首先说一下源码到底在哪里找。
我们在文件中包含<cstring>时,如果点击右键打开文档,
会打开cstring,我们会发现路径为:
D:Program Filesvisual studioVCincludecstring
这个文件内容如下:
// cstring standard header #pragma once #ifndef _CSTRING_ #define _CSTRING_ #include <yvals.h> #ifdef _STD_USING #undef _STD_USING #include <string.h> #define _STD_USING #else /* _STD_USING */ #include <string.h> #endif /* _STD_USING */ #if _GLOBAL_USING && !defined(RC_INVOKED) _STD_BEGIN using _CSTD size_t; using _CSTD memchr; using _CSTD memcmp; using _CSTD memcpy; using _CSTD memmove; using _CSTD memset; using _CSTD strcat; using _CSTD strchr; using _CSTD strcmp; using _CSTD strcoll; using _CSTD strcpy; using _CSTD strcspn; using _CSTD strerror; using _CSTD strlen; using _CSTD strncat; using _CSTD strncmp; using _CSTD strncpy; using _CSTD strpbrk; using _CSTD strrchr; using _CSTD strspn; using _CSTD strstr; using _CSTD strtok; using _CSTD strxfrm; _STD_END #endif /* _GLOBAL_USING */ #endif /* _CSTRING_ */ /* * Copyright (c) 1992-2009 by P.J. Plauger. ALL RIGHTS RESERVED. * Consult your license regarding permissions and restrictions. V5.20:0009 */
它没有cpp文件。包含了<string.h>头文件,也在这个目录下,内容如下;
/*** *string.h - declarations for string manipulation functions * * Copyright (c) Microsoft Corporation. All rights reserved. * *Purpose: * This file contains the function declarations for the string * manipulation functions. * [ANSI/System V] * * [Public] * ****/ #pragma once #ifndef _INC_STRING #define _INC_STRING #include <crtdefs.h> #ifdef __cplusplus extern "C" { #endif #ifndef _NLSCMP_DEFINED #define _NLSCMPERROR 2147483647 /* currently == INT_MAX */ #define _NLSCMP_DEFINED #endif /* Define NULL pointer value */ #ifndef NULL #ifdef __cplusplus #define NULL 0 #else #define NULL ((void *)0) #endif #endif /* For backwards compatibility */ #define _WConst_return _CONST_RETURN /* Function prototypes */ #ifndef _CRT_MEMORY_DEFINED #define _CRT_MEMORY_DEFINED _CRTIMP void * __cdecl _memccpy( _Out_opt_bytecap_(_MaxCount) void * _Dst, _In_ const void * _Src, _In_ int _Val, _In_ size_t _MaxCount); _Check_return_ _CRTIMP _CONST_RETURN void * __cdecl memchr( _In_opt_bytecount_(_MaxCount) const void * _Buf , _In_ int _Val, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _memicmp(_In_opt_bytecount_(_Size) const void * _Buf1, _In_opt_bytecount_(_Size) const void * _Buf2, _In_ size_t _Size); _Check_return_ _CRTIMP int __cdecl _memicmp_l(_In_opt_bytecount_(_Size) const void * _Buf1, _In_opt_bytecount_(_Size) const void * _Buf2, _In_ size_t _Size, _In_opt_ _locale_t _Locale); _Check_return_ int __cdecl memcmp(_In_opt_bytecount_(_Size) const void * _Buf1, _In_opt_bytecount_(_Size) const void * _Buf2, _In_ size_t _Size); _CRT_INSECURE_DEPRECATE_MEMORY(memcpy_s) void * __cdecl memcpy(_Out_opt_bytecapcount_(_Size) void * _Dst, _In_opt_bytecount_(_Size) const void * _Src, _In_ size_t _Size); #if __STDC_WANT_SECURE_LIB__ _CRTIMP errno_t __cdecl memcpy_s(_Out_opt_bytecap_post_bytecount_(_DstSize, _MaxCount) void * _Dst, _In_ rsize_t _DstSize, _In_opt_bytecount_(_MaxCount) const void * _Src, _In_ rsize_t _MaxCount); #if defined(__cplusplus) && _CRT_SECURE_CPP_OVERLOAD_STANDARD_NAMES_MEMORY extern "C++" { #ifndef _CRT_ENABLE_IF_DEFINED #define _CRT_ENABLE_IF_DEFINED template<bool _Enable, typename _Ty> struct _CrtEnableIf; template<typename _Ty> struct _CrtEnableIf<true, _Ty> { typedef _Ty _Type; }; #endif template <size_t _Size, typename _DstType> inline typename _CrtEnableIf<(_Size > 1), void *>::_Type __cdecl memcpy(_DstType (&_Dst)[_Size], _In_opt_bytecount_(_SrcSize) const void *_Src, _In_ size_t _SrcSize) _CRT_SECURE_CPP_NOTHROW { return memcpy_s(_Dst, _Size * sizeof(_DstType), _Src, _SrcSize) == 0 ? _Dst : 0; } } #endif #if defined(__cplusplus) && _CRT_SECURE_CPP_OVERLOAD_SECURE_NAMES_MEMORY extern "C++" { template <size_t _Size, typename _DstType> inline errno_t __CRTDECL memcpy_s(_DstType (&_Dst)[_Size], _In_opt_bytecount_(_SrcSize) const void * _Src, _In_ rsize_t _SrcSize) _CRT_SECURE_CPP_NOTHROW { return memcpy_s(_Dst, _Size * sizeof(_DstType), _Src, _SrcSize); } } #endif #endif void * __cdecl memset(_Out_opt_bytecapcount_(_Size) void * _Dst, _In_ int _Val, _In_ size_t _Size); #if !__STDC__ /* Non-ANSI names for compatibility */ _CRT_NONSTDC_DEPRECATE(_memccpy) _CRTIMP void * __cdecl memccpy(_Out_opt_bytecap_(_Size) void * _Dst, _In_opt_bytecount_(_Size) const void * _Src, _In_ int _Val, _In_ size_t _Size); _Check_return_ _CRT_NONSTDC_DEPRECATE(_memicmp) _CRTIMP int __cdecl memicmp(_In_opt_bytecount_(_Size) const void * _Buf1, _In_opt_bytecount_(_Size) const void * _Buf2, _In_ size_t _Size); #endif /* __STDC__ */ #endif _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl _strset_s(_Inout_z_cap_(_DstSize) char * _Dst, _In_ size_t _DstSize, _In_ int _Value); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _strset_s, _Deref_prepost_z_ char, _Dest, _In_ int, _Value) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1(char *, __RETURN_POLICY_DST, __EMPTY_DECLSPEC, _strset, _Inout_z_, char, _Dest, _In_ int, _Value) #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl strcpy_s(_Out_z_cap_(_SizeInBytes) char * _Dst, _In_ rsize_t _SizeInBytes, _In_z_ const char * _Src); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, strcpy_s, _Deref_post_z_ char, _Dest, _In_z_ const char *, _Source) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1(char *, __RETURN_POLICY_DST, __EMPTY_DECLSPEC, strcpy, _Pre_cap_for_(_Source) _Post_z_, char, _Dest, _In_z_ const char *, _Source) #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl strcat_s(_Inout_z_cap_(_SizeInBytes) char * _Dst, _In_ rsize_t _SizeInBytes, _In_z_ const char * _Src); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, strcat_s, _Deref_prepost_z_ char, _Dest, _In_z_ const char *, _Source) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1(char *, __RETURN_POLICY_DST, __EMPTY_DECLSPEC, strcat, _Pre_cap_for_(_Source) _Prepost_z_, char, _Dest, _In_z_ const char *, _Source) _Check_return_ int __cdecl strcmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ size_t __cdecl strlen(_In_z_ const char * _Str); _Check_return_ _CRTIMP size_t __cdecl strnlen(_In_z_ const char * _Str, _In_ size_t _MaxCount); #if __STDC_WANT_SECURE_LIB__ && !defined (__midl) _Check_return_ static __inline size_t __CRTDECL strnlen_s(_In_z_ const char * _Str, _In_ size_t _MaxCount) { return (_Str==0) ? 0 : strnlen(_Str, _MaxCount); } #endif #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP errno_t __cdecl memmove_s(_Out_opt_bytecap_post_bytecount_(_DstSize,_MaxCount) void * _Dst, _In_ rsize_t _DstSize, _In_opt_bytecount_(_MaxCount) const void * _Src, _In_ rsize_t _MaxCount); #endif #if defined(_M_IA64) _CRT_INSECURE_DEPRECATE_MEMORY(memmove_s) void * __cdecl memmove(_Out_opt_bytecapcount_(_Size) void * _Dst, _In_opt_bytecount_(_Size) const void * _Src, _In_ size_t _Size); #else /* defined (_M_IA64) */ _CRTIMP _CRT_INSECURE_DEPRECATE_MEMORY(memmove_s) void * __cdecl memmove(_Out_opt_bytecapcount_(_Size) void * _Dst, _In_opt_bytecount_(_Size) const void * _Src, _In_ size_t _Size); #endif /* defined (_M_IA64) */ #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma push_macro("_strdup") #undef _strdup #endif _Check_return_ _CRTIMP char * __cdecl _strdup(_In_opt_z_ const char * _Src); #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma pop_macro("_strdup") #endif _Check_return_ _CRTIMP _CONST_RETURN char * __cdecl strchr(_In_z_ const char * _Str, _In_ int _Val); _Check_return_ _CRTIMP int __cdecl _stricmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ _CRTIMP int __cdecl _strcmpi(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ _CRTIMP int __cdecl _stricmp_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl strcoll(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ _CRTIMP int __cdecl _strcoll_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _stricoll(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ _CRTIMP int __cdecl _stricoll_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _strncoll (_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _strncoll_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _strnicoll (_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _strnicoll_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP size_t __cdecl strcspn(_In_z_ const char * _Str, _In_z_ const char * _Control); _Check_return_ _CRT_INSECURE_DEPRECATE(_strerror_s) _CRTIMP char * __cdecl _strerror(_In_opt_z_ const char * _ErrMsg); _Check_return_wat_ _CRTIMP errno_t __cdecl _strerror_s(_Out_z_cap_(_SizeInBytes) char * _Buf, _In_ size_t _SizeInBytes, _In_opt_z_ const char * _ErrMsg); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _strerror_s, char, _Buffer, _In_opt_z_ const char *, _ErrorMessage) _Check_return_ _CRT_INSECURE_DEPRECATE(strerror_s) _CRTIMP char * __cdecl strerror(_In_ int); #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP errno_t __cdecl strerror_s(_Out_z_cap_(_SizeInBytes) char * _Buf, _In_ size_t _SizeInBytes, _In_ int _ErrNum); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, strerror_s, char, _Buffer, _In_ int, _ErrorMessage) _Check_return_wat_ _CRTIMP errno_t __cdecl _strlwr_s(_Inout_z_cap_(_Size) char * _Str, _In_ size_t _Size); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_0(errno_t, _strlwr_s, _Deref_prepost_z_ char, _String) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_0(char *, __RETURN_POLICY_DST, _CRTIMP, _strlwr, _Inout_z_, char, _String) _Check_return_wat_ _CRTIMP errno_t __cdecl _strlwr_s_l(_Inout_z_cap_(_Size) char * _Str, _In_ size_t _Size, _In_opt_ _locale_t _Locale); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _strlwr_s_l, _Deref_prepost_z_ char, _String, _In_opt_ _locale_t, _Locale) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1_EX(char *, __RETURN_POLICY_DST, _CRTIMP, _strlwr_l, _strlwr_s_l, _Deref_inout_z_cap_c_(_Size) char, _Inout_z_, char, _String, _In_opt_ _locale_t, _Locale) #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl strncat_s(_Inout_z_cap_(_SizeInBytes) char * _Dst, _In_ rsize_t _SizeInBytes, _In_z_ const char * _Src, _In_ rsize_t _MaxCount); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, strncat_s, _Deref_prepost_z_ char, _Dest, _In_z_ const char *, _Source, _In_ size_t, _Count) #pragma warning(push) #pragma warning(disable:6059) /* prefast noise VSW 489802 */ __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(char *, __RETURN_POLICY_DST, _CRTIMP, strncat, strncat_s, _Deref_inout_z_cap_c_(_Size) char, _Inout_z_cap_(_Count), char, _Dest, _In_z_ const char *, _Source, _In_ size_t, _Count) #pragma warning(pop) #if defined(_M_IA64) _Check_return_ int __cdecl strncmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount); #else _Check_return_ _CRTIMP int __cdecl strncmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount); #endif _Check_return_ _CRTIMP int __cdecl _strnicmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _strnicmp_l(_In_z_ const char * _Str1, _In_z_ const char * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl strncpy_s(_Out_z_cap_(_SizeInBytes) char * _Dst, _In_ rsize_t _SizeInBytes, _In_z_ const char * _Src, _In_ rsize_t _MaxCount); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, strncpy_s, char, _Dest, _In_z_ const char *, _Source, _In_ size_t, _Count) __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(char *, __RETURN_POLICY_DST, _CRTIMP_NOIA64, strncpy, strncpy_s, _Deref_out_z_cap_c_(_Size) char, _Out_cap_(_Count) _Post_maybez_, char, _Dest, _In_z_ const char *, _Source, _In_ size_t, _Count) _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl _strnset_s(_Inout_z_cap_(_SizeInBytes) char * _Str, _In_ size_t _SizeInBytes, _In_ int _Val, _In_ size_t _MaxCount); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, _strnset_s, _Deref_prepost_z_ char, _Dest, _In_ int, _Val, _In_ size_t, _Count) __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(char *, __RETURN_POLICY_DST, _CRTIMP, _strnset, _strnset_s, _Deref_inout_z_cap_c_(_Size) char, _Inout_z_cap_(_Count), char, _Dest, _In_ int, _Val, _In_ size_t, _Count) _Check_return_ _CRTIMP _CONST_RETURN char * __cdecl strpbrk(_In_z_ const char * _Str, _In_z_ const char * _Control); _Check_return_ _CRTIMP _CONST_RETURN char * __cdecl strrchr(_In_z_ const char * _Str, _In_ int _Ch); _CRTIMP char * __cdecl _strrev(_Inout_z_ char * _Str); _Check_return_ _CRTIMP size_t __cdecl strspn(_In_z_ const char * _Str, _In_z_ const char * _Control); _Check_return_ _CRTIMP _CONST_RETURN char * __cdecl strstr(_In_z_ const char * _Str, _In_z_ const char * _SubStr); _Check_return_ _CRT_INSECURE_DEPRECATE(strtok_s) _CRTIMP char * __cdecl strtok(_Inout_opt_z_ char * _Str, _In_z_ const char * _Delim); #if __STDC_WANT_SECURE_LIB__ _Check_return_ _CRTIMP_ALTERNATIVE char * __cdecl strtok_s(_Inout_opt_z_ char * _Str, _In_z_ const char * _Delim, _Inout_ _Deref_prepost_opt_z_ char ** _Context); #endif _Check_return_wat_ _CRTIMP errno_t __cdecl _strupr_s(_Inout_z_cap_(_Size) char * _Str, _In_ size_t _Size); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_0(errno_t, _strupr_s, _Deref_prepost_z_ char, _String) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_0(char *, __RETURN_POLICY_DST, _CRTIMP, _strupr, _Inout_z_, char, _String) _Check_return_wat_ _CRTIMP errno_t __cdecl _strupr_s_l(_Inout_z_cap_(_Size) char * _Str, _In_ size_t _Size, _locale_t _Locale); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _strupr_s_l, _Deref_prepost_z_ char, _String, _locale_t, _Locale) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1_EX(char *, __RETURN_POLICY_DST, _CRTIMP, _strupr_l, _strupr_s_l, _Deref_inout_z_cap_c_(_Size) char, _Inout_z_, char, _String, _In_opt_ _locale_t, _Locale) _Check_return_opt_ _CRTIMP size_t __cdecl strxfrm (_Out_opt_cap_(_MaxCount) _Post_maybez_ char * _Dst, _In_z_ const char * _Src, _In_ size_t _MaxCount); _Check_return_opt_ _CRTIMP size_t __cdecl _strxfrm_l(_Out_opt_cap_(_MaxCount) _Post_maybez_ char * _Dst, _In_z_ const char * _Src, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); #ifdef __cplusplus extern "C++" { #ifndef _CPP_NARROW_INLINES_DEFINED #define _CPP_NARROW_INLINES_DEFINED _Check_return_ inline char * __CRTDECL strchr(_In_z_ char * _Str, _In_ int _Ch) { return (char*)strchr((const char*)_Str, _Ch); } _Check_return_ inline char * __CRTDECL strpbrk(_In_z_ char * _Str, _In_z_ const char * _Control) { return (char*)strpbrk((const char*)_Str, _Control); } _Check_return_ inline char * __CRTDECL strrchr(_In_z_ char * _Str, _In_ int _Ch) { return (char*)strrchr((const char*)_Str, _Ch); } _Check_return_ inline char * __CRTDECL strstr(_In_z_ char * _Str, _In_z_ const char * _SubStr) { return (char*)strstr((const char*)_Str, _SubStr); } #endif #ifndef _CPP_MEMCHR_DEFINED #define _CPP_MEMCHR_DEFINED _Check_return_ inline void * __CRTDECL memchr(_In_opt_bytecount_(_N) void * _Pv, _In_ int _C, _In_ size_t _N) { return (void*)memchr((const void*)_Pv, _C, _N); } #endif } #endif #if !__STDC__ #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma push_macro("strdup") #undef strdup #endif _Check_return_ _CRT_NONSTDC_DEPRECATE(_strdup) _CRTIMP char * __cdecl strdup(_In_opt_z_ const char * _Src); #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma pop_macro("strdup") #endif /* prototypes for oldnames.lib functions */ _Check_return_ _CRT_NONSTDC_DEPRECATE(_strcmpi) _CRTIMP int __cdecl strcmpi(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _Check_return_ _CRT_NONSTDC_DEPRECATE(_stricmp) _CRTIMP int __cdecl stricmp(_In_z_ const char * _Str1, _In_z_ const char * _Str2); _CRT_NONSTDC_DEPRECATE(_strlwr) _CRTIMP char * __cdecl strlwr(_Inout_z_ char * _Str); _Check_return_ _CRT_NONSTDC_DEPRECATE(_strnicmp) _CRTIMP int __cdecl strnicmp(_In_z_ const char * _Str1, _In_z_ const char * _Str, _In_ size_t _MaxCount); _CRT_NONSTDC_DEPRECATE(_strnset) _CRTIMP char * __cdecl strnset(_Inout_z_cap_(_MaxCount) char * _Str, _In_ int _Val, _In_ size_t _MaxCount); _CRT_NONSTDC_DEPRECATE(_strrev) _CRTIMP char * __cdecl strrev(_Inout_z_ char * _Str); _CRT_NONSTDC_DEPRECATE(_strset) char * __cdecl strset(_Inout_z_ char * _Str, _In_ int _Val); _CRT_NONSTDC_DEPRECATE(_strupr) _CRTIMP char * __cdecl strupr(_Inout_z_ char * _Str); #endif /* !__STDC__ */ #ifndef _WSTRING_DEFINED /* wide function prototypes, also declared in wchar.h */ #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma push_macro("_wcsdup") #undef _wcsdup #endif _Check_return_ _CRTIMP wchar_t * __cdecl _wcsdup(_In_z_ const wchar_t * _Str); #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma pop_macro("_wcsdup") #endif #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl wcscat_s(_Inout_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ rsize_t _SizeInWords, _In_z_ const wchar_t * _Src); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, wcscat_s, _Deref_prepost_z_ wchar_t, _Dest, _In_z_ const wchar_t *, _Source) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, wcscat, _Pre_cap_for_(_Source) _Prepost_z_, wchar_t, _Dest, _In_z_ const wchar_t *, _Source) _Check_return_ _CRTIMP _CONST_RETURN wchar_t * __cdecl wcschr(_In_z_ const wchar_t * _Str, wchar_t _Ch); _Check_return_ _CRTIMP int __cdecl wcscmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl wcscpy_s(_Out_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ rsize_t _SizeInWords, _In_z_ const wchar_t * _Src); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, wcscpy_s, wchar_t, _Dest, _In_z_ const wchar_t *, _Source) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, wcscpy, _Pre_cap_for_(_Source) _Post_z_, wchar_t, _Dest, _In_z_ const wchar_t *, _Source) _Check_return_ _CRTIMP size_t __cdecl wcscspn(_In_z_ const wchar_t * _Str, _In_z_ const wchar_t * _Control); _Check_return_ _CRTIMP size_t __cdecl wcslen(_In_z_ const wchar_t * _Str); _Check_return_ _CRTIMP size_t __cdecl wcsnlen(_In_z_ const wchar_t * _Src, _In_ size_t _MaxCount); #if __STDC_WANT_SECURE_LIB__ && !defined (__midl) _Check_return_ static __inline size_t __CRTDECL wcsnlen_s(_In_z_ const wchar_t * _Src, _In_ size_t _MaxCount) { return (_Src == NULL) ? 0 : wcsnlen(_Src, _MaxCount); } #endif #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl wcsncat_s(_Inout_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ rsize_t _SizeInWords, _In_z_ const wchar_t * _Src, _In_ rsize_t _MaxCount); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, wcsncat_s, _Deref_prepost_z_ wchar_t, _Dest, _In_z_ const wchar_t *, _Source, _In_ size_t, _Count) #pragma warning(push) #pragma warning(disable:6059) __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, wcsncat, wcsncat_s, _Deref_inout_z_cap_c_(_Size) wchar_t, _Inout_z_cap_(_Count), wchar_t, _Dest, _In_z_ const wchar_t *, _Source, _In_ size_t, _Count) #pragma warning(pop) _Check_return_ _CRTIMP int __cdecl wcsncmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount); #if __STDC_WANT_SECURE_LIB__ _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl wcsncpy_s(_Out_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ rsize_t _SizeInWords, _In_z_ const wchar_t * _Src, _In_ rsize_t _MaxCount); #endif __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, wcsncpy_s, wchar_t, _Dest, _In_z_ const wchar_t *, _Source, _In_ size_t, _Count) __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, wcsncpy, wcsncpy_s, _Pre_notnull_ _Post_maybez_ wchar_t, _Out_cap_(_Count) _Post_maybez_, wchar_t, _Dest, _In_z_ const wchar_t *, _Source, _In_ size_t, _Count) _Check_return_ _CRTIMP _CONST_RETURN wchar_t * __cdecl wcspbrk(_In_z_ const wchar_t * _Str, _In_z_ const wchar_t * _Control); _Check_return_ _CRTIMP _CONST_RETURN wchar_t * __cdecl wcsrchr(_In_z_ const wchar_t * _Str, _In_ wchar_t _Ch); _Check_return_ _CRTIMP size_t __cdecl wcsspn(_In_z_ const wchar_t * _Str, _In_z_ const wchar_t * _Control); _Check_return_ _CRTIMP _CONST_RETURN wchar_t * __cdecl wcsstr(_In_z_ const wchar_t * _Str, _In_z_ const wchar_t * _SubStr); _Check_return_ _CRT_INSECURE_DEPRECATE(wcstok_s) _CRTIMP wchar_t * __cdecl wcstok(_Inout_opt_z_ wchar_t * _Str, _In_z_ const wchar_t * _Delim); #if __STDC_WANT_SECURE_LIB__ _Check_return_ _CRTIMP_ALTERNATIVE wchar_t * __cdecl wcstok_s(_Inout_opt_z_ wchar_t * _Str, _In_z_ const wchar_t * _Delim, _Inout_ _Deref_prepost_opt_z_ wchar_t ** _Context); #endif _Check_return_ _CRT_INSECURE_DEPRECATE(_wcserror_s) _CRTIMP wchar_t * __cdecl _wcserror(_In_ int _ErrNum); _Check_return_wat_ _CRTIMP errno_t __cdecl _wcserror_s(_Out_opt_z_cap_(_SizeInWords) wchar_t * _Buf, _In_ size_t _SizeInWords, _In_ int _ErrNum); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _wcserror_s, wchar_t, _Buffer, _In_ int, _Error) _Check_return_ _CRT_INSECURE_DEPRECATE(__wcserror_s) _CRTIMP wchar_t * __cdecl __wcserror(_In_opt_z_ const wchar_t * _Str); _Check_return_wat_ _CRTIMP errno_t __cdecl __wcserror_s(_Out_opt_z_cap_(_SizeInWords) wchar_t * _Buffer, _In_ size_t _SizeInWords, _In_z_ const wchar_t * _ErrMsg); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, __wcserror_s, wchar_t, _Buffer, _In_z_ const wchar_t *, _ErrorMessage) _Check_return_ _CRTIMP int __cdecl _wcsicmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); _Check_return_ _CRTIMP int __cdecl _wcsicmp_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _wcsnicmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _wcsnicmp_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl _wcsnset_s(_Inout_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ size_t _SizeInWords, _In_ wchar_t _Val, _In_ size_t _MaxCount); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_2(errno_t, _wcsnset_s, _Deref_prepost_z_ wchar_t, _Dst, wchar_t, _Val, _In_ size_t, _MaxCount) __DEFINE_CPP_OVERLOAD_STANDARD_NFUNC_0_2_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcsnset, _wcsnset_s, _Deref_inout_z_cap_c_(_Size) wchar_t, _Inout_z_cap_(_MaxCount), wchar_t, _Str, wchar_t, _Val, _In_ size_t, _MaxCount) _CRTIMP wchar_t * __cdecl _wcsrev(_Inout_z_ wchar_t * _Str); _Check_return_wat_ _CRTIMP_ALTERNATIVE errno_t __cdecl _wcsset_s(_Inout_z_cap_(_SizeInWords) wchar_t * _Dst, _In_ size_t _SizeInWords, _In_ wchar_t _Value); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _wcsset_s, _Deref_prepost_z_ wchar_t, _Str, wchar_t, _Val) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcsset, _wcsset_s, _Deref_inout_z_cap_c_(_Size) wchar_t, _Inout_z_, wchar_t, _Str, wchar_t, _Val) _Check_return_wat_ _CRTIMP errno_t __cdecl _wcslwr_s(_Inout_z_cap_(_SizeInWords) wchar_t * _Str, _In_ size_t _SizeInWords); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_0(errno_t, _wcslwr_s, _Deref_prepost_z_ wchar_t, _String) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_0(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcslwr, _Inout_z_, wchar_t, _String) _Check_return_wat_ _CRTIMP errno_t __cdecl _wcslwr_s_l(_Inout_z_cap_(_SizeInWords) wchar_t * _Str, _In_ size_t _SizeInWords, _In_opt_ _locale_t _Locale); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _wcslwr_s_l, _Deref_prepost_z_ wchar_t, _String, _In_opt_ _locale_t, _Locale) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcslwr_l, _wcslwr_s_l, _Deref_inout_z_cap_c_(_Size) wchar_t, _Inout_z_, wchar_t, _String, _In_opt_ _locale_t, _Locale) _Check_return_wat_ _CRTIMP errno_t __cdecl _wcsupr_s(_Inout_z_cap_(_Size) wchar_t * _Str, _In_ size_t _Size); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_0(errno_t, _wcsupr_s, _Deref_prepost_z_ wchar_t, _String) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_0(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcsupr, _Inout_z_, wchar_t, _String) _Check_return_wat_ _CRTIMP errno_t __cdecl _wcsupr_s_l(_Inout_z_cap_(_Size) wchar_t * _Str, _In_ size_t _Size, _In_opt_ _locale_t _Locale); __DEFINE_CPP_OVERLOAD_SECURE_FUNC_0_1(errno_t, _wcsupr_s_l, _Deref_prepost_z_ wchar_t, _String, _In_opt_ _locale_t, _Locale) __DEFINE_CPP_OVERLOAD_STANDARD_FUNC_0_1_EX(wchar_t *, __RETURN_POLICY_DST, _CRTIMP, _wcsupr_l, _wcsupr_s_l, _Deref_inout_z_cap_c_(_Size) wchar_t, _Inout_z_, wchar_t, _String, _In_opt_ _locale_t, _Locale) _Check_return_opt_ _CRTIMP size_t __cdecl wcsxfrm(_Out_opt_cap_(_MaxCount) _Post_maybez_ wchar_t * _Dst, _In_z_ const wchar_t * _Src, _In_ size_t _MaxCount); _Check_return_opt_ _CRTIMP size_t __cdecl _wcsxfrm_l(_Out_opt_cap_(_MaxCount) _Post_maybez_ wchar_t * _Dst, _In_z_ const wchar_t *_Src, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl wcscoll(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); _Check_return_ _CRTIMP int __cdecl _wcscoll_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _wcsicoll(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); _Check_return_ _CRTIMP int __cdecl _wcsicoll_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t *_Str2, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _wcsncoll(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _wcsncoll_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); _Check_return_ _CRTIMP int __cdecl _wcsnicoll(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount); _Check_return_ _CRTIMP int __cdecl _wcsnicoll_l(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount, _In_opt_ _locale_t _Locale); #ifdef __cplusplus #ifndef _CPP_WIDE_INLINES_DEFINED #define _CPP_WIDE_INLINES_DEFINED extern "C++" { _Check_return_ inline wchar_t * __CRTDECL wcschr(_In_z_ wchar_t *_Str, wchar_t _Ch) {return ((wchar_t *)wcschr((const wchar_t *)_Str, _Ch)); } _Check_return_ inline wchar_t * __CRTDECL wcspbrk(_In_z_ wchar_t *_Str, _In_z_ const wchar_t *_Control) {return ((wchar_t *)wcspbrk((const wchar_t *)_Str, _Control)); } _Check_return_ inline wchar_t * __CRTDECL wcsrchr(_In_z_ wchar_t *_Str, _In_ wchar_t _Ch) {return ((wchar_t *)wcsrchr((const wchar_t *)_Str, _Ch)); } _Check_return_ inline wchar_t * __CRTDECL wcsstr(_In_z_ wchar_t *_Str, _In_z_ const wchar_t *_SubStr) {return ((wchar_t *)wcsstr((const wchar_t *)_Str, _SubStr)); } } #endif #endif #if !__STDC__ #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma push_macro("wcsdup") #undef wcsdup #endif _Check_return_ _CRT_NONSTDC_DEPRECATE(_wcsdup) _CRTIMP wchar_t * __cdecl wcsdup(_In_z_ const wchar_t * _Str); #if defined(_DEBUG) && defined(_CRTDBG_MAP_ALLOC) #pragma pop_macro("wcsdup") #endif /* old names */ #define wcswcs wcsstr /* prototypes for oldnames.lib functions */ _Check_return_ _CRT_NONSTDC_DEPRECATE(_wcsicmp) _CRTIMP int __cdecl wcsicmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); _Check_return_ _CRT_NONSTDC_DEPRECATE(_wcsnicmp) _CRTIMP int __cdecl wcsnicmp(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2, _In_ size_t _MaxCount); _CRT_NONSTDC_DEPRECATE(_wcsnset) _CRTIMP wchar_t * __cdecl wcsnset(_Inout_z_cap_(_MaxCount) wchar_t * _Str, _In_ wchar_t _Val, _In_ size_t _MaxCount); _CRT_NONSTDC_DEPRECATE(_wcsrev) _CRTIMP wchar_t * __cdecl wcsrev(_Inout_z_ wchar_t * _Str); _CRT_NONSTDC_DEPRECATE(_wcsset) _CRTIMP wchar_t * __cdecl wcsset(_Inout_z_ wchar_t * _Str, wchar_t _Val); _CRT_NONSTDC_DEPRECATE(_wcslwr) _CRTIMP wchar_t * __cdecl wcslwr(_Inout_z_ wchar_t * _Str); _CRT_NONSTDC_DEPRECATE(_wcsupr) _CRTIMP wchar_t * __cdecl wcsupr(_Inout_z_ wchar_t * _Str); _Check_return_ _CRT_NONSTDC_DEPRECATE(_wcsicoll) _CRTIMP int __cdecl wcsicoll(_In_z_ const wchar_t * _Str1, _In_z_ const wchar_t * _Str2); #endif /* !__STDC__ */ #define _WSTRING_DEFINED #endif #ifdef __cplusplus } #endif #endif /* _INC_STRING */
在Vcinclude下面倒是有一个string的cpp文件,但是没有string操作函数的代码,那么strcpy,strcat源码到底在哪里?
在D:Program Filesvisual studioVCcrtsrc 目录下面。
这个目录下面包含所有C语言函数的源代码。
大多数函数的名字都是以名字命名的.c文件里,但是strcpy并没有strcpy.c文件,它的源码在strcat.c里面:
strcat.c内容如下:
/*** *strcat.c - contains strcat() and strcpy() * *Purpose: * Strcpy() copies one string onto another. * * Strcat() concatenates (appends) a copy of the source string to the * end of the destination string, returning the destination string. * *******************************************************************************/ #include <cruntime.h> #include <string.h> #ifndef _MBSCAT #pragma function(strcat,strcpy) #endif /* _MBSCAT */ /*** *char *strcat(dst, src) - concatenate (append) one string to another * *Purpose: * Concatenates src onto the end of dest. Assumes enough * space in dest. * *Entry: * char *dst - string to which "src" is to be appended * const char *src - string to be appended to the end of "dst" * *Exit: * The address of "dst" * *Exceptions: * *******************************************************************************/ char * __cdecl strcat ( char * dst, const char * src ) { char * cp = dst; while( *cp ) cp++; /* find end of dst */
/*不能写成while(*cp++)/ 因为这样的话为*cp为0时还会+1,导致cp执向了 的后一个。
while( *cp++ = *src++ ) ; /* Copy src to end of dst */ return( dst ); /* return dst */ } /*** *char *strcpy(dst, src) - copy one string over another * *Purpose: * Copies the string src into the spot specified by * dest; assumes enough room. * *Entry: * char * dst - string over which "src" is to be copied * const char * src - string to be copied over "dst" * *Exit: * The address of "dst" * *Exceptions: *******************************************************************************/ char * __cdecl strcpy(char * dst, const char * src) { char * cp = dst; while( *cp++ = *src++ ) ; /* Copy src over dst */ return( dst ); }
strcpy另一种实现策略:
林锐《高质量C++/C编程指南》
#include <assert.h> char *strcpy(char *strDest, const char *strSrc) { assert((strDest!=NULL) && (strSrc !=NULL)); // 2分 char *address = strDest; // 2分 while( (*strDest++ = * strSrc++) != ‘/0’ ) // 2分 ; return address ; // 2分 }
附:
strcpy能把strSrc的内容复制到strDest,为什么还要char * 类型的返回值?
答:为了实现链式表达式。 // 2分
例如 int length = strlen( strcpy( strDest, “hello world”) );
个人觉得
(*strDest++ = * strSrc++) != ‘/0’ 不能没有必要判断是否=0,因为但char内容为字符串结束符时ascii为0,dst=src; dst=0;
while 判断dst是否等于0,等于0就退出了。
strcmp怎么写,最开始我这么写的:
int strcmp(char *src,char *dst) { char *p=src,*q=dst; while( (*p!='