| // Copyright (c) 2010 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_BASICTYPES_H_ |
| #define BASE_BASICTYPES_H_ |
| #pragma once |
| |
| #include <limits.h> // So we can set the bounds of our types |
| #include <stddef.h> // For size_t |
| #include <string.h> // for memcpy |
| |
| #include "base/port.h" // Types that only need exist on certain systems |
| |
| #ifndef COMPILER_MSVC |
| // stdint.h is part of C99 but MSVC doesn't have it. |
| #include <stdint.h> // For intptr_t. |
| #endif |
| |
| typedef signed char schar; |
| typedef signed char int8; |
| typedef short int16; |
| // TODO: Remove these type guards. These are to avoid conflicts with |
| // obsolete/protypes.h in the Gecko SDK. |
| #ifndef _INT32 |
| #define _INT32 |
| typedef int int32; |
| #endif |
| |
| // The NSPR system headers define 64-bit as |long| when possible. In order to |
| // not have typedef mismatches, we do the same on LP64. |
| #if __LP64__ |
| typedef long int64; |
| #else |
| typedef long long int64; |
| #endif |
| |
| // NOTE: unsigned types are DANGEROUS in loops and other arithmetical |
| // places. Use the signed types unless your variable represents a bit |
| // pattern (eg a hash value) or you really need the extra bit. Do NOT |
| // use 'unsigned' to express "this value should always be positive"; |
| // use assertions for this. |
| |
| typedef unsigned char uint8; |
| typedef unsigned short uint16; |
| // TODO: Remove these type guards. These are to avoid conflicts with |
| // obsolete/protypes.h in the Gecko SDK. |
| #ifndef _UINT32 |
| #define _UINT32 |
| typedef unsigned int uint32; |
| #endif |
| |
| // See the comment above about NSPR and 64-bit. |
| #if __LP64__ |
| typedef unsigned long uint64; |
| #else |
| typedef unsigned long long uint64; |
| #endif |
| |
| // A type to represent a Unicode code-point value. As of Unicode 4.0, |
| // such values require up to 21 bits. |
| // (For type-checking on pointers, make this explicitly signed, |
| // and it should always be the signed version of whatever int32 is.) |
| typedef signed int char32; |
| |
| const uint8 kuint8max = (( uint8) 0xFF); |
| const uint16 kuint16max = ((uint16) 0xFFFF); |
| const uint32 kuint32max = ((uint32) 0xFFFFFFFF); |
| const uint64 kuint64max = ((uint64) GG_LONGLONG(0xFFFFFFFFFFFFFFFF)); |
| const int8 kint8min = (( int8) 0x80); |
| const int8 kint8max = (( int8) 0x7F); |
| const int16 kint16min = (( int16) 0x8000); |
| const int16 kint16max = (( int16) 0x7FFF); |
| const int32 kint32min = (( int32) 0x80000000); |
| const int32 kint32max = (( int32) 0x7FFFFFFF); |
| const int64 kint64min = (( int64) GG_LONGLONG(0x8000000000000000)); |
| const int64 kint64max = (( int64) GG_LONGLONG(0x7FFFFFFFFFFFFFFF)); |
| |
| // A macro to disallow the copy constructor and operator= functions |
| // This should be used in the private: declarations for a class |
| #define DISALLOW_COPY_AND_ASSIGN(TypeName) \ |
| TypeName(const TypeName&); \ |
| void operator=(const TypeName&) |
| |
| // An older, deprecated, politically incorrect name for the above. |
| // NOTE: The usage of this macro was baned from our code base, but some |
| // third_party libraries are yet using it. |
| // TODO(tfarina): Figure out how to fix the usage of this macro in the |
| // third_party libraries and get rid of it. |
| #define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName) |
| |
| // A macro to disallow all the implicit constructors, namely the |
| // default constructor, copy constructor and operator= functions. |
| // |
| // This should be used in the private: declarations for a class |
| // that wants to prevent anyone from instantiating it. This is |
| // especially useful for classes containing only static methods. |
| #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ |
| TypeName(); \ |
| DISALLOW_COPY_AND_ASSIGN(TypeName) |
| |
| // 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_UNSAFE() 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_UNSAFE 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_UNSAFE(a) is a compile-time constant of type |
| // size_t. |
| // |
| // ARRAYSIZE_UNSAFE catches a few type errors. If you see a compiler error |
| // |
| // "warning: division by zero in ..." |
| // |
| // when using ARRAYSIZE_UNSAFE, you are (wrongfully) giving it a pointer. |
| // You should only use ARRAYSIZE_UNSAFE on statically allocated arrays. |
| // |
| // The following comments are on the implementation details, and can |
| // be ignored by the users. |
| // |
| // ARRAYSIZE_UNSAFE(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. |
| |
| #define ARRAYSIZE_UNSAFE(a) \ |
| ((sizeof(a) / sizeof(*(a))) / \ |
| static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) |
| |
| |
| // Use implicit_cast as a safe version of static_cast or const_cast |
| // for upcasting in the type hierarchy (i.e. casting a pointer to Foo |
| // to a pointer to SuperclassOfFoo or casting a pointer to Foo to |
| // a const pointer to Foo). |
| // When you use implicit_cast, the compiler checks that the cast is safe. |
| // Such explicit implicit_casts are necessary in surprisingly many |
| // situations where C++ demands an exact type match instead of an |
| // argument type convertable to a target type. |
| // |
| // The From type can be inferred, so the preferred syntax for using |
| // implicit_cast is the same as for static_cast etc.: |
| // |
| // implicit_cast<ToType>(expr) |
| // |
| // implicit_cast would have been part of the C++ standard library, |
| // but the proposal was submitted too late. It will probably make |
| // its way into the language in the future. |
| template<typename To, typename From> |
| inline To implicit_cast(From const &f) { |
| return f; |
| } |
| |
| // The COMPILE_ASSERT macro can be used to verify that a compile time |
| // expression is true. For example, you could use it to verify the |
| // size of a static array: |
| // |
| // COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES, |
| // content_type_names_incorrect_size); |
| // |
| // or to make sure a struct is smaller than a certain size: |
| // |
| // COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); |
| // |
| // The second argument to the macro is the name of the variable. If |
| // the expression is false, most compilers will issue a warning/error |
| // containing the name of the variable. |
| |
| template <bool> |
| struct CompileAssert { |
| }; |
| |
| #undef COMPILE_ASSERT |
| #define COMPILE_ASSERT(expr, msg) \ |
| typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] |
| |
| // Implementation details of COMPILE_ASSERT: |
| // |
| // - COMPILE_ASSERT works by defining an array type that has -1 |
| // elements (and thus is invalid) when the expression is false. |
| // |
| // - The simpler definition |
| // |
| // #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] |
| // |
| // does not work, as gcc supports variable-length arrays whose sizes |
| // are determined at run-time (this is gcc's extension and not part |
| // of the C++ standard). As a result, gcc fails to reject the |
| // following code with the simple definition: |
| // |
| // int foo; |
| // COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is |
| // // not a compile-time constant. |
| // |
| // - By using the type CompileAssert<(bool(expr))>, we ensures that |
| // expr is a compile-time constant. (Template arguments must be |
| // determined at compile-time.) |
| // |
| // - The outter parentheses in CompileAssert<(bool(expr))> are necessary |
| // to work around a bug in gcc 3.4.4 and 4.0.1. If we had written |
| // |
| // CompileAssert<bool(expr)> |
| // |
| // instead, these compilers will refuse to compile |
| // |
| // COMPILE_ASSERT(5 > 0, some_message); |
| // |
| // (They seem to think the ">" in "5 > 0" marks the end of the |
| // template argument list.) |
| // |
| // - The array size is (bool(expr) ? 1 : -1), instead of simply |
| // |
| // ((expr) ? 1 : -1). |
| // |
| // This is to avoid running into a bug in MS VC 7.1, which |
| // causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. |
| |
| |
| // MetatagId refers to metatag-id that we assign to |
| // each metatag <name, value> pair.. |
| typedef uint32 MetatagId; |
| |
| // Argument type used in interfaces that can optionally take ownership |
| // of a passed in argument. If TAKE_OWNERSHIP is passed, the called |
| // object takes ownership of the argument. Otherwise it does not. |
| enum Ownership { |
| DO_NOT_TAKE_OWNERSHIP, |
| TAKE_OWNERSHIP |
| }; |
| |
| // bit_cast<Dest,Source> is a template function that implements the |
| // equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in |
| // very low-level functions like the protobuf library and fast math |
| // support. |
| // |
| // float f = 3.14159265358979; |
| // int i = bit_cast<int32>(f); |
| // // i = 0x40490fdb |
| // |
| // The classical address-casting method is: |
| // |
| // // WRONG |
| // float f = 3.14159265358979; // WRONG |
| // int i = * reinterpret_cast<int*>(&f); // WRONG |
| // |
| // The address-casting method actually produces undefined behavior |
| // according to ISO C++ specification section 3.10 -15 -. Roughly, this |
| // section says: if an object in memory has one type, and a program |
| // accesses it with a different type, then the result is undefined |
| // behavior for most values of "different type". |
| // |
| // This is true for any cast syntax, either *(int*)&f or |
| // *reinterpret_cast<int*>(&f). And it is particularly true for |
| // conversions betweeen integral lvalues and floating-point lvalues. |
| // |
| // The purpose of 3.10 -15- is to allow optimizing compilers to assume |
| // that expressions with different types refer to different memory. gcc |
| // 4.0.1 has an optimizer that takes advantage of this. So a |
| // non-conforming program quietly produces wildly incorrect output. |
| // |
| // The problem is not the use of reinterpret_cast. The problem is type |
| // punning: holding an object in memory of one type and reading its bits |
| // back using a different type. |
| // |
| // The C++ standard is more subtle and complex than this, but that |
| // is the basic idea. |
| // |
| // Anyways ... |
| // |
| // bit_cast<> calls memcpy() which is blessed by the standard, |
| // especially by the example in section 3.9 . Also, of course, |
| // bit_cast<> wraps up the nasty logic in one place. |
| // |
| // Fortunately memcpy() is very fast. In optimized mode, with a |
| // constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline |
| // code with the minimal amount of data movement. On a 32-bit system, |
| // memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8) |
| // compiles to two loads and two stores. |
| // |
| // I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1. |
| // |
| // WARNING: if Dest or Source is a non-POD type, the result of the memcpy |
| // is likely to surprise you. |
| |
| template <class Dest, class Source> |
| inline Dest bit_cast(const Source& source) { |
| // Compile time assertion: sizeof(Dest) == sizeof(Source) |
| // A compile error here means your Dest and Source have different sizes. |
| typedef char VerifySizesAreEqual [sizeof(Dest) == sizeof(Source) ? 1 : -1]; |
| |
| Dest dest; |
| memcpy(&dest, &source, sizeof(dest)); |
| return dest; |
| } |
| |
| // Used to explicitly mark the return value of a function as unused. If you are |
| // really sure you don't want to do anything with the return value of a function |
| // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: |
| // |
| // scoped_ptr<MyType> my_var = ...; |
| // if (TakeOwnership(my_var.get()) == SUCCESS) |
| // ignore_result(my_var.release()); |
| // |
| template<typename T> |
| inline void ignore_result(const T& ignored) { |
| } |
| |
| // The following enum should be used only as a constructor argument to indicate |
| // that the variable has static storage class, and that the constructor should |
| // do nothing to its state. It indicates to the reader that it is legal to |
| // declare a static instance of the class, provided the constructor is given |
| // the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a |
| // static variable that has a constructor or a destructor because invocation |
| // order is undefined. However, IF the type can be initialized by filling with |
| // zeroes (which the loader does for static variables), AND the destructor also |
| // does nothing to the storage, AND there are no virtual methods, then a |
| // constructor declared as |
| // explicit MyClass(base::LinkerInitialized x) {} |
| // and invoked as |
| // static MyClass my_variable_name(base::LINKER_INITIALIZED); |
| namespace base { |
| enum LinkerInitialized { LINKER_INITIALIZED }; |
| } // base |
| |
| #endif // BASE_BASICTYPES_H_ |