rippled/include/xrpl/ledger/helpers

Ledger Entry Helpers (helpers/)

Overview

This folder contains helper classes and free functions for working with Serialized Ledger Entries (SLEs). Its centerpiece is SLEBase.h, which defines the template class SLEBase<ViewT> — a type-safe, context-aware wrapper around the raw std::shared_ptr<SLE> used throughout the rest of the codebase.

The Problem: Untyped SLE Access

Historically, ledger entries are passed around as bare std::shared_ptr<SLE> (or std::shared_ptr<SLE const>). This has several drawbacks:

1. No compile-time entry-type safety. Any code holding an std::shared_ptr<SLE> can read or write any field on any ledger entry type. Nothing prevents you from calling sle->getFieldU32(sfOwnerCount) on an Offer SLE, even though Offers don't have that field.

2. No read/write distinction. A function that only needs to read an entry still receives a mutable std::shared_ptr<SLE>, making it easy to accidentally mutate state. Conversely, a function that must write has no way to express that requirement in its signature.

3. No association with the view. The SLE and the ReadView / ApplyView it came from travel as separate arguments, so callers must manually keep them in sync and remember to call view.update(sle) after mutations.

The Solution: SLEBase.h

SLEBase.h introduces a single template class SLEBase<ViewT> that pairs an SLE with its view context and enforces read/write semantics at compile time via requires clauses.

SLEBase<ReadView> holds a std::shared_ptr<SLE const> and a ReadView const&. Write-only members are excluded at compile time. holds a mutable std::shared_ptr<SLE>, an ApplyView&, and a Keylet. It exposes insert(), update(), erase(), and newSLE() to keep the SLE and its view in sync automatically.

A converting constructor allows implicit conversion from SLEBase<ApplyView> to SLEBase<ReadView>, so functions taking a read-only wrapper can accept a writable one without a cast.

Template Pattern

Each entry type is a single template class parameterized on the view type:

AccountRoot<ReadView>   — read-only:  RAccountRoot
AccountRoot<ApplyView>  — writable:   WAccountRoot

Both specializations share all domain read methods. Write methods on WAccountRoot are gated with requires is_writable so they are unavailable on RAccountRoot at compile time. The R/W prefix aliases (RAccountRoot, WAccountRoot) are provided for convenience and backward compatibility.

Files in This Directory

File	Description
SLEBase.h	Template base class SLEBase<ViewT> and ReadOnlySLE/WritableSLE aliases
AccountRootHelpers.h	AccountRoot<ViewT> wrapper (RAccountRoot, WAccountRoot) and free functions for pseudo-accounts
CredentialHelpers.h	Free functions for Credential ledger entries
DirectoryHelpers.h	Free functions for directory traversal (dirFirst, dirNext, forEachItem, etc.)
MPTokenHelpers.h	Free functions for MPToken and MPTokenIssuance ledger entries
OfferHelpers.h	Free function offerDelete for removing Offer entries
RippleStateHelpers.h	Free functions for RippleState (trust line) entries: credit, freeze, issuance, authorization
TokenHelpers.h	Shared token helpers (freeze/auth checks used by both IOU and MPT paths)
VaultHelpers.h	Free functions for Vault ledger entries

Migration Status

This migration is still in progress. New code should prefer the wrapper style where possible; existing free functions will be migrated incrementally.