check for buffer mismatch every boundary parse cycle

Author: tanner0101

Sources/Multipart/BoundaryParser.swift

@@ -43,8 +43,7 @@ final class BoundaryParser {
             let match = [.hyphen, .hyphen] + boundary
 
             if
-                (buffer.count <= 1 && byte == .hyphen) ||
-                    (buffer.count > 1 && buffer.count < match.count)
+                buffer.count < match.count && match[buffer.count] == byte
             {
                 state = .parsing(buffer: buffer + [byte], trailingHyphenCount: trailingHyphenCount)
                 break main

Tests/FormDataTests/ParserTests.swift

@@ -163,6 +163,6 @@ class ParserTests: XCTestCase {
         try parser.multipart.parse(message)
 
         XCTAssertEqual(fields["file"]?.filename, "test.txt")
-        XCTAssertEqual("---this is a test", fields["file"]?.part.body.string)
+        XCTAssertEqual("---this is a test", fields["file"]?.part.body.makeString())
     }
 }