This adds codecs for snappy and lz4, and a new nodeobject codec. The
nodeobject codec provides a highly efficient custom compression scheme
for inner nodes, which make up the majority of nodestore databases.
Non inner node objects are compressed using lz4.
The NuDB backend is modified to use the nodeobject codec. This change
is not backward compatible - older NuDB databases cannot be opened or
imported.
This introduces changes in nudb to improve speed, reduce database size,
and enhance correctness. The most significant change is to store hashes
rather than entire keys in the key file. The output of the hash function
is reduced to 48 bits, and stored directly in buckets.
The API is also modified to introduce a Codec parameter allowing for
compression and decompression to be supported in the implementation
itself rather than callers.
THe data file no longer contains a salt, as the salt is applicable
only to the key and log files. This allows a data file to have multiple
key files with different salt values. To distinguish physical files
belonging to the same logical database, a new field UID is introduced.
The UID is a 64-bit random value generated once on creation and stored
in all three files.
Buckets are zero filled to the end of each block, this is a security
measure to prevent unintended contents of memory getting stored to
disk. NuDB offers the varint integer type, this is identical to
the varint described by Google.
* Add varint
* Add Codec template argument
* Add "api" convenience traits
* Store hash in buckets
* istream can throw short read errors
* Support std::uint8_t format in streams
* Make file classes part of the public interface
* Remove buffers pessimization, replace with buffer
* Consolidate creation utility functions to the same header
* Zero fill unused areas of buckets on disk
* More coverage and improvements to the recover test
* Fix file read/write to loop until all bytes processed
* Add verify_fast, faster verify for large databases
The database version number is incremented to 2; older databases can
no longer be opened and should be deleted.
The NuDB database backend is a high performance key/value store presented
as an alternative to RocksDB on Mac and Linux deployments, and the preferred
backend option for Windows deployments. The LevelDB backend is deprecated for
all platforms.
This includes these changes:
* Add Backend::verify API for doing consistency checks
* Add Database::close so caller can catch exceptions
* Improved Timing test for NodeStore creates a simulated workload
