Implemented the public hexdump API

Sources/NIOCore/ByteBuffer-hexdump.swift

@@ -62,12 +62,14 @@ extension ByteBuffer {
 
             result += "\(String(byte: lineOffset, padding: 8))  "
 
+            // Start with a xxd-format hexdump that we already have, then pad it
+            // and insert a space in the middle.
             var lineHex = slice.hexDumpShort()
             lineHex.append(String(repeating: " ", count: 49 - lineHex.count))
             lineHex.insert(" ", at: lineHex.index(lineHex.startIndex, offsetBy: 24))
             result += lineHex
 
-            // ASCII column
+            // ASCII column renders the line as ASCII characters, or "." if the character is not printable.
             result += "|" + String(decoding: slice.getBytes(at: 0, length: slice.readableBytes)!, as: Unicode.UTF8.self).map {
                 $0 >= " " && $0 < "~" ? $0 : "."
             } + "|\n"
@@ -79,4 +81,51 @@ extension ByteBuffer {
         result += String(byte: lineOffset, padding: 8)
         return result
     }
+
+//    func hexDumpLong(limit: Int) -> String {
+//        var result = ""
+//
+//        // Start with long-format dump of limit/2 bytes
+//        // then insert an empty line with "..." in the middle
+//        // Add a dump of the last limit/2 bytes
+//        // The last line should be the final lineOffset
+//
+//        
+//
+//        return result
+//    }
+
+    /// Describes a ByteBuffer hexDump format. Can be either xxd output compatible, or hexdump compatible.
+    /// You can provide a `maxLength` argument to both formats that will limit the maximum length of the buffer to dump before clipping the dump for readability.
+    public enum HexDumpFormat {
+        /// A hexdump format compatible with the xxd utility.
+        /// - parameters:
+        ///     - maxLength: The maximum amount of bytes to dump before clipping for readability.
+        case xxdCompatible(maxLength: Int? = nil)
+
+        /// A hexdump format compatible with hexdump utility.
+        /// - parameters:
+        ///     - maxLength: The maximum amount of bytes to dump before clipping for readability.
+        case hexDumpCompatible(maxLength: Int? = nil)
+    }
+
+
+    public func hexDump(format: HexDumpFormat) -> String {
+        switch(format) {
+        case .xxdCompatible(let maxLength):
+            if let maxLength {
+                return self.hexDumpShort(limit: maxLength)
+            } else {
+                return self.hexDumpShort()
+            }
+
+        case .hexDumpCompatible(let maxLength):
+            if let maxLength {
+                return self.hexDumpLong()
+            } else {
+                return self.hexDumpLong()
+            }
+        }
+    }
+
 }

Tests/NIOCoreTests/ByteBufferTest.swift

@@ -1903,6 +1903,18 @@ class ByteBufferTest: XCTestCase {
         XCTAssertEqual(expected, actual)
     }
 
+    func testHexDumpSwitcher() {
+        let buf = ByteBuffer(string: "Goodbye, world! It was nice knowing you.\n")
+        let expected = """
+        00000000  47 6f 6f 64 62 79 65 2c  20 77 6f 72 6c 64 21 20  |Goodbye, world! |
+        00000010  49 74 20 77 61 73 20 6e  69 63 65 20 6b 6e 6f 77  |It was nice know|
+        00000020  69 6e 67 20 79 6f 75 2e  0a                       |ing you..|
+        00000029
+        """
+        let actual = buf.hexDump(format: .hexDumpCompatible())
+        XCTAssertEqual(expected, actual)
+    }
+
     func testReadableBytesView() throws {
         self.buf.clear()
         self.buf.writeString("hello world 012345678")