更新:这个问题的答案帮助我编写了开源项目AlicanC's Modern Warfare 2 Tool on GitHub的代码。您可以看到我如何在MW2Packets.cs中读取这些数据包以及我编写的扩展以读取Extensions.cs中的大端数据。
我在我的C#应用程序中使用Call of Duty: Modern Warfare 2捕获Pcap.Net的UDP数据包。我收到了图书馆的byte[]
。我试图像字符串一样解析它,但是效果不好。
我有byte[]
有一个通用数据包标题,然后是另一个特定于数据包类型的标题,然后是关于大厅中每个玩家的信息。
一个乐于助人的人为我检查了一些数据包并想出了这些结构:
// Fields are big endian unless specified otherwise.
struct packet_header
{
uint16_t magic;
uint16_t packet_size;
uint32_t unknown1;
uint32_t unknown2;
uint32_t unknown3;
uint32_t unknown4;
uint16_t unknown5;
uint16_t unknown6;
uint32_t unknown7;
uint32_t unknown8;
cstring_t packet_type; // \0 terminated string
};
// Fields are little endian unless specified otherwise.
struct header_partystate //Header for the "partystate" packet type
{
uint32_t unknown1;
uint8_t unknown2;
uint8_t player_entry_count;
uint32_t unknown4;
uint32_t unknown5;
uint32_t unknown6;
uint32_t unknown7;
uint8_t unknown8;
uint32_t unknown9;
uint16_t unknown10;
uint8_t unknown11;
uint8_t unknown12[9];
uint32_t unknown13;
uint32_t unknown14;
uint16_t unknown15;
uint16_t unknown16;
uint32_t unknown17[10];
uint32_t unknown18;
uint32_t unknown19;
uint8_t unknown20;
uint32_t unknown21;
uint32_t unknown22;
uint32_t unknown23;
};
// Fields are little endian unless specified otherwise.
struct player_entry
{
uint8_t player_id;
// The following fields may not actually exist in the data if it's an empty entry.
uint8_t unknown1[3];
cstring_t player_name;
uint32_t unknown2;
uint64_t steam_id;
uint32_t internal_ip;
uint32_t external_ip;
uint16_t unknown3;
uint16_t unknown4;
uint32_t unknown5;
uint32_t unknown6;
uint32_t unknown7;
uint32_t unknown8;
uint32_t unknown9;
uint32_t unknown10;
uint32_t unknown11;
uint32_t unknown12;
uint16_t unknown13;
uint8_t unknown14[???]; // Appears to be a bit mask, sometimes the length is zero, sometimes it's one. (First entry is always zero?)
uint8_t unknown15;
uint32_t unknown16;
uint16_t unknown17;
uint8_t unknown18[???]; // Most of the time this is 4 bytes, other times it is 3 bytes.
};
我在我的C#应用程序中重新创建了包头结构,如下所示:
[StructLayout(LayoutKind.Sequential, Pack=1)]
struct PacketHeader
{
public UInt16 magic;
public UInt16 packetSize;
public UInt32 unknown1;
public UInt32 unknown2;
public UInt32 unknown3;
public UInt32 unknown4;
public UInt16 unknown5;
public UInt16 unknown6;
public UInt32 unknown7;
public UInt32 unknown8;
public String packetType;
}
然后我尝试为“partystate”标题创建一个结构,但我得到错误,说fixed
关键字是不安全的:
[StructLayout(LayoutKind.Sequential, Pack=1)]
struct PartyStateHeader
{
UInt32 unknown1;
Byte unknown2;
Byte playerEntryCount;
UInt32 unknown4;
UInt32 unknown5;
UInt32 unknown6;
UInt32 unknown7;
Byte unknown8;
UInt32 unknown9;
UInt16 unknown10;
Byte unknown11;
fixed Byte unknown12[9];
UInt32 unknown13;
UInt32 unknown14;
UInt16 unknown15;
UInt16 unknown16;
fixed UInt32 unknown17[10];
UInt32 unknown18;
UInt32 unknown19;
Byte unknown20;
UInt32 unknown21;
UInt32 unknown22;
UInt32 unknown23;
}
由于unknown14
和unknown18
的大小不同,我无法为玩家条目做任何事情。 (玩家条目是最重要的。)
现在,不知何故,我必须将byte[]
投射到这些PacketHeader
结构。可悲的是,这并不像(PacketHeader)bytes
那么容易。我尝试过我在互联网上发现的这种方法,但它扔了一个AccessViolationException
:
GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
PacketHeader packetHeader = (PacketHeader)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(PacketHeader));
我怎样才能做到这一点?
我将字节数组转换为内存流。然后在该流上实例化二进制阅读器。然后定义辅助函数,它们接受二进制读取器并解析单个类。
内置的BinaryReader
类总是使用小端。
我在这里使用类而不是结构。
class PacketHeader
{
uint16_t magic;
uint16_t packet_size;
uint32_t unknown1;
uint32_t unknown2;
uint32_t unknown3;
uint32_t unknown4;
uint16_t unknown5;
uint16_t unknown6;
uint32_t unknown7;
uint32_t unknown8;
string packet_type; // replaced with a real string
};
PacketHeader ReadPacketHeader(BinaryReader reader)
{
var result=new PacketHeader();
result.magic = reader.ReadInt16();
...
result.packet_type=ReadCString();//Some helper function you might need to define yourself
return result;
}
//我发现了这个:http://code.cheesydesign.com/?p=572(我还没有测试过,但是//乍一看它会运行良好。)
/// <summary>
/// Reads in a block from a file and converts it to the struct
/// type specified by the template parameter
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="reader"></param>
/// <returns></returns>
private static T FromBinaryReader<T>(BinaryReader reader)
{
// Read in a byte array
byte[] bytes = reader.ReadBytes(Marshal.SizeOf(typeof(T)));
// Pin the managed memory while, copy it out the data, then unpin it
GCHandle handle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
T theStructure = (T)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(T));
handle.Free();
return theStructure;
}
这就是我做的:
using System;
using System.Runtime.InteropServices;
public static object GetObjectFromBytes(byte[] buffer, Type objType)
{
object obj = null;
if ((buffer != null) && (buffer.Length > 0))
{
IntPtr ptrObj = IntPtr.Zero;
try
{
int objSize = Marshal.SizeOf(objType);
if (objSize > 0)
{
if (buffer.Length < objSize)
throw new Exception(String.Format("Buffer smaller than needed for creation of object of type {0}", objType));
ptrObj = Marshal.AllocHGlobal(objSize);
if (ptrObj != IntPtr.Zero)
{
Marshal.Copy(buffer, 0, ptrObj, objSize);
obj = Marshal.PtrToStructure(ptrObj, objType);
}
else
throw new Exception(String.Format("Couldn't allocate memory to create object of type {0}", objType));
}
}
finally
{
if (ptrObj != IntPtr.Zero)
Marshal.FreeHGlobal(ptrObj);
}
}
return obj;
}
并且在结构定义中我没有使用任何fixed
区域,而是如果标准编组不起作用我使用了MarshalAs
属性。这是你需要的字符串。
你会像这样使用这个函数:
PacketHeader ph = (PacketHeader)GetObjectFromBytes(buffer, typeof(PacketHeader));
编辑:我没有在代码示例中看到您的BigEndian“限制”。只有字节为LittleEndian时,此解决方案才有效。
编辑2:在您的示例的字符串中,您将使用以下内容装饰它:
[MarshalAs(UnmanagedType.LPStr)]
在数组中,对于n大小的数组,我会使用类似的东西:
[MarshalAs(UnmanagedType.ByValArray, SizeConst = n)]
嗯,你真的有两个任务。首先是将byte []解释为struct本质上,其次是处理可能的不同字节序。
所以,他们有点分歧。 AFAIK如果你想使用封送处理 - 它只会将字节解释为管理结构。因此,从一个端到另一个端的转换留给你。这并不难,但它不会是自动的。
所以,要将byte []解释为struct,你必须有类似的东西:
[StructLayout(LayoutKind.Sequential)]
internal struct X
{
public int IntValue;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 3, ArraySubType = UnmanagedType.U1)]
public byte[] Array;
}
static void Main(string[] args)
{
byte[] data = {1, 0, 0, 0, 9, 8, 7}; // IntValue = 1, Array = {9,8,7}
IntPtr ptPoit = Marshal.AllocHGlobal(data.Length);
Marshal.Copy(data, 0, ptPoit, data.Length);
var x = (X) Marshal.PtrToStructure(ptPoit, typeof (X));
Marshal.FreeHGlobal(ptPoit);
Console.WriteLine("x.IntValue = {0}", x.IntValue);
Console.WriteLine("x.Array = ({0}, {1}, {2})", x.Array[0], x.Array[1], x.Array[2]);
}
所以前4个字节转到IntValue(1,0,0,0) - > [little endian] - > 1接下来3个字节直接转到数组。
如果你想要BigEndian,你应该自己做:
int LittleToBigEndian(int littleEndian)
{
byte[] buf = BitConverter.GetBytes(littleEndian).Reverse().ToArray();
return BitConverter.ToInt32(buf, 0);
}
这有点混乱,所以可能最好坚持使用自定义编写的解析器,它从源byte []逐个获取字节并填充数据类而不使用StructLayout和其他本机互操作。
我的方法不同。我不想复制任何字节。 我只是想使用它们,修改它们中的一些并在其他地方使用更改的byte []数组作为byte []。 在挖掘谷歌和stackoverflow后,我决定进入不安全/固定。 在玩代码我发现没有副本的快速代码。 这是DEBUG / TEST代码。在调试模式下检查。 请记住,这样您就不会复制并且正在处理原始byte []数据。 struct中的任何更改都将反映在byte []数组更改中,反之亦然。 ++ TESTED ++ WORKS
//FOR DEBUG/TEST ONLY
using System.Runtime.InteropServices;
namespace ByteStructCast1
{
class Program
{
[StructLayout(LayoutKind.Sequential, Pack = 1)]
unsafe struct StructTest//4B
{
[MarshalAs(UnmanagedType.U2)]
public ushort item1;//2B
public fixed byte item2[2];//2B =2x 1B
}
static void Main(string[] args)
{
//managed byte array
byte[] DB1 = new byte[7];//7B more than we need. byte buffer usually is greater.
DB1[0] = 2;//test data |> LITTLE ENDIAN
DB1[1] = 0;//test data |
DB1[2] = 3;//test data
DB1[3] = 4;//test data
unsafe //OK we are going to pin unmanaged struct to managed byte array
{
fixed(byte* db1 = DB1) //db1 is pinned pointer to DB1 byte[] array
{
//StructTest t1 = *(StructTest*)db1; //does not change DB1/db1
//t1.item1 = 11; //does not change DB1/db1
db1[0] = 22; //does CHANGE DB1/db1
DB1[0] = 33; //does CHANGE DB1/db1
StructTest* ptest = (StructTest*)db1; //does CHANGE DB1/db1
ptest->item1 = 44; //does CHANGE DB1/db1
ptest->item2[0]++; //does CHANGE DB1/db1
ptest->item2[1]--; //does CHANGE DB1/db1
}
}
}
}
}
对于那些有权访问C#7.3功能的人,我使用这段不安全的代码来“序列化”为字节:
public static class Serializer
{
public static unsafe byte[] Serialize<T>(T value) where T : unmanaged
{
byte[] buffer = new byte[sizeof(T)];
fixed (byte* bufferPtr = buffer)
{
Buffer.MemoryCopy(&value, bufferPtr, sizeof(T), sizeof(T));
}
return buffer;
}
public static unsafe T Deserialize<T>(byte[] buffer) where T : unmanaged
{
T result = new T();
fixed (byte* bufferPtr = buffer)
{
Buffer.MemoryCopy(bufferPtr, &result, sizeof(T), sizeof(T));
}
return result;
}
}
unmanaged
类型可以是结构(没有引用类型的简单结构,那些被认为是受管理的结构)或本地类型,如int
,short
等。
要将字节数组转换为字符串,请执行此操作;
byte [] dBytes = ...
string str;
System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();
str = enc.GetString(dBytes);
并将字符串转换回字节数组
public static byte[] StrToByteArray(string str)
{
System.Text.UTF8Encoding encoding=new System.Text.UTF8Encoding();
return encoding.GetBytes(str);
}
现在读取你的字符串,看看你的数据是什么。