1 files changed, 136 insertions, 0 deletions
diff --git a/Sources/WmapParser/Utils.swift b/Sources/WmapParser/Utils.swift
new file mode 100644
index 0000000..8bea13a
--- /dev/null
+++ b/Sources/WmapParser/Utils.swift
@@ -0,0 +1,136 @@
+/// 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)
+}