Here are the data structures with brief descriptions:

CbbOverlappingEntries_t	Holds interval:str associations
CbigWigFile_t	A structure that holds everything needed to access a bigWig file
CbigWigHdr_t	The header section of a bigWig file
CbwDataHeader_t	The header section of a given data block
CbwOverlapBlock_t	This structure holds the data blocks that overlap a given interval
CbwOverlapIterator_t	A structure to hold iterations One of intervals and entries should be used to access records from bigWig or bigBed files, respectively
CbwOverlappingIntervals_t	Holds interval:value associations
CbwRTree_t
CbwRTreeNode_t	A node within an R-tree holding the index for data
CbwWriteBuffer_t	This is only needed for writing bigWig files (and won't be created otherwise) This should be removed from bigWig.h
CbwZoomHdr_t	BigWig files have multiple "zoom" levels, each of which has its own header. This hold those headers
CchromList_t	Holds the chromosomes and their lengths
CURL_t	This structure holds the file pointers and buffers needed for raw access to local and remote files