Implement DER encoding for BOOLEAN, INTEGER and UTF8String in Client

client/src/der.vala

@@ -0,0 +1,90 @@
+namespace StudySystemClient.Der {
+	public abstract class Datum {
+		internal uint8 type;
+		internal uint8[] content;
+
+		public uint8[] encode() {
+			var buffer = new ByteArray();
+
+			buffer.append({type});
+			if (content.length >= 0x80) {
+				var length_bytes = encode_length(content.length);
+				buffer.append({0x80 | (uint8)length_bytes.length});
+				buffer.append(length_bytes);
+			} else {
+				buffer.append({(uint8)content.length});
+			}
+			buffer.append(content);
+
+			return buffer.data;
+		}
+
+		private static uint8[] encode_length(uint length) {
+			var buffer = new ByteArray();
+			int shift = 0;
+			while (length >> (shift + 8) != 0)
+				shift += 8;
+			for (; shift >= 0; shift -= 8)
+				buffer.append({(uint8)(length >> shift)});
+			return buffer.data;
+		}
+	}
+
+	public class Boolean : Datum {
+		internal const uint8 TYPE = 0x01;
+
+		public Boolean(bool val) {
+			type = TYPE;
+			content = new uint8[] { val ? 0xff : 0x00 };
+		}
+	}
+
+	public class Integer : Datum {
+		internal const uint8 TYPE = 0x02;
+
+		public Integer(int64 val) {
+			type = TYPE;
+			content = encode_int64(val);
+		}
+
+		private static uint64 twos_complement(uint64 x) {
+			return ~x + 1;
+		}
+
+		private static int min_bits(bool negative, uint64 x) {
+			int n = 0;
+			if (negative) {
+				while ((x >> (n + 8) & 0xff) != 0xff)
+					n += 8;
+			} else {
+				while (x >> (n + 8) > 0)
+					n += 8;
+			}
+			return n;
+		}
+
+		private static uint8[] encode_int64(int64 val) {
+			var negative = val < 0;
+			var uval = negative ? twos_complement(val.abs()) : val;
+			var shift = min_bits(negative, uval);
+
+			var buffer = new ByteArray();
+			for (; shift >= 0; shift -= 8)
+				buffer.append({(uint8)(uval >> shift)});
+
+			if (!negative && (buffer.data[0] & 0x80) != 0)
+				buffer.prepend({0x00});
+
+			return buffer.data;
+		}
+	}
+
+	public class Utf8String : Datum {
+		internal const uint8 TYPE = 0x0c;
+
+		public Utf8String(string val) {
+			type = TYPE;
+			content = val.data;
+		}
+	}
+}

client/src/meson.build

@@ -11,6 +11,7 @@ lib = library(
   'study-system-client',
   sources: files(
     'connection.vala',
+    'der.vala',
     'main_window.vala',
   ),
   dependencies: [gtk_dep],