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/// Parses a component with its coordinates.
func parseComponent<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Component?
where T.Element == UInt8, T.Index == Int {
guard let (label, parenthesisIndex) = extractComponentLabel(bytes, start, end) else {
return nil
}
guard
let (coordinates, endIndex) = parseCoordinates(
bytes, parenthesisIndex + 1, end)
else {
return nil
}
let shape = extractComponentShape(bytes, endIndex, end)
return Component(label: label, coordinates: coordinates, shape: shape)
}
/// Looks for a component label by taking the string before the first open
/// parenthesis.
@inline(__always)
private func extractComponentLabel<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> (
String, Int
)?
where T.Element == UInt8, T.Index == Int {
var index = start
while index < end {
if bytes[index] == kOpenParenthesis {
guard index > start else { return nil }
guard let label = extractTrimmedString(bytes, start, index) else { return nil }
return (label, index)
}
index += 1
}
return nil
}
/// Extracts a shape by looking for a shape label in square brackets.
/// If missing, incomplete or invalid, it returns a circle
@inline(__always)
private func extractComponentShape<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Shape
where T.Element == UInt8, T.Index == Int {
var index = skipWhitespace(bytes, end, start)
guard index < end && bytes[index] == kOpenSquareBracket else { return .circle }
index += 1
let shapeStart = index
while index < end && bytes[index] != kCloseSquareBracket { index += 1 }
guard index > shapeStart && index < end else { return .circle }
let shapeName = bytes[shapeStart..<index]
return parseShapeFromBytes(shapeName)
}
/// Given the contents of a shape label, return the right type.
@inline(__always)
private func parseShapeFromBytes<T: Collection>(_ shapeName: T) -> Shape
where T.Element == UInt8, T.Index == Int {
var trimStart = shapeName.startIndex
var trimEnd = shapeName.endIndex
trimStart = skipWhitespace(shapeName, trimEnd, trimStart)
trimEnd = shaveWhitespace(shapeName, trimStart, trimEnd)
let trimmedName = shapeName[trimStart..<trimEnd]
// "x"
if matchesKeyword(trimmedName, [120]) { return .xMark }
// "square"
if matchesKeyword(trimmedName, [115, 113, 117, 97, 114, 101]) { return .square }
// "triangle"
if matchesKeyword(trimmedName, [116, 114, 105, 97, 110, 103, 108, 101]) { return .triangle }
return .circle
}
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