关于API中的CreateFileA()

[shier]

FUNCTION ulong CreateFileA(ref string lpFileName,ulong
dwDesiredAccess,ulong dwShareMode,ulong dwCreationDisposition,ulong
dwFlagsAndAttributes,ulong hTemplateFile) LIBRARY "kernel32.dll"


哪位用过这个函数，可否写个实例出来，里面的参数，我虽然看了说明，但是不知道该如何写。比如说dwDesiredAccess为ULONG,说明里指出可以是GENERIC_READ或者GENERIC_WRITE，还可以组合使用。但是这也不是ULONG呀，我不知道该怎么写了，直接写肯定报错

[am2000]

FUNCTION ulong CreateFile(ref string lpFileName,ulong dwDesiredAccess,ulong dwShareMode,ref SECURITY_ATTRIBUTES lpSecurityAttributes,ulong dwCreationDisposition,ulong dwFlagsAndAttributes,ulong hTemplateFile) LIBRARY "kernel32.dll" ALIAS FOR "CreateFileA"

[shier]

下面是VB中声明的方法

Private Const GENERIC_WRITE = &H40000000
Private Const OPEN_EXISTING = 3
Private Const FILE_SHARE_READ = &H1
Private Const FILE_SHARE_WRITE = &H2

constant ulong GENERIC_WRITE = &H40000000 在PB中是错误的
我想问的是PB可否声明16进制的常量？如果不能，上面这些16进制转换为ULONG该是什么？

[billxia]

GENERIC_WRITE = 1073741824
OPEN_EXISTING = 3
FILE_SHARE_READ = 1
FILE_SHARE_WRITE = 2

[shier]

虫子你说的没错，我就是这个意思。可是不知道具体数值

[nthb2001]

对啊
不知谁那儿有这个计算或查看的方法

[musicworm]

结构要定义，
你还必须知道GENERIC_READ等参数值的具体数值大小。

[shier]

楼上的兄弟，看来单纯转换进制不好用。调用这个API时报参数错误

[Methodor]

The CreateFile function creates, opens, or truncates a file, pipe, communications resource, disk device, or console. It returns a handle that can be used to access the object. It can also open and return a handle to a directory.

HANDLE CreateFile(

LPCTSTR lpFileName, // address of name of the file
DWORD dwDesiredAccess, // access (read-write) mode
DWORD dwShareMode, // share mode
LPSECURITY_ATTRIBUTES lpSecurityAttributes, // address of security descriptor
DWORD dwCreationDistribution, // how to create
DWORD dwFlagsAndAttributes, // file attributes
HANDLE hTemplateFile // handle of file with attributes to copy
);
Parameters

lpFileName

Points to a null-terminated string that specifies the name of the file, pipe, communications resource, disk device, or console to create, open, or truncate.
If *lpFileName is a path, there is a default string size limit of MAX_PATH characters. This limit is related to how the CreateFile function parses paths.
Windows NT: You can transcend this limit and send in paths longer than MAX_PATH characters by calling the wide (W) version of CreateFile and prepending "\\?\" to the path. The "\\?\" tells the function to turn off path parsing. This lets you use paths that are nearly 32k Unicode characters long. You must use fully-qualified paths with this technique. This also works with UNC names. The "\\?\" is ignored as part of the path. For example, "\\?\C:\myworld\private" is seen as "C:\myworld\private", and "\\?\UNC\tom_1\hotstuff\coolapps" is seen as "\\tom_1\hotstuff\coolapps".

dwDesiredAccess

Specifies the type of access to the file or other object. An application can obtain read access, write access, read-write access, or device query access. You can use the following flag constants to build a value for this parameter. Both GENERIC_READ and GENERIC_WRITE must be set to obtain read-write access:

Value Meaning
0 Allows an application to query device attributes without actually accessing the device.
GENERIC_READ Specifies read access to the file. Data can be read from the file and the file pointer can be moved.
GENERIC_WRITE Specifies write access to the file. Data can be written to the file and the file pointer can be moved.
dwShareMode

Specifies how this file can be shared. This parameter must be some combination of the following values:

Value Meaning
0 Prevents the file from being shared.
FILE_SHARE_READ Other open operations can be performed on the file for read access. If the CreateFile function is opening the client end of a mailslot, this flag is specified.
FILE_SHARE_WRITE Other open operations can be performed on the file for write access.
lpSecurityAttributes

Points to a SECURITY_ATTRIBUTES structure that specifies the security attributes for the file. The file system must support this parameter for it to have an effect.

dwCreationDistribution

Specifies which action to take on files that exist, and which action to take when files do not exist. For more information about this parameter, see the following Remarks section. This parameter must be one of the following values:

Value Meaning
CREATE_NEW Creates a new file. The function fails if the specified file already exists.
CREATE_ALWAYS Creates a new file. The function overwrites the file if it exists.
OPEN_EXISTING Opens the file. The function fails if the file does not exist.
See the "Remarks" section, following, for a discussion of why you should use the OPEN_EXISTING flag if you are using the CreateFile function for a device, including the console.
OPEN_ALWAYS Opens the file, if it exists. If the file does not exist, the function creates the file as if dwCreationDistribution were CREATE_NEW.
TRUNCATE_EXISTING Opens the file. Once opened, the file is truncated so that its size is zero bytes. The calling process must open the file with at least GENERIC_WRITE access. The function fails if the file does not exist.
dwFlagsAndAttributes

Specifies the file attributes and flags for the file.
Any combination of the following attributes is acceptable, except all other file attributes override FILE_ATTRIBUTE_NORMAL.

Attribute Meaning
FILE_ATTRIBUTE_ARCHIVE The file is an archive file. Applications use this attribute to mark files for backup or removal.
FILE_ATTRIBUTE_NORMAL The file has no other attributes set. This attribute is valid only if used alone.
FILE_ATTRIBUTE_HIDDEN The file is hidden. It is not to be included in an ordinary directory listing.
FILE_ATTRIBUTE_READONLY The file is read only. Applications can read the file but cannot write to it or delete it.
FILE_ATTRIBUTE_SYSTEM The file is part of or is used exclusively by the operating system.
Any combination of the following flags is acceptable.

Flag Meaning
FILE_FLAG_WRITE_THROUGH
Instructs the operating system to write through any intermediate cache and go directly to the file. The operating system can still cache write operations, but cannot lazily flush them.
FILE_FLAG_OVERLAPPED
Instructs the operating system to initialize the file, so ReadFile, WriteFile, ConnectNamedPipe, and TransactNamedPipe operations that take a significant amount of time to process return ERROR_IO_PENDING. When the operation is finished, an event is set to the signaled state.
When you specify FILE_FLAG_OVERLAPPED, the ReadFile and WriteFile functions must specify an OVERLAPPED structure. That is, when FILE_FLAG_OVERLAPPED is specified, an application must perform overlapped reading and writing.
When FILE_FLAG_OVERLAPPED is specified, the operating system does not maintain the file pointer. The file position must be passed as part of the lpOverlapped parameter (pointing to an OVERLAPPED structure) to the ReadFile and WriteFile functions.
This flag also enables more than one operation to be performed simultaneously with the handle (a simultaneous read and write operation, for example).
FILE_FLAG_NO_BUFFERING
Instructs the operating system to open the file with no intermediate buffering or caching. This can provide performance gains in some situations. An application must meet certain requirements when working with files opened with FILE_FLAG_NO_BUFFERING:?File access must begin at offsets within the file that are integer multiples of the volume's sector size. ?File access must be for numbers of bytes that are integer multiples of the volume's sector size. For example, if the sector size is 512 bytes, an application can request reads and writes of 512, 1024, or 2048 bytes, but not of 335, 981, or 7171 bytes. ?Buffer addresses for read and write operations must be aligned on addresses in memory that are integer multiples of the volume's sector size. An application can determine a volume's sector size by calling the GetDiskFreeSpace function.
FILE_FLAG_RANDOM_ACCESS
Indicates that the file is accessed randomly. Windows uses this flag to optimize file caching.
FILE_FLAG_SEQUENTIAL_SCAN
Indicates that the file is to be accessed sequentially from beginning to end. Windows uses this flag to optimize file caching. If an application moves the file pointer for random access, optimum caching may not occur; however, correct operation is still guaranteed.
Specifying this flag can increase performance for applications that read large files using sequential access. Performance gains can be even more noticeable for applications that read large files mostly sequentially, but occasionally skip over small ranges of bytes.
FILE_FLAG_DELETE_ON_CLOSE
Indicates that the operating system is to delete the file immediately after all its handles have been closed.
FILE_FLAG_BACKUP_SEMANTICS
Windows NT only: Indicates that the file is being opened or created for a backup or restore operation. The operating system ensures that the calling process overrides file security checks, provided it has the necessary permission to do so. The relevant permissions are SE_BACKUP_NAME and SE_RESTORE_NAME.A Windows NT application can also set this flag to obtain a handle to a directory. A directory handle can be passed to some Win32 functions in place of a file handle.
FILE_FLAG_POSIX_SEMANTICS
Indicates that the file is to be accessed according to POSIX rules. This includes allowing multiple files with names, differing only in case, for file systems that support such naming. Use care when using this option because files created with this flag may not be accessible by applications written for MS-DOS, Windows 3.x, or Windows NT.
If the CreateFile function opens the client side of a named pipe, the dwFlagsAndAttributes parameter can also contain Security Quality of Service information. When the calling application specifies the SECURITY_SQOS_PRESENT flag, the dwFlagsAndAttributes parameter can contain one or more of the following values:

Value Meaning
SECURITY_ANONYMOUS Specifies to impersonate the client at the Anonymous impersonation level.
SECURITY_IDENTIFICATION Specifies to impersonate the client at the Identification impersonation level.
SECURITY_IMPERSONATION Specifies to impersonate the client at the Impersonation impersonation level.
SECURITY_DELEGATION Specifies to impersonate the client at the Delegation impersonation level.
SECURITY_CONTEXT_TRACKING Specifies that the security tracking mode is dynamic. If this flag is not specified, Security Tracking Mode is static.
SECURITY_EFFECTIVE_ONLY Specifies that only the enabled aspects of the client's security context are available to the server. If you do not specify this flag, all aspects of the client's security context are available.This flag allows the client to limit the groups and privileges that a server can use while impersonating the client.
hTemplateFile

Specifies a handle with GENERIC_READ access to a template file. The template file supplies extended attributes for the file being created.

Return Value

If the function succeeds, the return value is an open handle of the specified file. If the specified file exists before the function call and dwCreationDistribution is CREATE_ALWAYS or OPEN_ALWAYS, a call to GetLastError returns ERROR_ALREADY_EXISTS (even though the function has succeeded). If the file does not exist before the call, GetLastError returns zero.
If the function fails, the return value is INVALID_HANDLE_VALUE. To get extended error information, call GetLastError.

Remarks

When creating a new file, the CreateFile function performs the following actions:

?Combines the file attributes and flags specified by dwFlagsAndAttributes with FILE_ATTRIBUTE_ARCHIVE.
?Sets the file length to zero.
?Copies the extended attributes supplied by the template file to the new file if the hTemplateFile parameter is specified.

When opening an existing file, CreateFile performs the following actions:

?Combines the file flags specified by dwFlagsAndAttributes with existing file attributes. CreateFile ignores the file attributes specified by dwFlagsAndAttributes.
?Sets the file length according to the value of dwCreationDistribution.
?Ignores the hTemplateFile parameter.
?Ignores the lpSecurityDescriptor member of the SECURITY_ATTRIBUTES structure if the lpSecurityAttributes parameter is not NULL. The other structure members are valid. The bInheritHandle member is the only way to indicate whether the file handle can be inherited.

If CreateFile opens the client end of a named pipe, the function uses any instance of the named pipe that is in the listening state. The opening process can duplicate the handle as many times as required but, once opened, the named pipe instance cannot be opened by another client. The access specified when a pipe is opened must be compatible with the access specified in the dwOpenMode parameter of the CreateNamedPipe function. For more information about pipes, see Pipes.

If CreateFile opens the client end of a mailslot, the function always returns a valid handle, even if the mailslot does not exist. In other words, there is no relationship between opening the client end and opening the server end of the mailslot. For more information about mailslots, see Mailslots.
CreateFile can create a handle to a communications resource, such as the serial port COM1. For communications resources, the dwCreationDistribution parameter must be OPEN_EXISTING, and the hTemplate parameter must be NULL. Read, write, or read-write access can be specified, and the handle can be opened for overlapped I/O.

CreateFile can create a handle to console input (CONIN$). If the process has an open handle to it as a result of inheritance or duplication, it can also create a handle to the active screen buffer (CONOUT$).
The calling process must be attached to an inherited console or one allocated by the AllocConsole function. For console handles, set the CreateFile parameters as follows:

Parameter Value
lpFileName Use the CONIN$ value to specify console input and the CONOUT$ value to specify console output.
CONIN$ gets a handle of the console's input buffer, even if the SetStdHandle function redirected the standard input handle. To get the standard input handle, use the GetStdHandle function.
CONOUT$ gets a handle of the active screen buffer, even if SetStdHandle redirected the standard output handle. To get the standard output handle, use GetStdHandle.
dwDesiredAccess GENERIC_READ | GENERIC_WRITE is preferred, but either one can limit access.
dwShareMode If the calling process inherited the console or if a child process should be able to access the console, this parameter must be FILE_SHARE_READ | FILE_SHARE_WRITE.
lpSecurityAttributes If you want the console to be inherited, the bInheritHandle member of the SECURITY_ATTRIBUTES structure must be TRUE.
dwCreationDistribution The user should specify OPEN_EXISTING when using CreateFile to open the console.
dwFlagsAndAttributes Ignored.
hTemplateFile Ignored.
The following list shows the effects of various settings of fwdAccess and lpFileName.

lpFileName fwdAccess Result
CON GENERIC_READ Opens console for input.
CON GENERIC_WRITE Opens console for output.
CON GENERIC_READGENERIC_WRITE Causes CreateFile to fail, returning an error of ERROR_PATH_NOT_FOUND.
You can use the CreateFile function to open a disk drive or a partition on a disk drive. The function returns a handle to the disk device; that handle can be used with the DeviceIOControl function. The following requirements must be met in order for such a call to succeed:

?The caller must have administrative privileges for the operation to succeed on a hard disk drive.
?The lpFileName string should be of the form \\.\PHYSICALDRIVEx to open the hard disk x. Hard disk numbers start at zero. For example:

String Meaning
\\.\PHYSICALDRIVE2 Obtains a handle to the third physical drive on the user's computer.
?The lpFileName string should be \\.\x: to open a floppy drive x or a partition x on a hard disk. For example:

String Meaning
\\.\A: Obtains a handle to drive A on the user's computer.
\\.\C: Obtains a handle to drive C on the user's computer.
Windows 95: This technique does not work for opening a logical drive. In Windows 95, specifying a string in this form causes
CreateFile to return an error.

?The dwCreationDistribution parameter must have the OPEN_EXISTING value.
?When opening a floppy disk or a partition on a hard disk, you must set the FILE_SHARE_WRITE flag in the dwShareMode parameter.

The CloseHandle function is used to close a handle returned by CreateFile.
As noted above, specifying zero for dwDesiredAccess allows an application to query device attributes without actually accessing the device. This type of querying is useful, for example, if an application wants to determine the size of a floppy disk drive and the formats it supports without having a floppy in the drive.
As previously noted, if an application opens a file with FILE_FLAG_NO_BUFFERING set, buffer addresses for read and write operations must be aligned on memory addresses that are integer multiples of the volume's sector size. One way to do this is to use VirtualAlloc to allocate the buffer. The VirtualAlloc function allocates memory that is aligned on addresses that are integer multiples of the operating system's memory page size. Since both memory page and volume sector sizes are powers of 2, and memory pages are larger than volume sectors, this memory is also aligned on addresses that are integer multiples of a volume's sector size.

An application cannot create a directory with CreateFile; it must call CreateDirectory or CreateDirectoryEx to create a directory.

Windows NT:

You can obtain a handle to a directory by setting the FILE_FLAG_BACKUP_SEMANTICS flag. A directory handle can be passed to some Win32 functions in place of a file handle.
Some file systems, such as NTFS, support compression for individual files and directories. On volumes formatted for such a file system, a new directory inherits the compression attribute of its parent directory.