If the provided buffer is NULL, only the size of buffer needed is returned through nalloc.
IN: The size of the allocated buffer OUT: The size of the buffer needed
Given the data space ID, H5S_ENCODE converts a data space description into binary form in a buffer. Using this binary form in the buffer, a data space object can be reconstructed using H5S_DECODE to return a new object handle(hid_t) for this data space.
A preliminary H5S_ENCODE call can be made to find out the size of the buffer needed. This value is returned as nalloc. That value can then be assigned to nalloc for a second H5S_ENCODE call, which will retrieve the actual encoded object.
If the library finds out nalloc is not big enough for the object, it simply returns the size of the buffer needed through nalloc without encoding the provided buffer.
The types of data space we address in this function are null, scalar, and simple space. For simple data space, the information of selection, for example, hyperslab selection, is also encoded and decoded. Complex data space has not been implemented in the library.
Returns a non-negative value if successful; otherwise returns a negative value.