Create Data extension methods for searching for a string.

Modules/Parser/Sources/Parser/Utilities/Data+Parser.swift

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+//
+//  Data+Parser.swift
+//
+//
+//  Created by Brent Simmons on 8/24/24.
+//
+
+import Foundation
+
+extension Data {
+
+	/// Return true if the data contains a given String.
+	///
+	/// Assumes that the data is UTF-8 or similar encoding —
+	/// if it’s UTF-16 or UTF-32, for instance, this will always return false.
+	/// Luckily these are rare.
+	///
+	/// The String to search for should be something that could be encoded
+	/// in ASCII — like "<opml" or "<rss". (In other words,
+	/// the sequence of characters would always be the same in
+	/// commonly-used encodings.)
+	func containsASCIIString(_ searchFor: String) -> Bool {
+
+		contains(searchFor.utf8)
+	}
+
+	/// Return true if searchFor appears in self.
+	func contains(_ searchFor: Data) -> Bool {
+
+		let searchForCount = searchFor.count
+		let dataCount = self.count
+
+		guard searchForCount > 0, searchForCount <= dataCount else {
+			return false
+		}
+
+		let searchForInitialByte = searchFor[0]
+		var found = false
+
+		self.withUnsafeBytes { bytes in
+
+			let buffer = bytes.bindMemory(to: UInt8.self)
+
+			for i in 0...dataCount - searchForCount {
+
+				if buffer[i] == searchForInitialByte {
+
+					var match = true
+
+					for j in 1..<searchForCount {
+
+						if buffer[i + j] != searchFor[j] {
+							match = false
+							break
+						}
+					}
+
+					if match {
+						found = true
+						return
+					}
+				}
+			}
+		}
+
+		return found
+	}
+}