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int8_t、uint8_t、__INT 64等和size_t的阐述

作者：小丑西瓜9 | 2024-04-16 03:42:41

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int8_t

如题。

首先我们需要了解名为<stdint.h>的头文件

1.<stdint.h>头文件 和 int8_t等

①<stdint.h>是C99引进的标准C库文件，在之中有使用typedef定义了很多整型类型别名(如图为部分命名）。

②通过这些类型别名能直接看出类型的字节、有无符号，易于移植。因为在不同系统中，类型的字节是不一定相同的。而关于_t的含义，可能是指typedef。

——如此如图，你应该就能明白int8_t等是什么意思了，int8_t即等于char(char也是一种整型)，或者说有符号1字节整型

正点原子网课中的截图

                                       

2.__INT64

在上图中我们能看见有 typedef signed __INT64 int64_t的代码，其中__INT64是什么意思呢？

__INT64是一种老式的64位整型表示方式，在C99之后，long long是它的替代。它的占位符是%l64d(而long long是%lld)

3.size_t和ssize_t

这两个也是类型别名，可以在<types.h>头文件中找到定义。

size_t是无符号整型，在32位中等于unsigned int，在64位中等于unsigned long

ssize_t是有符号整型，在32位中等于int，在64位中等于long

4.附：<stdint.h>文件

  1. /* Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. The GNU C Library is free software; you can redistribute it and/or
  4. modify it under the terms of the GNU Lesser General Public
  5. License as published by the Free Software Foundation; either
  6. version 2.1 of the License, or (at your option) any later version.
  7. The GNU C Library is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10. Lesser General Public License for more details.
  11. You should have received a copy of the GNU Lesser General Public
  12. License along with the GNU C Library; if not, write to the Free
  13. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  14. 02111-1307 USA. */
  15.  
  16. /*
  17. * ISO C99: 7.18 Integer types <stdint.h>
  18. */
  19.  
  20. #ifndef _STDINT_H
  21. #define _STDINT_H   1
  22.  
  23. #include <features.h>
  24. #include <bits/wchar.h>
  25. #include <bits/wordsize.h>
  26.  
  27. /* Exact integral types. */
  28.  
  29. /* Signed. */
  30.  
  31. /* There is some amount of overlap with <sys/types.h> as known by inet code */
  32. #ifndef __int8_t_defined
  33. # define __int8_t_defined
  34. typedef signed char     int8_t;
  35. typedef short int       int16_t;
  36. typedef int         int32_t;
  37. # if __WORDSIZE == 64
  38. typedef long int        int64_t;
  39. # else
  40. __extension__
  41. typedef long long int       int64_t;
  42. # endif
  43. #endif
  44.  
  45. /* Unsigned. */
  46. typedef unsigned char       uint8_t;
  47. typedef unsigned short int uint16_t;
  48. #ifndef __uint32_t_defined
  49. typedef unsigned int        uint32_t;
  50. # define __uint32_t_defined
  51. #endif
  52. #if __WORDSIZE == 64
  53. typedef unsigned long int   uint64_t;
  54. #else
  55. __extension__
  56. typedef unsigned long long int uint64_t;
  57. #endif
  58.  
  59.  
  60. /* Small types. */
  61.  
  62. /* Signed. */
  63. typedef signed char     int_least8_t;
  64. typedef short int       int_least16_t;
  65. typedef int         int_least32_t;
  66. #if __WORDSIZE == 64
  67. typedef long int        int_least64_t;
  68. #else
  69. __extension__
  70. typedef long long int       int_least64_t;
  71. #endif
  72.  
  73. /* Unsigned. */
  74. typedef unsigned char       uint_least8_t;
  75. typedef unsigned short int uint_least16_t;
  76. typedef unsigned int        uint_least32_t;
  77. #if __WORDSIZE == 64
  78. typedef unsigned long int   uint_least64_t;
  79. #else
  80. __extension__
  81. typedef unsigned long long int uint_least64_t;
  82. #endif
  83.  
  84.  
  85. /* Fast types. */
  86.  
  87. /* Signed. */
  88. typedef signed char     int_fast8_t;
  89. #if __WORDSIZE == 64
  90. typedef long int        int_fast16_t;
  91. typedef long int        int_fast32_t;
  92. typedef long int        int_fast64_t;
  93. #else
  94. typedef int         int_fast16_t;
  95. typedef int         int_fast32_t;
  96. __extension__
  97. typedef long long int       int_fast64_t;
  98. #endif
  99.  
  100. /* Unsigned. */
  101. typedef unsigned char       uint_fast8_t;
  102. #if __WORDSIZE == 64
  103. typedef unsigned long int   uint_fast16_t;
  104. typedef unsigned long int   uint_fast32_t;
  105. typedef unsigned long int   uint_fast64_t;
  106. #else
  107. typedef unsigned int        uint_fast16_t;
  108. typedef unsigned int        uint_fast32_t;
  109. __extension__
  110. typedef unsigned long long int uint_fast64_t;
  111. #endif
  112.  
  113.  
  114. /* Types for `void *' pointers. */
  115. #if __WORDSIZE == 64
  116. # ifndef __intptr_t_defined
  117. typedef long int        intptr_t;
  118. # define __intptr_t_defined
  119. # endif
  120. typedef unsigned long int   uintptr_t;
  121. #else
  122. # ifndef __intptr_t_defined
  123. typedef int         intptr_t;
  124. # define __intptr_t_defined
  125. # endif
  126. typedef unsigned int        uintptr_t;
  127. #endif
  128.  
  129.  
  130. /* Largest integral types. */
  131. #if __WORDSIZE == 64
  132. typedef long int        intmax_t;
  133. typedef unsigned long int   uintmax_t;
  134. #else
  135. __extension__
  136. typedef long long int       intmax_t;
  137. __extension__
  138. typedef unsigned long long int uintmax_t;
  139. #endif
  140.  
  141.  
  142. /* The ISO C99 standard specifies that in C++ implementations these
  143. macros should only be defined if explicitly requested. */
  144. #if !defined __cplusplus || defined __STDC_LIMIT_MACROS
  145.  
  146. # if __WORDSIZE == 64
  147. # define __INT64_C(c) c ## L
  148. # define __UINT64_C(c) c ## UL
  149. # else
  150. # define __INT64_C(c) c ## LL
  151. # define __UINT64_C(c) c ## ULL
  152. # endif
  153.  
  154. /* Limits of integral types. */
  155.  
  156. /* Minimum of signed integral types. */
  157. # define INT8_MIN       (-128)
  158. # define INT16_MIN      (-32767-1)
  159. # define INT32_MIN      (-2147483647-1)
  160. # define INT64_MIN      (-__INT64_C(9223372036854775807)-1)
  161. /* Maximum of signed integral types. */
  162. # define INT8_MAX       (127)
  163. # define INT16_MAX      (32767)
  164. # define INT32_MAX      (2147483647)
  165. # define INT64_MAX      (__INT64_C(9223372036854775807))
  166.  
  167. /* Maximum of unsigned integral types. */
  168. # define UINT8_MAX      (255)
  169. # define UINT16_MAX     (65535)
  170. # define UINT32_MAX     (4294967295U)
  171. # define UINT64_MAX     (__UINT64_C(18446744073709551615))
  172.  
  173.  
  174. /* Minimum of signed integral types having a minimum size. */
  175. # define INT_LEAST8_MIN     (-128)
  176. # define INT_LEAST16_MIN    (-32767-1)
  177. # define INT_LEAST32_MIN    (-2147483647-1)
  178. # define INT_LEAST64_MIN    (-__INT64_C(9223372036854775807)-1)
  179. /* Maximum of signed integral types having a minimum size. */
  180. # define INT_LEAST8_MAX     (127)
  181. # define INT_LEAST16_MAX    (32767)
  182. # define INT_LEAST32_MAX    (2147483647)
  183. # define INT_LEAST64_MAX    (__INT64_C(9223372036854775807))
  184.  
  185. /* Maximum of unsigned integral types having a minimum size. */
  186. # define UINT_LEAST8_MAX    (255)
  187. # define UINT_LEAST16_MAX   (65535)
  188. # define UINT_LEAST32_MAX   (4294967295U)
  189. # define UINT_LEAST64_MAX   (__UINT64_C(18446744073709551615))
  190.  
  191.  
  192. /* Minimum of fast signed integral types having a minimum size. */
  193. # define INT_FAST8_MIN      (-128)
  194. # if __WORDSIZE == 64
  195. # define INT_FAST16_MIN    (-9223372036854775807L-1)
  196. # define INT_FAST32_MIN    (-9223372036854775807L-1)
  197. # else
  198. # define INT_FAST16_MIN    (-2147483647-1)
  199. # define INT_FAST32_MIN    (-2147483647-1)
  200. # endif
  201. # define INT_FAST64_MIN     (-__INT64_C(9223372036854775807)-1)
  202. /* Maximum of fast signed integral types having a minimum size. */
  203. # define INT_FAST8_MAX      (127)
  204. # if __WORDSIZE == 64
  205. # define INT_FAST16_MAX    (9223372036854775807L)
  206. # define INT_FAST32_MAX    (9223372036854775807L)
  207. # else
  208. # define INT_FAST16_MAX    (2147483647)
  209. # define INT_FAST32_MAX    (2147483647)
  210. # endif
  211. # define INT_FAST64_MAX     (__INT64_C(9223372036854775807))
  212.  
  213. /* Maximum of fast unsigned integral types having a minimum size. */
  214. # define UINT_FAST8_MAX     (255)
  215. # if __WORDSIZE == 64
  216. # define UINT_FAST16_MAX   (18446744073709551615UL)
  217. # define UINT_FAST32_MAX   (18446744073709551615UL)
  218. # else
  219. # define UINT_FAST16_MAX   (4294967295U)
  220. # define UINT_FAST32_MAX   (4294967295U)
  221. # endif
  222. # define UINT_FAST64_MAX    (__UINT64_C(18446744073709551615))
  223.  
  224.  
  225. /* Values to test for integral types holding `void *' pointer. */
  226. # if __WORDSIZE == 64
  227. # define INTPTR_MIN        (-9223372036854775807L-1)
  228. # define INTPTR_MAX        (9223372036854775807L)
  229. # define UINTPTR_MAX       (18446744073709551615UL)
  230. # else
  231. # define INTPTR_MIN        (-2147483647-1)
  232. # define INTPTR_MAX        (2147483647)
  233. # define UINTPTR_MAX       (4294967295U)
  234. # endif
  235.  
  236.  
  237. /* Minimum for largest signed integral type. */
  238. # define INTMAX_MIN     (-__INT64_C(9223372036854775807)-1)
  239. /* Maximum for largest signed integral type. */
  240. # define INTMAX_MAX     (__INT64_C(9223372036854775807))
  241.  
  242. /* Maximum for largest unsigned integral type. */
  243. # define UINTMAX_MAX        (__UINT64_C(18446744073709551615))
  244.  
  245.  
  246. /* Limits of other integer types. */
  247.  
  248. /* Limits of `ptrdiff_t' type. */
  249. # if __WORDSIZE == 64
  250. # define PTRDIFF_MIN       (-9223372036854775807L-1)
  251. # define PTRDIFF_MAX       (9223372036854775807L)
  252. # else
  253. # define PTRDIFF_MIN       (-2147483647-1)
  254. # define PTRDIFF_MAX       (2147483647)
  255. # endif
  256.  
  257. /* Limits of `sig_atomic_t'. */
  258. # define SIG_ATOMIC_MIN     (-2147483647-1)
  259. # define SIG_ATOMIC_MAX     (2147483647)
  260.  
  261. /* Limit of `size_t' type. */
  262. # if __WORDSIZE == 64
  263. # define SIZE_MAX      (18446744073709551615UL)
  264. # else
  265. # define SIZE_MAX      (4294967295U)
  266. # endif
  267.  
  268. /* Limits of `wchar_t'. */
  269. # ifndef WCHAR_MIN
  270. /* These constants might also be defined in <wchar.h>. */
  271. # define WCHAR_MIN     __WCHAR_MIN
  272. # define WCHAR_MAX     __WCHAR_MAX
  273. # endif
  274.  
  275. /* Limits of `wint_t'. */
  276. # define WINT_MIN       (0u)
  277. # define WINT_MAX       (4294967295u)
  278.  
  279. #endif /* C++ && limit macros */
  280.  
  281.  
  282. /* The ISO C99 standard specifies that in C++ implementations these
  283. should only be defined if explicitly requested. */
  284. #if !defined __cplusplus || defined __STDC_CONSTANT_MACROS
  285.  
  286. /* Signed. */
  287. # define INT8_C(c) c
  288. # define INT16_C(c) c
  289. # define INT32_C(c) c
  290. # if __WORDSIZE == 64
  291. # define INT64_C(c)    c ## L
  292. # else
  293. # define INT64_C(c)    c ## LL
  294. # endif
  295.  
  296. /* Unsigned. */
  297. # define UINT8_C(c) c ## U
  298. # define UINT16_C(c)    c ## U
  299. # define UINT32_C(c)    c ## U
  300. # if __WORDSIZE == 64
  301. # define UINT64_C(c)   c ## UL
  302. # else
  303. # define UINT64_C(c)   c ## ULL
  304. # endif
  305.  
  306. /* Maximal type. */
  307. # if __WORDSIZE == 64
  308. # define INTMAX_C(c)   c ## L
  309. # define UINTMAX_C(c) c ## UL
  310. # else
  311. # define INTMAX_C(c)   c ## LL
  312. # define UINTMAX_C(c) c ## ULL
  313. # endif
  314.  
  315. #endif /* C++ && constant macros */
  316.  
  317. #endif /* stdint.h */

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