Thread: _read return null

Hi, help plz with my problem.
There is a code:

Code:

while (1) {
        inlen = _read(in, ctext, key_size);
        printf("Read %i bytes\n", inlen);
        if (inlen <= 0) break;
        outlen = RSA_private_decrypt(512, ctext, ptext, privKey, RSA_PKCS1_PADDING);
        printf("RSA returns %i\n", outlen);
        if (outlen < 0)
        {
            fprintf(stderr, "OpenSSL error: %s\n", ERR_error_string(ERR_get_error(), NULL));
            exit(0);
        }
        _write(out, ptext, outlen);

This is program output:

Code:

Read 82 bytes
RSA returns 494
Read 0 bytes

File size is 2055 bytes. _read function at second cycle always returns null. Whats the problem with the code? Thanks.