Introduction

≈60 min · Intermediate · builds on The Application layer

A million lines of C++ can feel intimidating, until you know the map. In this module you'll learn to find your way around the modern rippled tree (include/xrpl, src/libxrpl, src/xrpld), decode the naming conventions that are everywhere in the code (ST*, SLE, sf*, keylet, TER…), and use a few grep strategies to trace any feature end to end. Get comfortable here and the rest of the bootcamp becomes reading, not searching.

Directory Structure Overview

In brief: the three source roots and what lives in each (include/xrpl, src/libxrpl, src/xrpld).

Top-Level Organization

The rippled top-level layout: include/xrpl (root 1, public headers), src/libxrpl (root 2, library implementation), src/xrpld (root 3, the daemon), src/test, plus bin, cfg, cmake, conan, docs, external and CMakeLists.txt

The source tree: three roots

Modern rippled no longer keeps everything under a single src/ tree. The code is now split across three roots:

include/xrpl, public headers of the reusable libxrpl library (protocol, ledger data structures, crypto, basics, JobQueue interface, etc.).
src/libxrpl, the implementation (.cpp) of that library, plus the transaction processing engine (src/libxrpl/tx).
src/xrpld, the daemon: everything specific to running a node (application layer, overlay/P2P, consensus glue, RPC handlers, node storage daemon side).

Private implementation files that used to sit in an impl/ subfolder now live in a detail/ subfolder.

Key Directories by Function

Transaction Processing:

src/libxrpl/tx/transactors - All transactor implementations (grouped by family)
include/xrpl/tx/Transactor.h + src/libxrpl/tx/Transactor.cpp - Base transactor
src/libxrpl/protocol/TxFormats.cpp - Transaction type definitions

Consensus:

src/xrpld/consensus - Generic consensus framework
src/xrpld/app/consensus - XRPL-specific consensus (RCLConsensus, RCLValidations)

Networking:

src/xrpld/overlay - P2P overlay network (detail/ holds the implementation)
include/xrpl/beast + src/libxrpl/beast - Low-level networking (HTTP, WebSocket)

Ledger Management:

src/xrpld/app/ledger - Ledger operations
include/xrpl/ledger - Ledger data structures (ReadView, ApplyView…)
include/xrpl/shamap + src/libxrpl/shamap - Merkle tree implementation

Storage:

include/xrpl/nodestore + src/libxrpl/nodestore - Key-value storage backend

RPC:

src/xrpld/rpc/handlers - RPC command implementations
src/xrpld/rpc - RPC infrastructure

Application Core:

src/xrpld/app/main - Application initialization
src/xrpld/core/Config.h - Configuration; include/xrpl/core/JobQueue.h - JobQueue

Naming Conventions

In brief: decode the prefixes you will see everywhere (ST, SLE, sf, tt, keylet, TER).

Common Prefixes and Abbreviations

Understanding naming conventions is essential for quickly identifying what a class or type represents:

ST* Classes (Serialized Types)

Classes representing serializable protocol objects:

STTx - Serialized Transaction

// Represents a transaction
class STTx : public STObject
{
    TransactionType getTransactionType() const;
    AccountID getAccountID(SField const& field) const;
    STAmount getFieldAmount(SField const& field) const;
};

STObject - Serialized Object (base class)

// Base for all serialized objects
class STObject
{
    void add(Serializer& s) const;
    Json::Value getJson(JsonOptions options) const;
};

STAmount - Serialized Amount

// Represents XRP or issued currency amount
class STAmount
{
    bool isXRP() const;
    Issue const& issue() const;
    std::int64_t mantissa() const;
};

STValidation - Serialized Validation

// Validator signature on a ledger
class STValidation
{
    uint256 getLedgerHash() const;
    std::uint32_t getLedgerSeq() const;
};

STArray - Serialized Array

// Array of STObjects
class STArray : public STBase
{
    std::size_t size() const;
    STObject const& operator[](std::size_t i) const;
};

SLE - Serialized Ledger Entry

Represents an object stored in the ledger:

// An entry in the ledger state
class SLE
{
    LedgerEntryType getType() const;
    Keylet const& key() const;
    
    // Field accessors
    STAmount const& getFieldAmount(SField const& field) const;
    AccountID getAccountID(SField const& field) const;
};

Common SLE Types:

Account (AccountRoot)
Offer
RippleState (Trust Line)
SignerList
PayChannel
Escrow
NFToken

TER - Transaction Engine Result

Result codes from transaction processing:

// Result code enumeration
enum TER : int
{
    // Success
    tesSUCCESS = 0,
    
    // Malformed (tem)
    temMALFORMED = -299,
    temBAD_FEE = -298,
    temBAD_SIGNATURE = -297,
    
    // Failure (tef)
    tefFAILURE = -199,
    tefPAST_SEQ = -198,
    
    // Retry (ter)
    terRETRY = -99,
    terQUEUED = -89,
    
    // Claimed fee (tec) — note: tec codes are positive (>= 100)
    tecCLAIM = 100,
    tecUNFUNDED_PAYMENT = 104,
    tecNO_TARGET = 138,
};

Categories:

tes* - Success
tem* - Malformed (permanent failure)
tef* - Failure (local, temporary)
ter* - Retry (waiting for condition)
tec* - Claimed fee (failed but fee charged)

SF* - Serialized Field

Field identifiers for serialized data:

// Field definitions
extern SField const sfAccount;
extern SField const sfDestination;
extern SField const sfAmount;
extern SField const sfFee;
extern SField const sfSequence;
extern SField const sfSigningPubKey;
extern SField const sfTxnSignature;

Naming Pattern: sf + CamelCase field name

Other Common Prefixes

LedgerEntryType - Types of ledger objects

enum LedgerEntryType
{
    ltACCOUNT_ROOT = 'a',
    ltOFFER = 'o',
    ltRIPPLE_STATE = 'r',
    ltESCROW = 'u',
    ltPAYCHAN = 'x',
};

Keylet - Keys for accessing ledger objects

// Factory functions for creating keylets
Keylet account(AccountID const& id);
Keylet offer(AccountID const& id, std::uint32_t seq);
Keylet escrow(AccountID const& src, std::uint32_t seq);

RPC* - RPC-related classes

class RPCHandler;
class RPCContext;

Key idea. The prefixes are your map. Once sf (serialized field), SLE (serialized ledger entry) and keylet (an entry's key) are second nature, most of the code reads itself.

Code Patterns and Idioms

In brief: the recurring C++ patterns (keylets, views, optional fields, RAII) that show up in every file.

Pattern 1: Keylet Access

Keylets are the standard way to access ledger objects:

// Create keylet for account
AccountID const accountID = ...;
Keylet const k = keylet::account(accountID);

// Read from ledger (immutable)
auto const sle = view.read(k);
if (!sle)
    return terNO_ACCOUNT;

// Access fields
auto const balance = (*sle)[sfBalance];
auto const sequence = (*sle)[sfSequence];

Common Keylet Functions:

// In include/xrpl/protocol/Indexes.h
namespace keylet {
    Keylet account(AccountID const& id);
    Keylet offer(AccountID const& id, std::uint32_t seq);
    Keylet line(AccountID const& id1, AccountID const& id2, Currency const& currency);
    Keylet escrow(AccountID const& src, std::uint32_t seq);
    Keylet payChan(AccountID const& src, AccountID const& dst, std::uint32_t seq);
}

Pattern 2: View Abstraction

Views provide read/write access to ledger state:

Read-Only View:

void analyzeAccount(ReadView const& view, AccountID const& id)
{
    // Can only read, cannot modify
    auto const sle = view.read(keylet::account(id));
    
    // Safe for concurrent access
    auto balance = (*sle)[sfBalance];
}

Modifiable View:

TER modifyAccount(ApplyView& view, AccountID const& id)
{
    // Can read and modify
    auto sle = view.peek(keylet::account(id));
    if (!sle)
        return terNO_ACCOUNT;
    
    // Modify
    (*sle)[sfBalance] = newBalance;
    (*sle)[sfSequence] = (*sle)[sfSequence] + 1;
    
    // Commit changes
    view.update(sle);
    
    return tesSUCCESS;
}

View Types:

ReadView - Read-only access
ApplyView - Read/write for transaction application
OpenView - Open ledger view
PaymentSandbox - Sandboxed view for payments

Pattern 3: Field Access with Optional

Many fields are optional, use ~ operator:

// Required field (asserts if missing)
auto const account = tx[sfAccount];

// Optional field (returns std::optional)
auto const destTag = tx[~sfDestinationTag];

if (destTag)
    useDestinationTag(*destTag);

// Optional with default
auto const flags = tx[~sfFlags].value_or(0);

Pattern 4: RAII and Smart Pointers

Extensive use of RAII and smart pointers:

// Unique ownership
std::unique_ptr<LedgerMaster> ledgerMaster_;

// Shared ownership
std::shared_ptr<Ledger const> ledger = getLedger();

// Weak references
std::weak_ptr<Peer> weakPeer_;

Pattern 5: Application Reference Pattern

Most components hold an Application reference:

class SomeComponent
{
public:
    SomeComponent(Application& app)
        : app_(app)
        , j_(app.journal("SomeComponent"))
    {
    }
    
    void doWork()
    {
        // Access other components via app_
        auto& ledgerMaster = app_.getLedgerMaster();
        auto& overlay = app_.overlay();
    }
    
private:
    Application& app_;
    beast::Journal j_;
};

Finding Functionality

In brief: practical strategies to trace any feature: grep, follow the types, start from entry points.

Strategy 1: Grep and Search

Command-line searching is often the fastest way:

Find where a function is defined:

# Find definition of a function
grep -r "void processTransaction" src/

# Find class definition
grep -r "class NetworkOPs" src/

Find where a variable is used:

# Find all uses of a variable
grep -r "ledgerMaster_" src/xrpld/app/

# Case-insensitive search
grep -ri "transaction" src/libxrpl/tx/

Find specific transaction type:

# Find Payment transactor
grep -r "class Payment" src/libxrpl/tx/transactors/

# Find all transactor implementations
ls src/libxrpl/tx/transactors/*.cpp

Find RPC command handler:

# Find account_info handler
grep -r "doAccountInfo" src/xrpld/rpc/handlers/

Strategy 2: Follow the Types

Use type information to navigate:

Example: Finding where STTx is used

# Find STTx usage
grep -r "STTx" src/ | grep -v ".h:" | head -20

# Find function taking STTx parameter
grep -r "STTx const&" src/

Example: Finding transaction submission

# Find where transactions are submitted
grep -r "submitTransaction" src/

# Follow to NetworkOPs
cat include/xrpl/server/NetworkOPs.h | grep submitTransaction

Strategy 3: Start from Entry Points

Entry Points:

main() - src/xrpld/app/main/Main.cpp
RPC handlers - src/xrpld/rpc/handlers/*.cpp
Transaction types - src/libxrpl/tx/transactors/*.cpp
Protocol messages - src/xrpld/overlay/detail/ProtocolMessage.h

Example: Tracing RPC Call

1. Client calls "account_info" RPC
2. Find handler: src/xrpld/rpc/handlers/account/AccountInfo.cpp
3. Handler function: doAccountInfo()
4. Calls: view.read(keylet::account(accountID))
5. View implementation: include/xrpl/ledger/ReadView.h

Strategy 4: Use IDE Features

Modern IDEs provide powerful navigation:

Visual Studio Code:

Ctrl/Cmd + Click - Go to definition
F12 - Go to definition
Shift + F12 - Find all references
Ctrl/Cmd + T - Go to symbol
Ctrl/Cmd + P - Quick file open

CLion:

Ctrl + B - Go to declaration
Ctrl + Alt + B - Go to implementation
Alt + F7 - Find usages
Ctrl + N - Go to class
Ctrl + Shift + N - Go to file

XCode:

Cmd + Click - Go to definition
Ctrl + 1 - Show related items
Cmd + Shift + O - Open quickly
Cmd + Shift + F - Find in project

Understanding File Organization

Transaction Files

Format: src/libxrpl/tx/transactors/<family>/<TransactionType>.cpp. Since 3.x the file names match the TransactionType exactly and are grouped by family:

payment/Payment.cpp        - Payment transactions
dex/OfferCreate.cpp        - Offer creation
dex/OfferCancel.cpp        - Offer cancellation
token/TrustSet.cpp         - Trust line creation/modification
account/AccountSet.cpp     - Account settings
escrow/EscrowCreate.cpp    - Escrow operations (Finish/Cancel alongside)
payment_channel/           - Payment channels
account/SignerListSet.cpp  - Multi-signature configuration

Finding Transaction Implementation:

# If you know the transaction type
ls src/libxrpl/tx/transactors/ | grep -i payment

# List all transaction implementations
ls src/libxrpl/tx/transactors/*.cpp

RPC Handler Files

Format: src/xrpld/rpc/handlers/<CommandName>.cpp

AccountInfo.cpp      - account_info command
AccountLines.cpp     - account_lines command
AccountTx.cpp        - account_tx command
Tx.cpp               - tx command
Submit.cpp           - submit command
LedgerCurrent.cpp    - ledger_current command
ServerInfo.cpp       - server_info command

Finding RPC Handler:

# Find specific handler
ls src/xrpld/rpc/handlers/ | grep -i account

# Find handler function
grep -r "doAccountInfo" src/xrpld/rpc/handlers/

Header vs Implementation

Header Files (.h):

Class declarations
Function prototypes
Template definitions
Inline functions

Implementation Files (.cpp):

Function implementations
Static variables
Template specializations

Finding Pattern:

# Find header
find src/ -name "NetworkOPs.h"

# Find implementation
find src/ -name "NetworkOPs.cpp"

Reading and Understanding Code

Step 1: Start with the Interface

Always read the header file first:

// In LedgerMaster.h
class LedgerMaster
{
public:
    // Public interface - what can be called
    std::shared_ptr<Ledger const> getValidatedLedger();
    std::shared_ptr<Ledger const> getClosedLedger();
    
    void addValidatedLedger(std::shared_ptr<Ledger const> const& ledger);
    
    // ...
    
private:
    // Implementation details - how it works
    std::shared_ptr<Ledger> mCurrentLedger;
    std::shared_ptr<Ledger> mClosedLedger;
    
    // ...
};

What to Look For:

Public methods (API)
Constructor parameters (dependencies)
Member variables (state)
Comments and documentation

Step 2: Trace Data Flow

Follow how data flows through functions:

// Example: Following a payment
void NetworkOPs::submitTransaction(STTx const& tx)
{
    // 1. Initial validation
    auto const result = checkTransaction(tx);
    if (!isTesSuccess(result))
        return;
    
    // 2. Apply to open ledger
    app_.openLedger().modify([&](OpenView& view)
    {
        return Transactor::apply(app_, view, tx);  // → Go here
    });
    
    // 3. Broadcast
    app_.overlay().relay(tx);  // → And here
}

Step 3: Understand Control Flow

Identify key decision points:

TER Payment::doApply()
{
    // Key decision: XRP or issued currency?
    if (isXRP(amount_))
    {
        // XRP path
        return payXRP();
    }
    else
    {
        // Issued currency path
        return payIssued();
    }
}

Step 4: Read Tests

Tests show how code is meant to be used:

// In Payment_test.cpp
void testPayment()
{
    // Setup
    Env env(*this);
    Account alice{"alice"};
    Account bob{"bob"};
    
    env.fund(XRP(10000), alice, bob);
    
    // Execute
    env(pay(alice, bob, XRP(100)));
    
    // Verify
    BEAST_EXPECT(env.balance(alice) == XRP(9900));
    BEAST_EXPECT(env.balance(bob) == XRP(10100));
}

IDE Setup and Configuration

Visual Studio Code Setup

Extensions:

C/C++ (Microsoft)
C/C++ Extension Pack
CMake Tools
GitLens

Configuration (.vscode/settings.json):

{
  "C_Cpp.default.configurationProvider": "ms-vscode.cmake-tools",
  "C_Cpp.default.compileCommands": "${workspaceFolder}/build/compile_commands.json",
  "files.associations": {
    "*.h": "cpp",
    "*.cpp": "cpp"
  },
  "search.exclude": {
    "**/build": true,
    "**/external": true
  }
}

CLion Setup

CMake Configuration:

Open rippled directory
CLion auto-detects CMakeLists.txt
Configure build profiles (Debug, Release)
Let CLion index the project

Tips:

Use "Find in Path" (Ctrl+Shift+F) for project-wide search
Use "Go to Symbol" (Ctrl+Alt+Shift+N) to find classes/functions
Enable "Compact Middle Packages" in Project view

Compile Commands Database

Generate for better IDE support:

cd rippled
mkdir build && cd build
cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ..

This creates compile_commands.json that IDEs use for accurate code intelligence.

Documentation and Comments

Code Documentation

Rippled uses various documentation styles:

Doxygen-Style Comments:

/**
 * @brief Apply a transaction to a view
 * 
 * @param app Application instance
 * @param view Ledger view to apply to
 * @param tx Transaction to apply
 * @return Pair of result code and success flag
 */
std::pair<TER, bool>
applyTransaction(
    Application& app,
    OpenView& view,
    STTx const& tx);

Inline Comments:

// Check if destination requires a tag
if (sleDest->getFlags() & lsfRequireDestTag)
{
    if (!ctx.tx.isFieldPresent(sfDestinationTag))
        return tecDST_TAG_NEEDED;
}

In-Source Documentation

README Files:

src/xrpld/README.md
src/xrpld/consensus/README.md

Design Documents:

docs/consensus.md
docs/build-unix.md

External Documentation

Dev Null Productions Source Code Guide:

Comprehensive walkthrough of rippled codebase
Available online
Covers architecture and key components

XRP Ledger Dev Portal:

https://xrpl.org/docs
Protocol documentation
API reference

Find class definition

grep -r "class ClassName" src/

Find function implementation

grep -r "ReturnType functionName(" src/

Find where something is used

grep -r "variableName" src/

Case-insensitive search

grep -ri "searchterm" src/

Search in specific file types

grep -r --include="*.cpp" "searchterm" src/

Exclude directories

grep -r --exclude-dir="test" "searchterm" src/


### IDE Shortcuts

**VS Code**:

Go to Definition: F12 or Ctrl+Click Find References: Shift+F12 Go to Symbol: Ctrl+T Search in Files: Ctrl+Shift+F


**CLion**:

Go to Declaration: Ctrl+B Go to Implementation: Ctrl+Alt+B Find Usages: Alt+F7 Search Everywhere: Double Shift


***

## Additional Resources

### Official Documentation

* **XRP Ledger Dev Portal**: [xrpl.org/docs](https://xrpl.org/docs)
* **Rippled Repository**: [github.com/XRPLF/rippled](https://github.com/XRPLF/rippled)
* **Build Instructions**: [github.com/XRPLF/rippled/BUILD.md](https://github.com/XRPLF/rippled/blob/develop/BUILD.md)

### Codebase Guides

* **Dev Null Productions Source Code Guide**: Comprehensive rippled walkthrough
* **In-Source Documentation**: [`src/xrpld/README.md`](https://github.com/XRPLF/rippled/blob/3.2.0/src/xrpld/README.md) and `docs/` directory
* **Code Comments**: Doxygen-style documentation throughout

### Tools

* **Visual Studio Code**: Free, excellent C++ support
* **CLion**: Powerful C++ IDE (commercial)
* **grep/ag/ripgrep**: Command-line search tools
* **ctags/cscope**: Code indexing tools

### Related Topics

* Application Layer - Understanding the overall architecture
* Transactors - How to read transaction implementations
* Debugging Tools - Tools for exploring code at runtime

---

## Summary

This module gave you a map of the rippled source. You learned the three roots ([`include/xrpl`](https://github.com/XRPLF/rippled/tree/3.2.0/include/xrpl) for public headers, [`src/libxrpl`](https://github.com/XRPLF/rippled/tree/3.2.0/src/libxrpl) for the library implementation, [`src/xrpld`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld) for the daemon), the naming conventions that appear everywhere (`ST`, `SLE`, `sf`, `tt`, `keylet`, `TER`), and the recurring C++ patterns (keylets, views, the Application reference). With those in hand you can trace any feature by grepping, following the types, or starting from an entry point.

**To remember:**

- Three roots: [`include/xrpl`](https://github.com/XRPLF/rippled/tree/3.2.0/include/xrpl) (public headers), [`src/libxrpl`](https://github.com/XRPLF/rippled/tree/3.2.0/src/libxrpl) (library impl), [`src/xrpld`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld) (the daemon)
- Prefixes: `ST*` serialized types, `SLE` ledger entry, `sf*` fields, `tt*` tx types, `lsf*` state flags, `tes/tec/ter/tef/tem/tel` results
- `keylet::account(...)`, `keylet::check(...)` compute the key that locates a ledger entry
- Transactors: `src/libxrpl/tx/transactors/<family>/`; RPC handlers: [`src/xrpld/rpc/handlers`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld/rpc/handlers)
- Consensus: [`src/xrpld/consensus`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld/consensus) (generic engine) + [`src/xrpld/app/consensus`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld/app/consensus) (RCL glue); overlay: [`src/xrpld/overlay`](https://github.com/XRPLF/rippled/tree/3.2.0/src/xrpld/overlay)
- Private implementation files sit in `detail/` subfolders
- To trace a feature: grep the symbol, follow the types, or start from an entry point (`main()`, a handler, a transactor)
- Watch out: older docs cite `src/ripple/...` paths; the tree was reorganized, translate to the three-root layout

> **Next up.** You can find any file; can you follow a transaction through all of them? Next you trace **the complete transaction lifecycle**, from submission to finality.

Navigating the rippled codebase