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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778//// drive.cpp//// Copyright (c) Microsoft Corporation. All rights reserved.//// The _getdrive() and _chdrive() functions, which get and set the current drive.//#include <corecrt_internal.h>#include <ctype.h>#include <direct.h>#include <errno.h>
static int __cdecl get_drive_number_from_path(wchar_t const* const path) throw(){ if (path[0] == L'\0' || path[1] != L':') return 0;
return __ascii_towupper(path[0]) - L'A' + 1;}
// Gets the current drive number (A: => 1, B: => 2, etc.). Returns zero if the// current drive cannot be determined.extern "C" int __cdecl _getdrive(){ wchar_t cwd[MAX_PATH + 1] = { 0 };
DWORD const cwd_length = GetCurrentDirectoryW(MAX_PATH + 1, cwd); if (cwd_length <= MAX_PATH) { return get_drive_number_from_path(cwd); }
// Otherwise, we need more space for the path, so we'll need to dynamically // allocate a buffer: __crt_unique_heap_ptr<wchar_t> const heap_cwd(_calloc_crt_t(wchar_t, cwd_length + 1)); if (heap_cwd.get() == nullptr) { errno = ENOMEM; return 0; }
DWORD const heap_cwd_length = GetCurrentDirectoryW(cwd_length + 1, heap_cwd.get()); if (heap_cwd_length == 0) { errno = ENOMEM; return 0; }
return get_drive_number_from_path(heap_cwd.get());}
// Changes the current drive to the specified drive number. Returns zero on// success; returns -1 and sets errno and _doserrno on failure.extern "C" int __cdecl _chdrive(int const drive_number){ if (drive_number < 1 || drive_number > 26) { _doserrno = ERROR_INVALID_DRIVE; _VALIDATE_RETURN(("Invalid Drive Index", 0), EACCES, -1); }
#pragma warning(suppress:__WARNING_UNUSED_ASSIGNMENT) // 28931 unused assignment of variable drive_letter wchar_t const drive_letter = static_cast<wchar_t>(L'A' + drive_number - 1); wchar_t const drive_string[] = { drive_letter, L':', L'\0' };
if (!SetCurrentDirectoryW(drive_string)) { __acrt_errno_map_os_error(GetLastError()); return -1; }
return 0;}