Here is a list of all documented files with brief descriptions:

include
sqfs
block.h	Contains on-disk data structures for data block management
block_processor.h	Contains declarations for the data block processor
block_writer.h	Contains declarations for the sqfs_block_writer_t structure
compressor.h	Contains declarations to everything related to data compression
data_reader.h	Contains declarations for the sqfs_data_reader_t
dir.h	Contains on-disk data structures for the directory table and declarations for the sqfs_dir_writer_t
dir_reader.h	Contains declarations for the sqfs_dir_reader_t
dir_writer.h	Contains declarations for the sqfs_dir_writer_t
error.h	Contains the SQFS_ERROR enumerator
frag_table.h	Contains declarations for the sqfs_frag_table_t data structure
id_table.h	Contains declarations for the sqfs_id_table_t data structure
inode.h	Contains on-disk data structures used for inodes
io.h	Contains the sqfs_file_t interface for abstracting file I/O
meta_reader.h	Contains declarations for the sqfs_meta_reader_t
meta_writer.h	Contains declarations for the sqfs_meta_writer_t
predef.h	Includes forward declarations of data structures, macros and integer types
super.h	Contains on-disk data structures, identifiers and functions for the SquashFS super block
table.h	Contains helper functions for reading or writing tables
xattr.h	Contains on-disk data structures for storing extended attributes
xattr_reader.h	Contains declarations for the sqfs_xattr_reader_t
xattr_writer.h	Contains declarations for the sqfs_xattr_writer_t