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The 15 smart-contract host functions were registered through `HostFuncWrapper.cpp` and `createWasmImport`, both of which upstream deleted. They are now declared where every other host function is: one `host_functions!` entry each in `crates/xrpl-host-functions`, which generates the trait, the spec table and the wasmi registration, with a body in the engine, a crossing in the cxx bridge, and a `HostContext` method lowering it onto the wire. They share the `host_lib` namespace with the escrow functions, whose host leaves them `Unimplemented`. Wire order and gas are unchanged, so a guest built against the old ABI still links, with two exceptions. `emit_built_txn` and `emit_txn` gain an output region and write the TER there as four little-endian bytes, returning the length. Their old signature returned the TER as the call's result, which the engine reads as a `HostError` when negative: every `tem`, `tef`, `ter` and `tel` code would have stopped the run instead of reaching the contract. `HostContext` decodes what the old wrappers decoded: the account region, the typed value a `set_data_*` call carries, the serialized transaction and the serialized event. A guest that writes those bytes wrongly gets `InvalidParams`, so the deserializers' exceptions are caught at the call rather than by `guarded`, which would report a node fault. Every Rust site that enumerates the ABI is extended: the two literal tables in `generated_abi.rs`, the import list and arity check in `preflight.rs`, the per-function wasm in `budgets.rs`, and the three fake hosts. `MockHostFunctions` gains the 15 methods and the matchers a contract expectation needs. Two `host_calls` tests cover the shapes that are new here: a typed value decoded on its way to the host, and a TER crossing as bytes, including the negative code that motivated the change.
The XRP Ledger
The XRP Ledger is a decentralized cryptographic ledger powered by a network of peer-to-peer nodes. The XRP Ledger uses a novel Byzantine Fault Tolerant consensus algorithm to settle and record transactions in a secure distributed database without a central operator.
XRP
XRP is a public, counterparty-free crypto-asset native to the XRP Ledger, and is designed as a gas token for network services and to bridge different currencies. XRP is traded on the open-market and is available for anyone to access. The XRP Ledger was created in 2012 with a finite supply of 100 billion units of XRP.
xrpld
The server software that powers the XRP Ledger is called xrpld and is available in this repository under the permissive ISC open-source license. The xrpld server software is written primarily in C++ and runs on a variety of platforms. The xrpld server software can run in several modes depending on its configuration.
If you are interested in running an API Server (including a Full History Server), take a look at Clio. (xrpld Reporting Mode has been replaced by Clio.)
Build from Source
- Read the build instructions in
BUILD.md - If you encounter any issues, please open an issue
Key Features of the XRP Ledger
- Censorship-Resistant Transaction Processing: No single party decides which transactions succeed or fail, and no one can "roll back" a transaction after it completes. As long as those who choose to participate in the network keep it healthy, they can settle transactions in seconds.
- Fast, Efficient Consensus Algorithm: The XRP Ledger's consensus algorithm settles transactions in 4 to 5 seconds, processing at a throughput of up to 1500 transactions per second. These properties put XRP at least an order of magnitude ahead of other top digital assets.
- Finite XRP Supply: When the XRP Ledger began, 100 billion XRP were created, and no more XRP will ever be created. The available supply of XRP decreases slowly over time as small amounts are destroyed to pay transaction fees.
- Responsible Software Governance: A team of full-time developers at Ripple & other organizations maintain and continually improve the XRP Ledger's underlying software with contributions from the open-source community. Ripple acts as a steward for the technology and an advocate for its interests.
- Secure, Adaptable Cryptography: The XRP Ledger relies on industry standard digital signature systems like ECDSA (the same scheme used by Bitcoin) but also supports modern, efficient algorithms like Ed25519. The extensible nature of the XRP Ledger's software makes it possible to add and disable algorithms as the state of the art in cryptography advances.
- Modern Features: Features like Escrow, Checks, and Payment Channels support financial applications atop of the XRP Ledger. This toolbox of advanced features comes with safety features like a process for amending the network and separate checks against invariant constraints.
- On-Ledger Decentralized Exchange: In addition to all the features that make XRP useful on its own, the XRP Ledger also has a fully-functional accounting system for tracking and trading obligations denominated in any way users want, and an exchange built into the protocol. The XRP Ledger can settle long, cross-currency payment paths and exchanges of multiple currencies in atomic transactions, bridging gaps of trust with XRP.
Source Code
Here are some good places to start learning the source code:
- Read the markdown files in the source tree:
src/xrpld/**/*.md. - Read the levelization document to get an idea of the internal dependency graph.
- In the big picture, the
mainfunction constructs anApplicationImpobject, which implements theApplicationvirtual interface. Almost every component in the application takes anApplication¶meter in its constructor, typically namedappand stored as a member variableapp_. This allows most components to depend on any other component.
Repository Contents
| Folder | Contents |
|---|---|
./bin |
Scripts and data files for XRPL developers. |
./Builds |
Platform-specific guides for building xrpld. |
./docs |
Source documentation files and doxygen config. |
./cfg |
Example configuration files. |
./src |
Source code. |
./crates |
Rust source code. |
Some of the directories under src are external repositories included using
git-subtree. See those directories' README files for more details.