This commit removes obsolete comments, dead or no longer useful
code, and workarounds for several issues that were present in older
compilers that we no longer support.
Specifically:
- It improves the transaction metadata handling class, simplifying
its use and making it less error-prone.
- It reduces the footprint of the Serializer class by consolidating
code and leveraging templates.
- It cleanups the ST* class hierarchy, removing dead code, improving
and consolidating code to reduce complexity and code duplication.
- It shores up the handling of currency codes and the conversation
between 160-bit currency codes and their string representation.
- It migrates beast::secure_erase to the ripple namespace and uses
a call to OpenSSL_cleanse instead of the custom implementation.
The XRP Ledger utilizes an account model. Unlike systems based on a UTXO
model, XRP Ledger accounts are first-class objects. This design choice
allows the XRP Ledger to offer rich functionality, including the ability
to own objects (offers, escrows, checks, signer lists) as well as other
advanced features, such as key rotation and configurable multi-signing
without needing to change a destination address.
The trade-off is that accounts must be stored on ledger. The XRP Ledger
applies reserve requirements, in XRP, to protect the shared global ledger
from growing excessively large as the result of spam or malicious usage.
Prior to this commit, accounts had been permanent objects; once created,
they could never be deleted.
This commit introduces a new amendment "DeletableAccounts" which, if
enabled, will allow account objects to be deleted by executing the new
"AccountDelete" transaction. Any funds remaining in the account will
be transferred to an account specified in the deletion transaction.
The amendment changes the mechanics of account creation; previously
a new account would have an initial sequence number of 1. Accounts
created after the amendment will have an initial sequence number that
is equal to the ledger in which the account was created.
Accounts can only be deleted if they are not associated with any
obligations (like RippleStates, Escrows, or PayChannels) and if the
current ledger sequence number exceeds the account's sequence number
by at least 256 so that, if recreated, the account can be protected
from transaction replay.
Replace Taker.cpp with calls to the payment flow() code.
This change required a number of tweaks in the payment flow code.
These tweaks are conditionalized on whether or not offer crossing
is taking place. The flag is explicitly passed as a parameter to
the flow code.
For testing, a class was added that identifies differences in the
contents of two PaymentSandboxes. That code may be reusable in
the future.
None of the Taker offer crossing code is removed. Both versions
of the code are co-resident to support an amendment cut-over.
The code that identifies differences between Taker and Flow offer
crossing is enabled by a feature. That makes it easy to enable
or disable difference logging by changing the config file. This
approach models what was done with the payment flow code. The
differencing code should never be enabled on a production server.
Extensive offer crossing unit tests are added to examine and
verify the behavior of corner cases. The tests are currently
configured to run against both Taker and Flow offer crossing.
This gives us confidence that most cases run identically and
some of the (few) differences in behavior are documented.
Escrow replaces the existing SusPay implementation with improved
code that also adds hashlock support to escrow payments, making
RCL ILP enabled.
The new functionality is under the `Escrow` amendment, which
supersedes and replaces the `SusPay` amendment.
This commit also deprecates the `CryptoConditions` amendment
which is replaced by the `CryptoConditionSuite` amendment which,
once enabled, will allow use of cryptoconditions others than
hashlocks.
Payment channels permit off-ledger checkpoints of XRP payments flowing
in a single direction. A channel sequesters the owner's XRP in its own
ledger entry. The owner can authorize the recipient to claim up to a
give balance by giving the receiver a signed message (off-ledger). The
recipient can use this signed message to claim any unpaid balance while
the channel remains open. The owner can top off the line as needed. If
the channel has not paid out all its funds, the owner must wait out a
delay to close the channel to give the recipient a chance to supply any
claims. The recipient can close the channel at any time. Any transaction
that touches the channel after the expiration time will close the
channel. The total amount paid increases monotonically as newer claims
are issued. When the channel is closed any remaining balance is returned
to the owner. Channels are intended to permit intermittent off-ledger
settlement of ILP trust lines as balances get substantial. For
bidirectional channels, a payment channel can be used in each direction.
Replace Journal public data members with member function accessors
in order to make Journal lighter weight. The change makes a
Journal cheaper to pass by value.
Also add missing stream checks (e.g., calls to JLOG) to avoid
text processing that ultimately will not be stored in the log.
Metadata is correctly generated for the case where a ledger entry is only changed as
a consequence of threading. This changes the result compared to previous versions,
which produced more than necessary for these cases.
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.
