文章目錄

• • 1. 簡介
  • 2.例子
  • 3.Reference

1. 簡介

_t 類的數據結構大都是用 typedef 來定義的，主要用于跨平臺時，平臺字長不一，會造成代碼不好維護的情況。

2.例子

一般整型對應的 *_t 類型有：

• unit8_t – 1 byte
• unit16_t – 2 byte
• unit32_t – 4 byte
• unit64_t – 8 byte

下面是一個與 c99標準中的一個 int_types.h 相類似的定義文件：

bash-3.00$ vi int_types.h "int_types.h" [Read only] 176 lines, 4367 characters /** Copyright 2004 Sun Microsystems, Inc. All rights reserved.* Use is subject to license terms.*/#ifndef _SYS_INT_TYPES_H #define _SYS_INT_TYPES_H#pragma ident "@(#)int_types.h 1.10 04/09/28 SMI"/** This file, <sys/int_types.h>, is part of the Sun Microsystems implementation* of <inttypes.h> defined in the ISO C standard, ISO/IEC 9899:1999* Programming language - C.** Programs/Modules should not directly include this file. Access to the* types defined in this file should be through the inclusion of one of the* following files:** <sys/types.h> Provides only the "_t" types defined in this* file which is a subset of the contents of* <inttypes.h>. (This can be appropriate for* all programs/modules except those claiming* ANSI-C conformance.)** <sys/inttypes.h> Provides the Kernel and Driver appropriate* components of <inttypes.h>.** <inttypes.h> For use by applications.** See these files for more details.*/#include <sys/feature_tests.h>#ifdef __cplusplus extern "C" { #endif/** Basic / Extended integer types** The following defines the basic fixed-size integer types.** Implementations are free to typedef them to Standard C integer types or* extensions that they support. If an implementation does not support one* of the particular integer data types below, then it should not define the* typedefs and macros corresponding to that data type. Note that int8_t* is not defined in -Xs mode on ISAs for which the ABI specifies "char"* as an unsigned entity because there is no way to define an eight bit* signed integral.*/ #if defined(_CHAR_IS_SIGNED) typedef char int8_t; #else #if defined(__STDC__) typedef signed char int8_t; #endif #endif typedef short int16_t; typedef int int32_t; #ifdef _LP64 #define _INT64_TYPE typedef long int64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) #define _INT64_TYPE typedef long long int64_t; #endif #endiftypedef unsigned char uint8_t; typedef unsigned short uint16_t; typedef unsigned int uint32_t; #ifdef _LP64 typedef unsigned long uint64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) typedef unsigned long long uint64_t; #endif #endif/** intmax_t and uintmax_t are to be the longest (in number of bits) signed* and unsigned integer types supported by the implementation.*/ #if defined(_INT64_TYPE) typedef int64_t intmax_t; typedef uint64_t uintmax_t; #else typedef int32_t intmax_t; typedef uint32_t uintmax_t; #endif/** intptr_t and uintptr_t are signed and unsigned integer types large enough* to hold any data pointer; that is, data pointers can be assigned into or* from these integer types without losing precision.*/ #if defined(_LP64) || defined(_I32LPx) typedef long intptr_t; typedef unsigned long uintptr_t; #else typedef int intptr_t; typedef unsigned int uintptr_t; #endif/** The following define the fastest integer types that can hold the* specified number of bits.*/ #if defined(_CHAR_IS_SIGNED) typedef char int_fast8_t; #else #if defined(__STDC__) typedef signed char int_fast8_t; #endif #endif typedef int int_fast16_t; typedef int int_fast32_t; #ifdef _LP64 typedef long int_fast64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) typedef long long int_fast64_t; #endif #endiftypedef unsigned char uint_fast8_t; typedef unsigned int uint_fast16_t; typedef unsigned int uint_fast32_t; #ifdef _LP64 typedef unsigned long uint_fast64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) typedef unsigned long long uint_fast64_t; #endif #endif/** The following define the smallest integer types that can hold the* specified number of bits.*/ #if defined(_CHAR_IS_SIGNED) typedef char int_least8_t; #else #if defined(__STDC__) typedef signed char int_least8_t; #endif #endif typedef short int_least16_t; typedef int int_least32_t; #ifdef _LP64 typedef long int_least64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) typedef long long int_least64_t; #endif #endiftypedef unsigned char uint_least8_t; typedef unsigned short uint_least16_t; typedef unsigned int uint_least32_t; #ifdef _LP64 typedef unsigned long uint_least64_t; #else /* _ILP32 */ #if defined(_LONGLONG_TYPE) typedef unsigned long long uint_least64_t; #endif #endif#ifdef __cplusplus } #endif#endif /* _SYS_INT_TYPES_H */

3.Reference

• c/c++: uint8_t uint16_t uint32_t uint64_t size_t ssize_t數據類型 csdn

總結

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