NAME
        ObtainDataTypeA - Examines a handle and return its datatype.
                                                               (V39)
   SYNOPSIS
        dtn = ObtainDataTypeA (type, handle, attrs);
        d0                      d0    a0      a1

        struct datatype *obtaindatatypea (ulong, aptr, struct tagitem *);

        dtn = ObtainDataType (type, handle, tag1, ...);

        struct datatype *obtaindatatype (ulong, aptr, tag tag1, ...);

   FUNCTION
        This function examines the data that the handle points to,
        and returns a datatype record that describes the data.

   INPUTS
        type - Type of handle.

        handle - Handle to examine.
            For DTST_FILE, handle must be bptr lock.
            For DTST_CLIPBOARD, handle must be struct iffhandle *.
            For DTST_MEMORY, handle will be ignored (you need
            to specify the additional information required by this
            source type through the attrs list).

        attrs - Additional attributes (see TAGS).

   TAGS
        DTA_SourceAddress (APTR) -- For DTST_MEMORY source data, this
            specifies the memory address at which the source data is
            located. This must be non-NULL. This attribute is required
            for DTST_MEMORY source data (V44).

        DTA_SourceSize (ULONG) -- For DTST_MEMORY source data, this
            specifies the size of the source data (in bytes). This must
            be greater than 0. This attribute is required for DTST_MEMORY
            source data (V44).

   NOTES
        The datatypes.library maintains a sorted list of all the
        datatype descriptors.  the descriptor can consist of a
        function, a data mask for the first 64 bytes of the data,
        and a name pattern.

        The sort order for the list is:

            Descriptors with a function and no mask or name pattern.
            Descriptors with a function and a mask or name pattern.
            Descriptors with no function and a mask or name pattern.

        Within each group, they are also sorted in descending priority
        and descending mask length.

        The DTST_MEMORY source type introduced in V44 makes in-memory
        data available to subclasses as if the data were stored in a
        file. Thus, subclasses will see the data as DTST_FILE. Since
        the data does not correspond to an on-disk file, subclasses
        and examine hook code must not assume that they will be able
        to reopen the "file" whose data has been provided to them.

   RETURNS
        Success returns a pointer to a datatype.  you must call
        FreeDataType() when you are done with the handle.

        A NULL return indicates failure.  Use ioerr() to get error value.
        Following is a summary of the error number used and there meaning
        as it relates to DataTypes.

        ERROR_NO_FREE_STORE - Not enough memory.
        ERROR_OBJECT_NOT_FOUND - Unable to open the data object.
        ERROR_NOT_IMPLEMENTED - Unknown handle type.

   SEE ALSO
        FreeDataType()