_t, compute a mask M for N such that
- * for all X, !(X & M) implies X * N will not overflow (w.r.t size_t)
- */
- template <size_t N> struct MulOverflowMask {
- static const size_t result =
- ~NBitMask<BitSize<size_t>::result - CeilingLog2<N>::result>::result;
- };
- template <> struct MulOverflowMask<0> { /* Error */ };
- template <> struct MulOverflowMask<1> { static const size_t result = 0; };
- /*
- * Generate a mask for T such that if (X & sUnsafeRangeSizeMask), an X-sized
- * array of T's is big enough to cause a ptrdiff_t overflow when subtracting
- * a pointer to the end of the array from the beginning.
- */
- template <class T> struct UnsafeRangeSizeMask {
- /*
- * The '2' factor means the top bit is clear, sizeof(T) converts from
- * units of elements to bytes.
- */
- static const size_t result = MulOverflowMask<2 * sizeof(T)>::result;
- };
- /* Return T stripped of any const-ness. */
- template <class T> struct StripConst { typedef T result; };
- template <class T> struct StripConst<const T> { typedef T result; };
- /*
- * Traits class for identifying POD types. Until C++0x, there is no automatic
- * way to detect PODs, so for the moment it is done manually.
- */
- template <class T> struct IsPodType { static const bool result = false; };
- template <> struct IsPodType<char> { static const bool result = true; };
- template <> struct IsPodType<signed char> { static const bool result = true; };
- template <> struct IsPodType<unsigned char> { static const bool result = true; };
- template <> struct IsPodType<short> { static const bool result = true; };
- template <> struct IsPodType<unsigned short> { static const bool result = true; };
- template <> struct IsPodType<int> { static const bool result = true; };
- template <> struct IsPodType<unsigned int> { static const bool result = true; };
- template <> struct IsPodType<long> { static const bool result = true; };
- template <> struct IsPodType<unsigned long> { static const bool result = true; };
- template <> struct IsPodType<long long> { static const bool result = true; };
- template <> struct IsPodType<unsigned long long> { static const bool result = true; };
- template <> struct IsPodType<float> { static const bool result = true; };
- template <> struct IsPodType<double> { static const bool result = true; };
- template <> struct IsPodType<wchar_t> { static const bool result = true; };
- template <typename T> struct IsPodType<T *> { static const bool result = true; };
- template <bool cond, typename T, T v1, T v2> struct If { static const T result = v1; };
- template <typename T, T v1, T v2> struct If<false, T, v1, v2> { static const T result = v2; };
- } /* namespace tl */
- } /* namespace js */
- #endif /* js_template_lib_h__ */