GostHashUtil.cpp

#include "GostHashUtil.h"

#include <windows.h>
#include <strsafe.h>
#include <array>
#include <vector>

extern "C"
{
#include "gost89.h"
#include "gosthash.h"
extern gost_subst_block GostR3411_94_TestParamSet;
}

namespace
{
    std::wstring HexEncodeUpper(const byte* data, size_t size)
    {
        static const wchar_t digits[] = L"0123456789ABCDEF";
        std::wstring out;
        out.reserve(size * 2);
        for (size_t i = 0; i < size; ++i)
        {
            byte b = data[i];
            out.push_back(digits[(b >> 4) & 0xF]);
            out.push_back(digits[b & 0xF]);
        }
        return out;
    }
}

bool ComputeGostHashFile(const std::wstring& filePath, std::wstring& outHex)
{
    gost_hash_ctx ctx{};
    if (!init_gost_hash_ctx(&ctx, &GostR3411_94_TestParamSet))
    {
        return false;
    }

    if (!start_hash(&ctx))
    {
        done_gost_hash_ctx(&ctx);
        return false;
    }

    HANDLE hFile = CreateFileW(filePath.c_str(), GENERIC_READ, FILE_SHARE_READ, nullptr,
                               OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
    if (hFile == INVALID_HANDLE_VALUE)
    {
        done_gost_hash_ctx(&ctx);
        return false;
    }

    const DWORD chunk = 64 * 1024;
    std::vector<byte> buffer(chunk);
    for (;;)
    {
        DWORD bytesRead = 0;
        if (!ReadFile(hFile, buffer.data(), chunk, &bytesRead, nullptr))
        {
            CloseHandle(hFile);
            done_gost_hash_ctx(&ctx);
            return false;
        }
        if (bytesRead == 0)
        {
            break;
        }
        if (!hash_block(&ctx, buffer.data(), bytesRead))
        {
            CloseHandle(hFile);
            done_gost_hash_ctx(&ctx);
            return false;
        }
    }
    CloseHandle(hFile);

    std::array<byte, 32> digest{};
    if (!finish_hash(&ctx, digest.data()))
    {
        done_gost_hash_ctx(&ctx);
        return false;
    }
    done_gost_hash_ctx(&ctx);

    outHex = HexEncodeUpper(digest.data(), digest.size());
    return true;
}