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 */