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/// Checks which keyword we're dealing with and routes it to the right parser.
func parseKeywordLine<T: Collection>(
_ bytes: T, _ start: Int, _ end: Int,
_ context: inout KeywordParserContext
) where T.Element == UInt8, T.Index == Int {
guard let (keyword, rest) = extractKeyword(bytes, start, end) else { return }
if matchesKeyword(keyword, kInertiaKeyword), let inertia = parseInertia(bytes, rest, end) {
context.inertias.append(inertia)
} else if matchesKeyword(keyword, kEvolutionKeyword),
let evolution = parseEvolution(bytes, rest, end) {
context.evolutions.append(evolution)
} else if matchesKeyword(keyword, kNoteKeyword), let note = parseNote(bytes, rest, end) {
context.notes.append(note)
} else if matchesKeyword(keyword, kGroupKeyword), let group = parseGroup(bytes, rest, end) {
context.groups.append(group)
} else if let stageNumber = isStageKeyword(keyword),
let stage = parseStage(bytes, stageNumber, rest, end) {
context.stages.append(stage)
}
}
/// Extracts a keyword from inside brackets. + the index of the rest of the
/// line.
@inline(__always)
func extractKeyword<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> (T.SubSequence, Int)?
where T.Element == UInt8, T.Index == Int {
var index = start + 1 // Skip '['
let keywordStart = index
while index < end && bytes[index] != kCloseSquareBracket { index += 1 } // Find ']'
if index >= end { return nil }
let keywordEnd = index
index += 1
// Skip whitespace after ']'
index = skipWhitespace(bytes, end, index)
return (bytes[keywordStart..<keywordEnd], index)
}
/// Checks the four potential values for the stage keyword.
@inline(__always)
func isStageKeyword<T: Collection>(_ keyword: T) -> StageNumber?
where T.Element == UInt8, T.Index == Int {
if matchesKeyword(keyword, kIKeyword) {
return .stageI
}
if matchesKeyword(keyword, kIIKeyword) {
return .stageII
}
if matchesKeyword(keyword, kIIIKeyword) {
return .stageIII
}
if matchesKeyword(keyword, kIVKeyword) {
return .stageIV
}
return nil
}
/// Compares a collection of bytes against a list of bytes.
/// Short-Circuits by length, only two have the same length (ii and iv)
@inline(__always)
func matchesKeyword<T: Collection>(_ keyword: T, _ expected: [UInt8]) -> Bool
where T.Element == UInt8, T.Index == Int {
guard keyword.count == expected.count else { return false }
var keywordIndex = keyword.startIndex
for index in 0..<expected.count {
let currentKeyword = keyword[keywordIndex]
let expectedKeyword = expected[index]
let lowercasedKeyword =
(currentKeyword >= kCapitalA && currentKeyword <= kCapitalZ)
? currentKeyword + kCapsToLowercaseDistance : currentKeyword
if lowercasedKeyword != expectedKeyword { return false }
keywordIndex += 1
}
return true
}
/// Parses the stage. Assumes we got the stage number in the keyword check
/// to avoid checking twice.
func parseStage<T: Collection>(
_ bytes: T, _ stageNumber: StageNumber, _ start: Int, _ end: Int
) -> Stage?
where T.Element == UInt8, T.Index == Int {
guard let value = parseDouble(bytes, start, end) else { return nil }
return Stage(stage: stageNumber, value: value)
}
/// Parses the note coordinates and text.
func parseNote<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Note?
where T.Element == UInt8, T.Index == Int {
var index = skipWhitespace(bytes, end, start)
guard index < end && bytes[index] == kOpenParenthesis else { return nil }
index += 1
guard let (coordinates, endIndex) = parseCoordinates(bytes, index, end) else {
return nil
}
index = skipWhitespace(bytes, end, endIndex)
let textEnd = shaveWhitespace(bytes, index, end)
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
let text = String(decoding: bytes[index..<textEnd], as: UTF8.self)
return Note(text: text, coordinates: coordinates)
}
/// Parses the comma separated labels for a group
func parseGroup<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Group?
where T.Element == UInt8, T.Index == Int {
var components = [String]()
var index = start
var componentStart = start
while index <= end {
if index == end || bytes[index] == kComma {
let trimStart = skipWhitespace(bytes, index, componentStart)
let trimEnd = shaveWhitespace(bytes, trimStart, index)
if trimStart < trimEnd {
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
let component = String(decoding: bytes[trimStart..<trimEnd], as: UTF8.self)
components.append(component)
}
componentStart = index + 1
}
index += 1
}
return components.isEmpty ? nil : Group(components: components)
}
/// Parses the component label for inertia
func parseInertia<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Inertia?
where T.Element == UInt8, T.Index == Int {
let trimStart = skipWhitespace(bytes, end, start)
let trimEnd = shaveWhitespace(bytes, trimStart, end)
guard trimStart < trimEnd else { return nil }
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
let component = String(decoding: bytes[trimStart..<trimEnd], as: UTF8.self)
return Inertia(component: component)
}
/// Parses the component label and value for inertia
func parseEvolution<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Evolution?
where T.Element == UInt8, T.Index == Int {
var signIndex: Int?
var sign = 1.0
var index = start
while index < end {
if bytes[index] == kPlus || bytes[index] == kDash {
signIndex = index
sign = bytes[index] == 45 ? -1.0 : 1.0
break
}
index += 1
}
guard let signIndex, signIndex > start else { return nil }
let trimStart = skipWhitespace(bytes, signIndex, start)
let trimEnd = shaveWhitespace(bytes, trimStart, signIndex)
guard trimStart < trimEnd else { return nil }
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
let component = String(decoding: bytes[trimStart..<trimEnd], as: UTF8.self)
guard let value = parseDouble(bytes, signIndex + 1, end) else { return nil }
return Evolution(component: component, value: sign * value)
}
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