Add optional `endian` argument for WriteBuffer/ReadBuffer (#46661)

packages/flutter/lib/src/foundation/serialization.dart

@@ -30,33 +30,33 @@ class WriteBuffer {
   }
 
   /// Write a Uint16 into the buffer.
-  void putUint16(int value) {
-    _eightBytes.setUint16(0, value, Endian.host);
+  void putUint16(int value, {Endian endian}) {
+    _eightBytes.setUint16(0, value, endian ?? Endian.host);
     _buffer.addAll(_eightBytesAsList, 0, 2);
   }
 
   /// Write a Uint32 into the buffer.
-  void putUint32(int value) {
-    _eightBytes.setUint32(0, value, Endian.host);
+  void putUint32(int value, {Endian endian}) {
+    _eightBytes.setUint32(0, value, endian ?? Endian.host);
     _buffer.addAll(_eightBytesAsList, 0, 4);
   }
 
   /// Write an Int32 into the buffer.
-  void putInt32(int value) {
-    _eightBytes.setInt32(0, value, Endian.host);
+  void putInt32(int value, {Endian endian}) {
+    _eightBytes.setInt32(0, value, endian ?? Endian.host);
     _buffer.addAll(_eightBytesAsList, 0, 4);
   }
 
   /// Write an Int64 into the buffer.
-  void putInt64(int value) {
-    _eightBytes.setInt64(0, value, Endian.host);
+  void putInt64(int value, {Endian endian}) {
+    _eightBytes.setInt64(0, value, endian ?? Endian.host);
     _buffer.addAll(_eightBytesAsList, 0, 8);
   }
 
   /// Write an Float64 into the buffer.
-  void putFloat64(double value) {
+  void putFloat64(double value, {Endian endian}) {
     _alignTo(8);
-    _eightBytes.setFloat64(0, value, Endian.host);
+    _eightBytes.setFloat64(0, value, endian ?? Endian.host);
     _buffer.addAll(_eightBytesAsList);
   }
 
@@ -122,37 +122,37 @@ class ReadBuffer {
   }
 
   /// Reads a Uint16 from the buffer.
-  int getUint16() {
-    final int value = data.getUint16(_position, Endian.host);
+  int getUint16({Endian endian}) {
+    final int value = data.getUint16(_position, endian ?? Endian.host);
     _position += 2;
     return value;
   }
 
   /// Reads a Uint32 from the buffer.
-  int getUint32() {
-    final int value = data.getUint32(_position, Endian.host);
+  int getUint32({Endian endian}) {
+    final int value = data.getUint32(_position, endian ?? Endian.host);
     _position += 4;
     return value;
   }
 
   /// Reads an Int32 from the buffer.
-  int getInt32() {
-    final int value = data.getInt32(_position, Endian.host);
+  int getInt32({Endian endian}) {
+    final int value = data.getInt32(_position, endian ?? Endian.host);
     _position += 4;
     return value;
   }
 
   /// Reads an Int64 from the buffer.
-  int getInt64() {
-    final int value = data.getInt64(_position, Endian.host);
+  int getInt64({Endian endian}) {
+    final int value = data.getInt64(_position, endian ?? Endian.host);
     _position += 8;
     return value;
   }
 
   /// Reads a Float64 from the buffer.
-  double getFloat64() {
+  double getFloat64({Endian endian}) {
     _alignTo(8);
-    final double value = data.getFloat64(_position, Endian.host);
+    final double value = data.getFloat64(_position, endian ?? Endian.host);
     _position += 8;
     return value;
   }

packages/flutter/test/foundation/serialization_test.dart

@@ -27,6 +27,14 @@ void main() {
       final ReadBuffer read = ReadBuffer(written);
       expect(read.getInt32(), equals(-9));
     });
+    test('of 32-bit integer in big endian', () {
+      final WriteBuffer write = WriteBuffer();
+      write.putInt32(-9, endian: Endian.big);
+      final ByteData written = write.done();
+      expect(written.lengthInBytes, equals(4));
+      final ReadBuffer read = ReadBuffer(written);
+      expect(read.getInt32(endian: Endian.big), equals(-9));
+    });
     test('of 64-bit integer', () {
       final WriteBuffer write = WriteBuffer();
       write.putInt64(-9000000000000);
@@ -35,6 +43,14 @@ void main() {
       final ReadBuffer read = ReadBuffer(written);
       expect(read.getInt64(), equals(-9000000000000));
     });
+    test('of 64-bit integer in big endian', () {
+      final WriteBuffer write = WriteBuffer();
+      write.putInt64(-9000000000000, endian: Endian.big);
+      final ByteData written = write.done();
+      expect(written.lengthInBytes, equals(8));
+      final ReadBuffer read = ReadBuffer(written);
+      expect(read.getInt64(endian: Endian.big), equals(-9000000000000));
+    });
     test('of double', () {
       final WriteBuffer write = WriteBuffer();
       write.putFloat64(3.14);
@@ -43,6 +59,14 @@ void main() {
       final ReadBuffer read = ReadBuffer(written);
       expect(read.getFloat64(), equals(3.14));
     });
+    test('of double in big endian', () {
+      final WriteBuffer write = WriteBuffer();
+      write.putFloat64(3.14, endian: Endian.big);
+      final ByteData written = write.done();
+      expect(written.lengthInBytes, equals(8));
+      final ReadBuffer read = ReadBuffer(written);
+      expect(read.getFloat64(endian: Endian.big), equals(3.14));
+    });
     test('of 32-bit int list when unaligned', () {
       final Int32List integers = Int32List.fromList(<int>[-99, 2, 99]);
       final WriteBuffer write = WriteBuffer();