有关stdint.h 文件
Google C++编程规范的P25页有如下叙述:
<stdint.h> 定义了 int16_t 、 uint32_t 、 int64_t 等整型,在需要确定大小的整型时可以使用它们代替 short 、 unsigned long long 等,在 C 整型中,只使用 int 。适当情况下,推 荐使用标准类型如 size_t 和 ptrdiff_t 。
最常使用的是,对整数来说,通常不会用到太大,如循环计数等,可以使用普通的 int 。 你可以认为 int 至少为 32 位,但不要认为它会多于 32 位,需要 64 位整型的话,可以使用int64_t 或 uint64_t 。对于大整数,使用 int64_t 。
不要使用 uint32_t 等无符号整型,除非你是在表示一个 位组( bit pattern ) 而不是一个 数值。即使数值不会为负值也不要使用无符号类型,使用断言来保护数据。
有些人,包括一些教科书作者,推荐使用无符号类型表示非负数,类型表明了数值取值形 式 。但是,在 C 语言中,这一优点被由其导致的 bugs 所淹没。看看:
for (unsigned int i = foo.Length()-1; i >= 0; --i)
上述代码永远不会终止!有时 gcc 会发现该 bug 并报警,但通常不会。类似的 bug 还会 出现在比较有符合变量和无符号变量时,主要是 C 的 类型提升机制( type-promotion
scheme , C 语言中各种内建类型之间的提升转换关系) 会致使无符号类型的行为出乎你 的意料。因此,使用断言声明变量为非负数,不要使用无符号型。
以下内容转载自http://apps.hi.baidu.com/share/detail/32935657
- 按照posix标准,一般整型对应的*_t类型为:
- 1字节 uint8_t
- 2字节 uint16_t
- 4字节 uint32_t
- 8字节 uint64_t
stdint.h文件如下:
- /* Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
- 02111-1307 USA. */
- /*
- * ISO C99: 7.18 Integer types <stdint.h>
- */
- #ifndef _STDINT_H
- #define _STDINT_H 1
- #include <features.h>
- #include <bits/wchar.h>
- #include <bits/wordsize.h>
- /* Exact integral types. */
- /* Signed. */
- /* There is some amount of overlap with <sys/types.h> as known by inet code */
- #ifndef __int8_t_defined
- # define __int8_t_defined
- typedef signed char int8_t;
- typedef short int int16_t;
- typedef int int32_t;
- # if __WORDSIZE == 64
- typedef long int int64_t;
- # else
- __extension__
- typedef long long int int64_t;
- # endif
- #endif
- /* Unsigned. */
- typedef unsigned char uint8_t;
- typedef unsigned short int uint16_t;
- #ifndef __uint32_t_defined
- typedef unsigned int uint32_t;
- # define __uint32_t_defined
- #endif
- #if __WORDSIZE == 64
- typedef unsigned long int uint64_t;
- #else
- __extension__
- typedef unsigned long long int uint64_t;
- #endif
- /* Small types. */
- /* Signed. */
- typedef signed char int_least8_t;
- typedef short int int_least16_t;
- typedef int int_least32_t;
- #if __WORDSIZE == 64
- typedef long int int_least64_t;
- #else
- __extension__
- typedef long long int int_least64_t;
- #endif
- /* Unsigned. */
- typedef unsigned char uint_least8_t;
- typedef unsigned short int uint_least16_t;
- typedef unsigned int uint_least32_t;
- #if __WORDSIZE == 64
- typedef unsigned long int uint_least64_t;
- #else
- __extension__
- typedef unsigned long long int uint_least64_t;
- #endif
- /* Fast types. */
- /* Signed. */
- typedef signed char int_fast8_t;
- #if __WORDSIZE == 64
- typedef long int int_fast16_t;
- typedef long int int_fast32_t;
- typedef long int int_fast64_t;
- #else
- typedef int int_fast16_t;
- typedef int int_fast32_t;
- __extension__
- typedef long long int int_fast64_t;
- #endif
- /* Unsigned. */
- typedef unsigned char uint_fast8_t;
- #if __WORDSIZE == 64
- typedef unsigned long int uint_fast16_t;
- typedef unsigned long int uint_fast32_t;
- typedef unsigned long int uint_fast64_t;
- #else
- typedef unsigned int uint_fast16_t;
- typedef unsigned int uint_fast32_t;
- __extension__
- typedef unsigned long long int uint_fast64_t;
- #endif
- /* Types for `void *' pointers. */
- #if __WORDSIZE == 64
- # ifndef __intptr_t_defined
- typedef long int intptr_t;
- # define __intptr_t_defined
- # endif
- typedef unsigned long int uintptr_t;
- #else
- # ifndef __intptr_t_defined
- typedef int intptr_t;
- # define __intptr_t_defined
- # endif
- typedef unsigned int uintptr_t;
- #endif
- /* Largest integral types. */
- #if __WORDSIZE == 64
- typedef long int intmax_t;
- typedef unsigned long int uintmax_t;
- #else
- __extension__
- typedef long long int intmax_t;
- __extension__
- typedef unsigned long long int uintmax_t;
- #endif
- /* The ISO C99 standard specifies that in C++ implementations these
- macros should only be defined if explicitly requested. */
- #if !defined __cplusplus || defined __STDC_LIMIT_MACROS
- # if __WORDSIZE == 64
- # define __INT64_C(c) c ## L
- # define __UINT64_C(c) c ## UL
- # else
- # define __INT64_C(c) c ## LL
- # define __UINT64_C(c) c ## ULL
- # endif
- /* Limits of integral types. */
- /* Minimum of signed integral types. */
- # define INT8_MIN (-128)
- # define INT16_MIN (-32767-1)
- # define INT32_MIN (-2147483647-1)
- # define INT64_MIN (-__INT64_C(9223372036854775807)-1)
- /* Maximum of signed integral types. */
- # define INT8_MAX (127)
- # define INT16_MAX (32767)
- # define INT32_MAX (2147483647)
- # define INT64_MAX (__INT64_C(9223372036854775807))
- /* Maximum of unsigned integral types. */
- # define UINT8_MAX (255)
- # define UINT16_MAX (65535)
- # define UINT32_MAX (4294967295U)
- # define UINT64_MAX (__UINT64_C(18446744073709551615))
- /* Minimum of signed integral types having a minimum size. */
- # define INT_LEAST8_MIN (-128)
- # define INT_LEAST16_MIN (-32767-1)
- # define INT_LEAST32_MIN (-2147483647-1)
- # define INT_LEAST64_MIN (-__INT64_C(9223372036854775807)-1)
- /* Maximum of signed integral types having a minimum size. */
- # define INT_LEAST8_MAX (127)
- # define INT_LEAST16_MAX (32767)
- # define INT_LEAST32_MAX (2147483647)
- # define INT_LEAST64_MAX (__INT64_C(9223372036854775807))
- /* Maximum of unsigned integral types having a minimum size. */
- # define UINT_LEAST8_MAX (255)
- # define UINT_LEAST16_MAX (65535)
- # define UINT_LEAST32_MAX (4294967295U)
- # define UINT_LEAST64_MAX (__UINT64_C(18446744073709551615))
- /* Minimum of fast signed integral types having a minimum size. */
- # define INT_FAST8_MIN (-128)
- # if __WORDSIZE == 64
- # define INT_FAST16_MIN (-9223372036854775807L-1)
- # define INT_FAST32_MIN (-9223372036854775807L-1)
- # else
- # define INT_FAST16_MIN (-2147483647-1)
- # define INT_FAST32_MIN (-2147483647-1)
- # endif
- # define INT_FAST64_MIN (-__INT64_C(9223372036854775807)-1)
- /* Maximum of fast signed integral types having a minimum size. */
- # define INT_FAST8_MAX (127)
- # if __WORDSIZE == 64
- # define INT_FAST16_MAX (9223372036854775807L)
- # define INT_FAST32_MAX (9223372036854775807L)
- # else
- # define INT_FAST16_MAX (2147483647)
- # define INT_FAST32_MAX (2147483647)
- # endif
- # define INT_FAST64_MAX (__INT64_C(9223372036854775807))
- /* Maximum of fast unsigned integral types having a minimum size. */
- # define UINT_FAST8_MAX (255)
- # if __WORDSIZE == 64
- # define UINT_FAST16_MAX (18446744073709551615UL)
- # define UINT_FAST32_MAX (18446744073709551615UL)
- # else
- # define UINT_FAST16_MAX (4294967295U)
- # define UINT_FAST32_MAX (4294967295U)
- # endif
- # define UINT_FAST64_MAX (__UINT64_C(18446744073709551615))
- /* Values to test for integral types holding `void *' pointer. */
- # if __WORDSIZE == 64
- # define INTPTR_MIN (-9223372036854775807L-1)
- # define INTPTR_MAX (9223372036854775807L)
- # define UINTPTR_MAX (18446744073709551615UL)
- # else
- # define INTPTR_MIN (-2147483647-1)
- # define INTPTR_MAX (2147483647)
- # define UINTPTR_MAX (4294967295U)
- # endif
- /* Minimum for largest signed integral type. */
- # define INTMAX_MIN (-__INT64_C(9223372036854775807)-1)
- /* Maximum for largest signed integral type. */
- # define INTMAX_MAX (__INT64_C(9223372036854775807))
- /* Maximum for largest unsigned integral type. */
- # define UINTMAX_MAX (__UINT64_C(18446744073709551615))
- /* Limits of other integer types. */
- /* Limits of `ptrdiff_t' type. */
- # if __WORDSIZE == 64
- # define PTRDIFF_MIN (-9223372036854775807L-1)
- # define PTRDIFF_MAX (9223372036854775807L)
- # else
- # define PTRDIFF_MIN (-2147483647-1)
- # define PTRDIFF_MAX (2147483647)
- # endif
- /* Limits of `sig_atomic_t'. */
- # define SIG_ATOMIC_MIN (-2147483647-1)
- # define SIG_ATOMIC_MAX (2147483647)
- /* Limit of `size_t' type. */
- # if __WORDSIZE == 64
- # define SIZE_MAX (18446744073709551615UL)
- # else
- # define SIZE_MAX (4294967295U)
- # endif
- /* Limits of `wchar_t'. */
- # ifndef WCHAR_MIN
- /* These constants might also be defined in <wchar.h>. */
- # define WCHAR_MIN __WCHAR_MIN
- # define WCHAR_MAX __WCHAR_MAX
- # endif
- /* Limits of `wint_t'. */
- # define WINT_MIN (0u)
- # define WINT_MAX (4294967295u)
- #endif /* C++ && limit macros */
- /* The ISO C99 standard specifies that in C++ implementations these
- should only be defined if explicitly requested. */
- #if !defined __cplusplus || defined __STDC_CONSTANT_MACROS
- /* Signed. */
- # define INT8_C(c) c
- # define INT16_C(c) c
- # define INT32_C(c) c
- # if __WORDSIZE == 64
- # define INT64_C(c) c ## L
- # else
- # define INT64_C(c) c ## LL
- # endif
- /* Unsigned. */
- # define UINT8_C(c) c ## U
- # define UINT16_C(c) c ## U
- # define UINT32_C(c) c ## U
- # if __WORDSIZE == 64
- # define UINT64_C(c) c ## UL
- # else
- # define UINT64_C(c) c ## ULL
- # endif
- /* Maximal type. */
- # if __WORDSIZE == 64
- # define INTMAX_C(c) c ## L
- # define UINTMAX_C(c) c ## UL
- # else
- # define INTMAX_C(c) c ## LL
- # define UINTMAX_C(c) c ## ULL
- # endif
- #endif /* C++ && constant macros */
- #endif /* stdint.h */