CString is based on the TCHAR data type. If the symbol
_UNICODE is defined for your program, TCHAR is defined as type
wchar_t, a 16-bit character type; otherwise, it is defined as
char, the normal 8-bit character type. Under Unicode, then,
CString objects are composed of 16-bit characters. Without Unicode, they
are composed of 8-bit char type.
When not using _UNICODE, CString is enabled for multibyte
character sets (MBCS, also known as double-byte character sets, DBCS). Note that
for MBCS strings, CString still counts, returns, and manipulates strings
based on 8-bit characters, and your application must interpret MBCS lead and
trail bytes itself.
CString objects also have the following characteristics:
(1)CString objects can grow as a result of concatenation(串联) operations.
(2)CString objects follow “value semantics.” Think of a CString
object as an actual string, not as a pointer to a string.
(3)You can freely substitute(替换) CString objects for const char* and
LPCTSTR function arguments.
(4)A conversion operator gives direct access to the string’s characters as a
read-only array of characters (a C-style string).
Tip Where possible, allocate CString objects on the frame
rather than on the heap. This saves memory and simplifies parameter passing.
CString assists you in conserving memory space by allowing two strings
sharing the same value also to share the same buffer space. However, if you
attempt to change the contents of the buffer directly (not using MFC), you can
alter both strings unintentionally. CString provides two member
functions, CString::LockBuffer
and CString::UnlockBuffer, to
help you protect your data. When you call LockBuffer, you create a copy
of a string, then set the reference count to -1, which "locks" the buffer. While
the buffer is locked, no other string can reference the data in that string, and
the locked string will not reference another string. By locking the string in
the buffer, you ensure that the string’s exclusive hold on the data will remain
intact. When you have finished with the data, call UnlockBuffer to reset
the reference count to 1.
详细介绍见MSDN。。。。。 呵呵。
C++自己实现的CString类：