Add Metadata collection (#1683)

Author: gjcairo

NOTICES.txt

@@ -31,10 +31,29 @@ It also uses derivations of SwiftNIO's lock 'NIOLock.swift' and locked value box
 
 ---
 
+This product uses derivations of SwiftNIOHTTP2's implementation of case
+insensitive comparison of strings, found in 'HPACKHeader.swift'.
+    
+    * LICENSE (Apache License 2.0):
+      * https://github.com/apple/swift-nio-http2/blob/main/LICENSE.txt
+    * HOMEPAGE:
+      * https://github.com/apple/swift-nio-http2
+
+---
+
 This product contains a derivation of the backpressure aware async stream from
 the Swift project.
 
   * LICENSE (Apache License 2.0):
     * https://github.com/apple/swift/blob/main/LICENSE.txt
   * HOMEPAGE:
     * https://github.com/apple/swift
+
+---
+
+This product uses derivations of swift-extras/swift-extras-base64 'Base64.swift'.
+
+  * LICENSE (Apache License 2.0):
+    * https://github.com/swift-extras/swift-extras-base64/blob/main/LICENSE
+  * HOMEPAGE:
+    * https://github.com/swift-extras/swift-extras-base64

Sources/GRPCCore/Internal/Base64.swift

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2023, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftNIO open source project
+//
+// Copyright (c) 2017-2023 Apple Inc. and the SwiftNIO project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+extension UInt8 {
+  @inlinable
+  var isASCII: Bool {
+    return self <= 127
+  }
+}
+
+extension String.UTF8View {
+  /// Compares two UTF8 strings as case insensitive ASCII bytes.
+  ///
+  /// - Parameter bytes: The string constant in the form of a collection of `UInt8`
+  /// - Returns: Whether the collection contains **EXACTLY** this array or no, but by ignoring case.
+  @inlinable
+  func compareCaseInsensitiveASCIIBytes(to other: String.UTF8View) -> Bool {
+    // fast path: we can get the underlying bytes of both
+    let maybeMaybeResult = self.withContiguousStorageIfAvailable { lhsBuffer -> Bool? in
+      other.withContiguousStorageIfAvailable { rhsBuffer in
+        if lhsBuffer.count != rhsBuffer.count {
+          return false
+        }
+
+        for idx in 0 ..< lhsBuffer.count {
+          // let's hope this gets vectorised ;)
+          if lhsBuffer[idx] & 0xdf != rhsBuffer[idx] & 0xdf && lhsBuffer[idx].isASCII {
+            return false
+          }
+        }
+        return true
+      }
+    }
+
+    if let maybeResult = maybeMaybeResult, let result = maybeResult {
+      return result
+    } else {
+      return self._compareCaseInsensitiveASCIIBytesSlowPath(to: other)
+    }
+  }
+
+  @inlinable
+  @inline(never)
+  func _compareCaseInsensitiveASCIIBytesSlowPath(to other: String.UTF8View) -> Bool {
+    return self.elementsEqual(other, by: { return (($0 & 0xdf) == ($1 & 0xdf) && $0.isASCII) })
+  }
+}
+
+extension String {
+  @inlinable
+  func isEqualCaseInsensitiveASCIIBytes(to: String) -> Bool {
+    return self.utf8.compareCaseInsensitiveASCIIBytes(to: to.utf8)
+  }
+}