FileType Key
Used by GetClassFile to match patterns against various file bytes in a non-compound file.
Registry Entry
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\FileType
{CLSID}
n = offset, cb, mask, value
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offset
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Determines how far from the beginning or end of the file to begin the comparison. If the offset is a negative value, the comparison begins from the end of the file minus the offset value. The offset value is a decimal type unless preceded by "0x".
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cb
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Represents the length in bytes from the beginning to the end of the file. Represents the byte range in the file. The cb value is a decimal unless preceded by "0x".
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mask
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A binary value used for masking, which is performed by using a logical AND operation, and the byte range specified by offset and cb. If this value is omitted, the bytes are set to all ones. This value is always hexadecimal.
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value
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Represents the pattern that must match for a file to be of this file type. The pattern is used to properly identify a known file format from its contents, not by its extension.
Remarks
Entries are used by the GetClassFile function to match patterns against various file bytes in a non-compound file. FileType has CLSID subkeys, each of which has a series of subkeys 0, 1, 2, 3. These values contain patterns that, if one matches, yield the indicated CLSID. For example, a value of "0, 4, FFFFFFFF, ABCD1234" indicates that the first 4 bytes must be ABCD1234, in that order. A value of "-4, 4, FEFEFEFE " indicates that the last four bytes in the file must be FEFEFEFE. If either pattern matches, the CLSID is returned.
The HKEY_LOCAL_MACHINE\SOFTWARE\Classes key corresponds to the HKEY_CLASSES_ROOT key, which was retained for compatibility with earlier versions of COM.
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