flutter foundation的WriteBuffer和ReadBuffer

foundation模块下有一个文件serialization.dart，里面有两个类：WriteBuffer和ReadBuffer，是关于字节流和int类型互相转换的，目前我只是在蓝牙硬件交互里常用到。

特别注意的是一个WriteBuffer和ReadBuffer的指针(引用)只能用一次

内部实现的其实很常规的，和其他类型没什么区别，在这里需要特别补充的资料是：

整型范围

• Int8-[-128:127]
• Int16-[-32768:32767]
• Int32-[-2147483648:2147483647]
• Int64-[-9223372036854775808:9223372036854775807]

无符号整型范围

• UInt8-[0:255]
• UInt16-[0:65535]
• UInt32-[0:4294967295]
• UInt64-[0:18446744073709551615]

关于WriteBuffer和ReadBuffer使用，贴出flutter的测试用例，就很清晰了。

  group('Write and read buffer round-trip', () {
    test('of single byte', () {
      final WriteBuffer write = WriteBuffer();
      write.putUint8(201);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(1));
      final ReadBuffer read = ReadBuffer(written);
      expect(read.getUint8(), equals(201));
    });
    test('of 32-bit integer', () {
      final WriteBuffer write = WriteBuffer();
      write.putInt32(-9);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(4));
      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);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(8));
      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);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(8));
      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([-99, 2, 99]);
      final WriteBuffer write = WriteBuffer();
      write.putUint8(9);
      write.putInt32List(integers);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(16));
      final ReadBuffer read = ReadBuffer(written);
      read.getUint8();
      expect(read.getInt32List(3), equals(integers));
    });
    test('of 64-bit int list when unaligned', () {
      final Int64List integers = Int64List.fromList([-99, 2, 99]);
      final WriteBuffer write = WriteBuffer();
      write.putUint8(9);
      write.putInt64List(integers);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(32));
      final ReadBuffer read = ReadBuffer(written);
      read.getUint8();
      expect(read.getInt64List(3), equals(integers));
    });
    test('of double list when unaligned', () {
      final Float64List doubles = Float64List.fromList([3.14, double.nan]);
      final WriteBuffer write = WriteBuffer();
      write.putUint8(9);
      write.putFloat64List(doubles);
      final ByteData written = write.done();
      expect(written.lengthInBytes, equals(24));
      final ReadBuffer read = ReadBuffer(written);
      read.getUint8();
      final Float64List readDoubles = read.getFloat64List(2);
      expect(readDoubles[0], equals(3.14));
      expect(readDoubles[1], isNaN);
    });
  });

这是flutter框架源码分析的其中一篇，因能力有限，有诸多不足之处，还请斧正。