结构体与指针应用_封包构造与解析

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封包：网络传输中的包
自定义协议如下：
4字节 命令类型
1字节 附加数据个数
4字节 保留字段




TLV结构
type - 1字节 1 - 代表字符串 2 - 二进制数据
length - 4字节大小
value - 值

// 构造数据
命令类型 110 保留字0填充
2个TLV 一个是字符串 hello 一个是字符串agp



封包要使用#pragma pack(1) 1字节对齐

用#pragma pack()还原

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#include <stdio.h>
#include <Windows.h>

#pragma pack(1)
typedef struct
{
	byte bType;
	int ilength;
	char* cValue;
}TLV;

typedef struct
{
	int iCmdID;
	byte bCount;
	int iResolve;
	TLV tlv[0];
}COMMAND;
#pragma pack()
 
// 发送命令函数
void SendCmd(void* pDate, int size);
void ParseCmd(void* pDate, int size);

// 命令类型 110 保留字0填充
// 2个TLV 一个是字符串 hello 一个是字符串agp
int main(void)
{	
	// 声明变量
	TLV tl1;
	TLV tl2;
	char* pString1 = NULL;
	char* pString2 = NULL;
	COMMAND* pCmd = NULL;
	int iCmdLength = 0;
	int iTLVCount = 0;
	memset(&tl1, 0, sizeof(TLV));
	memset(&tl2, 0, sizeof(TLV));

	// 构造字符串
	pString1 = malloc(strlen("hello"));
	memcpy(pString1, "hello", strlen("hello"));
	pString2 = malloc(strlen("agp"));
	memcpy(pString2, "agp", strlen("agp"));

	// 构造tlv1
	tl1.ilength = strlen("hello");
	tl1.bType = 1;
	tl1.cValue = pString1;

	// 构造tlv2
	tl2.ilength = strlen("agp");
	tl2.bType = 1;
	tl2.cValue = pString2;

	// 构造发送包
	iCmdLength = sizeof(COMMAND) + tl1.ilength + tl2.ilength + 2 * 5;
	pCmd = malloc(iCmdLength);
	pCmd->iCmdID = 110;
	pCmd->bCount = 2;
	pCmd->iResolve = 0;
	memcpy((void*)((int)pCmd + sizeof(COMMAND)), &tl1, 5);
	memcpy((void*)((int)pCmd + sizeof(COMMAND) + 5), tl1.cValue, tl1.ilength);
	memcpy((void*)((int)pCmd + sizeof(COMMAND) + 5 + tl1.ilength), &tl2, 5);
	memcpy((void*)((int)pCmd + sizeof(COMMAND) + 5 + tl1.ilength + 5), tl2.cValue, tl2.ilength);
	SendCmd(pCmd,iCmdLength);

	// 解析
	ParseCmd(pCmd,iCmdLength);

	system("pause");
	return 0;
}

void* g_PDate = NULL;
void SendCmd(void* pDate, int size)
{
	g_PDate = malloc(size);
	memcpy(g_PDate, pDate, size);
}

void ParseCmd(void* pDate, int size)
{
	int i = 0;
	COMMAND* cmd = (COMMAND*)pDate;
	TLV* ptl1 = malloc(sizeof(TLV));
	TLV* ptl2 = malloc(sizeof(TLV));
	char* pString1 = NULL;
	char* pString2 = NULL;
	memset(ptl1, 0, sizeof(TLV));
	memset(ptl2, 0, sizeof(TLV));

	printf("命令ID:%d\r\n", cmd->iCmdID);
	printf("TLV个数:%d\r\n", cmd->bCount);
	printf("保留字段:%d\r\n", cmd->iResolve);
	printf("TLV数据--------------------\r\n");
	ptl1 = (TLV*)((int)pDate + sizeof(COMMAND));
	printf("TL1类型:%d\r\n", ptl1->bType);
	printf("TL1长度:%d\r\n", ptl1->ilength);
	pString1 = malloc(ptl1->ilength + 1);
	memcpy(pString1, (void*)((int)ptl1 + sizeof(TLV) - 4), ptl1->ilength);
	pString1[ptl1->ilength] = 0;
	printf("TL1数据:%s\r\n", pString1);
	
	ptl2 = (TLV*)((int)pDate + sizeof(COMMAND) + ptl1->ilength + sizeof(TLV) - 4);
	printf("TL2类型:%d\r\n", ptl2->bType);
	printf("TL2长度:%d\r\n", ptl2->ilength);
	pString2 = malloc(ptl2->ilength + 1);
	memcpy(pString2, (void*)((int)ptl2 + sizeof(TLV) - 4), ptl2->ilength);
	pString2[ptl2->ilength] = 0;
	printf("TL2数据:%s\r\n", pString2);
}

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