reactos/sdk/lib/ucrt/lowio/open.cpp
2025-01-16 14:18:53 +02:00

909 lines
26 KiB
C++

//
// open.cpp
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// Defines _open() and its friends, who are used to open or create files.
//
// These functions are used to open a file.
//
// oflag: The primary file open flags are passed via this parameter. It may
// have a combination of the following flags:
// * _O_APPEND: Reposition file ptr to end before every write
// * _O_BINARY: Open in binary mode
// * _O_CREAT: Create a new file* no effect if file already exists
// * _O_EXCL: Return error if file exists, only use with O_CREAT
// * _O_RDONLY: Open for reading only
// * _O_RDWR: Open for reading and writing
// * _O_TEXT: Open in text mode
// * _O_TRUNC: Open and truncate to 0 length (must have write permission)
// * _O_WRONLY: Open for writing only
// * _O_NOINHERIT: Handle will not be inherited by child processes.
// Exactly one of _O_RDONLY, _O_WRONLY, and _O_RDWR must be present.
//
// shflag: Specifies the sharing options with which the file is to be opened.
// This parameter is only supported by the sharing-enabled open
// functions (_tsopen, _tsopen_s, etc.). The following flags are
// supported:
// * _SH_COMPAT: Set compatability mode
// * _SH_DENYRW: Deny read and write access to the file
// * _SH_DENYWR: Deny write access to the file
// * _SH_DENYRD: Deny read access to the file
// * _SH_DENYNO: Permit read and write access
//
// pmode: The pmode argument is only required when _O_CREAT is specified. Its
// flags are as follows:
// * _S_IWRITE:
// * _S_IREAD:
// These flags may be combined (_S_IWRITE | _S_IREAD) to enable both
// reading and writing. The current file permission mask is applied to
// pmode before setting the permission (see umask).
//
// Functions that return an errno_t return 0 on success and an error code on
// failure. Functions that return an int return the file handle on success, and
// return -1 and set errno on failure.
//
#include <corecrt_internal_lowio.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
namespace
{
DWORD const GENERIC_READ_WRITE = (GENERIC_READ | GENERIC_WRITE);
struct file_options
{
// These are the flags that are used for the osflag of the CRT file
// object that is created.
char crt_flags;
// These are the flags that are eventually passed to CreateFile to tell
// the Operating System how to create the file:
DWORD access;
DWORD create;
DWORD share;
DWORD attributes;
DWORD flags;
};
}
#define UTF16LE_BOM 0xFEFF // UTF16 Little Endian Byte Order Mark
#define UTF16BE_BOM 0xFFFE // UTF16 Big Endian Byte Order Mark
#define BOM_MASK 0xFFFF // Mask for testing Byte Order Mark
#define UTF8_BOM 0xBFBBEF // UTF8 Byte Order Mark
#define UTF16_BOMLEN 2 // No of Bytes in a UTF16 BOM
#define UTF8_BOMLEN 3 // No of Bytes in a UTF8 BOM
template <typename Character>
static int __cdecl common_open(
_In_z_ Character const* const path,
int const oflag,
int const pmode
) throw()
{
typedef __crt_char_traits<Character> traits;
_VALIDATE_RETURN(path != nullptr, EINVAL, -1);
int fh = -1;
int unlock_flag = 0;
errno_t error_code = 0;
__try
{
error_code = traits::tsopen_nolock(&unlock_flag, &fh, path, oflag, _SH_DENYNO, pmode, 0);
}
__finally
{
if (unlock_flag)
{
if (error_code)
{
_osfile(fh) &= ~FOPEN;
}
__acrt_lowio_unlock_fh(fh);
}
}
__endtry
if (error_code != 0)
{
errno = error_code;
return -1;
}
return fh;
}
extern "C" int _open(char const* const path, int const oflag, ...)
{
va_list arglist;
va_start(arglist, oflag);
int const pmode = va_arg(arglist, int);
va_end(arglist);
return common_open(path, oflag, pmode);
}
extern "C" int _wopen(wchar_t const* const path, int const oflag, ...)
{
va_list arglist;
va_start(arglist, oflag);
int const pmode = va_arg(arglist, int);
va_end(arglist);
return common_open(path, oflag, pmode);
}
template <typename Character>
static errno_t __cdecl common_sopen_dispatch(
_In_z_ Character const* const path,
int const oflag,
int const shflag,
int const pmode,
int* const pfh,
int const secure
) throw()
{
typedef __crt_char_traits<Character> traits;
_VALIDATE_RETURN_ERRCODE(pfh != nullptr, EINVAL);
*pfh = -1;
_VALIDATE_RETURN_ERRCODE(path != nullptr, EINVAL);
if(secure)
{
_VALIDATE_RETURN_ERRCODE((pmode & (~(_S_IREAD | _S_IWRITE))) == 0, EINVAL);
}
int unlock_flag = 0;
errno_t error_code = 0;
__try
{
error_code = traits::tsopen_nolock(&unlock_flag, pfh, path, oflag, shflag, pmode, secure);
}
__finally
{
if (unlock_flag)
{
if (error_code)
{
_osfile(*pfh) &= ~FOPEN;
}
__acrt_lowio_unlock_fh(*pfh);
}
}
__endtry
if (error_code != 0)
{
*pfh = -1;
}
return error_code;
}
extern "C" errno_t __cdecl _sopen_dispatch(
char const* const path,
int const oflag,
int const shflag,
int const pmode,
int* const pfh,
int const secure
)
{
return common_sopen_dispatch(path, oflag, shflag, pmode, pfh, secure);
}
extern "C" errno_t __cdecl _wsopen_dispatch(
wchar_t const* const path,
int const oflag,
int const shflag,
int const pmode,
int* const pfh,
int const secure
)
{
return common_sopen_dispatch(path, oflag, shflag, pmode, pfh, secure);
}
static HANDLE __cdecl create_file(
PCWSTR const path,
SECURITY_ATTRIBUTES* const security_attributes,
file_options const options
) throw()
{
return CreateFileW(
path,
options.access,
options.share,
security_attributes,
options.create,
options.flags | options.attributes,
nullptr);
}
static DWORD decode_access_flags(int const oflag) throw()
{
switch (oflag & (_O_RDONLY | _O_WRONLY | _O_RDWR))
{
case _O_RDONLY:
return GENERIC_READ;
case _O_WRONLY:
// If the file is being opened in append mode, we give read access as
// well because in append (a, not a+) mode, we need to read the BOM to
// determine the encoding (ANSI, UTF-8, or UTF-16).
if ((oflag & _O_APPEND) && (oflag & (_O_WTEXT | _O_U16TEXT | _O_U8TEXT)) != 0)
return GENERIC_READ | GENERIC_WRITE;
return GENERIC_WRITE;
case _O_RDWR:
return GENERIC_READ | GENERIC_WRITE;
}
// This is unreachable, but the compiler can't tell.
_VALIDATE_RETURN(("Invalid open flag", 0), EINVAL, static_cast<DWORD>(-1));
return 0;
}
static DWORD decode_open_create_flags(int const oflag) throw()
{
switch (oflag & (_O_CREAT | _O_EXCL | _O_TRUNC))
{
case 0:
case _O_EXCL: // ignore EXCL w/o CREAT
return OPEN_EXISTING;
case _O_CREAT:
return OPEN_ALWAYS;
case _O_CREAT | _O_EXCL:
case _O_CREAT | _O_TRUNC | _O_EXCL:
return CREATE_NEW;
case _O_TRUNC:
case _O_TRUNC | _O_EXCL: // ignore EXCL w/o CREAT
return TRUNCATE_EXISTING;
case _O_CREAT | _O_TRUNC:
return CREATE_ALWAYS;
}
// This is unreachable, but the compiler can't tell.
_VALIDATE_RETURN(("Invalid open flag", 0), EINVAL, static_cast<DWORD>(-1));
return 0;
}
static DWORD decode_sharing_flags(int const shflag, int const access) throw()
{
switch (shflag)
{
case _SH_DENYRW:
return 0;
case _SH_DENYWR:
return FILE_SHARE_READ;
case _SH_DENYRD:
return FILE_SHARE_WRITE;
case _SH_DENYNO:
return FILE_SHARE_READ | FILE_SHARE_WRITE;
case _SH_SECURE:
if (access == GENERIC_READ)
return FILE_SHARE_READ;
else
return 0;
}
_VALIDATE_RETURN(("Invalid sharing flag", 0), EINVAL, static_cast<DWORD>(-1));
return 0;
}
static bool is_text_mode(int const oflag) throw()
{
if (oflag & _O_BINARY)
return false;
if (oflag & (_O_TEXT | _O_WTEXT | _O_U16TEXT | _O_U8TEXT))
return true;
// Finally, check the global default mode:
int fmode;
_ERRCHECK(_get_fmode(&fmode));
if (fmode != _O_BINARY)
return true;
return false;
}
static file_options decode_options(int const oflag, int const shflag, int const pmode) throw()
{
file_options result;
result.crt_flags = 0;
result.access = decode_access_flags(oflag);
result.create = decode_open_create_flags(oflag);
result.share = decode_sharing_flags(shflag, result.access);
result.attributes = FILE_ATTRIBUTE_NORMAL;
result.flags = 0;
if (oflag & _O_NOINHERIT)
{
result.crt_flags |= FNOINHERIT;
}
if (is_text_mode(oflag))
{
result.crt_flags |= FTEXT;
}
if (oflag & _O_CREAT)
{
if (((pmode & ~_umaskval) & _S_IWRITE) == 0)
result.attributes = FILE_ATTRIBUTE_READONLY;
}
if (oflag & _O_TEMPORARY)
{
result.flags |= FILE_FLAG_DELETE_ON_CLOSE;
result.access |= DELETE;
result.share |= FILE_SHARE_DELETE;
}
if (oflag & _O_SHORT_LIVED)
{
result.attributes |= FILE_ATTRIBUTE_TEMPORARY;
}
if (oflag & _O_OBTAIN_DIR)
{
result.flags |= FILE_FLAG_BACKUP_SEMANTICS;
}
if (oflag & _O_SEQUENTIAL)
{
result.flags |= FILE_FLAG_SEQUENTIAL_SCAN;
}
else if (oflag & _O_RANDOM)
{
result.flags |= FILE_FLAG_RANDOM_ACCESS;
}
return result;
}
// If we open a text mode file for writing, and the file ends in Ctrl+Z, we need
// to remove the Ctrl+Z character so that appending will work. We do this by
// seeking to the end of the file, testing if the last character is a Ctrl+Z,
// truncating the file if it is, then rewinding back to the beginning.
static errno_t truncate_ctrl_z_if_present(int const fh) throw()
{
// No truncation is possible for devices and pipes:
if (_osfile(fh) & (FDEV | FPIPE))
return 0;
// No truncation is necessary for binary files:
if ((_osfile(fh) & FTEXT) == 0)
return 0;
// Find the end of the file:
__int64 const last_char_position = _lseeki64_nolock(fh, -1, SEEK_END);
// If the seek failed, either the file is empty or an error occurred.
// (It's not an error if the file is empty.)
if (last_char_position == -1)
{
if (_doserrno == ERROR_NEGATIVE_SEEK)
return 0;
return errno;
}
// Read the last character. If the read succeeds and the character
// is a Ctrl+Z, remove the character from the file by shortening:
wchar_t c = 0;
if (_read_nolock(fh, &c, 1) == 0 && c == 26)
{
if (_chsize_nolock(fh, last_char_position) == -1)
return errno;
}
// Now, rewind the file pointer back to the beginning:
if (_lseeki64_nolock(fh, 0, SEEK_SET) == -1)
return errno;
return 0;
}
// Computes the text mode to be used for a file, using a combination of the
// options passed into the open function and the BOM read from the file.
static errno_t configure_text_mode(
int const fh,
file_options const options,
int oflag,
__crt_lowio_text_mode& text_mode
) throw()
{
// The text mode is ANSI by default:
text_mode = __crt_lowio_text_mode::ansi;
// If the file is open in binary mode, it gets the default text mode:
if ((_osfile(fh) & FTEXT) == 0)
return 0;
// Set the default text mode per the oflag. The BOM may change the default,
// if one is present. If oflag does not specify a text mode, use the _fmode
// default:
DWORD const text_mode_mask = (_O_TEXT | _O_WTEXT | _O_U16TEXT | _O_U8TEXT);
if ((oflag & text_mode_mask) == 0)
{
int fmode = 0;
_ERRCHECK(_get_fmode(&fmode));
if ((fmode & text_mode_mask) == 0)
oflag |= _O_TEXT; // Default to ANSI.
else
oflag |= fmode & text_mode_mask;
}
// Now oflags should be set to one of the text modes:
_ASSERTE((oflag & text_mode_mask) != 0);
switch (oflag & text_mode_mask)
{
case _O_TEXT:
text_mode = __crt_lowio_text_mode::ansi;
break;
case _O_WTEXT:
case _O_WTEXT | _O_TEXT:
if ((oflag & (_O_WRONLY | _O_CREAT | _O_TRUNC)) == (_O_WRONLY | _O_CREAT | _O_TRUNC))
text_mode = __crt_lowio_text_mode::utf16le;
break;
case _O_U16TEXT:
case _O_U16TEXT | _O_TEXT:
text_mode = __crt_lowio_text_mode::utf16le;
break;
case _O_U8TEXT:
case _O_U8TEXT | _O_TEXT:
text_mode = __crt_lowio_text_mode::utf8;
break;
}
// If the file hasn't been opened with the UNICODE flags then we have
// nothing to do: the text mode is the default mode that we just set:
if ((oflag & (_O_WTEXT | _O_U16TEXT | _O_U8TEXT)) == 0)
return 0;
// If this file refers to a device, we cannot check the BOM, so we have
// nothing to do: the text mode is the default mode that we just set:
if ((options.crt_flags & FDEV) != 0)
return 0;
// Determine whether we need to check or write the BOM, by testing the
// access with which the file was opened and whether the file already
// existed or was just created:
int check_bom = 0;
int write_bom = 0;
switch (options.access & GENERIC_READ_WRITE)
{
case GENERIC_READ:
check_bom = 1;
break;
case GENERIC_WRITE:
case GENERIC_READ_WRITE:
switch (options.create)
{
// If this file was opened, we will read the BOM if the file was opened
// with read/write access. We will write the BOM if and only if the
// file is empty:
case OPEN_EXISTING:
case OPEN_ALWAYS:
{
if (_lseeki64_nolock(fh, 0, SEEK_END) != 0)
{
if (_lseeki64_nolock(fh, 0, SEEK_SET) == -1)
return errno;
// If we have read access, then we need to check the BOM. Note
// that we've taken a shortcut here: if the file is empty, then
// we do not set this flag because the file doesn't have a BOM
// to be read.
check_bom = (options.access & GENERIC_READ) != 0;
}
else
{
write_bom = 1;
break;
}
break;
}
// If this is a new or truncated file, then we always write the BOM:
case CREATE_NEW:
case CREATE_ALWAYS:
case TRUNCATE_EXISTING:
{
write_bom = 1;
break;
}
}
break;
}
if (check_bom)
{
int bom = 0;
int const count = _read_nolock(fh, &bom, UTF8_BOMLEN);
// Intrernal validation: This branch should never be taken if write_bom
// is true and count > 0:
if (count > 0 && write_bom == 1)
{
_ASSERTE(0 && "Internal Error");
write_bom = 0;
}
switch (count)
{
case -1:
return errno;
case UTF8_BOMLEN:
if (bom == UTF8_BOM)
{
text_mode = __crt_lowio_text_mode::utf8;
break;
}
case UTF16_BOMLEN:
if((bom & BOM_MASK) == UTF16BE_BOM)
{
_ASSERTE(0 && "Only UTF-16 little endian & UTF-8 is supported for reads");
errno = EINVAL;
return errno;
}
if((bom & BOM_MASK) == UTF16LE_BOM)
{
// We have read three bytes, so we should seek back one byte:
if(_lseeki64_nolock(fh, UTF16_BOMLEN, SEEK_SET) == -1)
return errno;
text_mode = __crt_lowio_text_mode::utf16le;
break;
}
// Fall through to default case to lseek to beginning of file
default:
// The file has no BOM, so we seek back to the beginning:
if (_lseeki64_nolock(fh, 0, SEEK_SET) == -1)
return errno;
break;
}
}
if (write_bom)
{
// If we are creating a new file, we write a UTF-16LE or UTF8 BOM:
int bom_length = 0;
int bom = 0;
switch (text_mode)
{
case __crt_lowio_text_mode::utf16le:
{
bom = UTF16LE_BOM;
bom_length = UTF16_BOMLEN;
break;
}
case __crt_lowio_text_mode::utf8:
{
bom = UTF8_BOM;
bom_length = UTF8_BOMLEN;
break;
}
}
for (int total_written = 0; bom_length > total_written; )
{
char const* const bom_begin = reinterpret_cast<char const*>(&bom);
// Note that the call to write may write less than bom_length
// characters but not really fail. We retry until the write fails
// or we have written all of the characters:
int const written = _write(fh, bom_begin + total_written, bom_length - total_written);
if (written == -1)
return errno;
total_written += written;
}
}
return 0; // Success!
}
extern "C" errno_t __cdecl _wsopen_nolock(
int* const punlock_flag,
int* const pfh,
wchar_t const* const path,
int const oflag,
int const shflag,
int const pmode,
int const secure
)
{
UNREFERENCED_PARAMETER(secure);
// First, do the initial parse of the options. The only thing that can fail
// here is the parsing of the share options, in which case -1 is returned
// and errno is set.
file_options options = decode_options(oflag, shflag, pmode);
if (options.share == static_cast<DWORD>(-1))
{
_doserrno = 0;
*pfh = -1;
return errno;
}
// Allocate the CRT file handle. Note that if a handle is allocated, it is
// locked when it is returned by the allocation function. It is our caller's
// responsibility to unlock the file handle (we do not unlock it before
// returning).
*pfh = _alloc_osfhnd();
if (*pfh == -1)
{
_doserrno = 0;
*pfh = -1;
errno = EMFILE;
return errno;
}
// Beyond this point, do not change *pfh, even if an error occurs. Our
// caller requires the handle in order to release its lock.
*punlock_flag = 1;
SECURITY_ATTRIBUTES security_attributes;
security_attributes.nLength = sizeof(security_attributes);
security_attributes.lpSecurityDescriptor = nullptr;
security_attributes.bInheritHandle = (oflag & _O_NOINHERIT) == 0;
// Try to open or create the file:
HANDLE os_handle = create_file(path, &security_attributes, options);
if (os_handle == INVALID_HANDLE_VALUE)
{
if ((options.access & GENERIC_READ_WRITE) == GENERIC_READ_WRITE && (oflag & _O_WRONLY))
{
// The call may have failed because we may be trying to open
// something for reading that does not allow reading (e.g. a pipe or
// a device). So, we try again with just GENERIC_WRITE. If this
// succeeds, we will have to assume the default encoding because we
// will have no way to read the BOM.
options.access &= ~GENERIC_READ;
os_handle = create_file(path, &security_attributes, options);
}
}
if (os_handle == INVALID_HANDLE_VALUE)
{
// We failed to open the file. We need to free the CRT file handle, but
// we do not release the lock--our caller releases the lock.
_osfile(*pfh) &= ~FOPEN;
__acrt_errno_map_os_error(GetLastError());
return errno;
}
// Find out what type of file this is (e.g., file, device, pipe, etc.)
DWORD const file_type = GetFileType(os_handle);
if (file_type == FILE_TYPE_UNKNOWN)
{
DWORD const last_error = GetLastError();
__acrt_errno_map_os_error(last_error);
_osfile(*pfh) &= ~FOPEN;
CloseHandle(os_handle);
// If GetFileType returns FILE_TYPE_UNKNOWN but doesn't fail, the file
// type really is unknown. This function is not designed to handle
// unknown types of files, so we must return an error.
if (last_error == ERROR_SUCCESS)
errno = EACCES;
return errno;
}
if (file_type == FILE_TYPE_CHAR)
{
options.crt_flags |= FDEV;
}
else if (file_type == FILE_TYPE_PIPE)
{
options.crt_flags |= FPIPE;
}
// The file is open and valid. Set the OS handle:
__acrt_lowio_set_os_handle(*pfh, reinterpret_cast<intptr_t>(os_handle));
// Mark the handle as open, and store the flags we gathered so far:
options.crt_flags |= FOPEN;
_osfile(*pfh) = options.crt_flags;
// The text mode is set to ANSI by default. If we find a BOM, then we will
// reset this to the appropriate type (this check happens below).
_textmode(*pfh) = __crt_lowio_text_mode::ansi;
// If the text mode file is opened for writing and allows reading, remove
// any trailing Ctrl+Z character, if present, to ensure appending works:
if (oflag & _O_RDWR)
{
errno_t const result = truncate_ctrl_z_if_present(*pfh);
if (result != 0)
{
_close_nolock(*pfh);
return result;
}
}
// Configure the text mode:
__crt_lowio_text_mode text_mode = __crt_lowio_text_mode::ansi;
errno_t const text_mode_result = configure_text_mode(*pfh, options, oflag, text_mode);
if (text_mode_result != 0)
{
_close_nolock(*pfh);
return text_mode_result;
}
_textmode(*pfh) = text_mode;
_tm_unicode(*pfh) = (oflag & _O_WTEXT) != 0;
// Set FAPPEND flag if appropriate. Don't do this for devices or pipes:
if ((options.crt_flags & (FDEV | FPIPE)) == 0 && (oflag & _O_APPEND))
_osfile(*pfh) |= FAPPEND;
// Finally, if we were asked only to open the file with write access but we
// opened it with read and write access in order to read the BOM, close the
// file and re-open it with only write access:
if ((options.access & GENERIC_READ_WRITE) == GENERIC_READ_WRITE && (oflag & _O_WRONLY))
{
CloseHandle(os_handle);
options.access &= ~GENERIC_READ;
os_handle = create_file(path, &security_attributes, options);
if (os_handle == INVALID_HANDLE_VALUE)
{
// Note that we can't use the normal close function here because the
// file isn't really open anymore. We need only release the file
// handle by unsetting the FOPEN flag:
__acrt_errno_map_os_error(GetLastError());
_osfile(*pfh) &= ~FOPEN;
_free_osfhnd(*pfh);
return errno;
}
else
{
// We were able to open the file successfully, set the file
// handle in the _ioinfo structure, then we are done. All
// the options.crt_flags should have been set properly already.
_osfhnd(*pfh) = reinterpret_cast<intptr_t>(os_handle);
}
}
return 0; // Success!
}
extern "C" errno_t __cdecl _sopen_nolock(
int* const punlock_flag,
int* const pfh,
char const* const path,
int const oflag,
int const shflag,
int const pmode,
int const secure
)
{
// At this point we know path is not null already
__crt_internal_win32_buffer<wchar_t> wide_path;
errno_t const cvt = __acrt_mbs_to_wcs_cp(path, wide_path, __acrt_get_utf8_acp_compatibility_codepage());
if (cvt != 0) {
return -1;
}
return _wsopen_nolock(punlock_flag, pfh, wide_path.data(), oflag, shflag, pmode, secure);
}
extern "C" int __cdecl _sopen(char const* const path, int const oflag, int const shflag, ...)
{
va_list ap;
va_start(ap, shflag);
int const pmode = va_arg(ap, int);
va_end(ap);
// The last argument is 0 so thta the pmode is not validated in open_s:
int fh = -1;
errno_t const result = _sopen_dispatch(path, oflag, shflag, pmode, &fh, FALSE);
return result ? -1 : fh;
}
extern "C" int __cdecl _wsopen(wchar_t const* const path, int const oflag, int const shflag, ...)
{
va_list ap;
va_start(ap, shflag);
int const pmode = va_arg(ap, int);
va_end(ap);
// The last argument is 0 so thta the pmode is not validated in open_s:
int fh = -1;
errno_t const result = _wsopen_dispatch(path, oflag, shflag, pmode, &fh, FALSE);
return result ? -1 : fh;
}
extern "C" errno_t __cdecl _sopen_s(
int* const pfh,
char const* const path,
int const oflag,
int const shflag,
int const pmode
)
{
// The last argument is 1 so that pmode is validated in open_s:
return _sopen_dispatch(path, oflag, shflag, pmode, pfh, TRUE);
}
extern "C" errno_t __cdecl _wsopen_s(
int* const pfh,
wchar_t const* const path,
int const oflag,
int const shflag,
int const pmode
)
{
// The last argument is 1 so that pmode is validated in open_s:
return _wsopen_dispatch(path, oflag, shflag, pmode, pfh, TRUE);
}