nimbus-eth1/nimbus/db/aristo/aristo_tx/tx_fork.nim

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Nim

# nimbus-eth1
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
# http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
# http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed
# except according to those terms.
## Aristo DB -- Transaction fork helpers
## =====================================
##
{.push raises: [].}
import
results,
./tx_frame,
".."/[aristo_desc, aristo_get, aristo_layers]
# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------
proc txFork*(
tx: AristoTxRef; # Transaction descriptor
): Result[AristoDbRef,AristoError] =
## Clone a transaction into a new DB descriptor accessing the same backend
## database (if any) as the argument `db`. The new descriptor is linked to
## the transaction parent and is fully functional as a forked instance (see
## comments on `aristo_desc.reCentre()` for details.)
##
## Input situation:
## ::
## tx -> db0 with tx is top transaction, tx.level > 0
##
## Output situation:
## ::
## tx -> db0 \
## > share the same backend
## tx1 -> db1 /
##
## where `tx.level > 0`, `db1.level == 1` and `db1` is returned. The
## transaction `tx1` can be retrieved via `db1.txTop()`.
##
## The new DB descriptor will contain a copy of the argument transaction
## `tx` as top layer of level 1 (i.e. this is he only transaction.) Rolling
## back will end up at the backend layer (incl. backend filter.)
##
## Use `aristo_desc.forget()` to clean up this descriptor.
##
let db = tx.db
# Verify `tx` argument
if db.txRef == tx:
if db.top.txUid != tx.txUid:
return err(TxArgStaleTx)
elif db.stack.len <= tx.level:
return err(TxArgStaleTx)
elif db.stack[tx.level].txUid != tx.txUid:
return err(TxArgStaleTx)
# Provide new empty stack layer
let stackLayer = block:
let rc = db.getTuvBE()
if rc.isOk:
LayerRef(vTop: rc.value)
elif rc.error == GetTuvNotFound:
LayerRef.init()
else:
return err(rc.error)
# Set up clone associated to `db`
let txClone = ? db.fork(noToplayer = true, noFilter = false)
txClone.top = db.layersCc tx.level # Provide tx level 1 stack
txClone.stack = @[stackLayer] # Zero level stack
txClone.top.txUid = 1
txClone.txUidGen = 1
# Install transaction similar to `tx` on clone
txClone.txRef = AristoTxRef(
db: txClone,
txUid: 1,
level: 1)
ok(txClone)
proc txForkTop*(
db: AristoDbRef;
): Result[AristoDbRef,AristoError] =
## Variant of `forkTx()` for the top transaction if there is any. Otherwise
## the top layer is cloned, and an empty transaction is set up. After
## successful fork the returned descriptor has transaction level 1.
##
## Use `aristo_desc.forget()` to clean up this descriptor.
##
if db.txRef.isNil:
let txClone = ? db.fork(noToplayer=true, noFilter=false)
txClone.top = db.layersCc # Is a deep copy
discard txClone.txFrameBegin()
return ok(txClone)
# End if()
db.txRef.txFork()
proc txForkBase*(
db: AristoDbRef;
): Result[AristoDbRef,AristoError] =
## Variant of `forkTx()`, sort of the opposite of `forkTop()`. This is the
## equivalent of top layer forking after all tranactions have been rolled
## back.
##
## Use `aristo_desc.forget()` to clean up this descriptor.
##
if db.txRef.isNil:
return db.txForkTop()
let txClone = ? db.fork(noToplayer=true, noFilter=false)
txClone.top = db.layersCc 0
discard txClone.txFrameBegin()
ok(txClone)
# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------