C++ int 与 byte[] 的相互转换
转自:http://www.cnblogs.com/ly4cn/archive/2005/09/08/232523.html关于 int 与 byte[] 的相互转换,Mattias Sjogren 介绍了3种方法。请参见 《将Integer转换成Byte Array》。其实应该还有不少方法。在这里,我归纳了包括Mattias Sjogren在内的4种方法。int 与 byte[] 的相互转换 沐枫网志1. 最普通的方法从byte[] 到 uint
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b = new byte [] {0xfe,0x5a,0x11,0xfa} ;
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u = ( uint )(b[ 0 ] | b[ 1 ] << 8 | b[ 2 ] << 16 | b[ 3 ] << 24 );从int 到 byte[]
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b[ 0 ] = ( byte )(u);
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b[ 1 ] = ( byte )(u >> 8 );
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b[ 2 ] = ( byte )(u >> 16 );
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b[ 3 ] = ( byte )(u >> 24 );
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2. 使用 BitConverter (强力推荐)从int 到byte[]
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byte [] b = BitConverter.GetBytes(
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0xba5eba11 );
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// {0x11,0xba,0x5e,0xba}从byte[]到int
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uint u = BitConverter.ToUInt32(
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new byte [] {0xfe, 0x5a, 0x11,
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0xfa} , 0 ); // 0xfa115afe3. Unsafe代码 (虽然简单,但需要更改编译选项)
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unsafe
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{
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// 从int 到byte[]
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fixed ( byte* pb = b );
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// 从byte[] 到 int
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u = *((uint*)pb);
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}4. 使用Marshal类
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IntPtr ptr = Marshal.AllocHGlobal( 4 ); // 要分配非托管内存
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byte [] b = new byte [ 4 ] {1,2,3,4} ;
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// 从byte[] 到 int
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Marshal.Copy(b, 0 , ptr, 4 );
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int u = Marshal.ReadInt32(ptr);
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// 从int 到byte[]
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Marshal.WriteInt32(ptr, u);
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Marshal.Copy(ptr,b, 0 , 4 );
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Marshal.FreeHGlobal(ptr); // 最后要记得释放内存使用第4种看起来比较麻烦,实际上,如果想把结构(struct)类型转换成byte[],则第4种是相当方便的。例如:
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int len = Marshal.Sizeof( typeof (MyStruct));
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MyStruct o;
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byte [] arr = new byte [len]; // {
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};
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IntPtr ptr = Marshal.AllocHGlobal(len);
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try
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{
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// 从byte[] 到struct MyStruct
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Marshal.Copy(arr, index, ptr, Math.Min(length, arr.Length - index));
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o = (MyStruct)Marshal.PtrToStructure(ptr, typeof(MyStruct));
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// 从struct MyStruct 到 byte[]
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Marshal.StructureToPtr(o, ptr, true); // 使用时要注意fDeleteOld参数
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Marshal.Copy(ptr, arr, 0, len);
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}
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finally
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{
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Marshal.FreeHGlobal(ptr);
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}
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return o;