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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173//// lseek.cpp//// Copyright (c) Microsoft Corporation. All rights reserved.//// Defines _lseek(), which seeks the file pointer of a file.//#include <corecrt_internal_lowio.h>#include <corecrt_internal_ptd_propagation.h>#include <stdlib.h>
#if SEEK_SET != FILE_BEGIN || SEEK_CUR != FILE_CURRENT || SEEK_END != FILE_END #error Xenix and Win32 seek constants not compatible#endif
// These functions actually seek the underlying operating system file handle.// The logic is different for 32-bit and 64-bit seek values because a seek may// end up moving out of range of 32-bit values.static long __cdecl common_lseek_do_seek_nolock(HANDLE const os_handle, long const offset, int const origin, __crt_cached_ptd_host& ptd) throw(){ LARGE_INTEGER const origin_pos = { 0 };
LARGE_INTEGER saved_pos; if (!SetFilePointerEx(os_handle, origin_pos, &saved_pos, FILE_CURRENT)) { __acrt_errno_map_os_error_ptd(GetLastError(), ptd); return -1; }
LARGE_INTEGER seek_pos = { 0 }; seek_pos.QuadPart = offset;
LARGE_INTEGER new_pos = { 0 }; if (!SetFilePointerEx(os_handle, seek_pos, &new_pos, origin)) { __acrt_errno_map_os_error_ptd(GetLastError(), ptd); return -1; }
// The call succeeded, but the new file pointer location is too large for // the return type or is a negative value. So, restore the file pointer // to the saved location and return an error: if (new_pos.QuadPart > LONG_MAX) { SetFilePointerEx(os_handle, saved_pos, nullptr, FILE_BEGIN); ptd.get_errno().set(EINVAL); return -1; }
return static_cast<long>(new_pos.LowPart);}
static __int64 __cdecl common_lseek_do_seek_nolock(HANDLE const os_handle, __int64 const offset, int const origin, __crt_cached_ptd_host& ptd) throw(){ LARGE_INTEGER new_pos; if (!SetFilePointerEx(os_handle, *reinterpret_cast<LARGE_INTEGER const*>(&offset), &new_pos, origin)) { __acrt_errno_map_os_error_ptd(GetLastError(), ptd); return -1; }
return new_pos.QuadPart;}
template <typename Integer>static Integer __cdecl common_lseek_nolock(int const fh, Integer const offset, int const origin, __crt_cached_ptd_host& ptd) throw(){ HANDLE const os_handle = reinterpret_cast<HANDLE>(_get_osfhandle(fh)); if (os_handle == reinterpret_cast<HANDLE>(-1)) { ptd.get_errno().set(EBADF); _ASSERTE(("Invalid file descriptor",0)); return -1; }
Integer const new_position = common_lseek_do_seek_nolock(os_handle, offset, origin, ptd); if (new_position == -1) { return -1; }
// The call succeeded, so return success: _osfile(fh) &= ~FEOFLAG; // Clear the Ctrl-Z flag return new_position;}
// Moves the file pointer associated with the given file to a new position. The// new position is 'offset' bytes (the offset may be negative) away from the// origin specified by 'origin'.//// If origin == SEEK_SET, the origin in the beginning of file// If origin == SEEK_CUR, the origin is the current file pointer position// If origin == SEEK_END, the origin is the end of the file//// Returns the offset, in bytes, of the new position, from the beginning of the// file. Returns -1 and sets errno on failure. Note that seeking beyond the// end of the file is not an error, but seeking before the beginning is.template <typename Integer>static Integer __cdecl common_lseek(int const fh, Integer const offset, int const origin, __crt_cached_ptd_host& ptd) throw(){ _UCRT_CHECK_FH_CLEAR_OSSERR_RETURN(ptd, fh, EBADF, -1); _UCRT_VALIDATE_CLEAR_OSSERR_RETURN(ptd, fh >= 0 && (unsigned)fh < (unsigned)_nhandle, EBADF, -1); _UCRT_VALIDATE_CLEAR_OSSERR_RETURN(ptd, _osfile(fh) & FOPEN, EBADF, -1);
__acrt_lowio_lock_fh(fh); Integer result = -1; __try { if ((_osfile(fh) & FOPEN) == 0) { ptd.get_errno().set(EBADF); ptd.get_doserrno().set(0); _ASSERTE(("Invalid file descriptor. File possibly closed by a different thread",0)); __leave; }
result = common_lseek_nolock(fh, offset, origin, ptd); } __finally { __acrt_lowio_unlock_fh(fh); } __endtry return result;}
extern "C" long __cdecl _lseek_internal(int const fh, long const offset, int const origin, __crt_cached_ptd_host& ptd){ return common_lseek(fh, offset, origin, ptd);}
extern "C" __int64 __cdecl _lseeki64_internal(int const fh, __int64 const offset, int const origin, __crt_cached_ptd_host& ptd){ return common_lseek(fh, offset, origin, ptd);}
extern "C" long __cdecl _lseek_nolock_internal(int const fh, long const offset, int const origin, __crt_cached_ptd_host& ptd){ return common_lseek_nolock(fh, offset, origin, ptd);}
extern "C" __int64 __cdecl _lseeki64_nolock_internal(int const fh, __int64 const offset, int const origin, __crt_cached_ptd_host& ptd){ return common_lseek_nolock(fh, offset, origin, ptd);}
extern "C" long __cdecl _lseek(int const fh, long const offset, int const origin){ __crt_cached_ptd_host ptd; return common_lseek(fh, offset, origin, ptd);}
extern "C" __int64 __cdecl _lseeki64(int const fh, __int64 const offset, int const origin){ __crt_cached_ptd_host ptd; return common_lseek(fh, offset, origin, ptd);}
extern "C" long __cdecl _lseek_nolock(int const fh, long const offset, int const origin){ __crt_cached_ptd_host ptd; return common_lseek_nolock(fh, offset, origin, ptd);}
extern "C" __int64 __cdecl _lseeki64_nolock(int const fh, __int64 const offset, int const origin){ __crt_cached_ptd_host ptd; return common_lseek_nolock(fh, offset, origin, ptd);}