nim-eth/eth/trie/db.nim

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import
tables, hashes, sets,
nimcrypto/[hash, keccak], eth/rlp,
trie_defs, db_tracing
type
MemDBRec = object
refCount: int
value: Bytes
MemoryLayer* = ref object of RootObj
records: Table[Bytes, MemDBRec]
deleted: HashSet[Bytes]
TrieDatabaseConcept* = concept DB
mixin put, del, get
put(var DB, KeccakHash, BytesRange)
del(var DB, KeccakHash)
get(DB, KeccakHash) is Bytes
contains(DB, KeccakHash) is bool
# XXX: poor's man vtref types
PutProc = proc (db: RootRef, key, val: openarray[byte]) {.gcsafe.}
GetProc = proc (db: RootRef, key: openarray[byte]): Bytes {.gcsafe.} # Must return empty seq if not found
DelProc = proc (db: RootRef, key: openarray[byte]) {.gcsafe.}
ContainsProc = proc (db: RootRef, key: openarray[byte]): bool {.gcsafe.}
TrieDatabaseRef* = ref object
obj: RootRef
putProc: PutProc
getProc: GetProc
delProc: DelProc
containsProc: ContainsProc
mostInnerTransaction: DbTransaction
TransactionState = enum
Pending
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Committed
RolledBack
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DbTransaction* = ref object
db: TrieDatabaseRef
parentTransaction: DbTransaction
modifications: MemoryLayer
state: TransactionState
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TransactionID* = distinct DbTransaction
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proc put*(db: TrieDatabaseRef, key, val: openarray[byte]) {.gcsafe.}
proc get*(db: TrieDatabaseRef, key: openarray[byte]): Bytes {.gcsafe.}
proc del*(db: TrieDatabaseRef, key: openarray[byte]) {.gcsafe.}
proc beginTransaction*(db: TrieDatabaseRef): DbTransaction {.gcsafe.}
proc keccak*(r: BytesRange): KeccakHash =
keccak256.digest r.toOpenArray
proc get*(db: MemoryLayer, key: openarray[byte]): Bytes =
result = db.records.getOrDefault(@key).value
traceGet key, result
proc del*(db: MemoryLayer, key: openarray[byte]) =
traceDel key
# The database should ensure that the empty key is always active:
if key != emptyRlpHash.data:
# TODO: This is quite inefficient and it won't be necessary once
# https://github.com/nim-lang/Nim/issues/7457 is developed.
let key = @key
db.records.withValue(key, v):
dec v.refCount
if v.refCount <= 0:
db.records.del(key)
db.deleted.incl(key)
proc contains*(db: MemoryLayer, key: openarray[byte]): bool =
db.records.hasKey(@key)
proc put*(db: MemoryLayer, key, val: openarray[byte]) =
tracePut key, val
# TODO: This is quite inefficient and it won't be necessary once
# https://github.com/nim-lang/Nim/issues/7457 is developed.
let key = @key
db.deleted.excl(key)
if key.len != 32:
# This is not a Trie key, but a regular system mutable key
# (e.g. the cannonical head hash). We don't need to ref count such keys.
db.records[key] = MemDBRec(refCount: 1, value: @val)
else:
db.records.withValue(key, v) do:
inc v.refCount
if v.value != val: v.value = @val
do:
db.records[key] = MemDBRec(refCount: 1, value: @val)
proc newMemoryLayer: MemoryLayer =
result.new
result.records = initTable[Bytes, MemDBRec]()
result.deleted = initSet[Bytes]()
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proc commit(memDb: MemoryLayer, db: TrieDatabaseRef, applyDeletes: bool = true) =
if applyDeletes:
for k in memDb.deleted:
db.del(k)
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for k, v in memDb.records:
db.put(k, v.value)
proc init(db: var MemoryLayer) =
db = newMemoryLayer()
proc newMemoryDB*: TrieDatabaseRef =
new result
discard result.beginTransaction
put(result, emptyRlpHash.data, emptyRlp)
template isMemoryDB(db: TrieDatabaseRef): bool =
# Make sure this is really a MemoryDB
db.obj == nil and
db.mostInnerTransaction != nil and
db.mostInnerTransaction.parentTransaction == nil
proc totalRecordsInMemoryDB*(db: TrieDatabaseRef): int =
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doAssert isMemoryDB(db)
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return db.mostInnerTransaction.modifications.records.len
iterator pairsInMemoryDB*(db: TrieDatabaseRef): (Bytes, Bytes) =
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doAssert isMemoryDB(db)
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for k, v in db.mostInnerTransaction.modifications.records:
yield (k, v.value)
proc beginTransaction*(db: TrieDatabaseRef): DbTransaction =
new result
result.db = db
init result.modifications
result.state = Pending
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result.parentTransaction = db.mostInnerTransaction
db.mostInnerTransaction = result
proc rollback*(t: DbTransaction) =
# Transactions should be handled in a strictly nested fashion.
# Any child transaction must be committed or rolled-back before
# its parent transactions:
doAssert t.db.mostInnerTransaction == t and t.state == Pending
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t.db.mostInnerTransaction = t.parentTransaction
t.state = RolledBack
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proc commit*(t: DbTransaction, applyDeletes: bool = true) =
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# Transactions should be handled in a strictly nested fashion.
# Any child transaction must be committed or rolled-back before
# its parent transactions:
doAssert t.db.mostInnerTransaction == t and t.state == Pending
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t.db.mostInnerTransaction = t.parentTransaction
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t.modifications.commit(t.db, applyDeletes)
t.state = Committed
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proc dispose*(t: DbTransaction) {.inline.} =
if t.state == Pending:
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t.rollback()
proc safeDispose*(t: DbTransaction) {.inline.} =
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if (not isNil(t)) and (t.state == Pending):
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t.rollback()
proc putImpl[T](db: RootRef, key, val: openarray[byte]) =
mixin put
put(T(db), key, val)
proc getImpl[T](db: RootRef, key: openarray[byte]): Bytes =
mixin get
return get(T(db), key)
proc delImpl[T](db: RootRef, key: openarray[byte]) =
mixin del
del(T(db), key)
proc containsImpl[T](db: RootRef, key: openarray[byte]): bool =
mixin contains
return contains(T(db), key)
proc trieDB*[T: RootRef](x: T): TrieDatabaseRef =
mixin del, get, put
new result
result.obj = x
result.putProc = putImpl[T]
result.getProc = getImpl[T]
result.delProc = delImpl[T]
result.containsProc = containsImpl[T]
proc put*(db: TrieDatabaseRef, key, val: openarray[byte]) =
var t = db.mostInnerTransaction
if t != nil:
t.modifications.put(key, val)
else:
db.putProc(db.obj, key, val)
proc get*(db: TrieDatabaseRef, key: openarray[byte]): Bytes =
# TODO: This is quite inefficient and it won't be necessary once
# https://github.com/nim-lang/Nim/issues/7457 is developed.
let key = @key
var t = db.mostInnerTransaction
while t != nil:
result = t.modifications.records.getOrDefault(key).value
if result.len > 0 or key in t.modifications.deleted:
return
t = t.parentTransaction
if db.getProc != nil:
result = db.getProc(db.obj, key)
proc del*(db: TrieDatabaseRef, key: openarray[byte]) =
var t = db.mostInnerTransaction
if t != nil:
t.modifications.del(key)
else:
db.delProc(db.obj, key)
proc contains*(db: TrieDatabaseRef, key: openarray[byte]): bool =
# TODO: This is quite inefficient and it won't be necessary once
# https://github.com/nim-lang/Nim/issues/7457 is developed.
let key = @key
var t = db.mostInnerTransaction
while t != nil:
result = key in t.modifications.records
if result or key in t.modifications.deleted:
return
t = t.parentTransaction
if db.containsProc != nil:
result = db.containsProc(db.obj, key)
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# TransactionID imitate subset of JournalDB behaviour
# but there is no need to rollback or dispose
# TransactionID, because it will be handled elsewhere
# this is useful when we need to jump back to specific point
# in history where the database still in 'original' state
# and retrieve data from that point
proc getTransactionID*(db: TrieDatabaseRef): TransactionID =
TransactionID(db.mostInnerTransaction)
proc setTransactionID*(db: TrieDatabaseRef, id: TransactionID) =
db.mostInnerTransaction = DbTransaction(id)
template shortTimeReadOnly*(db: TrieDatabaseRef, id: TransactionID, body: untyped) =
# hmm, how can we prevent unwanted database modification
# inside this block?
block:
let tmpID = db.getTransactionID()
db.setTransactionID(id)
body
db.setTransactionID(tmpID)