1 // Copyright (c) 2011 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 8 #include <limits.h> // So we can set the bounds of our types 9 #include <stddef.h> // For size_t 10 #include <string.h> // for memcpy 11 12 #include "base/port.h" // Types that only need exist on certain systems 13 14 #ifndef COMPILER_MSVC 15 // stdint.h is part of C99 but MSVC doesn't have it. 16 #include <stdint.h> // For intptr_t. 17 #endif 18 19 typedef signed char schar; 20 typedef signed char int8; 21 typedef short int16; 22 typedef int int32; 23 24 // The NSPR system headers define 64-bit as |long| when possible, except on 25 // Mac OS X. In order to not have typedef mismatches, we do the same on LP64. 26 // 27 // On Mac OS X, |long long| is used for 64-bit types for compatibility with 28 // <inttypes.h> format macros even in the LP64 model. 29 #if defined(__LP64__) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) 30 typedef long int64; 31 #else 32 typedef long long int64; 33 #endif 34 35 // NOTE: It is DANGEROUS to compare signed with unsigned types in loop 36 // conditions and other conditional expressions, and it is DANGEROUS to 37 // compute object/allocation sizes, indices, and offsets with signed types. 38 // Integer overflow behavior for signed types is UNDEFINED in the C/C++ 39 // standards, but is defined for unsigned types. 40 // 41 // Use the unsigned types if your variable represents a bit pattern (e.g. a 42 // hash value), object or allocation size, object count, offset, 43 // array/vector index, etc. 44 // 45 // Do NOT use 'unsigned' to express "this value should always be positive"; 46 // use assertions for this. 47 // 48 // See the Chromium style guide for more information. 49 // https://sites.google.com/a/chromium.org/dev/developers/coding-style 50 51 typedef unsigned char uint8; 52 typedef unsigned short uint16; 53 typedef unsigned int uint32; 54 55 // See the comment above about NSPR and 64-bit. 56 #if defined(__LP64__) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) 57 typedef unsigned long uint64; 58 #else 59 typedef unsigned long long uint64; 60 #endif 61 62 // A type to represent a Unicode code-point value. As of Unicode 4.0, 63 // such values require up to 21 bits. 64 // (For type-checking on pointers, make this explicitly signed, 65 // and it should always be the signed version of whatever int32 is.) 66 typedef signed int char32; 67 68 const uint8 kuint8max = (( uint8) 0xFF); 69 const uint16 kuint16max = ((uint16) 0xFFFF); 70 const uint32 kuint32max = ((uint32) 0xFFFFFFFF); 71 const uint64 kuint64max = ((uint64) GG_LONGLONG(0xFFFFFFFFFFFFFFFF)); 72 const int8 kint8min = (( int8) 0x80); 73 const int8 kint8max = (( int8) 0x7F); 74 const int16 kint16min = (( int16) 0x8000); 75 const int16 kint16max = (( int16) 0x7FFF); 76 const int32 kint32min = (( int32) 0x80000000); 77 const int32 kint32max = (( int32) 0x7FFFFFFF); 78 const int64 kint64min = (( int64) GG_LONGLONG(0x8000000000000000)); 79 const int64 kint64max = (( int64) GG_LONGLONG(0x7FFFFFFFFFFFFFFF)); 80 81 // Put this in the private: declarations for a class to be uncopyable. 82 #define DISALLOW_COPY(TypeName) \ 83 TypeName(const TypeName&) 84 85 // Put this in the private: declarations for a class to be unassignable. 86 #define DISALLOW_ASSIGN(TypeName) \ 87 void operator=(const TypeName&) 88 89 // A macro to disallow the copy constructor and operator= functions 90 // This should be used in the private: declarations for a class 91 #define DISALLOW_COPY_AND_ASSIGN(TypeName) \ 92 TypeName(const TypeName&); \ 93 void operator=(const TypeName&) 94 95 // An older, deprecated, politically incorrect name for the above. 96 // NOTE: The usage of this macro was banned from our code base, but some 97 // third_party libraries are yet using it. 98 // TODO(tfarina): Figure out how to fix the usage of this macro in the 99 // third_party libraries and get rid of it. 100 #define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName) 101 102 // A macro to disallow all the implicit constructors, namely the 103 // default constructor, copy constructor and operator= functions. 104 // 105 // This should be used in the private: declarations for a class 106 // that wants to prevent anyone from instantiating it. This is 107 // especially useful for classes containing only static methods. 108 #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ 109 TypeName(); \ 110 DISALLOW_COPY_AND_ASSIGN(TypeName) 111 112 // The arraysize(arr) macro returns the # of elements in an array arr. 113 // The expression is a compile-time constant, and therefore can be 114 // used in defining new arrays, for example. If you use arraysize on 115 // a pointer by mistake, you will get a compile-time error. 116 // 117 // One caveat is that arraysize() doesn't accept any array of an 118 // anonymous type or a type defined inside a function. In these rare 119 // cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below. This is 120 // due to a limitation in C++'s template system. The limitation might 121 // eventually be removed, but it hasn't happened yet. 122 123 // This template function declaration is used in defining arraysize. 124 // Note that the function doesn't need an implementation, as we only 125 // use its type. 126 template <typename T, size_t N> 127 char (&ArraySizeHelper(T (&array)[N]))[N]; 128 129 // That gcc wants both of these prototypes seems mysterious. VC, for 130 // its part, can't decide which to use (another mystery). Matching of 131 // template overloads: the final frontier. 132 #ifndef _MSC_VER 133 template <typename T, size_t N> 134 char (&ArraySizeHelper(const T (&array)[N]))[N]; 135 #endif 136 137 #define arraysize(array) (sizeof(ArraySizeHelper(array))) 138 139 // ARRAYSIZE_UNSAFE performs essentially the same calculation as arraysize, 140 // but can be used on anonymous types or types defined inside 141 // functions. It's less safe than arraysize as it accepts some 142 // (although not all) pointers. Therefore, you should use arraysize 143 // whenever possible. 144 // 145 // The expression ARRAYSIZE_UNSAFE(a) is a compile-time constant of type 146 // size_t. 147 // 148 // ARRAYSIZE_UNSAFE catches a few type errors. If you see a compiler error 149 // 150 // "warning: division by zero in ..." 151 // 152 // when using ARRAYSIZE_UNSAFE, you are (wrongfully) giving it a pointer. 153 // You should only use ARRAYSIZE_UNSAFE on statically allocated arrays. 154 // 155 // The following comments are on the implementation details, and can 156 // be ignored by the users. 157 // 158 // ARRAYSIZE_UNSAFE(arr) works by inspecting sizeof(arr) (the # of bytes in 159 // the array) and sizeof(*(arr)) (the # of bytes in one array 160 // element). If the former is divisible by the latter, perhaps arr is 161 // indeed an array, in which case the division result is the # of 162 // elements in the array. Otherwise, arr cannot possibly be an array, 163 // and we generate a compiler error to prevent the code from 164 // compiling. 165 // 166 // Since the size of bool is implementation-defined, we need to cast 167 // !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final 168 // result has type size_t. 169 // 170 // This macro is not perfect as it wrongfully accepts certain 171 // pointers, namely where the pointer size is divisible by the pointee 172 // size. Since all our code has to go through a 32-bit compiler, 173 // where a pointer is 4 bytes, this means all pointers to a type whose 174 // size is 3 or greater than 4 will be (righteously) rejected. 175 176 #define ARRAYSIZE_UNSAFE(a) \ 177 ((sizeof(a) / sizeof(*(a))) / \ 178 static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) 179 180 181 // Use implicit_cast as a safe version of static_cast or const_cast 182 // for upcasting in the type hierarchy (i.e. casting a pointer to Foo 183 // to a pointer to SuperclassOfFoo or casting a pointer to Foo to 184 // a const pointer to Foo). 185 // When you use implicit_cast, the compiler checks that the cast is safe. 186 // Such explicit implicit_casts are necessary in surprisingly many 187 // situations where C++ demands an exact type match instead of an 188 // argument type convertible to a target type. 189 // 190 // The From type can be inferred, so the preferred syntax for using 191 // implicit_cast is the same as for static_cast etc.: 192 // 193 // implicit_cast<ToType>(expr) 194 // 195 // implicit_cast would have been part of the C++ standard library, 196 // but the proposal was submitted too late. It will probably make 197 // its way into the language in the future. 198 template<typename To, typename From> 199 inline To implicit_cast(From const &f) { 200 return f; 201 } 202 203 // The COMPILE_ASSERT macro can be used to verify that a compile time 204 // expression is true. For example, you could use it to verify the 205 // size of a static array: 206 // 207 // COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES, 208 // content_type_names_incorrect_size); 209 // 210 // or to make sure a struct is smaller than a certain size: 211 // 212 // COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); 213 // 214 // The second argument to the macro is the name of the variable. If 215 // the expression is false, most compilers will issue a warning/error 216 // containing the name of the variable. 217 218 template <bool> 219 struct CompileAssert { 220 }; 221 222 #undef COMPILE_ASSERT 223 #define COMPILE_ASSERT(expr, msg) \ 224 typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] 225 226 // Implementation details of COMPILE_ASSERT: 227 // 228 // - COMPILE_ASSERT works by defining an array type that has -1 229 // elements (and thus is invalid) when the expression is false. 230 // 231 // - The simpler definition 232 // 233 // #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] 234 // 235 // does not work, as gcc supports variable-length arrays whose sizes 236 // are determined at run-time (this is gcc's extension and not part 237 // of the C++ standard). As a result, gcc fails to reject the 238 // following code with the simple definition: 239 // 240 // int foo; 241 // COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is 242 // // not a compile-time constant. 243 // 244 // - By using the type CompileAssert<(bool(expr))>, we ensures that 245 // expr is a compile-time constant. (Template arguments must be 246 // determined at compile-time.) 247 // 248 // - The outer parentheses in CompileAssert<(bool(expr))> are necessary 249 // to work around a bug in gcc 3.4.4 and 4.0.1. If we had written 250 // 251 // CompileAssert<bool(expr)> 252 // 253 // instead, these compilers will refuse to compile 254 // 255 // COMPILE_ASSERT(5 > 0, some_message); 256 // 257 // (They seem to think the ">" in "5 > 0" marks the end of the 258 // template argument list.) 259 // 260 // - The array size is (bool(expr) ? 1 : -1), instead of simply 261 // 262 // ((expr) ? 1 : -1). 263 // 264 // This is to avoid running into a bug in MS VC 7.1, which 265 // causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. 266 267 268 // bit_cast<Dest,Source> is a template function that implements the 269 // equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in 270 // very low-level functions like the protobuf library and fast math 271 // support. 272 // 273 // float f = 3.14159265358979; 274 // int i = bit_cast<int32>(f); 275 // // i = 0x40490fdb 276 // 277 // The classical address-casting method is: 278 // 279 // // WRONG 280 // float f = 3.14159265358979; // WRONG 281 // int i = * reinterpret_cast<int*>(&f); // WRONG 282 // 283 // The address-casting method actually produces undefined behavior 284 // according to ISO C++ specification section 3.10 -15 -. Roughly, this 285 // section says: if an object in memory has one type, and a program 286 // accesses it with a different type, then the result is undefined 287 // behavior for most values of "different type". 288 // 289 // This is true for any cast syntax, either *(int*)&f or 290 // *reinterpret_cast<int*>(&f). And it is particularly true for 291 // conversions between integral lvalues and floating-point lvalues. 292 // 293 // The purpose of 3.10 -15- is to allow optimizing compilers to assume 294 // that expressions with different types refer to different memory. gcc 295 // 4.0.1 has an optimizer that takes advantage of this. So a 296 // non-conforming program quietly produces wildly incorrect output. 297 // 298 // The problem is not the use of reinterpret_cast. The problem is type 299 // punning: holding an object in memory of one type and reading its bits 300 // back using a different type. 301 // 302 // The C++ standard is more subtle and complex than this, but that 303 // is the basic idea. 304 // 305 // Anyways ... 306 // 307 // bit_cast<> calls memcpy() which is blessed by the standard, 308 // especially by the example in section 3.9 . Also, of course, 309 // bit_cast<> wraps up the nasty logic in one place. 310 // 311 // Fortunately memcpy() is very fast. In optimized mode, with a 312 // constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline 313 // code with the minimal amount of data movement. On a 32-bit system, 314 // memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8) 315 // compiles to two loads and two stores. 316 // 317 // I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1. 318 // 319 // WARNING: if Dest or Source is a non-POD type, the result of the memcpy 320 // is likely to surprise you. 321 322 template <class Dest, class Source> 323 inline Dest bit_cast(const Source& source) { 324 // Compile time assertion: sizeof(Dest) == sizeof(Source) 325 // A compile error here means your Dest and Source have different sizes. 326 typedef char VerifySizesAreEqual [sizeof(Dest) == sizeof(Source) ? 1 : -1]; 327 328 Dest dest; 329 memcpy(&dest, &source, sizeof(dest)); 330 return dest; 331 } 332 333 // Used to explicitly mark the return value of a function as unused. If you are 334 // really sure you don't want to do anything with the return value of a function 335 // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: 336 // 337 // scoped_ptr<MyType> my_var = ...; 338 // if (TakeOwnership(my_var.get()) == SUCCESS) 339 // ignore_result(my_var.release()); 340 // 341 template<typename T> 342 inline void ignore_result(const T&) { 343 } 344 345 // The following enum should be used only as a constructor argument to indicate 346 // that the variable has static storage class, and that the constructor should 347 // do nothing to its state. It indicates to the reader that it is legal to 348 // declare a static instance of the class, provided the constructor is given 349 // the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a 350 // static variable that has a constructor or a destructor because invocation 351 // order is undefined. However, IF the type can be initialized by filling with 352 // zeroes (which the loader does for static variables), AND the destructor also 353 // does nothing to the storage, AND there are no virtual methods, then a 354 // constructor declared as 355 // explicit MyClass(base::LinkerInitialized x) {} 356 // and invoked as 357 // static MyClass my_variable_name(base::LINKER_INITIALIZED); 358 namespace base { 359 enum LinkerInitialized { LINKER_INITIALIZED }; 360 361 // Use these to declare and define a static local variable (static T;) so that 362 // it is leaked so that its destructors are not called at exit. If you need 363 // thread-safe initialization, use base/lazy_instance.h instead. 364 #define CR_DEFINE_STATIC_LOCAL(type, name, arguments) \ 365 static type& name = *new type arguments 366 367 } // base 368 369 #endif // BASE_BASICTYPES_H_ 370