Get the key at a given index within the KeyMap astMapKey
This function is intended primarily as a means of iterating round all the elements in a KeyMap. For this purpose, the number of entries in the KeyMap should first be found using astMapSize and this function should then be called in a loop, with the index value going from zero to one less than the size of the KeyMap. The index associated with a given entry is determined by the SortBy attribute.
" size-1" , where "
size" is the value returned by the astMapSize function. The returned pointer is guaranteed to remain valid and the string to which it points will not be over-written for a total of 50 successive invocations of this function. After this, the memory containing the string may be re-used, so a copy of the string should be made if it is needed for longer than this.
A NULL pointer will be returned if this function is invoked with the AST error status set, or if it should fail for any reason.