Some of these directories come from entire outside repositories brought in using git-subtree. This means that the source files are inserted directly into the rippled repository. They can be edited and committed just as if they were normal files.

If you create a commit that contains files both from a subtree, and from the rippled source tree, please use care when designing the commit message, since it will appear in the subtree's individual repository when the changes are pushed back to the upstream. Better yet, do not mix files from subtrees and ripple in the same commit at all.

Source folders:

Folder	Upstream Repo	Description
`beast`	N/A	legacy utility code that was formerly associated with boost::beast
`ed25519-donna`	https://github.com/floodyberry/ed25519-donna	Ed25519 digital signatures
`ripple`	N/A	Core source code for `rippled`
`secp256k1`	https://github.com/bitcoin-core/secp256k1	ECDSA digital signatures using the secp256k1 curve
`test`	N/A	Unit tests for `rippled`

The following dependencies are downloaded and built using ExternalProject (or FetchContent, where possible). Refer to CMakeLists.txt file for details about how these sources are built :

Name	Upstream Repo	Description
`lz4`	https://github.com/lz4/lz4	LZ4 lossless compression algorithm
`nudb`	https://github.com/vinniefalco/NuDB	Constant-time insert-only key/value database for SSD drives (Less memory usage than RocksDB.)
`snappy`	https://github.com/google/snappy	"Snappy" lossless compression algorithm.
`soci`	https://github.com/SOCI/soci	Abstraction layer for database access.
`sqlite`	https://www.sqlite.org/src	An embedded database engine that writes to simple files.
`rocksdb`	https://github.com/facebook/rocksdb	Fast key/value database. (Supports rotational disks better than NuDB.)
`protobuf`	https://github.com/google/protobuf	Protocol buffer data interchange format. Only downloaded/built if a suitable version is not found by find_package, or if the local_protobuf option is explicitly set