entropy.c

#ifdef _WIN32
#include <windows.h>
#else
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#endif

#if defined(__cplusplus)
extern "C"
{
#endif

#ifdef _WIN32
int entropy_fun(unsigned char buf[], unsigned int len)
{
    HCRYPTPROV provider;
    unsigned __int64 pentium_tsc[1];
    unsigned int i;
    int result = 0;


    if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
    {
        result = CryptGenRandom(provider, len, buf);
        CryptReleaseContext(provider, 0);
        if (result)
            return len;
    }

    QueryPerformanceCounter((LARGE_INTEGER *)pentium_tsc);

    for(i = 0; i < 8 && i < len; ++i)
        buf[i] = ((unsigned char*)pentium_tsc)[i];

    return i;
}
#else
int entropy_fun(unsigned char buf[], unsigned int len)
{
    int frand = open("/dev/random", O_RDONLY);
    int rlen = 0;
    if (frand != -1)
    {
        rlen = (int)read(frand, buf, len);
        close(frand);
    }
    return rlen;
}
#endif

#if defined(__cplusplus)
}
#endif