请问REG_SZ型注册表值项的最大长度是多少？

[sdcer]

如题，在做一个注册表程序，但不知道这种类型的最大长度是多少，所以分配缓冲区比较麻烦。


谢谢各位。经过测试，没有发现这种类型的最长值。

[liufeng24]

最好用1024

[DentistryDoctor]

一般来说键值的长度你事先大概已经知道了吧。

[superhandsome]

双字节够了吧

[w100]

REG_BINARY Binary data in any form.
REG_DWORD A 32-bit number.
REG_DWORD_LITTLE_ENDIAN A 32-bit number in little-endian format. This is equivalent to REG_DWORD.
In little-endian format, a multi-byte value is stored in memory from the lowest byte (the "little end") to the highest byte. For example, the value 0x12345678 is stored as (0x78 0x56 0x34 0x12) in little-endian format.

Windows NT/Windows 2000, Windows 95, and Windows 98 are designed to run on little-endian computer architectures. A user may connect to computers that have big-endian architectures, such as some UNIX systems.

REG_DWORD_BIG_ENDIAN A 32-bit number in big-endian format.
In big-endian format, a multi-byte value is stored in memory from the highest byte (the "big end") to the lowest byte. For example, the value 0x12345678 is stored as (0x12 0x34 0x56 0x78) in big-endian format.
msdn中定义：
REG_EXPAND_SZ A null-terminated string that contains unexpanded references to environment variables (for example, "%PATH%"). It will be a Unicode or ANSI string depending on whether you use the Unicode or ANSI functions. To expand the environment variable references, use the ExpandEnvironmentStrings function.
REG_LINK A Unicode symbolic link. Used internally; applications should not use this type.
REG_MULTI_SZ An array of null-terminated strings, terminated by two null characters.
REG_NONE No defined value type.
REG_QWORD A 64-bit number.
REG_QWORD_LITTLE_ENDIAN A 64-bit number in little-endian format. This is equivalent to REG_QWORD.
REG_RESOURCE_LIST A device-driver resource list.
REG_SZ A null-terminated string. It will be a Unicode or ANSI string, depending on whether you use the Unicode or ANSI functions.
Winnt.h中的定义：
#define REG_NONE ( 0 ) // No value type
#define REG_SZ ( 1 ) // Unicode nul terminated string
#define REG_EXPAND_SZ ( 2 ) // Unicode nul terminated string
// (with environment variable references)
#define REG_BINARY ( 3 ) // Free form binary
#define REG_DWORD ( 4 ) // 32-bit number
#define REG_DWORD_LITTLE_ENDIAN ( 4 ) // 32-bit number (same as REG_DWORD)
#define REG_DWORD_BIG_ENDIAN ( 5 ) // 32-bit number
#define REG_LINK ( 6 ) // Symbolic Link (unicode)
#define REG_MULTI_SZ ( 7 ) // Multiple Unicode strings
#define REG_RESOURCE_LIST ( 8 ) // Resource list in the resource map
#define REG_FULL_RESOURCE_DESCRIPTOR ( 9 ) // Resource list in the hardware description
#define REG_RESOURCE_REQUIREMENTS_LIST ( 10 )

[sdcer]

长度事先是知道的，

但假如你想将这个值通过网络传递给另一方，那另一方不知道数据的长度，所以，它的接收缓冲区就没法分配。

[sdcer]

说了半天谁也没告诉我，到底REG_SZ型键值的最大长度到底是多少。!!!??

[hc_z]

Remarks
Value lengths are limited by available memory. Long values (more than 2048 bytes) should be stored as files with the file names stored in the registry. This helps the registry perform efficiently. Application elements such as icons, bitmaps, and executable files should be stored as files and not be placed in the registry.

The key identified by the hKey parameter must have been opened with KEY_SET_VALUE access. To open the key, use the RegCreateKeyEx or RegOpenKeyEx function.

If dwType is the REG_SZ, REG_MULTI_SZ, or REG_EXPAND_SZ type and the ANSI version of this function is used (either by explicitly calling RegSetValueExA or by not defining UNICODE before including the Windows.h file), the data pointed to by the lpData parameter must be an ANSI character string. The string is converted to Unicode before it is stored in the registry.

Windows 95/98/Me: The maximum size of a single registry value is 16,300 bytes. This limit includes the size of the data (cbData) and the size of the value name (lpValueName).

Windows 95/98/Me: There is a 64K limit for the total size of all values of a key.

Windows 95/98/Me: RegSetValueExW is supported by the Microsoft Layer for Unicode. To use this, you must add certain files to your application, as outlined in Microsoft Layer for Unicode on Windows 95/98/Me Systems.