Example for polkadart scale codec (leonardocustodio#304)

* readme update + version 4

* add example file for polkadart_scale_codec

* undo some version changes

packages/polkadart_scale_codec/example/polkadart_scale_codec_example.dart

@@ -0,0 +1,179 @@
+import 'package:polkadart_scale_codec/polkadart_scale_codec.dart';
+
+void main() {
+  ///
+  ///
+  /// Array Example
+  ///
+  ///
+  {
+    final output = HexOutput();
+    ArrayCodec(U8Codec.codec, 4).encodeTo([1, 2, 3, 4], output);
+    print(output.toString()); // 0x01020304
+  }
+
+  {
+    final input = Input.fromHex('0x0001010002010300');
+    final result = ArrayCodec(
+      TupleCodec([U8Codec.codec, BoolCodec.codec]),
+      4,
+    ).decode(input);
+    print(result); // [ [0, true], [1, false], [2, true], [3, false] ]
+  }
+
+  ///
+  ///
+  /// Btree Map Example
+  ///
+  ///
+
+  {
+    final output = HexOutput();
+    BTreeMapCodec(
+            keyCodec: BTreeMapCodec(
+                keyCodec: U32Codec.codec, valueCodec: BoolCodec.codec),
+            valueCodec: BoolCodec.codec)
+        .encodeTo({
+      {632: false}: true
+    }, output);
+    print(output.toString()); // '0x0404780200000001'
+  }
+
+  {
+    final input = Input.fromHex('0x0404780200000001');
+    final result = BTreeMapCodec(
+      keyCodec: BTreeMapCodec(
+        keyCodec: U32Codec.codec,
+        valueCodec: BoolCodec.codec,
+      ),
+      valueCodec: BoolCodec.codec,
+    ).decode(input);
+    print(result.toString()); // { {632: false}: true }
+  }
+
+  ///
+  ///
+  /// Compact Big Int Example
+  ///
+  ///
+  {
+    final byteInput = Input.fromHex('0x130000000000000001');
+    final decoded = CompactCodec.codec.decode(byteInput);
+    print(decoded); // 72057594037927936
+
+    final output = HexOutput();
+    CompactCodec.codec.encodeTo(decoded, output);
+    print(output.toString()); // 0x130000000000000001
+  }
+
+  ///
+  ///
+  /// Compact Big Int Example
+  ///
+  ///
+  {
+    final byteInput = Input.fromHex('13ffffffffffffffff');
+    final decoded = CompactBigIntCodec.codec.decode(byteInput);
+    print(decoded); // 18446744073709551615
+
+    final output = HexOutput();
+    CompactBigIntCodec.codec.encodeTo(decoded, output);
+    print(output.toString()); // 13ffffffffffffffff
+  }
+
+  ///
+  ///
+  /// Composite Example
+  ///
+  ///
+  {
+    final codec = CompositeCodec(
+      {
+        'a': U8Codec.codec,
+        'b': BoolCodec.codec,
+      },
+    );
+
+    final input = Input.fromHex('0x2a01');
+    final decoded = codec.decode(input);
+    print(decoded); // {a: 42, b: true}
+
+    final output = HexOutput();
+    codec.encodeTo(
+      {'a': 42, 'b': true},
+      output,
+    );
+    print(output.toString()); // '0x2a01'
+  }
+
+  ///
+  ///
+  /// Option Example
+  ///
+  ///
+  {
+    final codec =
+        OptionCodec(TupleCodec([CompactCodec.codec, BoolCodec.codec]));
+
+    final output = HexOutput();
+    codec.encodeTo([3, true], output);
+    print(output.toString()); // '0x010c01'
+
+    final input = Input.fromHex('0x010c01');
+    final decoded = codec.decode(input);
+    print(decoded); // [3, true]
+  }
+
+  ///
+  ///
+  /// Signed Int Example
+  ///
+  ///
+  {
+    final input = Input.fromHex(
+        '0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f');
+    final decoded = I256Codec.codec.decode(input);
+    print(
+        decoded); // BigInt.parse('57896044618658097711785492504343953926634992332820282019728792003956564819967')
+
+    final output = HexOutput();
+    I256Codec.codec.encodeTo(decoded, output);
+    print(output
+        .toString()); // 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f
+  }
+
+  ///
+  ///
+  /// Un-signed Int Example
+  ///
+  ///
+  {
+    final input = Input.fromHex(
+        '0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff');
+    final decoded = U256Codec.codec.decode(input);
+    print(
+        decoded); //  BigInt.parse('115792089237316195423570985008687907853269984665640564039457584007913129639935')
+
+    final output = HexOutput();
+    U256Codec.codec.encodeTo(decoded, output);
+    print(output
+        .toString()); // 0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+  }
+
+  ///
+  ///
+  /// Tuple Example
+  ///
+  ///
+  {
+    final codec = TupleCodec([CompactCodec.codec, BoolCodec.codec]);
+
+    final output = HexOutput();
+    codec.encodeTo([3, true], output);
+    print(output.toString()); // 0x0c01
+
+    final input = Input.fromHex('0x0c01');
+    final decoded = codec.decode(input);
+    print(decoded); // [3, true]
+  }
+}