API 函数地址的修改，帮助！！！！

[woshinidelover]

/* 1 */HANDLE hCurrent = GetModuleHandle(NULL);
/* 2 */IMAGE_DOS_HEADER *pidh;
/* 3 */IMAGE_NT_HEADERS *pinh;
/* 4 */IMAGE_DATA_DIRECTORY *pSymbolTable;
/* 5 */IMAGE_IMPORT_DESCRIPTOR *piid;

/* 6 */pidh = (IMAGE_DOS_HEADER *)hCurrent;
/* 7 */pinh = (IMAGE_NT_HEADERS *)((DWORD)hCurrent + pidh->e_lfanew);
/* 8 */pSymbolTable = &pinh->OptionalHeader.DataDirectory[1];
/* 9 */piid =(IMAGE_IMPORT_DESCRIPTOR *)((DWORD)hCurrent + pSymbolTable->VirtualAddress);
/*10 */do {
/*11 */ IMAGE_THUNK_DATA *pitd,*pitd2;
/*12 */ pitd = (IMAGE_THUNK_DATA *)((DWORD)hCurrent + piid->OriginalFirstThunk);
/*13 */ pitd2 = (IMAGE_THUNK_DATA *)((DWORD)hCurrent + piid->FirstThunk);
/*14 */ do {
/*15 */ IMAGE_IMPORT_BY_NAME *piibn;
/*16 */ piibn = (IMAGE_IMPORT_BY_NAME *)((DWORD)hCurrent + *((DWORD *)pitd));
/*17 */ PROC *ppfn = (PROC *)(pitd2->u1.Function);
/*18 */ if (!strcmp("MessageBoxW",(char *)piibn->Name)) {
/*19 */ oldMsg = (MsgBoxType)(ppfn);
/*20 */ DWORD addr = (DWORD)MyMessage;
/*21 */ DWORD written = 0;
/* 改变内存读写状态 */
/*22 */ DWORD oldAccess;
/*23 */ VirtualProtect(&pitd2->u1.Function,sizeof(DWORD),PAGE_WRITECOPY,&oldAccess);
/*24 */ APIAddress = (DWORD)&pitd2->u1.Function;
/* 向内存映像写入数据 */
/*25 */ WriteProcessMemory(GetCurrentProcess(),&pitd2->u1.Function, &addr,sizeof(DWORD), &written);
/*26 */ }
/*27 */ pitd++;pitd2++;
/*28 */ } while (pitd->u1.Function);

/*29 */ piid++;
/*30 */} while (piid->FirstThunk + piid->Characteristics
+ piid->ForwarderChain + piid->Name + piid->TimeDateStamp);


这是一个修改PE文件导入函数地址的代码，有两句看不懂，谁能帮我解释一下：
/*16 */ piibn = (IMAGE_IMPORT_BY_NAME *)((DWORD)hCurrent + *((DWORD *)pitd));
/*17 */ PROC *ppfn = (PROC *)(pitd2->u1.Function);
pitd2->u1.Function 好象是保存一个函数的地址，我查过PE文件的教程，可是u1.Function根本
没有解释，pitd2做为一个地址指向的地方才是导入函数的地址啊，pitd2 指向一个IMAGE_IMPORT_BY_NAME 类型的结构啊，搞不懂了，到底什么意思啊！！

[hxzb7215191]

这是得到这个导出表的结构吧.