Basic Definitions

#typedefs

#Fixed-length integer type

co/def.h defines the following 8 types of integers:

typedef int8_t   int8;
typedef int16_t  int16;
typedef int32_t  int32;
typedef int64_t  int64;
typedef uint8_t  uint8;
typedef uint16_t uint16;
typedef uint32_t uint32;
typedef uint64_t uint64;

These types have the same length on different platforms, and there is no portability problem. Google Code Style recommends not to use built-in integer types such as short, long, long long, etc.

#macros

#Maximum and minimum values of integer types

MAX_UINT8  MAX_UINT16  MAX_UINT32  MAX_UINT64
MAX_INT8   MAX_INT16   MAX_INT32   MAX_INT64
MIN_INT8   MIN_INT16   MIN_INT32   MIN_INT64

These macros respectively defines the maximum and minimum values of the 8 integer types.

#DISALLOW_COPY_AND_ASSIGN

This macro is used to disable copy constructor and assignment operations in C++ classes.

Example

class T {
  public:
    T();
    DISALLOW_COPY_AND_ASSIGN(T);
};

#arch64, arch32

__arch64 is defined as 1 on 64 bit platforms, __arch32 is defined as 1 on 32 bit platforms.

Example

#if __arch64
inline size_t murmur_hash(const void* s, size_t n) {
    return murmur_hash64(s, n, 0);
}
#else
inline size_t murmur_hash(const void* s, size_t n) {
    return murmur_hash32(s, n, 0);
}
#endif

#__forceinline

__forceinline is a keyword in VS. Linux and mac platforms use the following macro simulation:

#define __forceinline __attribute__((always_inline))

#__thread

__thread is a keyword in gcc/clang to support TLS, the windows platform uses the following macro simulation:

#define __thread __declspec(thread)

Example

// get id of the current thread
__forceinline unsigned int gettid() {
    static __thread unsigned int id = 0;
    if (id != 0) return id;
    return id = __gettid();
}

#unlikely

This macro is used for branch prediction optimization. It only supports gcc/clang.

Example

// It is logically equivalent to if (v == 0)
if (unlikey(v == 0)) {
    cout << "v == 0" << endl;
}