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Avoid allocating temporary containers during assembly
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When assembly top-level declerations, allocating a new container
(dictionary or array) for each level of recursion is really slow.
Use `inout` to mutate the existing container instead.
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@dduan
dduan committed Dec 16, 2024
1 parent b3b3767 commit d7ab506
Showing 1 changed file with 27 additions and 29 deletions.
56 changes: 27 additions & 29 deletions Sources/Deserializer/Parser.swift
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1872,7 +1872,7 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
var headersSeen = Set<String>()

func insert(
table: TOMLTable,
table: inout TOMLTable,
reference: String,
header: Array<Traced<String>>.SubSequence,
key: Array<Traced<String>> = [],
Expand All @@ -1881,7 +1881,7 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
value: Any,
isArrayTable: Bool = false,
isTable: Bool = false
) throws -> TOMLTable {
) throws {
let keys = header + key
assert(!keys.isEmpty)
let keysDescription = keys.map { $0.value }.joined(separator: ".")
Expand All @@ -1904,16 +1904,16 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
)
)
}
var mutable = table
switch (keys.count, table[key.value]) {
case (1, nil):
mutable[key.value] = value
table[key.value] = value
if context.isEmpty && isTable {
headersSeen.insert(keysDescription)
}
case (_, nil):
mutable[key.value] = try insert(
table: TOMLTable(),
var newTable = TOMLTable()
try insert(
table: &newTable,
reference: reference,
header: keys.dropFirst(),
originalKeyDescription: originalKeyDescription ?? headerDescription,
Expand All @@ -1922,20 +1922,21 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
isArrayTable: isArrayTable,
isTable: isTable
)
table[key.value] = newTable
if context.isEmpty && isTable {
headersSeen.insert(keysDescription)
}
case (1, var existing as TOMLArrayTable) where isArrayTable && !existing.storage.isEmpty:
existing.storage.append(TOMLTable())
mutable[key.value] = existing
table[key.value] = existing

case (_, let existing as TOMLTable) where keys.count > 1:
case (_, var existing as TOMLTable) where keys.count > 1:
if !existing.isMutable {
throw DeserializationError.structural(.init(reference, key.index, "Cannot mutate inline table"))
}

mutable[key.value] = try insert(
table: existing,
try insert(
table: &existing,
reference: reference,
header: keys.dropFirst(),
originalKeyDescription: originalKeyDescription ?? headerDescription,
Expand All @@ -1944,6 +1945,7 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
isArrayTable: isArrayTable,
isTable: isTable
)
table[key.value] = existing
case (1, _ as TOMLTable) where isTable && context.isEmpty:
if headersSeen.contains(keysDescription) {
throw DeserializationError.conflictingValue(
Expand All @@ -1954,11 +1956,9 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
)
)
}
return table
case (_, let existing as TOMLArrayTable) where keys.count > 1:
var mutableArray = existing
mutableArray[mutableArray.storage.count - 1] = try insert(
table: mutableArray[mutableArray.storage.count - 1],
case (_, var existing as TOMLArrayTable) where keys.count > 1:
try insert(
table: &existing[existing.storage.count - 1],
reference: reference,
header: keys.dropFirst(),
originalKeyDescription: originalKeyDescription ?? keysDescription,
Expand All @@ -1967,11 +1967,10 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
isArrayTable: isArrayTable,
isTable: isTable
)
mutable[key.value] = mutableArray
case (_, let existing as TOMLArrayTable) where keys.count > 1:
var mutableArray = existing
mutableArray[mutableArray.storage.count - 1] = try insert(
table: mutableArray[mutableArray.storage.count - 1],
table[key.value] = existing
case (_, var existing as TOMLArrayTable) where keys.count > 1:
try insert(
table: &existing[existing.storage.count - 1],
reference: reference,
header: keys.dropFirst(),
originalKeyDescription: originalKeyDescription ?? keysDescription,
Expand All @@ -1980,7 +1979,7 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
isArrayTable: isArrayTable,
isTable: isTable
)
mutable[key.value] = mutableArray
table[key.value] = existing
case (_, let .some(existing)):
let path = context.isEmpty ? "\(key.value)" : "\(context.joined(separator: ".")).\(key.value)"
throw DeserializationError.conflictingValue(
Expand All @@ -1991,9 +1990,8 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
)
)
}

return mutable
}

for entry in entries {
switch entry {
case .error(let index, let reason):
Expand All @@ -2002,8 +2000,8 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
errors.append(DeserializationError.value(.init(referenceInput, index, reason.description)))
case .keyValue(let pair):
do {
result = try insert(
table: result,
try insert(
table: &result,
reference: referenceInput,
header: context[...],
key: pair.key,
Expand All @@ -2015,8 +2013,8 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
}
case .table(let tableKey):
do {
result = try insert(
table: result,
try insert(
table: &result,
reference: referenceInput,
header: tableKey[...],
context: [],
Expand All @@ -2030,8 +2028,8 @@ func assembleTable(from entries: [TopLevel], referenceInput: String) throws -> T
context = tableKey
case .arrayTable(let arrayTableKey):
do {
result = try insert(
table: result,
try insert(
table: &result,
reference: referenceInput,
header: arrayTableKey[...],
context: [],
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