The Owner count could decrease while evaluating a strand, causing
different behavior in forward passes and reverses passes. The fix treats
a decreased owner count like a deferred credit.
In some situations, deferred credits could cause an XRP balance to be
calculated as negative, triggering some asserts.
When XRP is used as a bridge currency, a path could be falsely marked as
dry. This happens when the XRP/XXX offer recursively checks the XXX/XRP
offer and the XXX/XRP offer could not satisfy the request in a single
call.
With a single strand and limit quality the old payment code incorrectly
computed with multiquailty set to true. This could cause the total
quality to go below the requested quality even if there was liquidity
available above the requested quality value.
Add a new algorithm for finding the liquidity in a payment path. There
is still a reverse and forward pass, but the forward pass starts at the
limiting step rather than the payment source. This insures the limiting
step is completely consumed rather than potentially leaving a 'dust'
amount in the forward pass.
Each step in a payment is either a book step, a direct step (account to
account step), or an xrp endpoint. Each step in the existing
implementation is a triple, where each element in the triple is either
an account of a book, for a total of eight step types.
Since accounts are considered in pairs, rather than triples, transfer
fees are handled differently. In V1 of payments, in the payment path
A -> gw ->B, if A redeems to gw, and gw issues to B, a transfer fee is
changed. In the new code, a transfer fee is changed even if A issues to
gw.
The View hierarchy of classes is reorganized to include new
classes with member functions moved and renamed, to solve
defects in the original design:
OpenView accumulates raw state and tx changes and
can be applied to the base. ApplyView accumulates changes
for a single transaction, including metadata, and can be
applied to an OpenView. The Sandbox allows changes with
the option to apply or throw them out. The PaymentSandbox
provides a sandbox with account credit deferral.
Call sites are changed to use the class appropriate for
the task.
Member functions and free functions on Ledger and LedgerEntrySet are
rewritten in terms of new abstract interfaces `BasicView` and `View`,
representing the set of non-decomposable primitives necessary to read
and write state map items in a ledger, and to overlay a discardable
view onto a Ledger that can calculate metadata during transaction
processing. const-correctness is enforced through the parameter and
return types.
The MetaView now supports multi-level stacking: A MetaView can be
stacked on top of either a Ledger or another MetaView, up to any
number of levels.
The getSLEi member function is removed. The CachedView wrapper
replaces it, wrapping a View such that any function called with a
CachedView will go through the SLECache.
* Add BasicView, View, CachedView
* Rename LedgerEntrySet to MetaView
* Factor out free functions
* Consolidate free functions in ViewAPI
* Remove unused class members and free functions
An alternative to the unity build, the classic build compiles each
translation unit individually. This adds more modules to the classic build:
* Remove unity header app.h
* Add missing includes as needed
* Remove obsolete NodeStore backend code
* Add app/, core/, crypto/, json/, net/, overlay/, peerfinder/ to classic build
* Restrict to 80-columns and other style cleanups.
* Make pathfinding a free function and hide the class Pathfinder.
* Split off unrelated utility functions into separate files.
Conflicts:
src/ripple/rpc/handlers/RipplePathFind.cpp
