cdb is a fast, reliable, lightweight package for creating and reading constant databases. Its database structure provides several features: * Fast lookups: A successful lookup in a large database normally takes just two disk accesses. An unsuccessful lookup takes only one. * Low overhead: A database uses 2048 bytes, plus 24 bytes per record, plus the space for keys and data. * No random limits: cdb can handle any database up to 4 gigabytes. There are no other restrictions; records don't even have to fit into memory. Databases are stored in a machine-independent format. * Fast atomic database replacement: cdbmake can rewrite an entire database two orders of magnitude faster than other hashing packages. * Fast database dumps: cdbdump prints the contents of a database in cdbmake-compatible format. cdb is designed to be used in mission-critical applications like e-mail. Database replacement is safe against system crashes. Readers don't have to pause during a rewrite. Note for developers: packages that need to read cdb files should incorporate the necessary portions of the cdb library rather than relying on an external cdb library. (See