计算哈希值MD5

时间:2013-06-11 08:03:14

标签: c delphi c++builder hashcode vcl

我正在尝试使用SubDB API但是我在计算文件的哈希时遇到了问题。哈希是通过获取视频文件的第一个和最后一个64kb组成的,将所有数据放在一起并生成md5的结果数据(128kb)。以python编写的以下函数实现了哈希算法:

def get_hash(name):
        readsize = 64 * 1024
        with open(name, 'rb') as f:
            size = os.path.getsize(name)
            data = f.read(readsize)
            f.seek(-readsize, os.SEEK_END)
            data += f.read(readsize)
        return hashlib.md5(data).hexdigest()

我正在使用C ++ Builder XE2,我尝试将其翻译如下:

String __fastcall MD5Hash(const AnsiString filename)
{
     String result;
     char firstbits[60*1024], lastbits[60*1024];
     char bits[120*1024];

     FILE* f = fopen(filename.c_str(), "rb");
     if(f ==NULL) {ShowMessage("Error!"); return "";}
     TIdHashMessageDigest5 *idmd5= new TIdHashMessageDigest5();
     try  {
        fread(firstbits, 60*1024, 1, f);
        fseek(f, -(long)60*1024, SEEK_END);
        fread(lastbits, 60*1024, 1, f);
        strcpy(bits, firstbits);
        strcpy(bits, lastbits);
        result= idmd5->HashBytesAsHex(RawToBytes(bits, 120*1024));
     }
     __finally    {
        delete idmd5;
     }
     fclose(f);
     return result;
}

测试文件是这样的:http://thesubdb.com/api/samples/dexter.mp4,它的哈希值(来自上面的算法)应该是ffd8d4aa68033dc03d1c8ef373b9028c。但是,我无法做对......

Delphi解决方案也可以。

1 个答案:

答案 0 :(得分:4)

尝试以下代码怎么样?我只是改变了尺寸,做了适当的踩踏,并删除了strcpy。

String __fastcall MD5Hash(const AnsiString filename)
{
     String result;
     char bits[128*1024];

     FILE* f = fopen(filename.c_str(), "rb");
     if(f ==NULL) {ShowMessage("Error!"); return "";}
     TIdHashMessageDigest5 *idmd5= new TIdHashMessageDigest5();
     try  {
        fread(bits, 64*1024, 1, f);
        fseek(f, -(long)64*1024, SEEK_END);
        fread(&bits[64*1024], 64*1024, 1, f);
        result= idmd5->HashBytesAsHex(RawToBytes(bits, 128*1024));
     }
     __finally    {
        delete idmd5;
     }
     fclose(f);
     return result;
}