1// Copyright (c) 2010 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef BASE_BASICTYPES_H_ 6#define BASE_BASICTYPES_H_ 7#pragma once 8 9#include <limits.h> // So we can set the bounds of our types 10#include <stddef.h> // For size_t 11#include <string.h> // for memcpy 12 13#include "base/port.h" // Types that only need exist on certain systems 14 15#ifndef COMPILER_MSVC 16// stdint.h is part of C99 but MSVC doesn't have it. 17#include <stdint.h> // For intptr_t. 18#endif 19 20typedef signed char schar; 21typedef signed char int8; 22typedef short int16; 23// TODO: Remove these type guards. These are to avoid conflicts with 24// obsolete/protypes.h in the Gecko SDK. 25#ifndef _INT32 26#define _INT32 27typedef int int32; 28#endif 29 30// The NSPR system headers define 64-bit as |long| when possible, except on 31// Mac OS X. In order to not have typedef mismatches, we do the same on LP64. 32// 33// On Mac OS X, |long long| is used for 64-bit types for compatibility with 34// <inttypes.h> format macros even in the LP64 model. 35#if defined(__LP64__) && !defined(OS_MACOSX) 36typedef long int64; 37#else 38typedef long long int64; 39#endif 40 41// NOTE: unsigned types are DANGEROUS in loops and other arithmetical 42// places. Use the signed types unless your variable represents a bit 43// pattern (eg a hash value) or you really need the extra bit. Do NOT 44// use 'unsigned' to express "this value should always be positive"; 45// use assertions for this. 46 47typedef unsigned char uint8; 48typedef unsigned short uint16; 49// TODO: Remove these type guards. These are to avoid conflicts with 50// obsolete/protypes.h in the Gecko SDK. 51#ifndef _UINT32 52#define _UINT32 53typedef unsigned int uint32; 54#endif 55 56// See the comment above about NSPR and 64-bit. 57#if defined(__LP64__) && !defined(OS_MACOSX) 58typedef unsigned long uint64; 59#else 60typedef unsigned long long uint64; 61#endif 62 63// A type to represent a Unicode code-point value. As of Unicode 4.0, 64// such values require up to 21 bits. 65// (For type-checking on pointers, make this explicitly signed, 66// and it should always be the signed version of whatever int32 is.) 67typedef signed int char32; 68 69const uint8 kuint8max = (( uint8) 0xFF); 70const uint16 kuint16max = ((uint16) 0xFFFF); 71const uint32 kuint32max = ((uint32) 0xFFFFFFFF); 72const uint64 kuint64max = ((uint64) GG_LONGLONG(0xFFFFFFFFFFFFFFFF)); 73const int8 kint8min = (( int8) 0x80); 74const int8 kint8max = (( int8) 0x7F); 75const int16 kint16min = (( int16) 0x8000); 76const int16 kint16max = (( int16) 0x7FFF); 77const int32 kint32min = (( int32) 0x80000000); 78const int32 kint32max = (( int32) 0x7FFFFFFF); 79const int64 kint64min = (( int64) GG_LONGLONG(0x8000000000000000)); 80const int64 kint64max = (( int64) GG_LONGLONG(0x7FFFFFFFFFFFFFFF)); 81 82// A macro to disallow the copy constructor and operator= functions 83// This should be used in the private: declarations for a class 84#define DISALLOW_COPY_AND_ASSIGN(TypeName) \ 85 TypeName(const TypeName&); \ 86 void operator=(const TypeName&) 87 88// An older, deprecated, politically incorrect name for the above. 89// NOTE: The usage of this macro was baned from our code base, but some 90// third_party libraries are yet using it. 91// TODO(tfarina): Figure out how to fix the usage of this macro in the 92// third_party libraries and get rid of it. 93#define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName) 94 95// A macro to disallow all the implicit constructors, namely the 96// default constructor, copy constructor and operator= functions. 97// 98// This should be used in the private: declarations for a class 99// that wants to prevent anyone from instantiating it. This is 100// especially useful for classes containing only static methods. 101#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ 102 TypeName(); \ 103 DISALLOW_COPY_AND_ASSIGN(TypeName) 104 105// The arraysize(arr) macro returns the # of elements in an array arr. 106// The expression is a compile-time constant, and therefore can be 107// used in defining new arrays, for example. If you use arraysize on 108// a pointer by mistake, you will get a compile-time error. 109// 110// One caveat is that arraysize() doesn't accept any array of an 111// anonymous type or a type defined inside a function. In these rare 112// cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below. This is 113// due to a limitation in C++'s template system. The limitation might 114// eventually be removed, but it hasn't happened yet. 115 116// This template function declaration is used in defining arraysize. 117// Note that the function doesn't need an implementation, as we only 118// use its type. 119template <typename T, size_t N> 120char (&ArraySizeHelper(T (&array)[N]))[N]; 121 122// That gcc wants both of these prototypes seems mysterious. VC, for 123// its part, can't decide which to use (another mystery). Matching of 124// template overloads: the final frontier. 125#ifndef _MSC_VER 126template <typename T, size_t N> 127char (&ArraySizeHelper(const T (&array)[N]))[N]; 128#endif 129 130#define arraysize(array) (sizeof(ArraySizeHelper(array))) 131 132// ARRAYSIZE_UNSAFE performs essentially the same calculation as arraysize, 133// but can be used on anonymous types or types defined inside 134// functions. It's less safe than arraysize as it accepts some 135// (although not all) pointers. Therefore, you should use arraysize 136// whenever possible. 137// 138// The expression ARRAYSIZE_UNSAFE(a) is a compile-time constant of type 139// size_t. 140// 141// ARRAYSIZE_UNSAFE catches a few type errors. If you see a compiler error 142// 143// "warning: division by zero in ..." 144// 145// when using ARRAYSIZE_UNSAFE, you are (wrongfully) giving it a pointer. 146// You should only use ARRAYSIZE_UNSAFE on statically allocated arrays. 147// 148// The following comments are on the implementation details, and can 149// be ignored by the users. 150// 151// ARRAYSIZE_UNSAFE(arr) works by inspecting sizeof(arr) (the # of bytes in 152// the array) and sizeof(*(arr)) (the # of bytes in one array 153// element). If the former is divisible by the latter, perhaps arr is 154// indeed an array, in which case the division result is the # of 155// elements in the array. Otherwise, arr cannot possibly be an array, 156// and we generate a compiler error to prevent the code from 157// compiling. 158// 159// Since the size of bool is implementation-defined, we need to cast 160// !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final 161// result has type size_t. 162// 163// This macro is not perfect as it wrongfully accepts certain 164// pointers, namely where the pointer size is divisible by the pointee 165// size. Since all our code has to go through a 32-bit compiler, 166// where a pointer is 4 bytes, this means all pointers to a type whose 167// size is 3 or greater than 4 will be (righteously) rejected. 168 169#define ARRAYSIZE_UNSAFE(a) \ 170 ((sizeof(a) / sizeof(*(a))) / \ 171 static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) 172 173 174// Use implicit_cast as a safe version of static_cast or const_cast 175// for upcasting in the type hierarchy (i.e. casting a pointer to Foo 176// to a pointer to SuperclassOfFoo or casting a pointer to Foo to 177// a const pointer to Foo). 178// When you use implicit_cast, the compiler checks that the cast is safe. 179// Such explicit implicit_casts are necessary in surprisingly many 180// situations where C++ demands an exact type match instead of an 181// argument type convertable to a target type. 182// 183// The From type can be inferred, so the preferred syntax for using 184// implicit_cast is the same as for static_cast etc.: 185// 186// implicit_cast<ToType>(expr) 187// 188// implicit_cast would have been part of the C++ standard library, 189// but the proposal was submitted too late. It will probably make 190// its way into the language in the future. 191template<typename To, typename From> 192inline To implicit_cast(From const &f) { 193 return f; 194} 195 196// The COMPILE_ASSERT macro can be used to verify that a compile time 197// expression is true. For example, you could use it to verify the 198// size of a static array: 199// 200// COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES, 201// content_type_names_incorrect_size); 202// 203// or to make sure a struct is smaller than a certain size: 204// 205// COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); 206// 207// The second argument to the macro is the name of the variable. If 208// the expression is false, most compilers will issue a warning/error 209// containing the name of the variable. 210 211template <bool> 212struct CompileAssert { 213}; 214 215#undef COMPILE_ASSERT 216#define COMPILE_ASSERT(expr, msg) \ 217 typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] 218 219// Implementation details of COMPILE_ASSERT: 220// 221// - COMPILE_ASSERT works by defining an array type that has -1 222// elements (and thus is invalid) when the expression is false. 223// 224// - The simpler definition 225// 226// #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] 227// 228// does not work, as gcc supports variable-length arrays whose sizes 229// are determined at run-time (this is gcc's extension and not part 230// of the C++ standard). As a result, gcc fails to reject the 231// following code with the simple definition: 232// 233// int foo; 234// COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is 235// // not a compile-time constant. 236// 237// - By using the type CompileAssert<(bool(expr))>, we ensures that 238// expr is a compile-time constant. (Template arguments must be 239// determined at compile-time.) 240// 241// - The outter parentheses in CompileAssert<(bool(expr))> are necessary 242// to work around a bug in gcc 3.4.4 and 4.0.1. If we had written 243// 244// CompileAssert<bool(expr)> 245// 246// instead, these compilers will refuse to compile 247// 248// COMPILE_ASSERT(5 > 0, some_message); 249// 250// (They seem to think the ">" in "5 > 0" marks the end of the 251// template argument list.) 252// 253// - The array size is (bool(expr) ? 1 : -1), instead of simply 254// 255// ((expr) ? 1 : -1). 256// 257// This is to avoid running into a bug in MS VC 7.1, which 258// causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. 259 260 261// MetatagId refers to metatag-id that we assign to 262// each metatag <name, value> pair.. 263typedef uint32 MetatagId; 264 265// Argument type used in interfaces that can optionally take ownership 266// of a passed in argument. If TAKE_OWNERSHIP is passed, the called 267// object takes ownership of the argument. Otherwise it does not. 268enum Ownership { 269 DO_NOT_TAKE_OWNERSHIP, 270 TAKE_OWNERSHIP 271}; 272 273// bit_cast<Dest,Source> is a template function that implements the 274// equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in 275// very low-level functions like the protobuf library and fast math 276// support. 277// 278// float f = 3.14159265358979; 279// int i = bit_cast<int32>(f); 280// // i = 0x40490fdb 281// 282// The classical address-casting method is: 283// 284// // WRONG 285// float f = 3.14159265358979; // WRONG 286// int i = * reinterpret_cast<int*>(&f); // WRONG 287// 288// The address-casting method actually produces undefined behavior 289// according to ISO C++ specification section 3.10 -15 -. Roughly, this 290// section says: if an object in memory has one type, and a program 291// accesses it with a different type, then the result is undefined 292// behavior for most values of "different type". 293// 294// This is true for any cast syntax, either *(int*)&f or 295// *reinterpret_cast<int*>(&f). And it is particularly true for 296// conversions betweeen integral lvalues and floating-point lvalues. 297// 298// The purpose of 3.10 -15- is to allow optimizing compilers to assume 299// that expressions with different types refer to different memory. gcc 300// 4.0.1 has an optimizer that takes advantage of this. So a 301// non-conforming program quietly produces wildly incorrect output. 302// 303// The problem is not the use of reinterpret_cast. The problem is type 304// punning: holding an object in memory of one type and reading its bits 305// back using a different type. 306// 307// The C++ standard is more subtle and complex than this, but that 308// is the basic idea. 309// 310// Anyways ... 311// 312// bit_cast<> calls memcpy() which is blessed by the standard, 313// especially by the example in section 3.9 . Also, of course, 314// bit_cast<> wraps up the nasty logic in one place. 315// 316// Fortunately memcpy() is very fast. In optimized mode, with a 317// constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline 318// code with the minimal amount of data movement. On a 32-bit system, 319// memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8) 320// compiles to two loads and two stores. 321// 322// I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1. 323// 324// WARNING: if Dest or Source is a non-POD type, the result of the memcpy 325// is likely to surprise you. 326 327template <class Dest, class Source> 328inline Dest bit_cast(const Source& source) { 329 // Compile time assertion: sizeof(Dest) == sizeof(Source) 330 // A compile error here means your Dest and Source have different sizes. 331 typedef char VerifySizesAreEqual [sizeof(Dest) == sizeof(Source) ? 1 : -1]; 332 333 Dest dest; 334 memcpy(&dest, &source, sizeof(dest)); 335 return dest; 336} 337 338// Used to explicitly mark the return value of a function as unused. If you are 339// really sure you don't want to do anything with the return value of a function 340// that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: 341// 342// scoped_ptr<MyType> my_var = ...; 343// if (TakeOwnership(my_var.get()) == SUCCESS) 344// ignore_result(my_var.release()); 345// 346template<typename T> 347inline void ignore_result(const T& ignored) { 348} 349 350// The following enum should be used only as a constructor argument to indicate 351// that the variable has static storage class, and that the constructor should 352// do nothing to its state. It indicates to the reader that it is legal to 353// declare a static instance of the class, provided the constructor is given 354// the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a 355// static variable that has a constructor or a destructor because invocation 356// order is undefined. However, IF the type can be initialized by filling with 357// zeroes (which the loader does for static variables), AND the destructor also 358// does nothing to the storage, AND there are no virtual methods, then a 359// constructor declared as 360// explicit MyClass(base::LinkerInitialized x) {} 361// and invoked as 362// static MyClass my_variable_name(base::LINKER_INITIALIZED); 363namespace base { 364enum LinkerInitialized { LINKER_INITIALIZED }; 365} // base 366 367#endif // BASE_BASICTYPES_H_ 368