Question

Currently I am implementing into my C++/CLI code a function that return the SHA1 value of a file. It is a Windows Forms application in Visual Studio.

I chose to implement the .NetFramework class SHA1CryptoServiceProvider because it is really fast (believe me). I have tested several algorithms but none of them were as fast as the SHA1CryptoServiceProvider class.

The problem is that in my application there is a progressBar showing the progress of computing SHA1 and the SHA1CryptoServiceProvider class doesn’t have any function that returns progress of computing SHA1.

Here is the code:

using namespace System::Security::Cryptography;
using namespace System::IO;

StreamReader^ Reader = gcnew StreamReader("C:\\abc.exe");
SHA1CryptoServiceProvider^ SHA1 = gcnew SHA1CryptoServiceProvider();

String^ Hash = "";

Hash = BitConverter::ToString(SHA1->ComputeHash(Reader->BaseStream));
return Hash;

Answer 1

Finally I have done it. I post the code, maybe someone will find it useful. I know the code is not clean, I am still learning. It can compute SHA1 of files larger that 2^31 bytes. Tested it on a 22GB file. Works fine in backgroundWorker 🙂

#define SHA1_BUFFER_SIZE  65535
//input buffer
array<unsigned char,1>^ buf = gcnew array<unsigned char,1>(SHA1_BUFFER_SIZE);
pin_ptr<unsigned char> pointer = &buf[0];

//Open file in 64-bit mode
FILE *file = _fopeni64("some_large_file.txt","rb");
SHA1CryptoServiceProvider^ SHA1 = gcnew SHA1CryptoServiceProvider();

//Move pointer to End of File
_fseeki64(file,0,SEEK_END);
//Read pointer position (file size)
unsigned __int64 size = (__int64)_ftelli64(file);

// Move pointer to begining of file
_fseeki64(file,0,SEEK_SET);
__int64 i = 1;    // counter
float wyn = 0;    // help variable for progress Percentage (float)
__int64 conv = 0; // help variable for progress Percentage (int)

//output buffer
array<unsigned char,1>^ outputbuffer = gcnew array<unsigned char,1>(SHA1_BUFFER_SIZE);
while(1)
{
    //Read SHA1_BUFFER_SIZE bytes to buffer
    size_t bufLen = fread( pointer, 1, SHA1_BUFFER_SIZE, file );
    if (bufLen == 0) //End of file
    {
        if (ferror(file)) //Error opening file
            return;
        break;
    }
    //buffer has the last block of bytes of the file
    if ( SHA1_BUFFER_SIZE*i >= size  )
        SHA1->TransformFinalBlock(buf,0,bufLen);
    else
        SHA1->TransformBlock(buf,0,bufLen,outputbuffer,0);

    wyn = SHA1_BUFFER_SIZE*100; /* Getting    */
    wyn /= size;                /* the        */
    wyn *= i;                   /* progress   */
    conv = wyn;                 /* Percentage */
    ComputeSHA1->ReportProgress(conv);
    \\Update our progressBar
    i++;
} //End main loop

String^ sHash = "";
//Get the computed hash and convert to System::String
sHash = BitConverter::ToString(SHA1->Hash);
//Replace the '-' characters in hash to white spaces
sHash = sHash->Replace('-',' ');
//Removing whitespaces from hash
sHash = System::Text::RegularExpressions::Regex::Replace(sHash, "\\s+", System::String::Empty);

//Filling a textBox with the SHA1
ComputeSHA1->ReportProgress(0,sHash);