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/// Check if a byte is a digit
@inline(__always)
func isDigit(_ byte: UInt8) -> Bool {
byte >= kZero && byte <= kNine
}
/// Looks for x and y separated by a comma.
func parseCoordinates<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> (
MapPoint, Int
)?
where T.Element == UInt8, T.Index == Int {
var index = skipWhitespace(bytes, end, start)
guard let (xCoordinate, nextIndex) = parseSingleCoordinate(bytes, index, end) else {
return nil
}
index = nextIndex
guard expectComma(bytes, &index, end) else { return nil }
guard let (yCoordinate, nextIndex) = parseSingleCoordinate(bytes, index, end) else {
return nil
}
index = nextIndex
guard expectClosingParen(bytes, &index, end) else { return nil }
return (MapPoint(xCoordinate: xCoordinate, yCoordinate: yCoordinate), index)
}
/// Checks if a candidate for a coordinate is a digit, and parses it.
@inline(__always)
func parseSingleCoordinate<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> (Double, Int)?
where T.Element == UInt8, T.Index == Int {
var index = start
while index < end && (isDigit(bytes[index]) || bytes[index] == 46) { index += 1 }
guard index > start else { return nil }
guard let value = parseDouble(bytes, start, index) else { return nil }
return (value, index)
}
/// Advances the index until we find a comma.
@inline(__always)
func expectComma<T: Collection>(_ bytes: T, _ index: inout Int, _ end: Int) -> Bool
where T.Element == UInt8, T.Index == Int {
index = skipWhitespace(bytes, end, index)
guard index < end && bytes[index] == kComma else { return false }
index += 1
index = skipWhitespace(bytes, end, index)
return true
}
/// Advances the index until we find a closing parenthesis
@inline(__always)
func expectClosingParen<T: Collection>(_ bytes: T, _ index: inout Int, _ end: Int) -> Bool
where T.Element == UInt8, T.Index == Int {
index = skipWhitespace(bytes, end, index)
guard index < end && bytes[index] == kCloseParenthesis else { return false }
index += 1
return true
}
/// Parses a double
@inline(__always)
func parseDouble<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Double?
where T.Element == UInt8, T.Index == Int {
var index = skipWhitespace(bytes, end, start)
let numStart = index
while index < end && (isDigit(bytes[index]) || bytes[index] == kPeriod) { index += 1 }
guard index > numStart else { return nil }
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
let str = String(decoding: bytes[numStart..<index], as: UTF8.self)
return Double(str)
}
/// Advances an index by looking for whitespace left-to-right
func skipWhitespace<T: Collection>(_ bytes: T, _ end: Int, _ start: Int) -> Int
where T.Element == UInt8, T.Index == Int {
var index = start
while index < end && (bytes[index] == kSpace || bytes[index] == kTab) { index += 1 }
return index
}
/// Decreases an index by looking for whitespace right-to-left
func shaveWhitespace<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> Int
where T.Element == UInt8, T.Index == Int {
var index = end
while index > start && (bytes[index - 1] == kSpace || bytes[index - 1] == kTab) { index -= 1 }
return index
}
/// Given the bytes buffer, finds the next non-empty line.
@inline(__always)
func extractLine<T: Collection>(_ bytes: T, _ index: inout Int, _ length: Int) -> (
Int, Int
)?
where T.Element == UInt8, T.Index == Int {
while index < length && (bytes[index] == kNewline || bytes[index] == kCarriageReturn) {
index += 1
}
let lineStart = index
while index < length && bytes[index] != kNewline && bytes[index] != kCarriageReturn { index += 1 }
if lineStart == index { return nil }
var start = lineStart
var end = index
start = skipWhitespace(bytes, end, start)
end = shaveWhitespace(bytes, start, end)
if start == end { return nil }
return (start, end)
}
/// Trims a byte collection and returns a string
@inline(__always)
func extractTrimmedString<T: Collection>(_ bytes: T, _ start: Int, _ end: Int) -> String?
where T.Element == UInt8, T.Index == Int {
var trimStart = start
var trimEnd = end
trimStart = skipWhitespace(bytes, trimEnd, trimStart)
trimEnd = shaveWhitespace(bytes, trimStart, trimEnd)
guard trimStart < trimEnd else { return nil }
// Why not String(data:encoding:)? This is much faster.
// swiftlint:disable:next optional_data_string_conversion
return String(decoding: bytes[trimStart..<trimEnd], as: UTF8.self)
}
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