#include <windows.h>

#define MAXLEN_PATCH_CODE       15
#define PATCH_JUMP_CODE         0xE9
#define PATCH_CALL_CODE         0xE8
#define PATCH_PRET_CODE         0x68

bool ReplaceMem(BYTE *pbMemAddr,const BYTE *pbMemData,int nLen)
{
    DWORD dwProtectFlag;

    VirtualProtect(pbMemAddr,nLen,PAGE_EXECUTE_READWRITE,&dwProtectFlag);
    memcpy(pbMemAddr,pbMemData,nLen);
    VirtualProtect(pbMemAddr,nLen,dwProtectFlag,NULL);

    return TRUE;
}

bool WritePatchCode(BYTE *pbMemoAddr,BYTE *pbFuncAddr,BYTE bCodeType,int  nCodeLen)
{
    BYTE pbPatchCode[MAXLEN_PATCH_CODE];

    memset(pbPatchCode,0x90,MAXLEN_PATCH_CODE);

    switch(bCodeType)
    {
        case PATCH_JUMP_CODE:
            pbPatchCode[0] = (char)0xE9;
            break;
        case PATCH_CALL_CODE:
            pbPatchCode[0] = (char)0xE8;
            break;
        case PATCH_PRET_CODE:
            pbPatchCode[0] = (char)0x68;
            pbPatchCode[5] = (char)0xC3;
            break;
        default:
            pbPatchCode[0] = (char)0xCC;
            break;
    }

    ((int *)(pbPatchCode+1))[0] = (int)pbFuncAddr - (int)pbMemoAddr - (1+4);

    return ReplaceMem(pbMemoAddr,pbPatchCode,nCodeLen);
}