OpenSSL::PKey::PKey#decrypt

static VALUE
ossl_pkey_decrypt(int argc, VALUE *argv, VALUE self)
{
    EVP_PKEY *pkey;
    EVP_PKEY_CTX *ctx;
    VALUE data, options, str;
    size_t outlen;
    int state;

    GetPKey(self, pkey);
    rb_scan_args(argc, argv, "11", &data, &options);
    StringValue(data);

    ctx = EVP_PKEY_CTX_new(pkey, /* engine */NULL);
    if (!ctx)
        ossl_raise(ePKeyError, "EVP_PKEY_CTX_new");
    if (EVP_PKEY_decrypt_init(ctx) <= 0) {
        EVP_PKEY_CTX_free(ctx);
        ossl_raise(ePKeyError, "EVP_PKEY_decrypt_init");
    }
    if (!NIL_P(options)) {
        pkey_ctx_apply_options(ctx, options, &state);
        if (state) {
            EVP_PKEY_CTX_free(ctx);
            rb_jump_tag(state);
        }
    }
    if (EVP_PKEY_decrypt(ctx, NULL, &outlen,
                         (unsigned char *)RSTRING_PTR(data),
                         RSTRING_LEN(data)) <= 0) {
        EVP_PKEY_CTX_free(ctx);
        ossl_raise(ePKeyError, "EVP_PKEY_decrypt");
    }
    if (outlen > LONG_MAX) {
        EVP_PKEY_CTX_free(ctx);
        rb_raise(ePKeyError, "decrypted data would be too large");
    }
    str = ossl_str_new(NULL, (long)outlen, &state);
    if (state) {
        EVP_PKEY_CTX_free(ctx);
        rb_jump_tag(state);
    }
    if (EVP_PKEY_decrypt(ctx, (unsigned char *)RSTRING_PTR(str), &outlen,
                         (unsigned char *)RSTRING_PTR(data),
                         RSTRING_LEN(data)) <= 0) {
        EVP_PKEY_CTX_free(ctx);
        ossl_raise(ePKeyError, "EVP_PKEY_decrypt");
    }
    EVP_PKEY_CTX_free(ctx);
    rb_str_set_len(str, outlen);
    return str;
}