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• XE7

System.UnicodeString.IsLeadSurrogate

bool IsLeadSurrogate(int index)

Tests whether the element is a lead surrogate.

IsLeadSurrogate returns true if the indexed element is a lead surrogate and false otherwise. Note that index is an element index into the string, not a character or byte index. 

System.UnicodeString.IsTrailSurrogate

bool         IsTrailSurrogate(int index)

Tests whether the element is a trail surrogate.

IsTrailSurrogate returns True if the indexed element is a trail surrogate and False, otherwise. Note that index is an element index into the string, not a character or byte index. 

• c6

IsLeadByte

IsTrailByte

Returns true if the specified byte is a lead byte.

bool __fastcall IsLeadByte(int index) const;

Description

IsLeadByte returns true if the byte indicated by index (counting from 0) is the lead byte in a multi-byte character. If the byte is a trailing byte, or not part of a multi-byte character, IsLeadByte returns false.

Returns true if the specified byte is of type mbTrailByte.

bool __fastcall IsTrailByte(int index) const;

Description

IsTrailByte returns true if the byte indicated by index (counting from 0) is the trailing byte in a multi-byte character. If the byte is a lead byte, or not part of a multi-byte character, IsTrailByte returns false.

System.SysUtils.TMbcsByteType

TMbcsByteType = (mbSingleByte, mbLeadByte, mbTrailByte);

TMbcsByteType represents the use of a single byte in a string that uses a multi-byte character set (MBCS).

TMbcsByteType represents the possible return values of the ByteType and StrByteType functions. Possible values are as follows. 

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原文：http://www.cnblogs.com/cb168/p/4535328.html